Water Quality Information Center of the National Agricultural Library
Agricultural Research Service, U.S. Department of Agriculture


Simulation Models, GIS and Nonpoint-Source Pollution (I)

 January 1991 - December 1993
 Quick Bibliography Series:  QB 94-06 (Updates QB 92-69)
 337 citations from AGRICOLA
 
 Joe Makuch and Bonnie Emmert
 Water Quality Information Center
 
 Quick Bibliography Series 
 Bibliographies in the Quick Bibliography series of the
 National Agricultural Library (NAL), are intended primarily for
 current awareness, and as the title of the series implies, are
 not in-depth and exhaustive. However, the citations are a
 substantial resource for recent investigations on a given topic. 
 They also serve the purpose of bringing the literature of
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 access it by any other means.  The bibliographies are derived
 from online searches of the AGRICOLA database.  Timeliness of
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 criteria.  Send suggestions for Quick Bibliography topics to
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 index is provided along with the search strategy.
 
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      Simulation Models, GIS and Nonpoint-Source Pollution
 
 1                                    NAL Call. No.: 56.8 SO3
 An accurate and numerically stable model for one-dimensional
 solute transport in soils.
 Moldrup, P.; Yamaguchi, T.; Hansen, J.A.; Rolston, D.E.
 Baltimore, Md. : Williams & Wilkins; 1992 Apr.
 Soil science v. 153 (4): p. 261-273; 1992 Apr.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil solution; Solutes; Transport processes;
 Simulation models; Mathematical models; Soil water movement;
 Convection; Dispersion; Comparisons; Accuracy; Soil testing;
 Soil water content; Loam soils
 
 
 2                                    NAL Call. No.: QH540.N3
 Adsorption-desorption methodologies and selected estimation
 techniques for transport-modeling parameters.
 Roy, W.R.
 Berlin, W. Ger. : Springer-Verlag; 1993.
 NATO ASI series : Series G : Ecological sciences v. 32: p.
 169-188; 1993.  In the series analytic: Migration and fate of
 pollutants in soils and subsoils / edited by D. Petruzzelli
 and F.G. Helfferich. Proceedings of the NATO Advanced Study
 Institute, May 24-June 5, 1992, Maratea, Italy.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil pollution; Pollutants; Adsorption;
 Desorption; Transport processes; Computer simulation; Vapor;
 Organic compounds; Volatilization; Groundwater pollution;
 Trichloroethylene; Microbial degradation
 
 
 3                                 NAL Call. No.: HD1773.A2N6
 Aggregate analysis of site-specific pollution problems: the
 case of groundwater contamination from agriculture.
 Opaluch, J.J.; Segerson, K.
 Morgantown, W.Va. : The Northeastern Agricultural and Resource
 Economics Association; 1991 Apr.
 Northeastern journal of agricultural and resource economics v.
 20 (1): p. 83-97; 1991 Apr.  Paper submitted in response to
 call for papers on the theme "The Effects of Agricultural
 Production on Environmental Quality.".  Includes references.
 
 Language:  English
 
 Descriptors: Groundwater; Contamination; Water pollution;
 Agricultural sector; Agricultural policy; Microeconomic
 analysis; Aggregate data; Site factors; Spatial distribution;
 Information systems; Mathematical models
 
 
 4                                    NAL Call. No.: S900.R39
 Analysing water quality policy using microeconomic models of
 production practices and biophysical flow models of
 environmental processes. Weaver, R.D.; Harper, J.K.
 London : Harwood Academic Publishers; 1993.
 Resource management and optimization v. 9 (2): p. 95-105;
 1993.  Includes references.
 
 Language:  English
 
 Descriptors: U.S.A.; Water quality; Water policy;
 Microeconomics; Technology; Environmental factors;
 Mathematical models
 
 
 5                                  NAL Call. No.: 292.8 W295
 An analytical solution for one-dimensional transport in porous
 media with an exponential dispersion function.
 Yates, S.R.
 Washington, D.C. : American Geophysical Union; 1992 Aug.
 Water resources research v. 28 (8): p. 2149-2154; 1992 Aug. 
 Includes references.
 
 Language:  English
 
 Descriptors: Transport processes; Solutes; Hydrodynamic
 dispersion; Subsurface layers; Equations; Mathematical models
 
 Abstract:  An analytical solution describing the transport of
 dissolved substances in heterogeneous porous media with an
 asymptotic distance-dependent dispersion relationship has been
 developed. The solution has a dispersion function which is
 linear near the origin (i.e., for short travel distances) and
 approaches an asymptotic value as the travel distance becomes
 infinite. This solution can be used to characterize
 differences in the transport process relative to both the
 classical convection-dispersion equation which assumes that
 the hydrodynamic dispersion in the porous medium remains
 constant and a dispersion solution which has a strictly linear
 dispersion function. The form of the hydrodynamic dispersion
 function used in the analytical solution is D(x) = alpha(x)
 average pore water velocity + D(diff), where a(x) = a L[1 -e(-
 bx/L)]. The proposed model may provide an alternate means for
 obtaining a description of the transport of solutes in
 heterogeneous porous media, when the scale dependence of the
 dispersion relationship follows the behavior given by
 alpha(x). The overall behavior of the model is illustrated by
 several examples for constant concentration and flux boundary
 conditions.
 
 
 6                                    NAL Call. No.: 56.9 SO3
 Analytical solution of solute diffusion and biodegradation in
 spherical aggregates.
 Priesack, E.
 Madison, Wis. : The Society; 1991 Sep.
 Soil Science Society of America journal v. 55 (5): p.
 1227-1230; 1991 Sep. Includes references.
 
 Language:  English
 
 Descriptors: Microbial degradation; Soil flora; Organic
 compounds; Solutes; Diffusion; Soil solution; Aggregates;
 Spatial distribution; Mathematical models; Soil pore system;
 Pores; Transport processes; Movement in soil; Diffusivity;
 Growth rate; Adsorption; Biomass; Substrates
 
 Abstract:  Microbial degradation and transformation of
 substances in soils plays a crucial role ii the nutrient
 turnover of ecosystems. To quantify these processes, a
 mathematical description is needed. For this purpose, an
 analytical solution to a model of solute diffusion and
 biodegradation in soil aggregates was developed. The model is
 a first approach toward understanding the influence of
 geometric arrangement of microorganisms and substrates in
 structured soils. These soils are considered to consist of
 uniformly sized and shaped aggregates surrounded by surface
 films of the soil solution. The model simulates transient
 diffusion of finite substrate amounts from the surface films
 into spherical aggregates. Biodegradation is considered for
 the special case of unlimited microbial growth, and adsorption
 is assumed to follow a linear Freundlich isotherm. The system
 is represented by a composite sphere, the outer sphere being
 the solution film and the inner sphere representing the soil
 aggregate. The diffusion equations are solved by Laplace
 transformation. The model solution gives a direct relationship
 between the initial substrate and biomass concentrations, the
 diffusion coefficient, the specific growth rate, and the
 adsorption coefficient. Good agreement between this closed
 form solution and numerical solutions is obtained for
 diffusion with and without biodegradation. Since the substrate
 is exhausted by organisms close to the surface, the centers of
 large aggregates are not reached by the diffusing substrate.
 These unaffected centers become lager as the growth rate is
 higher, the diffusion constant is lower, and adsorption of the
 substrate is stronger.
 
 
 7                                  NAL Call. No.: 292.8 W295
 Analytical solutions for solute transport in three-dimensional
 semi-infinite porous media.
 Leij, F.J.; Skaggs, T.H.; Van Genuchten, M.T.
 Washington, D.C. : American Geophysical Union; 1991 Oct.
 Water resources research v. 27 (10): p. 2719-2733; 1991 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: Transport processes; Solutes; Flow; Mathematical
 models; Prediction
 
 Abstract:  This paper presents several analytical solutions
 for three-dimensional solute transport in semi-infinite porous
 media with unidirectional flow using first-type (or
 concentration) and third-type (or flux) boundary conditions at
 the inlet location of the medium. The solutions may be used
 for predicting solute concentrations in homogeneous media,
 verification of more comprehensive numerical models, and
 laboratory or field determination of solute transport
 parameters. The transport equation incorporates terms
 accounting for advection, dispersion, zero-order production,
 and first-order decay. General solutions were derived for an
 arbitrary initial distribution and solute input with the help
 of Laplace, Fourier, and Hankel transforms. Specific solutions
 are presented for rectangular and circular solute inflow
 regions, as well as for solutes initially present in the form
 of parallelepipedal or cylindrical regions of the medium. The
 solutions were mathematically verified against simplified
 analytical solutions. Examples of concentration profiles are
 presented for several solute transport parameters using both
 first- and third-type boundary conditions. A mass balance
 constraint is defined based on a prescribed solute influx; the
 third-type condition is shown to conserve mass whereas the
 first-type condition was found to always overestimate resident
 solute concentrations in the medium.
 
 
 8                                  NAL Call. No.: 292.8 W295
 Applicability of the steady state flow assumption for solute
 advection in field soils.
 Destouni, G.
 Washington, D.C. : American Geophysical Union; 1991 Aug.
 Water resources research v. 27 (8): p. 2129-2140; 1991 Aug. 
 Includes references.
 
 Language:  English
 
 Descriptors: Agricultural soils; Solutes; Transport processes;
 Transient flow; Soil water movement; Soil texture; Soil depth;
 Plant water relations; Simulation models
 
 Abstract:  A comparison between solute travel times predicted
 by a transient and a steady state flow model is made. Data for
 five different soil profiles with detailed measurements of
 their hydraulic properties and their variation with depth are
 used. Daily measurements of meteorological data are used as
 input parameters in the transient simulations that include
 snow and frost dynamics, interception of precipitation, and
 evapotranspiration. The parameters of the steady state flow
 model are related to the measured soil properties and the
 hydrological characteristics of each transient simulation.
 Furthermore, the influence of solute injection time on the
 predicted travel time is analyzed, and the effect of root
 water uptake on the applicability, of the steady state flow
 assumption for solute advection is investigated. The results
 indicate that the steady, state flow model may provide
 estimates of the mean solute advection that are compatible
 with those of the transient flow model. The constant rate of
 recharge in the steady state flow, model should then be
 interpreted as the average annual effective infiltration
 (i.e., infiltration minus actual evapotranspiration). When
 root water uptake is accounted for, an arithmetic depth-
 averaging of the soil parameters appears to yield steady state
 estimates of arrival time that are closest to the transient
 predictions. When root water uptake is neglected, a harmonic
 depth-averaging of the soil parameters provides the best
 steady state results. The discrepancy between the arrival
 times predicted with the two flow models decreases with the
 travel distance from the soil surface.
 
 
 9                            NAL Call. No.: 100 G29So no.372
 Application and enhancement of hydrologic/water quality
 models..  S-211 final report
 Thomas, Daniel L.; Shirmohammadi, Adel,_1952-; Engel, Bernard
 A. Tifton, Ga. : Biological and Agricultural Engineering Dept.
 : University of Georgia-Coastal Plain Experiment Station,;
 1992.
 xi, 114 p. : ill. ; 28 cm. (Southern cooperative series
 bulletin ; no. 372). Running title: S-211 final report.  June,
 1992.  Includes bibliographical references.
 
 Language:  English; English
 
 Descriptors: Hydrology; Water quality
 
 
 10                                  NAL Call. No.: SB951.P47
 Application and validation of pesticide leaching models.
 Klein, M.
 Essex : Elsevier Applied Science Publishers; 1991.
 Pesticide science v. 31 (3): p. 389-398; 1991.  Includes
 references.
 
 Language:  English
 
 Descriptors: German federal republic; Bentazone; Cloethocarb;
 Simulation models; Environmental factors; Leaching;
 Lysimeters; Pesticide residues; Soil properties; Climatic
 factors
 
 Abstract:  Two lysimeter studies with the pesticides
 cloethocarb and bentazone were used to validate a modified
 version of the computer model SESOIL (Seasonal Soil
 Compartment Model), developed by Bonazountas and Wagner and to
 transfer the results of the lysimeter study to another climate
 scenario. For cloethocarb, an experimental insecticide without
 marked mobility in the soil, as indicated by the lysimeter
 study, the simulations were in excellent agreement with the
 lysimeter study. Calculations for bentazone revealed higher
 leaching than found in the lysimeter study. This discrepancy
 was resolved by a more careful and realistic inclusion of
 sorption in the lysimeter soil into the simulation model.
 
 
 11                                  NAL Call. No.: 292.8 J82
 An application of a physically based semi-distributed model to
 the Balquhidder catchments.
 Robson, A.J.; Whitehead, P.G.; Johnson, R.C.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 May15.
 Journal of hydrology v. 145 (3/4): p. 357-370; 1993 May15. 
 Special Issue: The Balquhidder Catchment and Process Studies /
 edited by P.G. Whitehead and I.R. Calder.  Includes
 references.
 
 Language:  English
 
 Descriptors: Scotland; Watersheds; Simulation models;
 Catchment hydrology; Rain; Runoff; Flow
 
 Abstract:  A physically based semi-distributed model,
 TOPMODEL, is applied to the two catchments at Balquhidder. The
 model uses a topographic index which highlights hydrologically
 significant areas within the catchments. The model is used to
 simulate runoff and to compare the behaviour of the two
 catchments. The results indicate that a large proportion of
 stream water is generated from saturated contributing areas
 (source areas); the Monachyle has higher contributions of
 water of this type. The results may also indicate that the
 hydrology of the Monachyle catchment has changed following
 agricultural improvement by increased drainage; a damped
 subsurface response is observed.
 
 
 12                              NAL Call. No.: QA76.76.E95A5
 Application of case-based reasoning concepts to the WEPP soil
 erosion model. Meyer, C.R.; Flanagan, D.C.
 Moscow, Idaho : AI Applications; 1992.
 AI applications v. 6 (3): p. 63-71; 1992.  Includes
 references.
 
 Language:  English
 
 Descriptors: U.S.A.; Water erosion; Prediction; Simulation
 models; Information retrieval; Usda; Improvement; Management;
 Practice; Information storage; Data banks; Program
 development; Computer techniques
 
 
 13                                   NAL Call. No.: 56.9 SO3
 Applications of a laser scanner to quantify soil
 microtopography. Huang, C.H.; Bradford, J.M.
 Madison, Wis. : The Society; 1992 Jan.
 Soil Science Society of America journal v. 56 (1): p. 14-21;
 1992 Jan. Includes references.
 
 Language:  English
 
 Descriptors: North Carolina; Hapludults; Inceptisols; Surface
 roughness; Measurement; Quantitative techniques; Surface
 layers; Topography; Height; Spatial variation; Mathematical
 models; Mathematics; Transport processes; Soil boundaries;
 Artificial precipitation; Tillage; Interrill erosion; Soil
 water content; Size; Lasers
 
 Abstract:  Many transport processes on or across the soil
 surface boundary are controlled by surface microtopography, or
 roughness. How roughness affects the transport process depends
 on the length scale of the process. The most commonly used
 method of expressing soil surface roughness, the roughness
 length or random roughness, is constrained by the measurement
 technique and does not embody the concept of scale. The
 structural function, or variogram, plotted on a log-log scale
 was used in this study to express the surface roughness at
 different scales. With the aid of a laser scanner, surface
 topography was measured down to 0.5-mm grid spacing. Data
 collected from a variety of surface conditions showed that
 soil roughness can be quantified by a combination of fractal
 and Markov-Gaussian processes at different scales. Potential
 applications of the roughness quantification were also
 discussed.
 
 
 14                                  NAL Call. No.: TD426.J68
 An approach to estimating uncertainties in modeling transport
 of solutes through soils.
 Zhang, H.; Haan, C.T.; Nofziger, D.L.
 Amsterdam : Elsevier; 1993 Feb.
 Journal of contaminant hydrology v. 12 (1/2): p. 35-50; 1993
 Feb.  Includes references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution;
 Pollutants; Chemicals; Solutes; Movement in soil; Uncertainty;
 Rain; Variation; Prediction; Simulation models
 
 
 15                                 NAL Call. No.: 292.8 W295
 Approximate analytical solution for soil chemical transfer to
 runoff: a modified boundary condition.
 Wallach, R.
 Washington, D.C. : American Geophysical Union; 1993 May.
 Water resources research v. 29 (5): p. 1467-1474; 1993 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Soil solution; Surface
 water; Runoff water; Overland flow; Boundaries; Transport
 processes; Equations; Mathematical models; Comparisons
 
 Abstract:  Two mass balance equations were used to model the
 transfer of dissolved chemicals from the soil solution to the
 surface runoff water and the transport of these chemicals to
 the field outlet. One mass balance equation was written for
 chemicals dissolved in the overland water, the other for
 chemicals within the soil profile. Chemical input into the
 surface water (upper boundary condition) was expressed as a
 rate-limited convective mass transfer, depending on both soil
 surface and runoff concentrations. Isolating a slow and fast
 time scale and scaling the mass balance equations to the slow
 one yielded a parameter, epsilon, which multiplies the time
 derivative of the mass balance equation written for overland
 flow. In most cases epsilon << 1, providing a singular
 perturbation problem that was solved by using the method of
 matched asymptotic expansion. The approximate solution,
 uniformly valid over the entire domain, was made up of two
 terms: a leading-order solution and a first-order solution,
 the latter of which was relatively small, even for epsilon =
 O(1). The leading-order solution was compared with that for a
 simpler case, in which the convective mass transfer (upper
 boundary condition) depends only on the soil surface
 concentration. The comparison indicated those limited cases to
 which the simpler boundary condition can be applied resulting
 in a very small error. Although it is not possible to get a
 strictly analytical solution for a problem involving a
 modified upper boundary condition, the approximate analytical
 solution is easily obtained.
 
 
 16                                 NAL Call. No.: 292.9 AM34
 Assessing ground water pollution potential from nitrogen
 fertilizer using a geographic information system.
 Halliday, S.L.; Wolfe, M.L.
 Bethesda, Md. : American Water Resources Association; 1991
 Mar. Water resources bulletin v. 27 (2): p. 237-245; 1991 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Texas; Groundwater pollution; Nitrogen
 fertilizers; Pollutants; Susceptibility; Expert systems
 
 Abstract:  A geographic information system (GRASS 3.1) was
 used to correlate the availability of nitrogen fertilizer with
 the susceptibility of ground water to pollution in Texas to
 identify potential ground water quality problems. An
 agricultural pollution susceptibility map, produced by the
 Texas Water Commission using the DRASTIC methodology, was
 combined with information on cropped areas, recommended
 nitrogen fertilizer application rates, and aquifer outcrops. A
 Nitrogen Fertilizer Pollution Potential Index was generated,
 identifying 24 percent or Texas within the high pollution
 potential category. An analysis of the susceptibility of major
 aquifer outcrops to potential pollution from nitrogen
 fertilizer indicated that 34 percent of the outcrop areas fall
 in the high pollution potential range. It is proposed that
 correlating the availability of a pollutant with an assessment
 of the susceptibility of ground water to pollution yields a
 more accurate screening tool for identifying potential
 pollution problems than considering susceptibility alone.
 
 
 17                                 NAL Call. No.: S542.A8A34
 Assessment and alleviation of the impact of runoff and erosion
 on crop production.
 Okwach, G.E.; Williams, J.; Wambua, J.
 Canberra : Australian Centre for International Agricultural
 Research; 1992. ACIAR proceedings (41): p. 72-82; 1992.  In
 the series analytic: A search for strategies for sustainable
 dryland cropping in semi-arid eastern Kenya / edited by M.E.
 Probert. Paper presented at a symposium held Dec 10-11, 1990,
 Nairobi, Kenya.  Includes references.
 
 Language:  English
 
 Descriptors: Kenya; Runoff; Erosion; Soil fertility; Tillage;
 Mulches; Soil conservation; Semiarid zones; Simulation models
 
 
 18                                  NAL Call. No.: 292.8 J82
 An assessment of the dynamic response characteristics of
 streamflow in the Balquhidder catchments.
 Jakeman, A.J.; Littlewood, I.G.; Whitehead, P.G.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 May15.
 Journal of hydrology v. 145 (3/4): p. 337-355; 1993 May15. 
 Special Issue: The Balquhidder Catchment and Process Studies /
 edited by P.G. Whitehead and I.R. Calder.  Includes
 references.
 
 Language:  English
 
 Descriptors: Scotland; Watersheds; Stream flow; Catchment
 hydrology; Clearcutting; Afforestation; Rain; Runoff;
 Simulation models
 
 Abstract:  The method of rainfall-runoff modelling and
 hydrograph separation developed in an earlier paper is applied
 to the Kirkton and Monachyle catchments situated near
 Balquhidder, Scotland. Using daily rainfall and streamflow
 data, natural differences between the quick and slow flow
 responses for the Kirkton and Monachyle catchments are
 quantified, and an attempt is made to detect the impact of
 land-use changes on these natural regimes (clear-felling in
 part of the Kirkton and drainage ditching and conifer planting
 in part of the Monachyle). Dynamic response characteristics
 for the quick and slow flow components are defined in terms of
 time constants, relative throughput volumes and unit
 hydrograph peaks. These response characteristics are estimated
 and compared for annual periods before and after the land-use
 changes. For both the Kirkton and Monachyle, the effects of
 the land-use changes (affecting part of each catchment) on the
 hydrological response are not detectable at the catchment
 outlets. The interannual variation of the dynamic response
 characteristics falls within the inherent uncertainty expected
 if no land-use changes had occurred.
 
 
 19                              NAL Call. No.: aS21.A8U5/ARS
 Basin scale water quality model.
 Arnold, J.G.
 Washington, D.C. : The Service; 1993.
 Reprints - U.S. Department of Agriculture, Agricultural
 Research Service [512]: 9 p.; 1993.  Indexed from reprint:
 Proceedings of the CREAMS and GLEAMS Conference. p. 192-200. 
 Includes references.
 
 Language:  English
 
 Descriptors: Catchment hydrology; Simulation models; Water
 quality; Climatic factors; Geological sedimentation; Runoff;
 Agricultural chemicals
 
 
 20                                  NAL Call. No.: S612.I756
 Best management of pesticide--furrow irrigation systems.
 Ranjha, A.Y.; Peralta, R.C.; Requena, A.M.; Deer, H.M.;
 Ehteshami, M.; Hill, R.W.; Walker, W.R.
 Berlin, W. Ger. : Springer International; 1992.
 Irrigation science v. 13 (1): p. 9-14; 1992.  Includes
 references.
 
 Language:  English
 
 Descriptors: Utah; Furrow irrigation; Design; Simulation
 models; Pesticides; Leaching; Losses from soil systems; Water
 management; Groundwater pollution; Soil texture
 
 Abstract:  Effects of furrow irrigation designs, water
 management practices (irrigation scheduling, etc.), soil types
 and pesticide parameters on pesticide leaching were simulated.
 A hydraulic kinematic-wave irrigation model was used to
 estimate water infiltration for alternative furrow lengths and
 inflow rates. A one-dimensional simulation model then
 simulated the movement of pesticides through soils following
 furrow irrigation. Potential ground-water contamination by
 pesticides can be reduced by an integrated use of the best
 management practices (BMPs) such as careful selection and use
 of pesticides, efficient furrow irrigation designs and
 improved water management techniques (irrigation scheduling,
 etc.). Procedures for designing an appropriate furrow
 irrigation system for a particular site and pesticide, and
 selecting pesticides for a particular site, crop and furrow
 irrigation system are illustrated. These procedures are being
 used to develop decision support computer models for
 developing different BMPs for pesticide-agricultural
 management decisions.
 
 
 21                      NAL Call. No.: GB701.W375 no.91-4055
 Calibration, verification, and use of a steady-state stream
 water-quality model for Monument and Fountain Creeks, east-
 central Colorado. Kuhn, Gerhard
 Pikes Peak Area Council of Governments, Geological Survey
 (U.S.) Denver, CO : U.S. Dept. of the Interior, U.S.
 Geological Survey : Books and Open-File Reports Section
 [distributor],; 1991.
 vii, 149 p. : ill. ; 28 cm. (Water-resources investigations
 report ; 91-4055).  Includes bibliographical references (p.
 139-142).
 
 Language:  English
 
 Descriptors: Water quality
 
 
 22                                NAL Call. No.: 290.9 AM32T
 Characterization of macropore transport studied with the ARS
 root zone water quality model.
 Ahuja, L.R.; DeCoursey, D.G.; Barnes, B.B.; Rojas, K.W.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1993 Mar. Transactions of the ASAE v. 36 (2): p.
 369-380; 1993 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Macropores; Movement in soil; Root zone flux;
 Soil water; Water flow; Fertilizers; Pesticides; Simulation
 models
 
 Abstract:  The ARS Root Zone Water Quality Model components
 dealing with preferential water and chemical transport are
 presented and used to study macropore flow and transport in a
 silty clay loam soil. Macroporosity of the soil was assumed to
 be 0.05% by volume, half of which was continuous and the rest
 discontinuous. Two rainfall sequences with two initial soil
 water contents, evaporation versus transpiration, macropore
 radius ranging from 1.0 to 0.125 mm, and three different
 chemicals were evaluated. Over a five-week period, weekly
 rainfall of 25.4 mm in one hour, with soil water
 redistribution and evaporation or transpiration occurring
 between storms, generated no macropore flow when the soil was
 initially dry (-1500 kPa). A slight amount of macropore flow
 was generated under the same rainfall when the soil was
 initially wet (-33 kPa). Doubling the weekly rainfall amount
 and intensity generated macropore flow varying between 30 to
 50% of rainfall depending on initial and boundary conditions.
 Chemicals transported with this flow were 0.05 to 8% of the
 surface-applied amount, depending on conditions and type of
 chemical. A moderately adsorbed chemical (Atrazine) was the
 most susceptible to macropore transport, followed in order by
 a strongly adsorbed chemical (Prometryn), and a mobile
 chemical (Nitrate). The flow entering the macropores was
 partially absorbed by soil at progressively deeper depths; it
 increased the water content of the root zone, and created a
 tail of low concentrations in the soil chemical content
 distributions. The macropore size had very little effect on
 macropore flow and transport, but the smallest size pores
 retarded the downward chemical movement by wall adsorption a
 little more than the largest size pores. Surface evaporation
 decreased macropore flow, soil water contents, and downward
 chemical movement, but increased chemical content of the
 macropore flow. Transpiration, on the other hand, decreased
 both macropore flow and its chemical content. Thu
 
 
 23                                  NAL Call. No.: HC79.E5E5
 Classification and spatial mapping of riparian habitat with
 applications toward management of streams impacted by nonpoint
 source pollution. Delong, M.D.; Brusven, M.A.
 New York, N.Y. : Springer-Verlag; 1991 Jul.
 Environmental management v. 15 (4): p. 565-571; 1991 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Idaho; Habitats; Riparian vegetation; Erosion;
 Pollution; Information systems; Mapping; Watersheds; Farmland
 
 
 24                                  NAL Call. No.: 56.8 J822
 Classifying remotely sensed data for use in an agricultural
 nonpoint-source pollution model.
 Jakubauskas, M.E.; Whistler, J.L.; Dillworth, M.E.; Martinko,
 E.A. Ankeny, Iowa : Soil and Water Conservation Society of
 America; 1992 Mar. Journal of soil and water conservation v.
 47 (2): p. 179-183; 1992 Mar. Includes references.
 
 Language:  English
 
 Descriptors: Kansas; Water quality; Water pollution; Remote
 sensing; Watersheds; Simulation models; Landsat; Thematic
 mapper; Data collection
 
 
 25                                  NAL Call. No.: SB610.W39
 Combining computer simulation with physical simulation: an
 attempt to validate turf runoff models.
 Lin, J.C.; Graney, R.L.
 Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 688-695; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Pesticides; Simulation
 models; Runoff; Risk; Aquatic environment; Calibration; Field
 tests; Prediction
 
 
 26                                   NAL Call. No.: 56.9 SO3
 Comparison of models for describing the transport of dissolved
 organic carbon in aquifer columns.
 Jardine, P.M.; Dunnivant, F.M.; Selim, H.M.; McCarthy, J.F.
 Madison, Wis. : The Society; 1992 Mar.
 Soil Science Society of America journal v. 56 (2): p. 393-401;
 1992 Mar. Includes references.
 
 Language:  English
 
 Descriptors: Aquifers; Sediment; Organic matter; Carbon;
 Transport processes; Adsorption; Sorption isotherms; Kinetics;
 Contaminants; Movement in soil; Mathematical models;
 Comparisons
 
 Abstract:  Dissolved organic carbon (DOC) is a reactive
 constituent in aquifer and soil media and equilibrates between
 the mobile aqueous phase and the immobile solid phase. Since
 DOC is believed to accelerate the transport of associated
 contaminants, yet is known to interact with aquifer and soil
 material, our objective was to define and model those
 processes governing DOC adsorption to porous media that may
 affect the cotransport of contaminants. Column displacement
 experiments of DOC through aquifer sediments were modeled with
 various formulations of the convective-dispersive equation,
 which considered time-dependent adsorption reactions and
 linear or nonlinear adsorption processes. Batch equilibrium
 adsorption isotherm and kinetic studies for DOC interaction
 with the sediments were used to parameterize the transport
 models. The equilibrium DOC-adsorption isotherm was nonlinear
 and was adequately described by the Langmuir equation. The
 adsorption of DOC to the aquifer sediment was also time
 dependent and the batch results could be described by two
 simultaneous reaction rates for solution concentrations
 greater than or equal to 19 mg DOC L-1 and a slow reaction
 rate for solution concentrations < 10 mg DOC L-1. Observed DOC
 breakthrough curves (BTCs) with influent concentrations
 greater than or equal to 10 mg DOC L-1, were adequately
 modeled as two-site, non-linear adsorption processes, with DOC
 interactions with both types of sites being time dependent.
 Batch adsorption and kinetic parameters were generally
 successful in describing DOC transport; however, the magnitude
 of the initial batch rate coefficient was significantly larger
 than that observed for the displacement experiments. The
 extended tailing of the observed DOC BTCs was influenced more
 by the slow, time-dependent adsorption of DOC during transport
 than to the nonlinear features of the adsorption isotherms.
 Observed DOC BTCs with influent concentrations < 10 mg DOC L-1
 did not exhibit extensive tailing and were
 
 
 27                                NAL Call. No.: QH545.A1E58
 Comparison of PRZM and GLEAMS computer model predictions with
 field data for alachlor, metribuzin and norflurazon leaching.
 Mueller, T.C.; Jones, R.E.; Bush, P.B.; Banks, P.A.
 Elmsford, N.Y. : Pergamon Press; 1992.
 Environmental toxicology and chemistry v. 11 (3): p. 427-436;
 1992.  Includes references.
 
 Language:  English
 
 Descriptors: Alachlor; Norflurazon; Metribuzin; Herbicide
 residues; Leaching; Computer simulation; Simulation models;
 Soil depth; Sandy loam soils
 
 
 28                                  NAL Call. No.: 292.8 J82 A
 comprehensive surface-groundwater flow model.
 Arnold, J.G.; Allen, P.M.; Bernhardt, G.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 Feb.
 Journal of hydrology v. 142 (1/4): p. 47-69; 1993 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Texas; Groundwater; Groundwater flow; Groundwater
 level; Surface water; Runoff; Flow; Stream flow; Watersheds;
 Catchment hydrology; Land management; Climate; Vegetation;
 Water management; Simulation models
 
 Abstract:  In this study, a simple groundwater flow and height
 model was added to an existing basin-scale surface water
 model. The linked model is: (1) watershed scale, allowing the
 basin to be subdivided; (2) designed to accept readily
 available inputs to allow general use over large regions; (3)
 continuous in time to allow simulation of land management,
 including such factors as climate and vegetation changes, pond
 and reservoir management, groundwater withdrawals, and stream
 and reservoir withdrawals. The model is described, and is
 validated on a 471 km2 watershed near Waco, Texas. This linked
 model should provide a comprehensive tool for water resource
 managers in development and planning.
 
 
 29                                  NAL Call. No.: 1.98 AG84
 Computer model helps ensure clean water.
 Cooke, L.
 Washington, D.C. : The Service; 1991 Apr.
 Agricultural research - U.S. Department of Agriculture,
 Agricultural Research Service v. 39 (4): p. 10-12; 1991 Apr.
 
 Language:  English
 
 Descriptors: Michigan; Groundwater pollution; Nitrates;
 Leaching; Prevention; Computer simulation; Computer techniques
 
 
 30                                  NAL Call. No.: SB610.W39
 Computer models for fate assessment during the registration
 process: data needs.
 Behl, E.
 Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 696-700; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Pesticides; Registration; Simulation models;
 Groundwater; Water quality
 
 
 31                      NAL Call. No.: GB701.W375 no.90-4200
 Computer software for converting ground-water and water-
 quality data from the National Water Information System for
 use in a geographic information system..  Software for
 converting data from NWIS for use in GIS
 Scott, J. C.
 Geological Survey (U.S.)
 Oklahoma City, Okla. : U.S. Geological Survey ; Denver, Colo.
 : Books and Open-File Reports [distributor],; 1991.
 iv, 55 p. : ill. ; 28 cm. (Water-resources investigations
 report ; 90-4200). Spine title: Software for converting data
 from NWIS for use in GIS.  Includes bibliographical references
 (p. 38-39).
 
 Language:  English
 
 Descriptors: Geographic information systems; Water
 
 
 32                                NAL Call. No.: 290.9 AM32T
 Computing watershed storage probabilities from rainfall and
 runoff data. Mills, W.C.; Thomas, A.W.; Dillard, A.L.; Snyder,
 W.M.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 May. Transactions of the ASAE v. 35 (3): p.
 891-897; 1992 May.  Includes references.
 
 Language:  English
 
 Descriptors: Rain; Runoff; Water conservation; Watersheds;
 Mathematical models; Probability
 
 Abstract:  This article describes the development and
 application of a computational procedure for obtaining
 watershed storage probabilities that are corrected for bias
 toward lower storage, which is inherent in storage values
 computed directly from rainfall and runoff data. The developed
 procedure makes use of rainfall and runoff data from
 watersheds, and also incorporates probabilities for rainfall
 needed to produce runoff for various storages. The procedure
 is derived mathematically using basic probability concepts and
 employs numerical integration and nonlinear least squares
 optimization in the solution. The procedure is applied to
 rainfall and runoff data collected from a Southern Piedmont
 field watershed over a 10-year period during which a
 conventional tillage system for crops was followed by two
 successive conservation tillage systems. Results of the
 application show that the developed computational procedure
 performs adequately in providing bias-corrected watershed
 storage probabilities that reflect effects of the three
 cropping/tillage systems on watershed storage.
 
 
 33                                  NAL Call. No.: TD426.J68
 Conditional simulation of flow and transport.
 Rogowski, A.S.; Wolf, J.K.; Simmons, D.E.
 Amsterdam : Elsevier; 1991 Jan.
 Journal of contaminant hydrology v. 7 (1/2): p. 95-121; 1991
 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Leachates; Movement in
 soil; Groundwater recharge; Clay; Subsoil; Infiltration;
 Spatial distribution; Simulation models; Spatial variation
 
 
 34                                  NAL Call. No.: aSD11.A42
 The conservation reserve program: effects on soil, water and
 environmental quality.
 Blackburn, W.H.; Newman, J.B.; Wood, J.C.
 Fort Collins, Colo. : The Station; 1991 May.
 General technical report RM - Rocky Mountain Forest and Range
 Experiment Station, U.S. Department of Agriculture, Forest
 Service (203): p. 27-36; 1991 May.  Includes references.
 
 Language:  English
 
 Descriptors: U.S.A.; Soil conservation; Erosion control;
 Federal programs; Reserved areas; Simulation models;
 Percolation; Evapotranspiration; Water erosion; Runoff
 
 
 35                                 NAL Call. No.: TD420.A1E5
 Convective transport of gases in moist porous media: effect of
 absorption, adsorption, and diffusion in soil aggregates.
 McCoy, B.J.; Rolston, D.E.
 Washington, D.C. : American Chemical Society; 1992 Dec.
 Environmental science & technology v. 26 (12): p. 2468-2476;
 1992 Dec. Includes references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution; Volatile
 compounds; Mathematical models
 
 
 36                                  NAL Call. No.: TC401.W27 A
 coupled rainfall-runoff and runoff-routing model for adaptive
 real-time flood forecasting.
 Habaieb, H.; Troch, P.A.; Troch, F.P. de
 Hingham, Mass. : Kluwer Academic Publishers; 1991.
 Water resources management v. 5 (1): p. 47-61; 1991.  Includes
 references.
 
 Language:  English
 
 Descriptors: Belgium; Floods; Forecasting; Rain; Runoff;
 Models; On line; Identification; Case studies
 
 
 37                                  NAL Call. No.: 292.8 J82
 Coupled simulations of water flow from a field-investigated
 glacial till slope using a quasi-two-dimensional water and
 heat model with bypass flow. Espeby, B.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Feb.
 Journal of hydrology v. 131 (1/4): p. 105-132; 1992 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Sweden; Glacial till soils; Forest soils;
 Coniferous forests; Picea abies; Pinus sylvestris; Slopes;
 Water flow; Macropore flow; Meltwater; Precipitation; Runoff;
 Soil water retention; Saturated hydraulic conductivity;
 Macropores; Soil temperature; Soil depth; Physical models;
 Simulation models
 
 Abstract:  Substantial field investigations of soil physical
 properties and stratification in a forested slope (10 degrees
 slope) covered with glacial till revealed that macropores in
 the form of old root channels as well as coarse structures in
 the form of well-sorted layers dominate a very permeable upper
 solid horizon. Rapid response and quick recessions during
 snowmelt and heavy rains in 1986 were observed in the runoff
 from the slope. Based on field tracer experiments it was found
 that such macropores and macrostructures played an important
 role on these occasions. In order to verify these findings
 one-dimensional water and heat models were coupled in a serial
 manner to simulate the formation of runoff from the slope,
 using a quasi-two-dimensional approach. Both a strict Darcian
 concept and a Darcian concept with a simple bypass flow
 concept introduced were tested. The drainage gradient in the
 model was made equal with the angle of the slope. Coupled
 slope simulations, with water retention properties and
 hydraulic conductivities taken from three different levels on
 the slope, indicated that the conditions in the lower region
 of the slope were most important in explaining the discharge
 rate. With a shallow groundwater table in the lower region of
 the slope and low hydraulic conductivity of the deeper layers,
 rapid water flows are routed to the uppermost layers where the
 conductivity is higher. Most of the flow is well described by
 Richards' equation, although smaller peaks cannot be
 represented for small rain events, when the measured runoff
 and recession showed a more rapid response than that
 simulated, however, the introduction of a simple bypass flow
 improved the ability of the model to simulate the
 observations. Much of the simulated surface runoff generated
 in the Darcian simulation during the winter of 1986, could be
 diverted through a frost layer in the humus horizon and in the
 humus-impregnated mineral horizon with a silty-sand character,
 down to a more conductiv
 
 
 38                                   NAL Call. No.: QH540.J6
 Coupling groundwater contamination with economic returns when
 applying farm pesticides.
 Hoag, D.L.; Hornsby, A.G.
 Madison, Wis. : American Society of Agronomy; 1992 Oct.
 Journal of environmental quality v. 21 (4): p. 579-586; 1992
 Oct.  Includes references.
 
 Language:  English
 
 Descriptors: North Carolina; Groundwater pollution;
 Methodology; Pesticides; Usage; Economic impact; Returns;
 Profitability; Environmental impact; Glycine max; Weed
 control; Costs; Crop yield; Weed competition; Leaching;
 Simulation models
 
 Abstract:  A methodology is presented that permits
 simultaneous consideration of the economics of production and
 groundwater contamination hazard of pesticide use. An example
 is constructed for weed control in soybean (Glycine max L.)
 production at Clayton, NC. A cost/groundwater hazard frontier
 is developed that can be used to identify and illustrate the
 cost tradeoffs of selecting alternative weed control
 strategies that reduce the risk of adverse health effects from
 drinking contaminated groundwater. The methodology relies on
 models to estimate costs, crop yields, pest competition, and
 leaching of pesticides; thus, its applicability depends on
 availability of local data and appropriately validated models
 for the site considered. The cost/groundwater hazard frontier
 provides a useful decision aid to assist pesticide users in
 making cost-effective and environmentally favorable production
 decisions. It is also useful in evaluating policy or the value
 of new pest control technologies, as it indicates a farmer's
 ability to substitute alternatives for currently used
 practices.
 
 
 39                                  NAL Call. No.: 381 J8224
 Criteria to assess when biodegradation is kinetically limited
 by intraparticle diffusion and sorption.
 Chung, G.Y.; McCoy, B.J.; Scow, K.M.
 New York, N.Y. : John Wiley & Sons; 1993 Mar15.
 Biotechnology and bioengineering v. 41 (6): p. 625-632; 1993
 Mar15.  Includes references.
 
 Language:  English
 
 Descriptors: Soil flora; Microbial degradation; Pollutants;
 Transport processes; Diffusion; Sorption; Desorption; Polluted
 soils; Soil pollution; Mathematical models; Bioremediation
 
 Abstract:  To determine when intraparticle diffusion and
 sorption can influence the rate of biodegradation, we consider
 the biodegradation of a pollutant diffusing into or out of
 porous aggregates suspended in a liquid medium, where the
 reactant is metabolized by bacteria. The pollutant that
 diffuses into the aggregates obeys a sorption-desorption
 equilibrium isotherm at sites on inner pore surfaces. The
 governing partial differential equations for the transient
 process describe (a) the local equilibrium sorption-desorption
 and the diffusion of the pollutant in the porous aggregate,
 (b) the mass transfer of the pollutant from the external
 surface of the spherical aggregates to the reaction medium,
 and (c) the biodegradation of the pollutant in the external
 medium. Illustrative calculations are presented for a linear
 sorption isotherm and first-order biodegradation kinetics. A
 dimensionless group, comprised of the diffusion coefficient,
 biodegradation rate coefficient, aggregate characteristic
 length (radius), and adsorption capacity, serves as a
 criterion for determining when intraparticle diffusion
 resistance can be ignored. The model provides a realistic
 description of experimental data for biodegradation of a
 pollutant subject to intraparticle diffusion and sorption.
 
 
 40                                 NAL Call. No.: TD420.A1P7
 DBAPE--a database and model parameter analysis system for
 agricultural soils to support water quality management.
 Imhoff, J.C.; Carsel, R.F.; Kittle, J.L. Jr; Hummel, P.R.
 Oxford : Pergamon Press; 1991.
 Water science and technology : a journal of the International
 Association on Water Pollution Research and Control v. 24 (6):
 p. 331-337; 1991.  In the series analytic: Watermatex '91 /
 edited by T.O. Barnwell, P.J. Ossenbruggen and M.B. Beck.
 Proceedings of the "Second International Conference on Systems
 Analysis in Water Quality Management," June 3-6, 1991, Durham,
 New Hampshire. Includes references.
 
 Language:  English
 
 Descriptors: Soil properties; Water quality; Management;
 Agricultural soils; Computer software; Subsurface runoff;
 Models; Databases
 
 
 41                                   NAL Call. No.: QH540.J6
 Degradation and transport of dicamba in a clay soil.
 Comfort, S.D.; Inskeep, W.P.; Macur, R.E.
 Madison, Wis. : American Society of Agronomy; 1992 Oct.
 Journal of environmental quality v. 21 (4): p. 653-658; 1992
 Oct.  Includes references.
 
 Language:  English
 
 Descriptors: Dicamba; Clay soils; Degradation; Leaching; Soil
 water movement; Soil temperature; Persistence; Half life;
 Precipitation; Irrigation scheduling; Simulation models
 
 Abstract:  Dicamba (3,6-dichloro-2-methoxybenzoic acid) has
 been identified as one of five pesticides present in Montana
 groundwaters. We determined the effects of degradation and
 time of water application on the transport of dicamba in a
 Lohmiller clay soil (fine, montmorillonitic, mesic Ustic
 Torrifluvent). Carbon 14-labeled dicamba was surface applied
 (0.35 kg ha-1) to disturbed soil columns (5.0 cm diam; 29 cm
 length) previously conditioned with 3 mM CaCl2. The columns
 were allowed to incubate (23.5 degrees C) in triplicate for 0,
 14, 21, 28, and 42 d. Following incubation, the columns were
 attached to a vacuum chamber containing a fraction collector
 and leached with 3 mM CaCl2 under unsaturated conditions.
 Dicamba breakthrough curves were determined for each
 incubation period. The percentage of dicamba recovered in the
 column effluent decreased from 85% (of total applied) after no
 incubation to 9.5% after 42 d of incubation. The decline of
 dicamba in the effluent coincided with an accumulation of
 dichlorosalicyclic acid at the soil surface. Dicamba half-
 lives determined under batch conditions were 23.5 d at 28
 degrees C, 38 d at 20 degrees C, and 151 d at 12 degrees C,
 and were all higher than the half-life estimated from the
 decrease in column effluent concentrations over time (13.5 d).
 The simulation model, LEACHM, was used to predict transport of
 dicamba after the different incubation periods. LEACHM
 adequately estimated the mass of dicamba leached, but
 underestimated the maximum dicamba concentrations observed in
 the effluent. Both simulated and observed results indicated
 that the transport of dicamba can be greatly reduced if
 sufficient degradation of dicamba is allowed to occur before
 irrigation or precipitation.
 
 
 42                                  NAL Call. No.: QC851.J62 A
 description of rainfall interception over large areas.
 Eltahir, E.A.B.; Bras, R.L.
 Boston, MA : American Meteorological Society, c1988-; 1993
 Jun. Journal of climate v. 6. (6): p. 1002-1008; 1993 Jun. 
 Includes references.
 
 Language:  English
 
 Descriptors: Rain; Ground vegetation; Canopy; Drainage; Runoff
 water; Interception; Evaporation; Models; Climatic factors
 
 Abstract:  A new scheme is developed for describing
 interception at spatial scales comparable to the typical
 resolution of climate models. The scheme is based on the
 Rutter model of interception and statistical description of
 the subgrid-scale spatial variability of canopy storage and
 rainfall. The interception loss simulated by the new scheme is
 significantly smaller than those simulated by other schemes
 that do not include considerations for spatial variability.
 The explanation of this result is partly in the enhancement of
 spatially averaged canopy drainage due to the large local
 drainage from the few buckets of large canopy storage. The
 relative reduction in interception loss simulated by the new
 scheme may explain the overestimation of interception loss by
 climate models that do not include the effects of spatial
 variability on interception processes.
 
 
 43                                   NAL Call. No.: TD403.G7
 Design and evaluation of a mesoscale model vadose zone and
 ground-water system.
 Lawrence, J.R.; Zanyk, B.N.; Hendry, M.J.; Wolfaardt, G.M.;
 Robarts, R.D.; Caldwell, D.E.
 Dublin, Ohio : Ground Water Pub. Co; 1993 May.
 Ground water v. 31 (3): p. 446-455; 1993 May.  Includes
 references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Soil pollution;
 Contaminants; Movement in soil; Chemical degradation;
 Microbial degradation; Models; Agricultural chemicals
 
 Abstract:  A mesoscale model soil and ground-water system was
 constructed and instrumented to study physical, chemical, and
 microbial processes, including transport and degradation of
 contaminants. The model system was 4.6 m in height by 2.4 m in
 diameter and contained up to 65 tonnes of soil and geologic
 materials. The model was filled with Ap (11 cm), B (20 cm), Cl
 and C2 (369 cm) horizons; the water table was 3.3 m from the
 soil surface. A rain simulation system applied uniform
 coverage of rain and/or chloride tracer to the model. Sampling
 of soil, sediment, pore waters, and gas phase was carried out
 using a series of in situ collectors and sampling ports. Major
 anions, metals, pH, alkalinity, CO2, N2, O2, CH4, microbial
 numbers, microbial biomass and heterotrophic potential (14 C-
 amino-acid uptake) were monitored over time (120 days) and
 depth. The system approached steady state with respect to
 solution chemistry and gases after approximately 60-70 days.
 During this interval, carbon dioxide rose from atmospheric to
 3-5% of total gas volume measured at each sampling depth above
 the water table. Physical, chemical, and biological conditions
 in the model system after the initial 120 days were comparable
 to those reported for vadose and saturated zones during field
 studies on shallow phreatic aquifers. These results indicated
 that the mesoscale model preserved many of the features of
 natural systems while providing controlled conditions for
 studies such as evaluating the fate, and ground-water
 contamination potential, of agricultural and industrial
 chemicals.
 
 
 44                                   NAL Call. No.: TD201.A4
 Design of optimal pump-and-treat strategies of contaminated
 groundwater remediation using the simulated annealing
 algorithm.
 Kuo, C.H.; Michel, A.N.; Gray, W.G.
 Essex : Elsevier Science Publishers Ltd; 1992.
 Advances in water resources v. 15 (2): p. 95-105; 1992. 
 Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Problem solving; Pumps;
 Placement; Optimization methods; Hydraulics; Constraints;
 Simulation models; Algorithms
 
 
 45                                   NAL Call. No.: TD403.G7
 Designing a nitrate monitoring program in a heterogeneous,
 carbonate aquifer. Smith, R.T.; Ritzi, R.W. Jr
 Dublin, Ohio : Ground Water Pub. Co; 1993 Jul.
 Ground water v. 31 (4): p. 576-584; 1993 Jul.  Includes
 references.
 
 Language:  English
 
 Descriptors: Ohio; Aquifers; Carbonates; Hydraulic
 conductivity; Finite element analysis; Simulation models;
 Nitrates; Movement in soil; Zea mays; Glycine max; Rotations;
 Groundwater pollution
 
 
 46                                 NAL Call. No.: 292.9 AM34
 Determination of best timing for poultry waste disposal: a
 modeling approach. Edwards, D.R.; Daniel, T.C.; Marbun, O.
 Bethesda, Md. : American Water Resources Association; 1992
 May. Water resources bulletin v. 28 (3): p. 487-494; 1992 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Arkansas; Poultry manure; Waste disposal;
 Application to land; Application date; Timing; Surface water;
 Runoff water; Water quality; Nitrogen; Phosphorus; Losses from
 soil systems; Grasses; Crop production; Crop yield
 
 Abstract:  Confined production of poultry results in
 significant volumes of waste material which are typically
 disposed of by land application. Concerns over the potential
 environmental impacts of poultry waste disposal have resulted
 in ongoing efforts to develop management practices which
 maintain high quality of water downstream of disposal areas.
 The timing of application to minimize waste constituent losses
 is a management practice with the potential to ensure high
 quality of streams, rivers, and lakes downstream of receiving
 areas. This paper describes the development and application of
 a method to identify which time of year is best, from the
 standpoint of surface water quality, for land application of
 poultry waste. The procedure consists of using a mathematical
 simulation model to estimate average nitrogen and phosphorus
 losses resulting from different application timings, and then
 identifying the timings which minimize losses of these
 nutrients. The procedure was applied to three locations in
 Arkansas, and three different criteria for optimality of
 application timing were investigated. One criterion was
 oriented strictly to water quality, one was oriented only to
 crop production, and the last was a combination. The criteria
 resulted in different windows of time being identified as
 optimal. Optimal windows also varied with location of the
 receiving area. The results indicate that it is possible to
 land-apply poultry waste at times which both minimize nutrient
 losses and maximize crop yield.
 
 
 47                                  NAL Call. No.: SB951.P47
 Development and validation of a modified fugacity model of
 pesticide leaching from farmland.
 Brooke, D.; Matthiessen, P.
 Essex : Elsevier Applied Science Publishers; 1991.
 Pesticide science v. 31 (3): p. 349-361; 1991.  Includes
 references.
 
 Language:  English
 
 Descriptors: England; Mecoprop; Simazine; Concentration;
 Leaching; Measurement; Models; Monitoring; Soil properties;
 Water pollution; Agricultural soils
 
 Abstract:  To test whether a simple model could provide
 reasonable quantitative estimates of chemical concentrations
 in a dynamic situation, Mackay's fugacity model was adapted to
 represent an agricultural field. The intention was to
 determine the extent of modification required to obtain
 reasonable agreement with experimental results, or indeed if
 such agreement could be achieved. The validity of the model
 was tested at Rosemaund Experimental Husbandry Farm in
 Herefordshire, where the chemical input and output could be
 monitored and meteorological and other parameters measured
 regularly. Results from monitoring concentrations of two
 pesticides at this site in recent years. and changes that have
 been made to the model in attempting to fit the observed
 behaviour are described.
 
 
 48                                   NAL Call. No.: QH540.J6
 Development of a database and model parameter analysis system
 for agricultural soils.
 Carsel, R.F.; Imhoff, J.C.; Kittle, J.L. Jr; Hummel, P.R.
 Madison, Wis. : American Society of Agronomy; 1991 Jul.
 Journal of environmental quality v. 20 (3): p. 642-647; 1991
 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Water quality; Water management; Databases;
 Computer software; Water flow
 
 Abstract:  An interactive computer program was developed for
 obtaining soils data for geographic analyses and estimation of
 soil water retention data for simplistic and classical water
 flow models. The soils data base contains 8080 soil series
 identified from the USDA-SCS. The data are organized in
 sequential files that contain textural, morphological crop
 support, and geographical location (at a county level) and
 density (ha/county). The computer program allows the
 exploration of the database, clarifying the impact of data on
 modeled processes, screening geographically based data to
 identify potential sites for model application or testing, and
 developing initial guidance on alternative water quality
 management strategies. The program allows the display of data
 in the form of generated reports and production of geographic
 maps and plots of soil water functional relationships.
 Indirect methods are used in the program for estimating soil
 water retention characteristics using textural information
 from the soil data base. Estimates of variability can be
 developed within a soil series or among series by using
 reported ranges for textural information on each series
 contained in the soil database.
 
 
 49                                NAL Call. No.: S592.7.A1S6
 Dispersion effect on the apparent nitrogen isotope
 fractionation factor associated with denitrification in soil;
 evaluation by a mathematical model. Kawanishi, T.; Hayashi,
 Y.; Kihou, N.; Yoneyama, T.; Ozaki, Y. Exeter : Pergamon
 Press; 1993 Mar.
 Soil biology and biochemistry v. 25 (3): p. 349-354; 1993 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Denitrification; Quantitative analysis;
 Agricultural soils; Solutes; Dispersion; Transport processes;
 Soil water; Water flow; Mathematical models; Nitrate;
 Groundwater pollution
 
 Abstract:  An analytical model is constructed to investigate
 the effect of dispersion on the apparent 15N/14N fractionation
 factor associated with denitrification in soil. The steady
 input of solute with a fixed isotope ratio, uniform flow of
 the solute, and the first-order reaction for each isotope are
 assumed, and the relationship between the concentration
 distribution and the change of isotope ratio in the steady
 state is examined. The only dimensionless parameter, kl4ND/v2,
 the product of the first-order reaction rate constant and the
 dispersion coefficient divided by the square of the
 superficial velocity, determines the effect of dispersion, and
 if its value is larger than 0.01, the dispersion will affect
 the apparent isotope fractionation factor. As kl4ND/v2
 increases, the effect becomes more prominent, and when it
 approaches infinity, the ratio of the apparent per mille
 enrichment factor to the true one, (alpha ap-1)/(alpha tr-1),
 reaches 0.5.
 
 
 50                      NAL Call. No.: GB701.W375 no.93-4015
 Documentation of geographic-information-system coverages and
 data-input files used for analysis of the geohydrology of the
 Virginia Coastal Plain.. Documentation of geographic
 information system coverages and data input files used for
 analysis of the geohydrology of the Virginia Coastal Plain
 Focazio, Michael J.; Samsel, Theodore B.
 Geological Survey (U.S.),Hampton Roads Planning District
 Commission (Va.),Virginia Water Control Board
 Richmond, Va. : U.S. Geological Survey ; Denver, CO : Books
 and Open-File Reports Section [distributor],; 1993; I
 19.42/4:93-4015.
 vi, 53 p. : maps ; 28 cm. (Water-resources investigations
 report ; 93-4015). Shipping list no.: 93-0451-P.  Includes
 bibliographical references (p. 11).
 
 Language:  English; English
 
 Descriptors: Hydrogeology; Geographic information systems
 
 
 51                                 NAL Call. No.: 292.8 W295 A
 dual-porosity model for simulating the preferential movement
 of water and solutes in structured porous media.
 Gerke, H.H.; Van Genuchten, M.T.
 Washington, D.C. : American Geophysical Union; 1993 Feb.
 Water resources research v. 29 (2): p. 305-319; 1993 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Transport processes; Solutes; Water flow;
 Saturated flow; Transient flow; Leaching; Porous media;
 Physicochemical properties; Deterministic models; Mathematical
 models; Equations
 
 Abstract:  A one-dimensional dual-porosity model has been
 developed for the purpose of studying variably saturated water
 flow and solute transport in structured soils or fractured
 rocks. The model involves two overlaying continua at the
 macroscopic level: a macropore or fracture pore system and a
 less permeable matrix pore system. Water in both pore systems
 is assumed to be mobile. Variably saturated water flow in the
 matrix as well as in the fracture pore system is described
 with the Richards' equation, and solute transport is described
 with the convection-dispersion equation. Transfer of water and
 solutes between the two pore regions is simulated by means of
 first-order rate equations. The mass transfer term for solute
 transport includes both convective and diffusive components.
 The formulation leads to two coupled systems of nonlinear
 partial differential equations which were solved numerically
 using the Galerkin finite element method. Simulation results
 demonstrate the complicated nature of solute leaching in
 structured, unsaturated porous media during transient water
 flow. Sensitivity studies show the importance of having
 accurate estimates of the hydraulic conductivity near the
 surface of soil aggregates or rock matrix blocks. The proposed
 model is capable of simulating preferential flow situations
 using parameters which can be related to physical and chemical
 properties of the medium.
 
 
 52                                 NAL Call. No.: 100 C12CAG
 Dupuit-Forchheimer approximation may underestimate groundwater
 flow to San Joaquin River.
 Grismer, M.E.; Rashmawi, E.A.
 Oakland, Calif. : Division of Agriculture and Natural
 Resources, University of California; 1993 Jan.
 California agriculture v. 47 (1): p. 12, 13-15; 1993 Jan.
 
 Language:  English
 
 Descriptors: California; Groundwater flow; River water; Water
 quality; Water management; Salinity; Estimation; Water table;
 Errors; Mathematical models
 
 
 53                                  NAL Call. No.: GB746.W33
 Dynamic-probabilistic models for the formation of rainfall and
 snowmelt runoff.
 Kuchment, L.S.; Gel'fan, A.N.
 New York, N.Y. : Consultants Bureau; 1992 May.
 Water resources v. 18 (4): p. 335-343; 1992 May.  Translated
 from: Vodnye Resursy, v. 18 (4), 1991, p. 5-14, (GB746.V55). 
 Includes references.
 
 Language:  English; Russian
 
 Descriptors: U.S.S.R.in europe; Rain; Meltwater; Floods;
 Runoff water; Watersheds; Forest steppe; Zoning; Probabilistic
 models; Dynamic models; Physical models; Mathematical models;
 Weather data
 
 
 54                                   NAL Call. No.: HD101.S6
 Economic impacts of chemical use reduction on the South.
 Taylor, C.R.; Penson, J.B. Jr; Smith, E.G.; Knutson, R.D.
 Experiment, Ga. : The Association; 1991 Jul.
 Southern journal of agricultural economics - Southern
 Agricultural Economics Association v. 23 (1): p. 15-23; 1991
 Jul.  Discussion by J.R. Schaub, p. 25-26.  Includes
 references.
 
 Language:  English
 
 Descriptors: Southern states of U.S.A.; Agricultural
 chemicals; Pesticide residues; Water quality; Groundwater;
 Contamination; Food safety; Agricultural policy; Models;
 Economic impact; Income
 
 
 55                                     NAL Call. No.: HD1.A3
 The economics of water harvesting and supplementary irrigation
 in the semi-arid tropics of India.
 Pandey, S.
 Essex : Elsevier Applied Science Publishers; 1991.
 Agricultural systems v. 36 (2): p. 207-220; 1991.  Includes
 references.
 
 Language:  English
 
 Descriptors: Madhya pradesh; Soybeans; Wheat; Water
 harvesting; Irrigation; Cropping systems; Semiarid zones;
 Agricultural regions; Economic evaluation; Feasibility; Risk;
 Simulation models; Soil water balance; Yield response
 functions; Water relations; Decision making; Rain; Runoff
 water
 
 
 56                                   NAL Call. No.: 56.8 SO3
 The effect of soil P sorption kinetics on parameters used for
 modeling P uptake.
 Shnek, M.; Shaviv, A.; Ravina, I.
 Baltimore, Md. : Williams & Wilkins; 1991 May.
 Soil science v. 151 (5): p. 333-342; 1991 May.  Includes
 references.
 
 Language:  English
 
 Descriptors: Calcareous soils; Soil physics; Phosphorus;
 Sorption; Kinetics; Diffusion models; Desorption; Mathematical
 models; Soil solution; Equilibrium; Buffering capacity;
 Nutrient uptake; Prediction; Equations; Solubility; Nutrient
 availability; Transport processes
 
 
 57                                   NAL Call. No.: 56.8 SO3
 The effect of soil properties on phosphorus sorption by
 everglades histosols. Porter, P.S.; Sanchez, C.A.
 Baltimore, Md. : Williams & Wilkins; 1992 Nov.
 Soil science v. 154 (5): p. 387-398; 1992 Nov.  Includes
 references.
 
 Language:  English
 
 Descriptors: Florida; Histosols; Agricultural soils;
 Phosphorus; Sorption; Movement in soil; Leaching; Losses from
 soil systems; Soil chemistry; Soil properties; Water
 pollution; Indexes; Models
 
 
 58                                  NAL Call. No.: 292.8 J82
 The effect of transverse dispersion on solute transport in
 soils. Leij, F.J.; Dane, J.H.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Jan.
 Journal of hydrology v. 122 (1/4): p. 407-422; 1991 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Solutes; Transport processes; Horizontal flow;
 Two dimensional flow; Transverse distribution; Permeability;
 Simulation; Mathematical models
 
 Abstract:  Most theoretical and experimental investigations of
 solute transport involve one-dimensional problems (i.e. soil
 column studies), whereas in reality many soil pollution
 problems concern transport and flow in more than one
 dimension. This study investigates two-dimensional transport,
 with emphasis on the contribution of transverse dispersion to
 solute transport. Three problems were studied with a finite
 element code. The first problem involved one-dimensional flow
 parallel to the interface of two layers with differing pore-
 water velocity. The early arrival of the solute at the end of
 the low-permeability layer and the increase-in solute
 spreading for both layers, as a result of transverse
 dispersion, were demonstrated. The two other problems
 concerned transport of a pollutant from a point source and a
 diffuse source, respectively, located at the soil surface. The
 magnitude of the transverse dispersion coefficient influenced
 the region to which the pollution extended as well as the
 intensity of the pollution.
 
 
 59                                 NAL Call. No.: 292.8 W295
 The effect of vertical soil heterogeneity on field scale
 solute flux. Destouni, G.
 Washington, D.C. : American Geophysical Union; 1992 May.
 Water resources research v. 28 (5): p. 1303-1309; 1992 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Solutes; Transport processes; Flow; Saturated
 hydraulic conductivity; Soil depth; Stochastic models
 
 Abstract:  Vertical heterogeneity is incorporated in a
 stochastic transport model, in which the soil is viewed as
 consisting of an ensemble of essentially vertical, independent
 stream tubes. The saturated hydraulic conductivity in each
 stream tube is defined as the vertical average of the
 corresponding point random process. The statistics of the
 vertically averaged hydraulic conductivity and the resulting
 statistics of solute travel time are depth dependent. The
 evolution of the field scale breakthrough curve with depth is
 analyzed in terms of the first two moments of solute travel
 time to an arbitrary depth below the soil surface. The arrival
 time of the solute center of mass, quantified by the expected
 travel time, grows linearly with depth also for vertically
 heterogeneous soil. The temporal solute spreading around its
 center, quantified by the travel time variance, may exhibit a
 compression-expansion that is qualitatively analogous to the
 solute plume behavior in the studies of Butters and Jury
 (1989), Russo (1991), and Ellsworth and Jury (1991). The
 relative solute spreading, quantified by the travel time
 coefficient of variation, decreases with increasing depth.
 
 
 60                                   NAL Call. No.: QH540.J6
 Effects of climatic variations over 11 years on nitrate-
 nitrogen concentrations in the Raccoon River, Iowa.
 Lucey, K.J.; Goolsby, D.A.
 Madison, Wis. : American Society of Agronomy; 1992 Jan.
 Journal of environmental quality v. 22 (1): p. 38-46; 1992
 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Iowa; Nitrate nitrogen; Drinking water; Seasonal
 variation; Precipitation; Stream flow; Water quality; Water
 pollution; Nitrogen fertilizers; Mathematical models
 
 Abstract:  Nitrate-nitrogen (NO3-N) concentrations at public
 water-supply intakes on the Des Moines and Raccoon Rivers in
 Iowa exceeded the maximum contaminant level (MCL) of 10 mg L-1
 for public water supplies established by the USEPA for
 extended periods of time from March through early August 1990.
 The excessive NO3-N levels followed 2 yr of less than normal
 precipitation in 1988 and 1989. The largest daily NO3-N load
 (771 t) transported during the last 17 yr in the Raccoon River
 occurred in June 1990. The streamflow hydrograph for the
 Raccoon River for March 1990 prior to seasonal fertilizer
 application indicates that high NO3-N concentrations
 characterize the recession side of the hydrograph. High NO3-N
 concentrations in streamflow persisted as streamflow decreased
 to baseflow conditions. This implies that substantial
 quantities of NO3-N were being leached from the soil and
 transported by subsurface flow during early 1990. A multiple
 linear-regression model was developed to predict NO3-N
 concentrations in the Raccoon River from readily-obtainable
 streamflow and climatic data. The four-variable model
 explained about 70% of the variability in the concentration of
 NO3-N. The mean streamflow for the previous 7-d period
 accounted for about 50% of the total variability.
 
 
 61                                NAL Call. No.: 290.9 AM32T
 Effects of pesticide, soil, and rainfall characteristics on
 potential pesticide loss by percolation--a GLEAMS simulation.
 Truman, C.C.; Leonard, R.A.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Nov. Transactions of the ASAE v. 34 (6): p.
 2461-2468; 1991 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Pesticides; Percolation; Leaching;
 Losses from soil systems; Water pollution; Groundwater;
 Computer simulation; Zea mays
 
 Abstract:  Potential pesticide loss in soil percolate is
 influenced by pesticide persistence and sorption by soil
 constituents (organic matter). Pesticide persistence,
 expressed as half-life (t1/2), changes with soil depth as
 microbial activity and soil properties change. Little is
 known, however, how these changes influence potential
 pesticide transport out of the root zone. Objectives of this
 study were to investigate relative differences in potential
 pesticide losses from the root zone by percolation due to 1)
 different soil surface and subsurface textures and pesticide
 t1/2, and 2) interactions between pesticide t1/2 arid timing
 of rainfall after pesticide application. The GLEAMS
 (Groundwater Loading Effects of Agricultural Management
 Systems) model and a 50-year historical rainfall record at
 Tifton, Georgia, were used to simulate pesticide losses by
 percolation from three soils ranging in surface texture from
 sand to sandy clay loam. Hypothetical pesticides had surface
 t1/2 of 5, 15, 30, and 60 d and a range of subsurface t1/2
 (2.5-360 d), and were applied to continuous corn (Zea maize,
 L.) at 2 kg ha-1 as surface spray at planting each year on 1
 April. Simulated pesticide losses by percolation increased
 with increased surface and subsurface t1/2, and decreased with
 increased KOC (adsorption constant based on soil organic
 matter) values. Potential pesticide leaching was greatest for
 Lakeland sand and least for Greenville sandy clay loam.
 Rainfall timing affected simulated pesticide loss by
 percolation, especially for nonpersistent pesticides. For
 short pesticide t1/2 (0-5 d), excessive rainfall events within
 1 t1/2 were largely responsible for simulated pesticide loss
 by percolation. Results indicate that changes in pesticide
 t1/2 in surface and subsurface horizons of different soils
 influence potential pesticide leaching from the root zone, and
 models (i.e., GLEAMS) can be used to provide comparative
 analysis of soil-pesticide-climate interactions. For example,
 dependi
 
 
 62                                 NAL Call. No.: 292.8 W295
 Effects of rainfall, vegetation, and microtopography on
 infiltration and runoff.
 Dunne, T.; Zhang, W.; Aubry, B.F.
 Washington, D.C. : American Geophysical Union; 1991 Sep.
 Water resources research v. 27 (9): p. 2271-2285; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil water; Infiltration; Runoff; Rain; Hill
 grasslands; Slope; Plant density; Hydraulic conductivity;
 Mathematical models
 
 Abstract:  Apparent, or effective, infiltration rates on
 grassland hillslopes vary with rainfall intensity and flow
 depth because of the interaction between rainfall, runoff, and
 vegetated microtopography. The higher parts of the
 microtopography are occupied by greater densities of
 macropores and therefore have much greater hydraulic
 conductivities than the intervening microdepressions. On short
 hillslopes and plots the apparent infiltration rate is simply
 the spatial average of the saturated and unsaturated
 conductivities of this surface. The proportion of the surface
 which is saturated and the value to which the unsaturated
 conductivity is raised depends on the rainfall intensity. On
 longer hillslopes the downslope increase in flow depth in
 microtopographic depressions progressively inundates more
 permeable, vegetated mounds so that the hydraulic conductivity
 of a greater proportion of the surface is raised to its
 saturated value. For this reason the apparent infiltration
 rate increases downslope, even in the absence of spatial
 trends in any of the surface characteristics that affect
 infiltration. Apparent, or effective, infiltration rate
 depends on hillslope length. Consequently, steady state
 discharge does not increase linearly with distance downslope.
 These two fundamental relationships between infiltration,
 rainfall intensity, and runoff are analyzed on the basis of
 sprinkling-infiltrometer measurements and a mathematical
 model.
 
 
 63                                 NAL Call. No.: 292.8 W295
 Effects of soil heterogeneity on pesticide leaching to
 groundwater. Zee, S.E.A.T.M. van der; Boesten, J.J.T.I.
 Washington, D.C. : American Geophysical Union; 1991 Dec.
 Water resources research v. 27 (12): p. 3051-3063; 1991 Dec. 
 Includes references.
 
 Language:  English
 
 Descriptors: Pesticides; Groundwater; Leaching; Hydrodynamic
 dispersion; Sorption; Transformation; Uptake; Physicochemical
 properties; Spatial variation; Stochastic models; Monte carlo
 method
 
 Abstract:  Pesticide leaching was simulated numerically
 assuming Freundlich adsorption, first-order transformation and
 passive plant uptake, taking transient flow, hydrodynamic
 dispersion, and depth as well as temperature dependence of
 (bio)chemical parameters into account. The dependency of the
 leached fraction on sorption and transformation parameters
 appeared to be in good general agreement with the model
 developed by Jury et al. (1987). We incorporated spatial
 variability of (bio)chemical parameters into the piston flow
 model and showed how spatial variability may be accounted for
 without having to resort to demanding Monte Carlo techniques.
 Such spatial variability affects the leached fraction
 significantly. The data requirement of the simple stochastic
 model is small and the versatility relatively high. For
 parameter values often not of prime practical interest for
 pesticide screening this model fails. Considering transport by
 convection and dispersion in the semi-infinite domain, this
 spatial variability can be easily accounted for using
 parameter ranges for which our original analytical model for
 spatially variable piston transport failed. In this revised
 model, hydrodynamic dispersion, preferential flow, and spatial
 variability of transformation, sorption and soil thickness are
 dealt with in a similar fashion, while both correlation or the
 absence of correlation of parameters can be incorporated
 through an approximation of apparent residence time variance.
 
 
 64                                   NAL Call. No.: QH540.J6
 Effects of spatial accumulation of runoff on watershed
 response. Garbrecht, J.
 Madison, Wis. : American Society of Agronomy; 1991 Jan.
 Journal of environmental quality v. 20 (1): p. 31-35; 1991
 Jan.  Literature review.  Includes references.
 
 Language:  English
 
 Descriptors: Watersheds; Drainage; Hydrology; Rain; Runoff;
 Simulation models
 
 Abstract:  The drainage network accumulates upstream
 subwatershed runoff into a single downstream response, with
 runoff accumulating at network junctions. The effects of this
 accumulation on the magnitude and spatial variability of the
 downstream response are reviewed for simplified boundary
 conditions. Runoff parameters are runoff depth and
 corresponding unit area peak runoff rate. At the subwatershed
 level these parameters are referred to as d and q,
 respectively, and they vary from one subwatershed to another.
 At a downstream location, after accumulation by the drainage
 network, corresponding parameters are referred to as D and Q.
 Equations expressing the effects of runoff accumulation are
 formulated and discussed for uniform rainfall conditions. The
 review shows that the effects of runoff accumulation gain in
 importance as the number of upstream subwatersheds and the
 size of the watershed increase in the downstream direction.
 The accumulation process cancels extreme values of d and q to
 yield a representative D and Q value for the entire upstream
 drainage area. The impact of individual d and q values on the
 downstream D and Q values in the channel diminishes as the
 number of upstream subwatersheds increases. This results in a
 decrease in the spatial variability of D and Q in the
 downstream direction. The review suggests that the role of
 spatial variability of upstream d and q in the determination
 of downstream D and Q diminishes as watershed size increases.
 However, nonuniform rainfall distributions and storm movement
 may overshadow the effects of runoff accumulation when
 watershed size increases beyond the size of the storm.
 
 
 65                                 NAL Call. No.: 325.28 P56
 Effects of suspended particle size and concentration on
 reflectance measurements.
 Bhargava, D.S.; Mariam, D.W.
 Bethesda, Md. : American Society of Photogrammetry and Remote
 Sensing; 1991 May.
 Photogrammetric engineering and remote sensing v. 57 (5): p.
 519-529; 1991 May.  Includes references.
 
 Language:  English
 
 Descriptors: Soil types; Suspensions; Particle size; Sediment;
 Concentration; Reflectance; Responses; Prediction; Models;
 Turbidity; Water quality; Equations; Remote sensing
 
 
 66                                   NAL Call. No.: TD403.G7
 Effects of waste-water irrigation on aqueous geochemistry near
 Paris, Texas. Tedaldi, D.J.; Loehr, R.C.
 Dublin, Ohio : Ground Water Pub. Co; 1992 Sep.
 Ground water v. 30 (5): p. 709-719; 1992 Sep.  Includes
 references.
 
 Language:  English
 
 Descriptors: Texas; Waste water; Irrigation; Long term
 experiments; Groundwater; Water quality; Soil chemistry;
 Geochemistry; Prediction; Thermodynamics; Equilibrium; Models;
 Aquifers; Saline water; Recharge; Infiltration; Hydraulic
 conductivity
 
 
 67                                 NAL Call. No.: TD420.A1E5
 Elution of aged and freshly added herbicides from a soil.
 Pignatello, J.J.; Ferrandino, F.J.; Huang, L.Q.
 Washington, D.C. : American Chemical Society; 1993 Aug.
 Environmental science & technology v. 27 (8): p. 1563-1571;
 1993 Aug. Includes references.
 
 Language:  English
 
 Descriptors: Connecticut; Soil pollution; Herbicide residues;
 Atrazine; Metolachlor; Leaching; Profiles; Models
 
 
 68                                 NAL Call. No.: S539.5.J68
 Environmental and economic impacts of pesticide and irrigation
 practices: EPIC-PST simulation.
 Sabbagh, G.J.; Norris, P.E.; Geleta, S.; Bernado, D.J.;
 Elliott, R.L.; Mapp, H.P.; Stone, J.F.
 Madison, Wis. : American Society of Agronomy; 1992 Jul.
 Journal of production agriculture v. 5 (3): p. 312-317; 1992
 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Oklahoma; Groundwater pollution; Crop management;
 Environmental impact; Economic impact; Pest control;
 Irrigation; Computer techniques; Simulation models;
 Pesticides; Movement in soil; Runoff
 
 
 69                                 NAL Call. No.: 292.8 W295
 Estimating changes in recreational fishing participation from
 national water quality policies.
 Ribaudo, M.O.; Piper, S.L.
 Washington, D.C. : American Geophysical Union; 1991 Jul.
 Water resources research v. 27 (7): p. 1757-1763; 1991 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Water quality; Water policy; Water pollution;
 Angling; Participation; Estimation; Models
 
 Abstract:  The complete evaluation of the offsite effects of
 national policies or programs that affect levels of
 agricultural nonpoint source pollution requires linking
 extensive water quality changes to changes in recreational
 activity. A sequential decision model is specified to describe
 an individual's decisions about fishing. A participation model
 for recreational fishing that includes a water quality index
 reflecting regional water quality is developed and estimated
 as a logit model with national level data. A visitation model
 for those who decide to fish that also includes the water
 quality index is estimated using ordinary least squares. The
 water quality index is found to be significant in the
 participation model but not in the visitation model. Together,
 the two models provide a means of estimating how changes in
 water quality might influence the number of recreation days
 devoted to fishing. The model is used to estimate changes in
 fishing participation for the Conservation Reserve Program.
 
 
 70                                  NAL Call. No.: TC401.W27
 Estimating low flow characteristics in ungauged catchments.
 Nathan, R.J.; McMahon, T.A.
 Dordrecht : Kluwer Academic Publishers; 1992.
 Water resources management v. 6 (2): p. 85-100; 1992. 
 Includes references.
 
 Language:  English
 
 Descriptors: New South Wales; Victoria; Watersheds; Rural
 areas; Flow; Characteristics; Water yield; Rain; Runoff;
 Models; Multivariate analysis; Climatic factors; Hydrological
 data; Equations
 
 
 71                                  NAL Call. No.: 292.8 J82
 Estimating transport parameters at the grid scale: on the
 value of a single measurement.
 Beven, K.J.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 Mar01.
 Journal of hydrology v. 143 (1/2): p. 109-123; 1993 Mar01. 
 Special Issue: Modelling Flow and Transport in the Unsaturated
 Zone: Scale Problems and Spatial Variability.  Includes
 references.
 
 Language:  English
 
 Descriptors: Solutes; Transport processes; Soil water; Flow;
 Spatial variation; Hydrodynamic dispersion; Prediction;
 Estimation; Probabilistic models
 
 Abstract:  Distributed models of solute transport at the field
 and catchment scales require the specification of effective
 parameters at the model grid scale. The grid scale will
 generally be much larger than the scale at which it is
 possible to make measurements to derive parameter values but
 may be of the same order as the scale of variability of such
 'point' values. In addition, measurements are usually
 expensive and time consuming to make and where, for example,
 'undisturbed' soil cores are used, may be destructive. This
 paper describes a conditional probability based approach for
 estimating grid scale effective parameter values in the light
 of expected spatial heterogeneity, given only one or a small
 number of available measurements. Initial results show,
 somewhat surprisingly, that despite the integrative nature of
 the spatial averaging involved in moving to the grid scale,
 the variance of the effective grid element values does not
 decrease. There is a small shift in the location of the
 distribution, as a result of the macrodispersive effect of the
 grid scale variability.
 
 
 72                                  NAL Call. No.: GB746.W33
 Estimation of possible anthropogenic changes in the runoff and
 removal of biogenic elements from small watersheds of the
 forest zone on the basis of a mathematical model.
 Kondrat'ev, S.A.
 New York, N.Y. : Consultants Bureau; 1991 Mar.
 Water resources v. 17 (3): p. 240-248; 1991 Mar.  Tranlated
 from: Vodnye Resursy, V. 17, No. 3, May/June 1990, p. 24-32.
 (GB746.V55).  Includes references.
 
 Language:  English; Russian
 
 Descriptors: U.S.S.R.in europe; Rsfsr; Runoff water; Sediment;
 Formation; Water pollution; Nutrients; Removal; Phosphorus;
 Nitrogen; Agricultural production; Effects; Watersheds;
 Forests; Hydrology; Mathematical models
 
 
 73                                  NAL Call. No.: 292.8 J82
 Evaluating the green and ampt infiltration parameter values
 for tilled and crusted soils.
 Mohamoud, Y.M.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Feb.
 Journal of hydrology v. 123 (1/2): p. 25-38; 1991 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Illinois; Agricultural soils; Rain; Infiltration;
 Soil water content; Runoff; Surface layers; Tillage; Crop
 residues; Crusts; Permeability; Capillary rise; Wetting front;
 Hydraulic conductivity; Mathematical models; Green and ampt
 equation
 
 Abstract:  Methods for determining Green-Ampt infiltration
 parameter values for tilled and crusted soils are not well
 established. A two-stage method is developed to determine the
 Green and Ampt parameter values for soils under different
 management practices. The first stage is aimed at calculating
 rainfall infiltration from rainfall and runoff data of small
 field plots which had different soil surface conditions (e.g.
 tillage, residue cover and crusting). To determine accurate
 rainfall infiltration rates from field plots, we employed a
 water balance model which accounted for depression storage,
 detention storage as well as surface routing of runoff. The
 second stage is aimed at evaluating the values of the Green
 and Ampt infiltration equation parameters by the linear least
 squares parameter estimation technique. The Green and Ampt
 parameter values determined were the effective capillary
 suction at the wetting front and the effective hydraulic
 conductivity. The results of this study indicated that this
 procedure is sufficiently sensitive to reflect the effects of
 tillage, residue cover and crusting on infiltration data.
 Raindrop impact reduced infiltration rates by crusting the
 soil surface. However, most of the management systems that
 left about 30% of residue cover protected the soil from
 raindrop impact as evidenced by the higher effective hydraulic
 conductivity. It is concluded that the model developed by
 Green and Ampt in 1911 satisfactorily fitted the infiltration
 data obtained from protected and crusted soil profiles. Also,
 residue cover and crusting greatly influenced the Green and
 Ampt infiltration parameter values.
 
 
 74                                 NAL Call. No.: TP995.A1I5
 Evaluating transport of organic chemicals in soil resulting
 from underground fuel tank leaks.
 Lee, D.Y.; Chang, A.C.
 Chelsen, Mich. : Lewis Publishers; 1992.
 Proceedings of the Industrial Waste Conference (46): p.
 131-140; 1992. Meeting held May 14-16, 1991, West Lafayette,
 Indiana.  Includes references.
 
 Language:  English
 
 Descriptors: Polluted soils; Soil pollution; Organic
 compounds; Petroleum; Petroleum hydrocarbons; Transport
 processes; Fuel tanks; Leakage; Underground storage;
 Simulation models; Equations; Mathematics; Groundwater
 pollution; Soil water movement; Movement in soil
 
 
 75                      NAL Call. No.: GB701.W375 no.91-4142
 Evaluation of a ground-water flow and transport model of the
 upper Coachella Valley, California..  Evaluation of a ground
 water flow and transport model of the upper Coachella Valley,
 California
 Reichard, Eric George; Meadows, J. Kevin
 Geological Survey (U.S.),California Regional Water Quality
 Control Board--Colorado River Basin Region
 Sacramento, Calif. : U.S. Geological Survey ; Denver, CO :
 Books and Open-File Reports Section [distributor],; 1992.
 vi, 101 p. : ill., maps ; 28 cm. (Water-resources
 investigations report ; 91-4142).  Includes bibliographical
 references (p. 42).
 
 Language:  English
 
 Descriptors: Groundwater flow; Water, Underground
 
 
 76                                  NAL Call. No.: TD426.J68
 Evaluation of a pesticide mobility index: impact of recharge
 variation and soil profile heterogeneity.
 Kleveno, J.J.; Loague, K.; Green, R.E.
 Amsterdam : Elsevier; 1992 Oct.
 Journal of contaminant hydrology v. 11 (1/2): p. 83-99; 1992
 Oct.  Includes references.
 
 Language:  English
 
 Descriptors: Hawaii; Soil pollution; Pesticides; Profiles;
 Movement in soil; Attenuation; Leaching; Assessment;
 Simulation models; Errors; Movement to roots; Rain
 
 
 77                                NAL Call. No.: 290.9 AM32T
 Evaluation of fluvial sediment transport equations for
 overland flow. Guy, B.T.; Dickinson, W.T.; Rudra, R.P.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Mar. Transactions of the ASAE v. 35 (2): p.
 545-555. ill; 1992 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Geological sedimentation; Overland flow; Rain;
 Runoff; Splash erosion; Simulation models
 
 Abstract:  Sediment transport capacity was measured under a
 range of conditions in two types of overland flow: shallow
 uniform flow in the absence of rainfall, and shallow flow
 affected by rainfall impact. The abilities of six fluvial
 sediment transport equations to represent each dataset are
 evaluated. For both flow types, common aspects of equation
 performance include poor representation of sediment transport
 thresholds, underprediction of transport rates, and
 significant scatter about measured values. These problems,
 particularly the equations' inability to predict transport
 threshold, are more evident with the rain-impacted now data.
 Only the Schoklitsch equation is suitable for uniform overland
 flow without rain-impact, and none am suitable for rain-
 impacted overland flow.
 
 
 78                                NAL Call. No.: 290.9 AM32T
 Evaluation of PRZM and LEACHMP on intact soil columns.
 Smith, W.N.; Prasher, S.O.; Barrington, S.F.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Nov. Transactions of the ASAE v. 34 (6): p.
 2413-2420; 1991 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Atrazine; Computer simulation; Leaching; Soil
 properties; Water pollution
 
 Abstract:  Limiting factors towards the utilization of
 pesticide transport models are lack of both detailed data and
 cognizant personnel available to test and validate model
 predictions. In this study, computer simulations were carried
 out to test the performance of PRZM (a management model) and
 LEACHMP (a research model) on leaching characteristics of
 atrazine in long intact soil columns. Also, in an attempt to
 evaluate model uncertainty, a sensitivity analysis of several
 parameters for each model was considered. LEACHMP was found to
 be superior in predicting hydrological characteristics in the
 soil columns as compared to PRZM which required calibration.
 Both models underestimated levels of atrazine near the soil
 surface and in the leachate (115 cm depth) and over-estimated
 them throughout most of the range in-between. Inaccurate
 predictions for the two models are attributed to simplistic
 linear adsorption equations and lack of a macropore flow
 subroutine. In increasing order, PRZM was most sensitive to
 rate of application, distribution coefficient, bulk density
 and field capacity, whereas LEACHMP was sensitive to rate of
 application, organic carbon distribution coefficient, air
 entry value, and bulk density.
 
 
 79                                  NAL Call. No.: 292.8 J82
 Evaluation of the accuracy and precision of annual phosphorus
 load estimates from two agricultural basins in Finland.
 Rekolainen, S.; Posch, M.; Kamari, J.; Ekholm, P.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Nov.
 Journal of hydrology v. 128 (1/4): p. 237-255; 1991 Nov. 
 Includes references.
 
 Language:  English
 
 Descriptors: Finland; Agricultural land; Drainage; Runoff;
 Pollution; Phosphorus; Transport processes; Flow; Estimates;
 Sampling; Frequency; Monitoring; Mathematical models;
 Comparisons
 
 Abstract:  The accuracy and precision of phosphorus load
 estimates from two agricultural drainage basins in western
 Finland were evaluated, based on continuous flow measurements
 and frequent flow-proportional sampling of total phosphorus
 concentration during a 2 year period. The objective was to
 compare different load calculation methods and to evaluate
 alternative sampling strategies. An hourly data set of
 concentrations was constructed by linear interpolation, and
 these data were used in Monte Carlo runs for producing
 replicate data sets for calculating the accuracy and precision
 of load estimates. All estimates were compared with reference
 values computed from the complete hourly data sets. The load
 calculation methods based on summing the products of regularly
 sampled flows and concentrations produced the best precision,
 whereas the best accuracy was achieved using methods based on
 multiplying annual flow by flow-weighted annual mean
 concentration. When comparing different sampling strategies,
 concentrating sampling in high runoff periods (spring and
 autumn) was found to give better accuracy and precision than
 strategies based on regular interval sampling throughout the
 year. However, the best result was obtained by taking samples
 flow-proportionally within the highest peak flows plus
 additional regular interval (e.g. biweekly) samples outside
 these flow peaks. Using this strategy, which calls for
 automatic sampling equipment, accuracies better than 5% and
 precisions better than 10% can be achieved with only 30-50
 samples per year.
 
 
 80                                NAL Call. No.: 290.9 AM32T
 Evaluation of the hydrologic component of the ADAPT water
 table management model.
 Chung, S.O.; Ward, A.D.; Schalk, C.W.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Mar. Transactions of the ASAE v. 35 (2): p.
 571-579; 1992 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Tile drainage; Water management; Water table;
 Evapotranspiration; Hydrology; Macropore flow; Runoff;
 Seepage; Simulation models
 
 Abstract:  A subsurface, water table management model ADAPT
 (Agricultural Drainage and Pesticide Transport) has been
 developed by combining drainage and subirrigation algorithms
 from DRAINMOD with the GLEAMS model. In addition, the model
 incorporates improved snow melt and runoff algorithms,
 macropore flow due to cracking, and deep seepage. Theory for
 the hydrologic components of the model is presented together
 with an evaluation of the model using data from a long-term
 field experiment at Castalia in North Central Ohio. Predicted
 surface runoff, subsurface drainage, and combined surface and
 subsurface drainage are compared with the field observations.
 In general, the model predictions are within the range of the
 variations of the observed replications. Sensitivity analysis
 shows that surface runoff estimates are sensitive to changes
 in curve number, while subsurface drainage flows are sensitive
 to deep seepage estimates. Model input requirements are not
 excessive and the model gives reasonable estimates of the
 hydrologic component of water table management systems. ADAPT
 can be used in designing water table management systems and
 does not require extensive calibration. The pesticide
 component of ADAPT is currently being evaluated and
 development of a nutrient component has been initiated.
 
 
 81                                    NAL Call. No.: 4 AM34P
 Evaluation of the nitrogen submodel of CERES-maize following
 legume green manure incorporation.
 Bowen, W.T.; Jones, J.W.; Carsky, R.J.; Quintana, J.O.
 Madison, Wis. : American Society of Agronomy; 1993 Jan.
 Agronomy journal v. 85 (1): p. 153-159; 1993 Jan.  Includes
 references.
 
 Language:  English
 
 Descriptors: Simulation models; Prediction; Nutrient uptake;
 Nitrogen; Green manures; Nutrient availability;
 Mineralization; Leaching; Nitrate; Losses from soil; Nitrogen
 balance
 
 Abstract:  Crop simulation models that accurately predict the
 availability of N from decomposing plant residues would
 provide a powerful tool for evaluating legume green manures as
 potential N sources for nonlegume crops. Using measured data
 from a series of field experiments conducted on an Oxisol in
 central Brazil, we conducted this study to test the N submodel
 of CERES-Maize for its ability to simulate N mineralization,
 nitrate leaching, and N uptake by maize (Zea Mays L.)
 following the incorporation of 10 different legume green
 manures. Legume or weed residue N at the time of incorporation
 varied from 25 to 300 kg ha-1 with C/N ratios varying from 13
 to 37. Comparison of predicted and measured accumulation of
 inorganic N in uncropped soil showed that the model usually
 provided a realistic simulation of legume N release, although
 N release was overpredicted for some legumes. For all legumes,
 both simulated and measured data showed that about 60% of the
 organic N applied was recovered as inorganic N within 120 to
 150 d after incorporation. To realistically simulate N
 availability when rainfall was excessive, we modified the
 model to account for delayed leaching due to nitrate retention
 in the subsoil. Nitrogen uptake by maize was generally
 overpredicted at high levels of available N. The N submodel
 was shown to realistically simulate legume N release, but
 further work is needed to determine the importance of subsoil
 nitrate retention in other soils and how best such retention
 might be described in the model.
 
 
 82                                NAL Call. No.: 290.9 AM32T
 An evaluation of unit stream power theory for estimating soil
 detachment and sediment discharge from tilled soils.
 McIsaac, G.F.; Mitchell, J.K.; Hummel, J.W.; Elliot, W.J. St.
 Joseph, Mich. : American Society of Agricultural Engineers;
 1992 Mar. Transactions of the ASAE v. 35 (2): p. 535-544; 1992
 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Illinois; Water erosion; Aggregates; Runoff;
 Sediment yield; Simulation models; Soil properties; Streams;
 Tillage
 
 Abstract:  Unit Stream Power (USP) and the associated Yang
 (1973) sediment transport equations were compared to soil
 detachment rates and sediment concentrations in runoff from
 eroding soils. Although USP was significantly correlated with
 rill detachment rates, potential energy dissipation rate per
 unit rill area was a better predictor of soil detachment
 rates. The Yang (1973) equations estimated sediment
 concentrations within a factor of 10 of the observed
 concentrations, if the median soil aggregate diameter was
 within the range of diameters used by Yang to estimate the
 equation parameters. When median aggregate sizes were less
 than 0.15 mm, the lower limit of Yang's (1973) calibration
 range, the equations tended to produce unrealistically large
 estimates of sediment concentration.
 
 
 83                NAL Call. No.: ViBlbVLD5655.V856 1992.J663
 Evaluation of water distribution system monitoring using
 stochastic dynamic modeling.
 Jones, Philip Edward James,
 1992; 1992.
 xiv, 215 leaves : ill. ; 28 cm.  Vita.  Abstract. 
 Bibliography: leaves 181-191.
 
 Language:  English
 
 Descriptors: Water quality management; Water
 
 
 84                                   NAL Call. No.: 56.8 SO3
 Exit condition for miscible displacement experiments.
 Parlange, J.Y.; Starr, J.L.; Van Genuchten, M.Th; Barry, D.A.;
 Parker, J.C. Baltimore, Md. : Williams & Wilkins; 1992 Mar.
 Soil science v. 153 (3): p. 165-171; 1992 Mar.  Includes
 references.
 
 Language:  English
 
 Descriptors: Transport processes; Solutes; Soil solution; Soil
 analysis; Mathematical models; Determination; Convection;
 Dispersion; Length; Movement in soil; Kinetics
 
 
 85                                   NAL Call. No.: 56.8 SO3
 Experimental and simulated B transport in soil using a
 multireaction model. Mansell, R.S.; Bloom, S.A.; Burgoa, B.;
 Nkedi-Kizza, P.; Chen, J.S. Baltimore, Md. : Williams &
 Wilkins; 1992 Mar.
 Soil science v. 153 (3): p. 185-194; 1992 Mar.  Includes
 references.
 
 Language:  English
 
 Descriptors: Florida; Spodosols; Acid soils; Sandy soils; B
 horizons; Subsurface layers; Phosphorus; Movement in soil;
 Transport processes; Soil water movement; Determination;
 Laboratory methods; Simulation models; Mathematical models;
 Sorption; Kinetics; Sorption isotherms; Comparisons; Fixation;
 Soil organic matter; Aluminum oxide; Iron oxides
 
 
 86                                  NAL Call. No.: HC79.E5E5
 Exploring the effects of multiple management objectives and
 exotic species on Great Lakes food webs and contaminant
 dynamics.
 Fontaine, T.D.; Stewart, D.J.
 New York, N.Y. : Springer-Verlag; 1992 Mar.
 Environmental management v. 16 (2): p. 225-229; 1992 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Fishery management; Lakes; Water quality; Food
 chains; Objectives; Simulation models
 
 
 87                                 NAL Call. No.: S539.5.J68
 Farm-level economic and environmental impacts of eastern Corn
 Belt cropping systems.
 Foltz, J.C.; Lee, J.G.; Martin, M.A.
 Madison, WI : American Society of Agronomy, c1987-; 1993 Apr.
 Journal of production agriculture v. 6 (2): p. 290-296; 1993
 Apr.  Includes references.
 
 Language:  English
 
 Descriptors: Corn belt states of U.S.A.; Cabt; Zea mays;
 Medicago sativa; Glycine max; Microeconomic analysis; Economic
 impact; Alternative farming; Environmental impact; Rotations;
 Continuous cropping; Simulation models; Computer simulation;
 Erosion; Runoff; Pesticides; Water pollution
 
 
 88                                   NAL Call. No.: TD201.A4 A
 fast and accurate method for solving subsurface contaminant
 transport problems with a single uncertain parameter.
 Ahlfeld, D.P.; Pinder, G.F.
 Essex : Elsevier Science Publishers Ltd; 1992.
 Advances in water resources v. 15 (2): p. 143-150; 1992. 
 Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Contaminants; Transport;
 Equations; Random sampling; Stochastic models; Groundwater
 flow; Hydraulic conductivity
 
 
 89                                NAL Call. No.: QH545.A1E58
 Fate, dissipation and environmental effects of pesticides in
 southern forests: a review of a decade of research progress.
 Neary, D.G.; Bush, P.B.; Michael, J.L.
 Tarrytown, N.Y. : Pergamon Press; 1993 Mar.
 Environmental toxicology and chemistry v. 12 (3): p. 411-428;
 1993 Mar.  Paper presented at the "Symposium on Pesticides in
 Forest Management, 11th Annual Meeting of the Society of
 Environmental Toxicology and Chemistry," November 11-15, 1990,
 Arlington, Virginia.  Literature review.  Includes references.
 
 Language:  English
 
 Descriptors: Southern states of U.S.A.; Pesticides; Forestry;
 Ecosystems; Watersheds; Environmental impact; Water quality;
 Air quality; Groundwater pollution; Silviculture; Species
 diversity; Simulation models; Nontarget effects; Literature
 reviews
 
 
 90                                   NAL Call. No.: QH540.N3
 Fate of non-aqueous phase liquids: modeling of surfactant
 effects. Harwell, J.H.; Sabatini, D.A.; Soerens, T.S.
 Berlin, W. Ger. : Springer-Verlag; 1993.
 NATO ASI series : Series G : Ecological sciences v. 32: p.
 309-328; 1993.  In the series analytic: Migration and fate of
 pollutants in soils and subsoils / edited by D. Petruzzelli
 and F.G. Helfferich. Proceedings of the NATO Advanced Study
 Institute, May 24-June 5, 1992, Maratea, Italy.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution;
 Pollutants; Organic compounds; Transport processes;
 Groundwater flow; Soil water movement; Equations; Mathematics
 
 
 91                                 NAL Call. No.: TP963.A1F4
 Fertilization under drip irrigation.
 Bar-Yosef, B.
 New York, N.Y. : Marcel Dekker; 1991.
 Fertilizer science and technology series v. 7: p. 285-329;
 1991.  In the series analytic: Fluid fertilizer science and
 technology / edited by D.A. Palgrave.  Includes references.
 
 Language:  English
 
 Descriptors: Fertigation; Liquid fertilizers; Fluids; Trickle
 irrigation; Fertilizer requirement determination; Irrigation
 water; Ph; Salinity; Plant nutrition; Nutrient requirements;
 Nutrient uptake; Temporal variation; Nitrogen; Movement in
 soil; Transport processes; Spatial distribution; Root systems;
 Soil water content; Soil solution; Mathematical models;
 Monitoring; Fertilizer technology; Management; Crop production
 
 
 92                                    NAL Call. No.: QD1.A45
 Field and model estimates of pesticide runoff from turfgrass.
 Rosenthal, W.D.; Hipp, B.W.
 Washington, D.C. : The Society; 1993.
 ACS Symposium series - American Chemical Society (522): p.
 208-213; 1993.  In the series analytic: Pesticides in urban
 environments: Fate and significance / edited by K.D. Racke and
 A.R. Leslie. Paper presented at the 203rd National Meeting of
 the American Chemical Society, April 5-10, 1992, San
 Francisco, California.  Includes references.
 
 Language:  English
 
 Descriptors: Chlorpyrifos; Carbaryl; Diazinon; 2,4-d; Dicamba;
 Atrazine; Fertilizers; Herbicide residues; Insecticide
 residues; Runoff water; Mathematical models; Simulation
 models; Cynodon dactylon; Buchloe dactyloides
 
 Abstract:  Environmental awareness of surface runoff water
 quality is increasing. A study was conducted to analyze the
 impact of different turfgrass fertilizer and pesticide
 management systems on runoff water quality. A hydrologic and
 water quality model, Erosion Productivity Impact Calculator
 (EPIC), was used to estimate pesticide and nutrient
 concentrations in runoff from turfgrass on a Houston Black
 Clay. Nutrient and pesticide concentrations in the surface
 runoff increased significantly for highly maintained turfgrass
 systems. A larger fraction of the amount applied was observed
 in runoff for the moderate application rate treatments.
 Simulated results are being validated from measured runoff of
 turfgrass plots at Dallas, TX.
 
 
 93                          NAL Call. No.: S478.S68T43 no.31
 Field measurement and modelling of runoff and erosion response
 of small agricultural catchments in the mid north of South
 Australia. Punthakey, J.F.
 Adelaide, South Australia : Dept. of Agriculture,; 1992.
 v, 137 p. : ill. ; 30 cm. (Technical paper (South Australia.
 Dept. of Agriculture) ; no. 31.).  May 1992.  AGDEX 572. 
 Includes bibliographical references (p. 134-137) and index.
 
 Language:  English
 
 
 94                                   NAL Call. No.: 56.9 SO3
 Field study of bromacil transport under continuous-flood
 irrigation. Jaynes, D.B.
 Madison, Wis. : The Society; 1991 May.
 Soil Science Society of America journal v. 55 (3): p. 658-664;
 1991 May. Includes references.
 
 Language:  English
 
 Descriptors: Bromacil; Flood irrigation; Herbicide residues;
 Leaching; Movement in soil; Transport processes; Agricultural
 soils; Mathematical models
 
 Abstract:  The transport processes of sorbing chemicals in
 field soils are poorly understood. This study characterized
 the leaching behavior of the weakly sorbing herbicide bromacil
 (5-bromo-3-sec-butyl-6-methyluracil) in comparison to Br-
 during continuous-flood irrigation of a small field plot.
 Twenty-four solution samplers were used to periodically
 collect in situ samples from seven depths within four 1.83 by
 1.83 m subplots. Estimates of the pore water velocity (vs) and
 dispersion coefficient (D) were made by fitting an analytical
 solution of the convection-dispersion (CD) equation to the Br-
 data. Estimates of retardation (R) were made by fitting the CD
 equation to the bromacil data using the vs and D estimates
 from the Br- data and letting R be a fitting parameter.
 Estimates of R were also made from the results of batch
 equilibration studies using soil from seven depths. Best-fit
 vs and D values exhibited considerable variability from
 sampler to sampler (CV = 1.25 and 1.30, respectively) and
 showed no significant trends with depth. Retardation values
 estimated from the CD equation averaged 1.88, but varied from
 1.21 to 3.35 and also showed no significant trend with depth.
 In contrast, batch equilibration studies showed the absorption
 properties of the surface 0.6 m of soil to be significantly
 different than the 0.6- to 3-m depth, with R values decreasing
 from 1.62 for the surface 0.6 m to 1.31 at 3 m. Although the
 two methods gave the same estimate of R in the surface soil
 neither the lower R values at deeper depths nor the tendency
 to decrease with depth as predicted from the batch studies was
 apparent in the transport data. Using D as an additional
 fitting parameter to the bromacil data resulted in an average
 increase of 1.96 for this parameter, indicating more
 dispersion for the sorbing solute. Increased dispersion and
 increased tailing of the sorbed solute may be attributed to
 spatially variable adsorption and to a negative correlation
 between vs and R (r = -0.524)
 
 
 95                                NAL Call. No.: 290.9 AM32T
 Field testing and comparison of the PRZM and GLEAMS models.
 Smith, M.C.; Bottcher, A.B.; Campbell, K.L.; Thomas, D.L. St.
 Joseph, Mich. : American Society of Agricultural Engineers;
 1991 May. Transactions of the ASAE v. 34 (3): p. 838-847; 1991
 May.  Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Alachlor; Atrazine; Bromides; Field
 tests; Leaching; Groundwater; Pesticides; Precipitation;
 Runoff; Simulation models; Soil properties; Soil water
 
 Abstract:  The root/vadose zone transport models PRZM and
 GLEAMS were tested against an experimental data set.
 Parameters were not optimized or calibrated to produce the
 best fit. In all cases the measured and predicted peak
 concentrations agreed within an order of magnitude, and in
 most cases agreed within a factor of 2 to 3. This level of
 agreement between the models and the measured data is within
 the criteria for model acceptance suggested by the EPA. The
 small differences noted in simulated transport between the
 models are thought to be a result of differences in
 computational layering and chemical transport calculation
 methods.
 
 
 96                                  NAL Call. No.: TD426.J68
 Fluid flow and solute transport processes in unsaturated
 heterogeneous soils: Preliminary numerical experiments.
 Liu, C.C.K.; Loague, K.; Feng, J.S.
 Amsterdam : Elsevier; 1991 Feb.
 Journal of contaminant hydrology v. 7 (3): p. 261-283; 1991
 Feb.  Includes references.
 
 Language:  English
 
 Descriptors: Movement in soil; Pollutants; Unsaturated flow;
 Mathematical models; Finite element analysis; Prediction;
 Aquifers
 
 
 97                                 NAL Call. No.: S539.5.J68
 Functional form selection for regional crop response to
 salinity, water application, and climate.
 Lee, D.J.
 Madison, Wis. : American Society of Agronomy; 1992 Oct.
 Journal of production agriculture v. 5 (4): p. 445-454; 1992
 Oct.  Includes references.
 
 Language:  English
 
 Descriptors: Zea mays; Sorghum bicolor; Triticum aestivum;
 Triticum turgidum; Irrigation; Application rates; Saline
 water; Water quality; Mathematical models; Crop yield; Soil
 salinity; Climatic factors
 
 
 98                                   NAL Call. No.: QH540.J6 A
 functional model of solute transport that accounts for bypass.
 Corwin, D.L.; Waggoner, B.L.; Rhoades, J.D.
 Madison, Wis. : American Society of Agronomy; 1991 Jul.
 Journal of environmental quality v. 20 (3): p. 647-658; 1991
 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Groundwater; Water quality; Transport processes;
 Solutes; Water management; Mathematical models
 
 Abstract:  Public awareness of groundwater contamination has
 created renewed interest in solute transport models that can
 be practically applied as groundwater quality management
 tools. Because of their simplicity with regard to input
 requirements, functional models of solute transport are
 excellent groundwater quality management tools. A functional
 model of one-dimensional solute transport that accounts for
 hydraulic bypass is presented. The transport model TETrans,
 simulates the vertical movement of nonvolatile solutes (i.e.,
 trace elements and nonvolatile organic chemicals) through the
 vadose zone. Plant water uptake is taken into account assuming
 no solute uptake by the plant. TETrans requires minimal input
 data for its operation. Since TETrans uses a mass-balance
 approach to solute transport, it offers the speed of an
 analytical solution and the versatility of a numerical
 approach without the need for input parameters, which are
 difficult to measure. TETrans is able to account for bypass
 with a single term, the mobility coefficient. The mobility
 coefficient, gamma, represents the fraction of the soil liquid
 phase, which is subject to piston-type displacement;
 therefore, 1 - gamma represents the fraction of the liquid
 phase that is bypassed. The mobility coefficient is a
 temporally and spatially variable parameter (within a range of
 0 to l) which is calculated from the deviation of the measured
 chloride concentration from the predicted concentration
 assuming piston displacement and assuming complete mixing of
 the resident soil solution and incoming water for a given
 irrigation and volume of soil. A constant mobility coefficient
 for a given depth or entire profile can be determined by
 averaging temporally varying mobility coefficients or
 averaging spatially and temporally varying mobility
 coefficients, respectively. In essence, the mobility
 coefficient simplistically accounts for three physical
 transport phenomena in a single term. On a microscopic level
 there is flow thr
 
 
 99                                NAL Call. No.: 290.9 AM32T
 Generic anaerobic digestion model for the simulation of
 various reactor types and substrates.
 Thomas, M.V.; Nordstedt, R.A.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1993 Mar. Transactions of the ASAE v. 36 (2): p.
 537-544; 1993 Mar.  Literature review. Includes references.
 
 Language:  English
 
 Descriptors: Florida; Agricultural wastes; Animal wastes;
 Hyacinths; Manures; Straw; Waste disposal; Anaerobic
 digestion; Literature reviews; Mathematical models; Methane
 production
 
 Abstract:  A mathematical model was developed to represent a
 wide variety of anaerobic reactor types and substrates. The
 model is a generic, anaerobic digestion process model, using
 lumped substrate parameters, and was developed for use as
 type-specific reactor model operating within the sphere of a
 larger system model. Three types of anaerobic reactors were
 simulated: fixed-bed reactors, conventional stirred tank
 reactors, and continuously expanding reactors. The generic
 anaerobic digestion model provided a tool for testing various
 values of conversion efficiency and kinetic parameters for a
 wide range of substrate types and reactor designs.
 
 
 100                                NAL Call. No.: 292.8 W295 A
 geochemical transport model for redox-controlled movement of
 mineral fronts in groundwater flow systems: a case of nitrate
 removal by oxidation of pyrite. Engesgaard, P.; Kipp, K.L.
 Washington, D.C. : American Geophysical Union; 1992 Oct.
 Water resources research v. 28 (10): p. 2829-2843; 1992 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: Denmark; Groundwater flow; Transport processes;
 Denitrification; Pyrites; Oxidation; Nitrate; Reduction; Redox
 reactions; Geochemistry; Spatial distribution; Algorithms;
 Mathematical models; Simulation
 
 Abstract:  A one-dimensional prototype geochemical transport
 model was developed in order to handle simultaneous
 precipitation-dissolution and oxidation-reduction reactions
 governed by chemical equilibria. Total aqueous component
 concentrations are the primary dependent variables, and a
 sequential iterative approach is used for the calculation. The
 model was verified by analytical and numerical comparisons and
 is able to simulate sharp mineral fronts. At a site in
 Denmark, denitrification has been observed by oxidation of
 pyrite. Simulation of nitrate movement at this site showed a
 redox front movement rate of 0.58 m yr-1, which agreed with
 calculations of others. It appears that the sequential
 iterative approach is the most practical for extension to
 multidimensional simulation and for handling large numbers of
 components and reactions. However, slow convergence may limit
 the size of redox systems that can be handled.
 
 
 101                                 NAL Call. No.: 56.9 SO32
 Geographic information system for differentiating unused
 wells. Tan, Y.R.; Shih, S.F.
 S.l. : The Society; 1991.
 Proceedings - Soil and Crop Science Society of Florida v. 50:
 p. 110-116; 1991.  Paper presented at the "Symposium on
 Reality of Sustainable Agriculture in Florida, September
 26-28, 1990, Daytona Beach, FLorida.  Includes references.
 
 Language:  English
 
 Descriptors: Florida; Groundwater; Wells; Water management;
 Geographical distribution
 
 
 102                                    NAL Call. No.: QE1.E5
 Geostatistical modeling of salinity as a basis for irrigation
 management and crop selection--a case study in central
 Tunisia.
 Soderstrom, M.
 New York, N.Y. : Springer; 1992 Sep.
 Environmental geology and water sciences v. 20 (2): p. 85-92;
 1992 Sep. Includes references.
 
 Language:  English
 
 Descriptors: Tunisia; Groundwater; Saline water; Irrigation
 water; Spatial distribution; Soil salinity; Irrigated soils;
 Wells; Water; Soil; Sampling; Maps; Leaching; Models;
 Irrigation scheduling; Crop yield; Yield losses; Crops;
 Selection
 
 
 103                              NAL Call. No.: QH541.5.D4J6 A
 GIS approach to desertification assessment and mapping.
 Grunblatt, J.; Ottichilo, W.K.; Sinange, R.K.
 London : Academic Press; 1992 Jul.
 Journal of arid environments v. 23 (1): p. 81-102; 1992 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Kenya; Desertification; Remote sensing; Satellite
 imagery; Models; Geography
 
 
 104                                  NAL Call. No.: S671.A66
 GIS-assisted input data set development for the Finite Element
 Storm Hydrograph Model (FESHM).
 Wolfe, M.L.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Mar. Applied engineering in agriculture v. 8
 (2): p. 221-227; 1992 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Hydrology; Simulation models; Automation;
 Computer techniques
 
 Abstract:  A study was conducted to develop an automated
 proceedings to assist in the development of input data sets
 for the FESHM hydrologic model using the GRASS geographic
 information system. Shell scripts (executable sequences of
 commands in the UNIX operating system) were developed to
 overlay soils and land use maps to generate hydrologic
 response unit (HRU) maps and to compute the fractional areas
 of HRUs in overland flow elements. The automated procedures
 decreased the input data set development time significantly,
 by approximately 250% (from five to two hours) for a 122 ha
 (303 ac) watershed. The time savings on larger, more variable
 watersheds would be even greater. The input data set
 development procedure provides an efficient manner for
 considering alternative land use and management scenarios.
 
 
 105                                NAL Call. No.: 292.9 AM34
 Ground water quality implications of soil conservation
 measures: an economic perspective.
 Setia, P.; Piper, S.
 Bethesda, Md. : American Water Resources Association; 1991
 Mar. Water resources bulletin v. 27 (2): p. 201-208; 1991 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Corn belt of U.S.A.; Soil conservation;
 Groundwater; Water quality; Pesticides; Runoff; Leaching;
 Agricultural economics; Usda; Federal programs
 
 Abstract:  An evaluation of the intermedia movement of
 pesticides applied under various land management systems
 already in place, or to be implemented, under the Conservation
 Reserve and Conservation Compliance programs is presented. The
 simulation modeling approach followed in this analysis
 consists of a mathematical programming model and
 leaching/surface runoff, Pesticide Root Zone Model (PRZM)
 models. Special care was taken to ensure that the physical
 model was sensitive to the chemical characteristics of
 individual pesticides and the important physical changes
 brought about by different agricultural practices. Results
 show that, although these programs as now planned, increase
 farm income and achieve soil conservation goals, they may
 adversely affect ground water quality. Also, depending on soil
 and location characteristics, there are tradeoffs between
 surface and ground water quality implications. Hence, if these
 programs are to address water quality problems, the
 recommended practices must be evaluated for their impact on
 water quality, particularly in potentially vulnerable areas.
 
 
 106                                   NAL Call. No.: QD1.A45
 Groundwater and surface water risk assessments for proposed
 golf courses. Cohen, S.Z.; Durborow, T.E.; Barnes, N.L.
 Washington, D.C. : The Society; 1993.
 ACS Symposium series - American Chemical Society (522): p.
 214-227; 1993.  In the series analytic: Pesticides in urban
 environments: Fate and significance / edited by K.D. Racke and
 A.R. Leslie. Paper presented at the 203rd National Meeting of
 the American Chemical Society, April 5-10, 1992, San
 Francisco, California.  Includes references.
 
 Language:  English
 
 Descriptors: Hawaii; Massachusetts; Golf courses; Golf green
 soils; Herbicide residues; Insecticide residues; Leaching;
 Leachates; Runoff; Surface water; Water pollution; Groundwater
 pollution; Mathematical models; Simulation models; Risk;
 Fungicides; Pesticide residues; Fertilizers; Nitrogen
 
 Abstract:  Proposed golf course developments usually require
 environmental impact statements in the U.S. Concerns about
 ground water, surface water, and near-shore coastal water
 quality and wetlands often require state-of-the-art risk
 assessments and complex computerized simulation modeling. It
 is extremely important to obtain site-specific data for these
 risk assessments. Thus soil sampling, test borings, stream
 surveys, and coastal surveys are often done. Daily weather
 records are obtained or generated. The new PRZM-VADOFT model
 pair is used for leaching assessments, even though nonlinear
 adsorption isotherms cannot be used. The SWRRBWQ model is
 difficult to use but it is appropriate for the modeling of
 complex drainage patterns at the basin and sub-basin scale, as
 with golf courses. Annual and storm-event runoff values are
 computed for pesticides, nutrients, runoff water, and
 sediments. It is best used for areas expected to experience
 appreciable runoff. EXAMS II provides useful predictions of
 stream water quality. An uncertainty analysis is a critical
 but often overlooked part of modeling. These results help fine
 tune proposed turf management programs and may indicate the
 need for design changes. Risk assessments in Hawaii are
 especially complex; they often indicate the need for detention
 basins.
 
 
 107                                NAL Call. No.: TD420.A1E5
 Herbicide transport in rivers: importance of hydrology and
 geochemistry in nonpoint-source contamination.
 Squillace, P.J.; Thurman, E.M.
 Washington, D.C. : American Chemical Society; 1992 Mar.
 Environmental science & technology v. 26 (3): p. 538-545; 1992
 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Iowa; Minnesota; Herbicide residues; Water
 pollution; River water; Groundwater pollution; Concentration;
 Models; Overland flow
 
 
 108                                  NAL Call. No.: S601.A34
 High bed-low ditch system in the Pearl River Delta, South
 China. Ming, L.S.; Jian, L.R.
 Amsterdam : Elsevier; 1991 Jun14.
 Agriculture, ecosystems and environment v. 36 (1/2): p.
 101-109; 1991 Jun14. Includes references.
 
 Language:  English
 
 Descriptors: China; Delta soils; Alluvial soils; Deltas;
 Subtropics; Saccharum officinarum; Musa paradisiaca; Citrus
 reticulata; Oryza sativa; Sustainability; Ditches; High water
 tables; Soil depth; Roots; Growth; Erosion; Sediment;
 Nutrients; Losses from soil systems; Cycling; Flow; Models;
 Crop production; Agricultural byproducts; Irrigation water;
 Rain; Runoff water; Drainage water; Fertilizers; Dry matter
 accumulation; Decomposition; Crop residues; Nitrogen;
 Phosphorus pentoxide; Potassium; Nutrient content; Temporal
 variation; Dry season; Rainy season; Water quality; Organic
 matter
 
 
 109                            NAL Call. No.: TC163.I54 1992
 Hydraulic and environmental modelling--estuarine and river
 waters proceedings of the Second International Conference on
 Hydraulic and Environmental Modelling of Coastal, Estuarine,
 and River Waters.
 Falconer, R. A.; Shiono, K.; Matthew, R. G. S.
 International Conference on Hydraulic and Environmental
 Modelling of Coastal, Estuarine, and River Waters 2nd : 1992 :
 University of Bradford. Aldershot, Hants, UK ; Brookfield, Vt.
 : Ashgate,; 1992.
 2 v. : ill. ; 24 cm.  Proceedings of a conference held at the
 University of Bradford, UK Sept. 22-24, 1992.  Vol. 1 edited
 by F.A. Falconer, S.N. Chandler-Wilde, S.Q. Liu.  Includes
 bibliographical references.
 
 Language:  English
 
 Descriptors: Hydraulics; Water quality; Sediment transport
 
 
 110                               NAL Call. No.: 290.9 AM32T
 Hydraulic roughness coefficients as affected by random
 roughness. Gilley, J.E.; Finkner, S.C.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 May. Transactions of the ASAE v. 34 (3): p.
 897-903; 1991 May.  Includes references.
 
 Language:  English
 
 Descriptors: Nebraska; Hydraulic resistance; Runoff; Surface
 roughness; Tillage; Upland areas; Water flow; Simulation
 models
 
 Abstract:  Random roughness parameters are used to
 characterize surface microrelief. In this study, random
 roughness was determined following six selected tillage
 operations. Random roughness measurements agreed closely with
 values reported in the literature. Surface runoff on upland
 areas is analyzed using hydraulic roughness coefficients.
 Darcy-Weisbach and Manning hydraulic roughness coefficients
 were identified in this investigation on each soil surface
 where random roughness values were determined. Hydraulic
 roughness coefficients were obtained from measurements of
 discharge rate and flow velocity. The experimental data were
 used to derive regression relationships which related Darcy-
 Weisbach and Manning hydraulic roughness coefficients to
 random roughness and Reynolds number. Random roughness values
 available in the literature can be substituted into the
 regression equations to estimate hydraulic roughness
 coefficients for a wide range of tillage implements. The
 accurate prediction of hydraulic roughness coefficients will
 improve our ability to understand and properly model upland
 flow hydraulics.
 
 
 111                                 NAL Call. No.: 292.8 J82
 Hydrogeologic controls on peatland development in the
 Malloryville Wetland, New York (USA).
 McNamara, J.P.; Siegel, D.I.; Glaser, P.H.; Beck, R.M.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Dec.
 Journal of hydrology v. 140 (1/4): p. 279-296; 1992 Dec. 
 Includes references.
 
 Language:  English
 
 Descriptors: New York; Peatlands; Swamps; Bogs; Fens;
 Hydrology; Geology; Vegetation; Plant communities; Ecology;
 Surface water; Water quality; Groundwater; Groundwater flow;
 Discharge; Upward movement; Mounds; Water table; Indicator
 species; Simulation models
 
 Abstract:  The Malloryville Wetland Complex, a small kettle-
 hole peatland, contains a diversity of peatland types. The
 wetland has a 'rich' side that contains wetland vegetation
 associated with solute-rich, near-neutral pH (minerotrophic)
 water, and a 'poor' side containing vegetation that grows in
 solute-poor and acidic (ombrotrophic) water. Vertical head
 gradients at piezometer clusters located in the rich side
 clearly show that groundwater is moving upwards towards the
 land surface, consistent with the vegetation types and surface
 water quality. In contrast, vertical head gradients also show
 that groundwater is moving upward in the poor side even though
 the vegetation and surface water chemistry are not
 minerotrophic. An incipient raised bog in the center of the
 poor side is the only site where groundwater moves
 consistently downward. A peat core collected at the bog center
 shows that the bog site was initially covered by minerotrophic
 vegetation, typically found in groundwater discharge zones,
 which was later replaced by ombrotrophic bog vegetation.
 Theoretical computer simulation experiments of the bog
 hydrogeologic setting through time suggest that the direction
 of vertical groundwater flow at the bog site permanently
 changed from up to down when a water table mound developed
 under a convex-shaped fen peat mound that probably formed
 because of differential peat accumulation. Ombrotrophic
 conditions and bog vegetation probably began when the fen
 water table mound grew sufficiently large enough to divert the
 upward movement of regional groundwater. The transition from
 rich to poor environments probably occurred when the wetland
 water table was substantially below the elevation of the
 surrounding regional water table.
 
 
 112                                 NAL Call. No.: HD1750.W4
 The impact of pollution controls on livestock--crop producers.
 Schnitkey, G.D.; Miranda, M.J.
 Bozeman, Mont. : Western Agricultural Economics Association;
 1993 Jul. Journal of agricultural and resource economics v. 18
 (1): p. 25-36; 1993 Jul. Includes references.
 
 Language:  English
 
 Descriptors: Phosphorus; Runoff; Soil pollution; Pollution
 control; Livestock enterprises; Agricultural land; Crop
 production; Farmyard manure; Commercial soil additives;
 Environmental policy; Livestock numbers; Application methods;
 Returns; Mathematical models; Pig farming; Maize
 
 
 113                               NAL Call. No.: 290.9 AM32T
 Impact of random data errors on parameter estimation in
 hydrologic modeling. Borah, A.; Haan, C.T.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 May. Transactions of the ASAE v. 34 (3): p.
 857-864; 1991 May.  Includes references.
 
 Language:  English
 
 Descriptors: Oklahoma; Hydrology; Rain; Runoff; Stream flow;
 Simulation models; Water resources; Watersheds
 
 Abstract:  Parameter uncertainty in hydrologic models is due,
 in part, to random errors in input data used for calibration.
 This work investigates the impact of various error
 distributions associated with input data on the final
 estimated parameter values using three different estimation
 criteria. Errors in precipitation data were found to introduce
 more uncertainty into parameter estimates than errors in
 runoff data. Parameter uncertainty increased as the level of
 error introduced into input data increased. Correlated errors
 in the input data greatly increased the uncertainty associated
 with parameter estimates.
 
 
 114                                 NAL Call. No.: 44.8 J822
 Impact of Texas water quality laws on dairy income and
 viability. Leatham, D.J.; Schmucker, J.F.; Lacewell, R.D.;
 Schwart, R.B.; Lovell, A.C.; Allen, G.
 Champaign, Ill. : American Dairy Science Association; 1992
 Oct. Journal of dairy science v. 75 (10): p. 2846-2856; 1992
 Oct.  Includes references.
 
 Language:  English
 
 Descriptors: Texas; Dairy farms; Dairy wastes; Water quality;
 Law; Profitability; Estimated costs; Cash flow; Farm
 indebtedness; Risk; Survival; Mathematical models
 
 Abstract:  A dairy waste management spreadsheet was developed
 and applied along with partial budgets and whole firm, Monte
 Carlo simulations for Texas dairies to evaluate the impact
 that Texas water quality laws have on dairy profitability and
 survival. Results showed that representative 300- and 720-cow
 dairies will incur additional annual costs of $60 and $81 per
 cow, respectively. Compliance with water quality laws reduces
 net farm income by 27 and 63% for 720-cow dairies with low and
 high debt positions, respectively. The probability of survival
 of the dairies with low debt was not affected by compliance.
 The probability of survival of firms with high debt positions
 decreased by 47 percentage points. Under the conditions
 modeled, net farm income for representative 300-cow dairies
 would be negative after compliance with water quality laws.
 
 
 115                                NAL Call. No.: 280.8 J822
 Impact targets versus discharge standards in agricultural
 pollution management.
 Braden, J.B.; Larson, R.S.; Herricks, E.E.
 Ames, Iowa : American Agricultural Economics Association; 1991
 May. American journal of agricultural economics v. 73 (2): p.
 388-397; 1991 May. Includes references.
 
 Language:  English
 
 Descriptors: Michigan; Fish; Lakes; Pollution; Losses;
 Habitats; Soil movement; Case studies; Watersheds; Pesticides;
 Water management; Environmental policy; Optimization;
 Mathematical models
 
 
 116                              NAL Call. No.: S494.5.S86S8
 Impacts of uncertainty on policy costs of managing nonpoint
 source ground water contamination.
 Halstead, J.M.; Batie, S.S.; Taylor, D.B.; Heatwole, C.D.;
 Diebel, P.L.; Kramer, R.A.
 Binghamton, N.Y. : Food Products Press; 1991.
 Journal of sustainable agriculture v. 1 (4): p. 29-48; 1991. 
 Includes references.
 
 Language:  English
 
 Descriptors: Virginia; Groundwater pollution; Nitrates;
 Stochastic models; Stochastic programming; Agricultural
 policy; Costs
 
 
 117                               NAL Call. No.: 290.9 AM32T
 The importance of precise rainfall inputs in nonpoint source
 pollution modeling.
 Rudra, R.P.; Dickinson, W.T.; Euw, E.L. von
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1993 Mar. Transactions of the ASAE v. 36 (2): p.
 445-450; 1993 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Ontario; Agricultural wastes; Losses from soil;
 Models; Pollutants; Rain; Soil properties
 
 Abstract:  Rainfall data provide a prime input in nonpoint
 source pollution (nps) modeling. The sensitivity of model
 outputs to variations in the time step selected for rainfall
 data has been explored for two nps models, a field-scale
 continuous model, and an event-based watershed-scale model,
 for the temperate climatic conditions of Southern Ontario,
 Canada. This study has revealed that model outputs regarding
 runoff, soil loss and sediment yield, and calibrated
 parameters representing soil hydraulic properties and erosion
 characteristics are extremely sensitive to small variations in
 the rainfall time step. Model users must use caution therefore
 to take these variations into account during the calibration
 and application of such models.
 
 
 118                               NAL Call. No.: 290.9 AM32T
 Infiltration and runoff simulation on a plane.
 Stone, J.J.; Lane, L.J.; Shirley, E.D.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Jan. Transactions of the ASAE v. 35 (1): p.
 161-170; 1992 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Erosion; Infiltration; Kinetics; Runoff;
 Simulation models; Computer software
 
 Abstract:  A program which computes infiltration and the
 overland flow hydrograph on a single, homogeneous plane is
 described. Infiltration is computed by the Green and Ampt
 equation and the hydrograph is computed by a semi-analytical
 method of characteristics solution of the kinematic wave model
 for overland flow. Default parameter estimation values are
 supplied by the program for both the infiltration and
 hydrograph models. Use of the model as a tool for parameter
 selection is illustrated with rangeland rainfall simulator
 data.
 
 
 119                                  NAL Call. No.: QH540.N3
 Integrating database, spreadsheet, graphics, GIS, statistics,
 simulation models and expert systems: experiences with the
 RAISON system on microcomputers.
 Lam, D.C.L.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 26: p.
 429-459; 1991.  In the series analytic: Decision support
 systems: Water resources planning / edited by D.P. Loucks and
 J.R. da Costa. Proceedings of the NATO Advanced Research
 Workshop on Computer-Aided Support Systems for Water
 Resources, Research and Management, September 24-28, 1990,
 Ericeira, Portugal.  Includes references.
 
 Language:  English
 
 Descriptors: Water resources; Water management; Computer
 software; Computer graphics; Databases; Computer simulation;
 Simulation models; Expert systems; Microcomputers
 
 
 120                                NAL Call. No.: HC79.P55J6
 Integrating fishery and water resource management: a
 biological model of a California salmon fishery.
 Fisher, A.C.; Hanemann, W.M.; Keeler, A.G.
 Duluth, Minn. : Academic Press; 1991 May.
 Journal of environmental economics and management v. 20 (3):
 p. 234-261; 1991 May.  Includes references.
 
 Language:  English
 
 Descriptors: California; Salmon; Fishery management; Water
 resources; Water management; Water flow; Hatcheries;
 Regulations; Water quality; Fresh water; Deltas; Dynamic
 models; Populations; Trends; Simulation; Quantitative analysis
 
 
 121                                  NAL Call. No.: QH540.N3
 The interface between GIS and hydrology.
 Wallis, J.R.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 26: p.
 189-197; 1991.  In the series analytic: Decision support
 systems: Water resources planning / edited by D.P. Loucks and
 J.R. da Costa. Proceedings of the NATO Advanced Research
 Workshop on Computer-Aided Support Systems for Water
 Resources, Research and Management, September 24-28, 1990,
 Ericeira, Portugal.  Includes references.
 
 Language:  English
 
 Descriptors: Water resources; Hydrology; Water management;
 Computer simulation; Simulation models; Computer hardware;
 Computer graphics; Computer software
 
 
 122                           NAL Call. No.: TD370.I575 1993
 An Introduction to water quality modelling., 2nd ed..
 James, A.
 Chichester ; New York : Wiley,; 1993.
 vi, 311 p. : ill. ; 25 cm.  Includes bibliographical
 references and index.
 
 Language:  English
 
 Descriptors: Water quality; Water quality management
 
 
 123                                  NAL Call. No.: 23 AU783
 Irrigation using groundwater for watertable control: a model
 of water and salt balance limitations.
 Salvich, P.G.
 Melbourne : Commonwealth Scientific and Industrial Research
 Organization; 1992.
 Australian journal of agricultural research v. 43 (1): p.
 225-239; 1992. Includes references.
 
 Language:  English
 
 Descriptors: New South Wales; Irrigation; Groundwater;
 Leaching; Recharge; Salinity; Simulation models
 
 
 124                                 NAL Call. No.: 292.8 J82
 Kinematic analysis of flood runoff for a small-scale upland
 field. Yomota, A.; Islam, M.N.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Aug15.
 Journal of hydrology v. 137 (1/4): p. 311-326; 1992 Aug15. 
 Includes references.
 
 Language:  English
 
 Descriptors: Japan; Reclamation; Runoff; Overland flow;
 Flooding; Sloping land; Upland areas; Mathematical models;
 Kinematics
 
 Abstract:  In Japan, many sloping fields are being reclaimed
 by the Ministry of Agriculture, Forestry and Fisheries to
 increase the upland field areas. To predict the flood
 discharge from these fields, a study was undertaken from one
 reclaimed sloping field, in the Hiroshima prefecture, with an
 area of 4.55 ha. For modelling purposes, the widely used
 kinematic wave equations and method of characteristics were
 used. Rainfall and runoff data were collected for a period of
 6 years (1984-1989) from the field, for both furrow and non-
 furrow conditions and were used in these analyses. Manning,
 Darcy and laminar resistance equations were used and Manning's
 equation was found to be the best of the three. Manning's
 roughness coefficient (n) for furrow flow and equivalent
 roughness (N) for non-furrow flow conditions were determined
 and are presented in tabular form. Application of the non-
 furrow flow equation to the furrow flow condition required
 selecting an adequate equivalent roughness. Finally,
 verification of time of concentration, velocity of sheet or
 furrow flow and runoff coefficient were made both for furrow
 and non-furrow conditions, and these are graphically
 presented.
 
 
 125                                  NAL Call. No.: TD201.A4 A
 kinematic model of infiltration and runoff generation in
 layered and sloped soils.
 Cabral, M.C.; Garrote, L.; Bras, R.L.; Entekhabi, D.
 Essex : Elsevier Science Publishers Ltd; 1992.
 Advances in water resources v. 15 (5): p. 311-324; 1992. 
 Includes references.
 
 Language:  English
 
 Descriptors: Infiltration; Rain; Movement in soil; Runoff
 water; Layered soils; Sloping land; Kinetics; Models
 
 
 126                                NAL Call. No.: 292.8 W295
 Kinematic routing using finite elements on a triangular
 irregular network. Goodrich, D.C.; Woolhiser, D.A.; Keefer,
 T.O.
 Washington, D.C. : American Geophysical Union; 1991 Jun.
 Water resources research v. 27 (6): p. 995-1003; 1991 Jun. 
 Includes references.
 
 Language:  English
 
 Descriptors: Overland flow; Rain; Runoff; Watersheds;
 Topography; Kinematics; Mathematical models
 
 Abstract:  Automated extraction of geometry for hydraulic
 routing from digital elevation models (DEM) is a procedure
 that must be easily accomplished for widespread application of
 distributed hydraulically based rainfall excess-runoff models.
 One-dimensional kinematic routing on a regular grid DEM is
 difficult due to flow division and convergence. Two-
 dimensional kinematic routing on a triangular irregular
 network (TIN) surmounts many of these difficulties. Because
 TIN DEMs typically require far fewer points to represent
 topography than regular grid DEMs, substantial computational
 economy is also realized. One-dimensional routing using vector
 contour data overcomes the grid-based routing disadvantages
 but often requires several orders of magnitude more storage
 points than a TIN. The methodology presented in this paper
 represents a compromise between slightly increased
 computational complexity and the economy of TIN topographic
 representation. We take the unique approach of subdividing
 each topographic triangle (TIN facet) into a set of coplanar
 triangular finite elements, performing routing on a single
 facet and then routing the resulting excess hydrograph to
 downstream facets and channels via upstream boundary
 conditions. Results indicate that shock conditions are readily
 handled, computed depths match analytic results to within +/-
 3% and volume balances are typically within 1%. This modeling
 system illustrates the viability of kinematic routing over a
 TIN DEM derived directly from digital mapping data.
 
 
 127                                  NAL Call. No.: S590.S62
 Kinetics of soil chemical reactions--a theoretical treatment.
 Aharoni, C.; Sparks, D.L.
 Madison, Wis. : Soil Science Society of America; 1991.
 SSSA special publication series (27): p. 1-18; 1991.  In the
 series analytic: Rates of soil chemical processes / edited by
 D.L. Sparks and D.L. Suarez. Proceedings of a Symposium,
 October 17, 1989, Las Vegas, Nevada.  Includes references.
 
 Language:  English
 
 Descriptors: Soil chemistry; Equations; Kinetics; Simulation
 models; Theory; Transport processes
 
 
 128                                 NAL Call. No.: 292.8 J82
 Laboratory and numerical investigations of immiscible
 multiphase flow in soil. Host-Madsen, J.; Jensen, K.H.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Jul.
 Journal of hydrology v. 135 (1/4): p. 13-52; 1992 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution; Petroleum;
 Flow; Hydraulics; Laboratory tests; Simulation models;
 Mathematical models; Quantitative analysis
 
 Abstract:  Immiscible multiphase flow in porous media is
 investigated by laboratory experiments and numerical
 simulations. The hydraulic parameters used in mathematical
 models for multiphase flow are determined experimentally, and
 the interrelations between the individual parameters are
 analysed. The experimental data support the applicability of
 analytical closed-form expressions for the constitutive
 relations, and a scaling procedure is verified in which the
 interfacial tensions are used to derive scaling factors. These
 simplifications in the parameter requirements are very
 valuable from an engineering point of view. A two-dimensional
 plexiglass flume is used for studying the flow of lighter-
 than-water, non-aqueous phase liquids (LNAPL) in sandy porous
 media. The migration of the LNAPL is observed both in the
 unsaturated zone and in the saturated zone at the bottom of
 the flume. A dual-gamma attenuation system is used for
 measuring the phase saturations of organic fluid, water, and
 air simultaneously without disturbing the flow. This permits a
 two-dimensional quantitative determination of the LNAPL plume
 in contrast to many earlier qualitative studies. A black oil
 reservoir model is used to simulate immiscible multiphase
 flow. By using the parameter estimation methods presented for
 establishing the constitutive relations, the model is applied
 to the simulation of the laboratory experiments. The
 experimental and numerical results compare reasonably well,
 thus supporting the adopted model formulation.
 
 
 129                       NAL Call. No.: 100 M38H (1) no.738
 Landscape planning for watershed protection the first step. la
 Cour, Niels; Fabos, Julius Gy; Ahern, Jack
 Massachusetts Agricultural Experiment Station
 Amherst, Mass. : Massachusetts Agricultural Experiment
 Station, College of Food and Natural Resources, University of
 Massachusetts at Amherst,; 1992. x, 77 p. : ill., maps ; 23
 cm. (Research bulletin (Massachusetts Agricultural Experiment
 Station) ; no. 738.).  Received for publication August 1991.
 Winter 1992.  Includes bibliographical references (p. 75-77).
 
 Language:  English; English
 
 Descriptors: Watershed management; Regional planning;
 Geographic information systems
 
 
 130                                NAL Call. No.: 292.8 W295
 The Las Cruces Trench site: characterization, experimental
 results, and one-dimensional flow predictions.
 Wierenga, P.J.; Hills, R.G.; Hudson, D.B.
 Washington, D.C. : American Geophysical Union; 1991 Oct.
 Water resources research v. 27 (10): p. 2695-2705; 1991 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: New Mexico; Soil water; Water flow; Solutes;
 Transport processes; Infiltration; Semiarid soils; Soil
 variability; Wetting front; Saturated hydraulic conductivity;
 Deterministic models; Prediction
 
 Abstract:  A comprehensive field trench study was conducted in
 a semiarid area of southern New Mexico to provide data to test
 deterministic and stochastic models of vadose zone flow and
 transport. A 4 m by 9 m area was irrigated with water
 containing a tracer using a carefully controlled drip
 irrigation system. The area was heavily instrumented with
 tensiometers and neutron probe access tubes to monitor water
 movement and with suction tubes to monitor solute transport.
 Approximately 600 disturbed and 600 core samples of soil were
 taken to support deterministic and stochastic characterization
 of the soil water hydraulic parameters. The core sample-based
 saturated hydraulic conductivities ranged from 1.4 to 6731
 cm/d with a mean of 533 cm/d and a standard deviation of 647
 cm/d, indicating significant spatial variability. However,
 visual observation of the wetting front on the trench wall
 shows no indication of preferential flow or water flow through
 visible root channels and cracks. The tensiometer readings and
 the neutron probe measurements also suggest that the wetting
 front moves in a fairly homogeneous fashion despite the
 significant spatial variability of the saturated hydraulic
 conductivity. In addition to the description of the experiment
 and the presentation of the experimental results, predictions
 of simple one-dimensional uniform and layered soil
 deterministic models for infiltration are presented and
 compared to field observations. These models are presented
 here to provide a base case against which more sophisticated
 deterministic and stochastic models can be compared in the
 future. The results indicate that the simple models give
 adequate predictions of the overall movement of the wetting
 front through the soil during infiltration. However, the
 models give poor predictions of point values for water content
 due to the spatial variability of the soil. Comparisons
 between the one-dimensional infiltration model predictions and
 field observations show that the use of t
 
 
 131                                 NAL Call. No.: 292.8 J82 A
 linear cascade model for predicting transport of dissolved
 agrochemicals by surface runoff.
 Wallach, R.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Sep.
 Journal of hydrology v. 126 (3/4): p. 207-224; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Runoff water; Surface
 layers; Transport processes; Flow; Mathematical models
 
 Abstract:  A cascade-based model is used to predict the
 dissolved chemical concentration profile at the effluent of a
 field. The source of chemicals is the soil surface layer, from
 which the chemicals are transferred to the surface runoff and
 transported to the field outlet. The model applies a cascade
 of perfectly mixed cells analogous to an equivalent surface
 runoff water and soil surface laver. Each cell is made of two
 interconnected units, where the upper unit represents the
 runoff water and the lower unit represents the soil bulk.
 Chemical transfer between the two units is controlled by the
 convective mass-transfer process through the laminar boundary
 laver of the surface runoff flow. The cells are interconnected
 through their upper units by runoff water flow. The lower unit
 applies a perfectly mixed reactor analog to an equivalent and
 homogeneous soil layer of uniform concentration near the soil
 surface. called the effective depth of transfer (EDT). The
 expression for the concentration within the EDT is simplified
 and agrees well with the soil surface concentration as
 determined by an analytical solution of the one-dimensional
 diffusion equation for the limiting case of no infiltration.
 The number of cells in the cascade is a measure of the extent
 of axial mixing in runoff flow where the limiting cases are:
 (1) a perfective mixed system represented by one cell, and (2)
 a zero-mixing system (plug flow) represented by a cascade made
 of an infinite number of cells. The distribution of chemical
 concentrations for these two extreme cases and for other flows
 with varying degrees of mixing are presented.
 
 
 132                                NAL Call. No.: 292.8 W295
 Linear transport models for adsorbing solutes.
 Roth, K.; Jury, W.A.
 Washington : American Geophysical Union, 1965-; 1993 Apr.
 Water resources research v. 29 (4): p. 1195-1203; 1993 Apr. 
 Includes references.
 
 Language:  English
 
 Descriptors: Transport processes; Movement in soil;
 Adsorption; Solutes; Linear models
 
 Abstract:  A unified linear theory for the transport of
 adsorbing solutes through soils is presented and applied to
 analyze movement of napropamide through undisturbed soil
 columns. The transport characteristics of the soil are
 expressed in terms of the travel time distribution of the
 mobile phase which is then used to incorporate local
 interaction processes. This approach permits the analysis of
 all linear transport processes, not only the small subset for
 which a differential description is known. From a practical
 point of view, it allows the direct use of measured
 concentrations or fluxes of conservative solutes to
 characterize the mobile phase without first subjecting them to
 any model. For complicated flow regimes, this may vastly
 improve the identification of models and estimation of their
 parameters for the local adsorption processes.
 
 
 133                          NAL Call. No.: TD196.M4B56 1992
 Long-term behavior of heavy metals in agricultural soils: a
 simple analytical model.
 Harmsen, K.
 Boca Raton : Lewis Publishers; 1992.
 Biogeochemistry of trace metals / edited by Domy C. Adriano.
 p. 217-247; 1992. (Advances in trace substances research). 
 Includes references.
 
 Language:  English
 
 Descriptors: Agricultural soils; Heavy metals; Solubility;
 Leaching; Uptake
 
 
 134                                 NAL Call. No.: TD426.J68
 Long-term effects of soil heterogeneity on cadmium behavior in
 soil. Boekhold, A.E.; Zee, S.E.A.T.M. van der
 Amsterdam : Elsevier; 1991 Jun.
 Journal of contaminant hydrology v. 7 (4): p. 371-390; 1991
 Jun.  Includes references.
 
 Language:  English
 
 Descriptors: Soil pollution; Cadmium; Behavior; Sandy soils;
 Uptake; Hordeum vulgare; Deterministic models; Soil;
 Physicochemical properties; Profiles; Leaching; Heterogeneity;
 Equations
 
 
 135                                NAL Call. No.: 292.9 AM34
 Low-input agriculture as a ground water protection strategy.
 Diebel, P.L.; Taylor, D.B.; Batie, S.S.; Heatwole, C.D.
 Bethesda, Md. : American Water Resources Association; 1992
 Jul. Water resources bulletin v. 28 (4): p. 755-761; 1992 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Virginia; Groundwater pollution; Water quality;
 Farm inputs; Farming systems; Profitability; Economic
 analysis; Mathematical models
 
 Abstract:  Protection of ground water quality is of
 considerable importance to local, state, and federal
 governments. This study uses a 15-year mathematical
 programming model to evaluate the effectiveness of low-input
 agriculture, under alternative policy scenarios, as a strategy
 to protect ground water quality in Richmond County, Virginia.
 The analysis considers eight policy alternatives: cost-sharing
 for green manures, two restrictions on atrazine applications
 levels, chemical taxation, a restriction on potential chemical
 and nitrogen levels in ground water only and in surface and
 ground water, and two types of land retirement programs. The
 CREAMS and GLEAMS models were used to estimate nitrate and
 chemical leaching from the crop root zone. The economic model
 evaluates production practices, policy constraints, and water
 quality given a long-term profit maximizing objective. The
 results indicate that low-input agriculture alone may not be
 an effective groundwater protection strategy. The policy
 impacts include partial adoption of low-input practices, land
 retirement, and the substitution of chemicals. Only mandatory
 land retirement policies reduced all chemical and nutrient
 loadings or ground water; however, they did not promote the
 use of low-input agricultural practices.
 
 
 136                                  NAL Call. No.: 56.8 SO3
 Lysimeter study of anion transport during steady flow through
 layered coarse-textured soil profiles.
 Jacobsen, O.H.; Leij, F.J.; Van Genuchten, M.T.
 Baltimore, Md. : Williams & Wilkins; 1992 Sep.
 Soil science v. 154 (3): p. 196-205; 1992 Sep.  Includes
 references.
 
 Language:  English
 
 Descriptors: Coarse textured soils; Layered soils; Unsaturated
 flow; Soil water movement; Soil variability; Transport
 processes; Chlorine; Nitrate; Mathematical models; Soil water
 retention
 
 
 137                                NAL Call. No.: TD420.A1P7
 Management of water resources and eutrophication in the
 Federal District of Brazil.
 Somlyody, L.; Altafin, I.
 Oxford : Pergamon Press; 1992.
 Water science and technology : a journal of the International
 Association on Water Pollution Research and Control v. 26
 (7/8): p. 1813-1822; 1992.  In the series analytic: Water
 Quality International '92. Part 4 / edited by M. Suzuki, et
 al. Proceedings of the Sixtennth Biennial Conference of the
 International Association on Water Pollution Research and
 Control, held May 24-30, 1992, Washington, D.C.  Includes
 references.
 
 Language:  English
 
 Descriptors: Brazil; Reservoirs; Eutrophication; Water
 purification; Sewage; Waste treatment; Algae; Biomass
 production; Water resources; Management; Water quality; Models
 
 
 138                                 NAL Call. No.: 56.8 J822
 Managing the land: a technology perspective.
 Shaw, R.R.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1991 Nov. Journal of soil and water conservation v. 46 (6): p.
 406-408; 1991 Nov.
 
 Language:  English
 
 Descriptors: Land management; Technology transfer; Remote
 sensing; Information systems; Computer software; Usda; Water
 management; Soil conservation
 
 
 139                       NAL Call. No.: FUQL628.F6M371 1992
 Marine resources geographic information system and fishery
 resources final report.
 Haddad, Kenneth D.
 Florida Marine Research Institute, Florida Office of Coastal
 Management St. Petersburg, Fla. : Dept. of Natural Resources,
 Division of Marine Resources, Florida Marine Research
 Institute,; 1992.
 1 v. (unpaged) : ill., maps (some col.) ; 28 cm.  January,
 1992.  Funds for this project were provided by the Department
 of Environmental Regulation, Office of Coastal Management... 
 Includes bibliographical references.
 
 Language:  English; English
 
 Descriptors: Information storage and retrieval systems; Marine
 resources; Watershed management; Fishery management;
 Geographic information systems
 
 
 140                                  NAL Call. No.: 56.9 SO3
 Mathematical analysis of one-dimensional solute transport in a
 layered soil profile.
 Leij, F.J.; Dane, J.H.; Van Genuchten, M.T.
 Madison, Wis. : The Society; 1991 Jul.
 Soil Science Society of America journal v. 55 (4): p. 944-953;
 1991 Jul. Includes references.
 
 Language:  English
 
 Descriptors: Layered soils; Movement in soil; Leaching;
 Contaminants; Solutes; Profiles; Interface; Soil boundaries;
 Subsurface barriers; Sand; Clay; Mathematical models;
 Qualitative techniques; Errors
 
 Abstract:  Solute transport studies involving layered media
 are important for investigating how restricting layers affect
 rates of solute migration in the soil profile and, more
 generally, for examining the influence of soil heterogeneity
 on solute transport. Analytical solutions of the one-
 dimensional advection-dispersion equation (ADE) were obtained
 with the help of Laplace transforms for transport in a two-
 layered soil profile. Assuming that the layers are, in effect,
 semi-infinite, solutions were obtained for first-type
 (constant concentration) and third-type (constant flux)
 conditions at both the inlet boundary and the interface of the
 two layers. Concentration profiles were also obtained for a
 finite first layer via numerical inversion of the Laplace
 transform solution, using a third-type condition at the inlet,
 and, simultaneously, a first- and third-type condition at the
 interface. Volume-averaged or resident-type concentrations
 were used in all cases. First-type conditions did not meet our
 criterion of mass conservation, whereas third-type conditions
 caused discontinuities in the concentration at the interfaces
 of layers with differing transport parameters. The
 concentration at the interface was found to be continuous, and
 no mass-balance error occurred, when first- and third-type
 conditions were imposed simultaneously at the interface.
 Several example calculations show the effect of soil layering
 on solute transport in a one-dimensional soil profile.
 
 
 141                                NAL Call. No.: 292.8 W295 A
 mathematical model of hillslope and watershed discharge.
 Stagnitti, F.; Parlange, J.Y.; Steenhuis, T.S.; Parlange,
 M.B.; Rose, C.W. Washington, D.C. : American Geophysical
 Union; 1992 Aug.
 Water resources research v. 28 (8): p. 2111-2122; 1992 Aug. 
 Includes references.
 
 Language:  English
 
 Descriptors: Connecticut; Watersheds; Water flow; Soil water;
 Slopes; Soil water balance; Soil physical properties; Soil
 depth; Runoff; Seepage; Evaporation; Water yield; Water
 holding capacity; Saturated hydraulic conductivity; Catchment
 hydrology; Mathematical models; Prediction
 
 Abstract:  A mathematical water balance model describing major
 hydrological processes operating within wet forested
 watersheds is proposed. The model is capable of predicting
 hillslope and watershed discharge, evapotranspiration demands,
 hillslope moisture status, and surface and subsurface flow
 rates. It is based on soil physical principles and requires
 the following input variables: average hillslope angle and
 width, average soil depth, precipitation, average daily
 evaporation rates, effective saturated hydraulic conductivity,
 soil moisture holding capacity and initial moisture content.
 These variables are often easily measured from field studies.
 However, in some cases, the absence of field data may require
 that some of the variables in the model, e.g., saturated
 hydraulic conductivity, be estimated or calibrated from
 hillslope hydrograph records. The watershed model is composed
 of two submodels: a storage model and a hillslope model. The
 storage model describes the dynamic variation in water table
 elevation in recharge zones and the hillslope model is used to
 predict runoff and seepage through flow from surrounding
 hillsides. Application of the model is illustrated on a small
 watershed located in North Madison, Connecticut.
 
 
 142                                  NAL Call. No.: QH540.N3 A
 mathematical systems model of nitrate contamination.
 Dkstein, L.; Head, K.L.; Bogardi, I.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 30: p.
 455-476; 1991.  In the series analytic: Nitrate contamination:
 Exposure, consequence, and control / edited by I. Bogardi and
 R.D. Kuzelka. Proceedings of the NATO Advanced Research
 Workshop on Nitrate Contamination: Exposure, Consequences, and
 Control, September 9-14, 1990, Lincoln, Nebraska.  Includes
 references.
 
 Language:  English
 
 Descriptors: Nitrate; Nitrate fertilizers; Groundwater
 pollution; Drinking water; Contamination; Carcinoma; Risk;
 Mathematical models; Epidemiology; Simulation models
 
 
 143                               NAL Call. No.: QH545.A1E58
 Matrix decision procedure to assess new pesticides based on
 relative groundwater leaching potential and chronic toxicity.
 Britt, J.K.; Dwinell, S.E.; McDowell, T.C.
 Tarrytown, N.Y. : Pergamon Press; 1992.
 Environmental toxicology and chemistry v. 11 (5): p. 721-728;
 1992.  Includes references.
 
 Language:  English
 
 Descriptors: Florida; Pesticides; Public health; Toxicity;
 Environment; Environmental impact; Groundwater; Groundwater
 pollution; Leaching; Registration; Indexes; Ranking;
 Environmental protection; Subtropics; Models
 
 
 144                          NAL Call. No.: TD224.I3P75 1991
 McCook Reservoir water quality model numerical model
 investigation. Price, Richard E.; Tillman, Dottie
 United States, Army, Corps of Engineers, Chicago District,
 U.S. Army Engineer Waterways Experiment Station
 Vicksburg : Miss. : U.S. Army Engineer Waterways Experiment
 Station ; Springfield, Va. : Available from National Technical
 Information Service,; 1991.
 48 p. : ill. ; 28 cm. (Technical report (U.S. Army Engineer
 Waterways Experiment Station) ; HL-91-17.).  September 1991. 
 Cover title. Bibliography: p. 46-48.
 
 Language:  English
 
 Descriptors: McCook Reservoir (Ill.); Reservoirs; Water
 quality; Flood dams and reservoirs
 
 
 145                                NAL Call. No.: QH84.8.B46
 Measured and simulated denitrification activity in a cropped
 sandy and loamy soil.
 Vinther, F.P.
 Berlin : Springer International; 1992.
 Biology and fertility of soils v. 14 (1): p. 43-48; 1992. 
 Includes references.
 
 Language:  English
 
 Descriptors: Denmark; Hordeum vulgare; Lolium multiflorum;
 Denitrification; Leaching; Losses from soil systems;
 Measurement; Nitrogen; Soil temperature; Soil water; Long term
 experiments; Loam soils; Sandy soils
 
 
 146                               NAL Call. No.: SB610.2.B74
 Measurement and modelling of pesticide residues at Rosemaund
 Farm. Williams, R.J.; Brooke, D.N.; Glendinning, P.J.;
 Matthiessen, P.; Mills, M.J.; Turnbull, A.
 Surrey : BCPC Registered Office; 1991.
 Brighton Crop Protection Conference-Weeds v. 2: p. 507-514;
 1991.  Conference held November 18-21, 1991, Brighton,
 England.  Includes references.
 
 Language:  English
 
 Descriptors: England; Pesticide residues; Water pollution;
 Models
 
 
 147                              NAL Call. No.: S541.5.W2R47
 Measuring economic benefits of water pollution abatement in an
 irrigated river basin.
 Willis, D.; May, L.; Gutema, Y.
 Pullman, Wash. : The Center; 1992.
 Research bulletin XB - Washington State University,
 Agricultural Research Center (1019): 24 p.; 1992.  Includes
 references.
 
 Language:  English
 
 Descriptors: Washington; Rivers; Water pollution; Water
 quality; Water recreation; Fishing; Irrigation; Pollutants;
 Environmental impact; Water purification; Economic impact;
 Mathematical models
 
 
 148                                  NAL Call. No.: 56.9 SO3
 Measuring field variability of disturbed soils for simulation
 purposes. Finke, P.A.; Bouma, J.; Stein, A.
 Madison, Wis. : The Society; 1992 Jan.
 Soil Science Society of America journal v. 56 (1): p. 187-192;
 1992 Jan. Includes references.
 
 Language:  English
 
 Descriptors: Netherlands; Disturbed soils; Soil variability;
 Profiles; Spatial variation; Soil surveys; Thickness;
 Determination; Soil structure; Porosity; Soil texture; Soil
 organic matter; Soil water content; Soil water retention;
 Hydraulic conductivity; Nitrate; Leaching; Soil morphology;
 Simulation models
 
 Abstract:  Spatial variation of soil profiles disturbed by
 leveling was inventoried on a field scale to obtain
 representative data for simulation purposes. Depth of
 occurrence, thickness, and morphology of functional layers,
 which are different pedogenetic horizons with comparable soil
 physical properties, were considered to be regionalized
 variables. The layers served as carriers of physical
 information, such as water-retention and hydraulic-
 conductivity characteristics and organic-matter content. An
 impression of the variability within each layer was obtained
 by six fold sampling. Spatial variability, expressed by
 variations in thickness of functional layers, was inventoried
 in a two-step soil survey. First, semivariograms were
 constructed using data obtained following a nested sampling
 scheme supplemented by a nugget estimation procedure.
 Variograms were used to evaluate cost/quality ratios at
 varying potential grid sampling densities, using the root of
 the prediction error variance (RPEV) to compare quality of
 interpolations. Based on these evaluations and a sequential
 sampling test, a grid mesh of 12 m was chosen. Second, a grid
 soil survey and an independent quality test were done, in
 which root mean square errors (RMSE) on test points were
 compared with RPEV. The RPEV to RMSE ratios varied between 0.7
 and 1.1 for the sampled grid mesh, and had comparable values
 for other grid meshes. Estimations on test points by an
 hypothesized spatial mean, based on 26 measurements by a
 sequential sampling method, produced RMSE values not
 significantly different from RMSE values from kriging
 interpolations. However, sequential sampling required 26
 observations whereas kriging required 153, a saving of 93%.
 
 
 149                                 NAL Call. No.: 56.8 J823
 Measuring the diffusion coefficient of rhizosphere exudates in
 soil. I. The diffusion of non-sorbing compounds.
 Darrah, P.R.
 Oxford : Blackwell Scientific Publications; 1991 Sep.
 The Journal of soil science v. 42 (3): p. 413-420; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Brown earths; Root exudates; Diffusivity;
 Measurement; Solutes; Transport processes; Rhizosphere;
 Mathematical models; Sorption
 
 Abstract:  A quick, convenient and robust method is presented
 for measuring the effective diffusion coefficients of non-
 sorbing solutes in soil. The method estimates the effective
 diffusion coefficient from a measured diffusion profile by
 optimizing the solution of a numerical simulation model
 describing the experimental system. The method was used to
 measure the effective diffusion coefficients of compounds
 found in root exudates.
 
 
 150                                 NAL Call. No.: 56.8 J823
 Measuring the diffusion coefficients or rhizosphere exudates
 in soil. II. The diffusion of sorbing compouds.
 Darrah, P.R.
 Oxford : Blackwell Scientific Publications; 1991 Sep.
 The Journal of soil science v. 42 (3): p. 421-434; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Brown earths; Root exudates; Diffusivity;
 Measurement; Transport processes; Rhizosphere; Sorption
 isotherms; Mathematical models; Simulation models; Sorption;
 Solutes
 
 Abstract:  A mathematical model was developed which was
 capable of simulating the diffusion of compounds with a
 concentration-dependent diffusion coefficient, by virtue of
 their sorption on the solid phase of the soil. Methods were
 developed which allowed the sorption characteristics and the
 effective diffusion coefficient of several organic compounds
 to be inferred from their measured diffusion profiles.
 
 
 151                                 NAL Call. No.: 56.8 J823 A
 method for assessing the goodness of computer simulation of
 soil processes. Whitmore, A.P.
 Oxford : Blackwell Scientific Publications; 1991 Jun.
 The Journal of soil science v. 42 (2): p. 289-299; 1991 Jun. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil testing; Bromide; Diffusion; Nitrate
 nitrogen; Leaching; Movement in soil; Computer simulation;
 Simulation models; Assessment; Evaluation; Statistical
 analysis; Statistical data; Measurement; Variation;
 Experimental design; Replication; Temporal variation;
 Mathematics; Errors
 
 Abstract:  Any satisfactory computer simulation model of a
 soil process must match actual behaviour in the laboratory or
 field; a model can be evaluated by how well it does so. This
 paper describes a method for assessing models using anion
 diffusion and nitrate leaching as examples. The method
 partitions the sum of squares of the differences between
 measurement and simulation into two components, one calculated
 from the differences between the simulation and the mean of
 replicate measurements (the 'lack of fit'), and the other
 calculated from the variance within each set of replicate
 measurements (the 'pure error'). If the former is not
 significantly larger than the latter than the data present no
 grounds for rejecting the model. Where a model simulates the
 change in a process with time the method can also take account
 of how experimental error in the initial measurements affects
 the goodness of fit of the simulation of subsequent
 measurements. The method is particularly valuable where it is
 difficult or costly to take many replicate measurements, such
 as often happens in soil science or agriculture; nonetheless,
 some replicates must be taken.
 
 
 152                                  NAL Call. No.: 56.8 SO3 A
 method for studying nonequilibrium sorption during transport
 of pesticides in soil.
 Kookana, R.S.; Gerritse, R.G.; Aylmore, L.A.G.
 Baltimore, Md. : Williams & Wilkins; 1992 Nov.
 Soil science v. 154 (5): p. 344-349; 1992 Nov.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil analysis; Linuron; Simazine; Sorption;
 Kinetics; Transport processes; Simulation models; Saturated
 conditions; Movement in soil
 
 
 153                                  NAL Call. No.: QH540.J6
 Microlysimeter soil columns for evaluating pesticide movement
 through the root zone.
 Fermanich, K.J.; Daniel, T.C.; Lowery, B.
 Madison, Wis. : American Society of Agronomy; 1991 Jan.
 Journal of environmental quality v. 20 (1): p. 189-195; 1991
 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Pesticides; Leaching; Lysimetry; Measurement;
 Movement in soil; Simulation models; Soil temperature; Soil
 water; Water balance
 
 Abstract:  Field approaches to studying pesticide movement are
 subject to numerous variables of the environment, many of
 which are difficult and expensive to monitor. This study
 describes the design, construction, operation, and performance
 of intact microlysimeter soil (Plainfield loamy sand-mixed,
 mesic, Typic Udipsamment) columns used to examine the mobility
 of two insecticides through soil from two tillage plots
 (conventional-moldboard plow and no-till tillage). Field
 leaching conditions were approximated by simulating a moisture
 and temperature regime characteristic of a natural soil
 profile. Measured daily and seasonal temperature fluctuated
 according to a pattern characteristic of a field soil.
 Evapotranspiration (ET) from the soil columns was 61% of the
 total water applied and was nearly equal to the ET measured
 (63%) from field lysimeters of this soil planted to corn (Zea
 mays L.). Variation in cumulative drainage was small, total
 drainage from all columns was within a range of 3.9 cm. There
 was no significant difference in the transport of bromide
 (conservative tracer) through columns from the two tillage
 plots. Bromide leachate loss was 62 and 63% of the amount
 applied for conventional-moldboard plow and no-till columns,
 respectively. Intact soil columns established in a
 microlysimeter fashion provided a means to compare the
 movement of agricultural chemicals under controlled conditions
 in the greenhouse that approximate conditions/processes in the
 field.
 
 
 154                                NAL Call. No.: 292.8 W295
 Microtargeting the acquistion of cropping rights to reduce
 nonpoint source water pollution.
 Kozloff, K.; Taff, S.J.; Wang, Y.
 Washington, D.C. : American Geophysical Union; 1992 Mar.
 Water resources research v. 28 (3): p. 623-628; 1992 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Minnesota; Agricultural land; Land use; Land
 management; Watersheds; Water pollution; Water quality;
 Erosion; Sediment yield; Simulation models; Cost effectiveness
 analysis
 
 Abstract:  Targeting cropland retirement programs to reduce
 agricultural nonpoint source pollution is accomplished by
 employing disaggregated information about physical and
 economic factors that influence the benefits and costs of
 adopting specific erosion control practices on specific land
 parcels. The agricultural nonpoint source (AGNPS) model is
 used in a Minnesota watershed to simulate the relative
 effectiveness of alternative targeting schemes with respect to
 budget outlays for annual payments to landowners, reduction in
 downstream sediment yield and nutrient loss, and reduction in
 on-site erosion. Cost-effectiveness increased with information
 on economic factors (the opportunity cost of retiring a parcel
 of land) as well as on physical factors (contribution of a
 parcel to downstream sediment yield). The marginal cost-
 effectiveness of all schemes decreased as the enrolled
 proportion of watershed land increased.
 
 
 155                                  NAL Call. No.: TD403.G7
 Model development and simulation of bioremediation in soil
 beds with aggregates.
 Dhawan, S.; Erickson, L.E.; Fan, L.T.
 Dublin, Ohio : Ground Water Pub. Co; 1993 Mar.
 Ground water v. 31 (2): p. 271-284; 1993 Mar.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution; Organic
 compounds; Biodegradation; Simulation models; Soil; Aggregates
 
 Abstract:  One method of remediating contaminated soil and
 ground water is through management of the subsurface
 environment so that indigenous microorganisms can biodegrade
 organic contaminants. Modeling and simulation offer promising
 means of assessing the migration and attenuation of such
 contaminants being treated in situ in the subsurface. In this
 paper, a macropore flow model has been developed to account
 for bioremediation in the interstitial spaces among soil
 aggregates. This model has been combined with another
 bioremediation model which accounts for diffusion and
 biodegradation in the micropores and soil particles in the
 aggregates. The combined model comprises a system of six
 coupled equations, of which three are nonlinear ordinary
 differential equations and three are nonlinear partial
 differential equations. Dimensional analysis of these
 equations has yielded useful dimensionless parameters for
 evaluating the relative significance of each mechanism in
 remediation. Numerical experiments have been conducted to
 evaluate the effects of initial contaminant concentration,
 aggregate size, and soil-water partition factor. The total
 time of remediation has been found to depend on the rate at
 which contaminants are consumed within the large aggregates
 which, in turn, depends on the biodegradation kinetics and the
 rates of diffusion of substrate and oxygen in the aggregates.
 For soil with aggregates whose radius is 1 cm or larger, the
 results of simulation indicate that the remediation time for
 the aggregates is significantly longer compared to the
 corresponding result for homogeneous soil. For contaminants
 with large partition coefficients, the estimated time for
 remediation achieved through microbial oxidation in situ is
 much shorter than that achieved through purely diffusional
 transport of the contaminants out of the soil bed.
 
 
 156                                 NAL Call. No.: TD419.R47 A
 model for evaluating the impacts of land application of
 organic waste on runoff water quality.
 Deizman, M.M.; Mostaghimi, S.
 Alexandria, Va. : The Federation; 1991 Jan.
 Research journal of the Water Pollution Control Federation v.
 63 (1): p. 17-27; 1991 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Organic wastes; Application to land; Organic
 fertilizers; Runoff water; Water pollution; Soil pollution;
 Simulation models; Agricultural land; Nitrogen;
 Transformation; Losses
 
 
 157                                 NAL Call. No.: 292.8 J82 A
 model for oxygen transport and consumption in the unsaturated
 zone. Refsgaard, J.C.; Christensen, T.H.; Ammentorp, H.C.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Dec.
 Journal of hydrology v. 129 (1/4): p. 349-369; 1991 Dec. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil water; Soil air; Oxygen transport; Oxygen
 consumption; Solutes; Transport processes; Unsaturated flow;
 Diffusion; Diffusivity; Soil water content; Crumbs; Size;
 Denitrification; Mathematical models
 
 Abstract:  An oxygen transport and consumption model has been
 developed as a submodel to a general numerical model for
 solute transport in the unsaturated zone. The model comprises
 diffusive and convective transport of oxygen in soil air,
 convective transport and oxygen consumption in free water, and
 diffusive transport and a constant-rate oxygen consumption in
 the water-saturated soil crumbs. The model also estimates the
 anaerobic fraction of the water-saturated crumbs where no
 oxygen consumption takes place. The model dynamics and
 applicability are illustrated using the examples of the
 operation of a waste water infiltration plant and of anaerobic
 zones in the soil of importance for modelling denitrification.
 
 
 158                                  NAL Call. No.: 56.9 SO3
 Model of boron movement in soils.
 Shani, U.; Dudley, L.M.; Hanks, R.J.
 Madison, Wis. : The Society; 1992 Sep.
 Soil Science Society of America journal v. 56 (5): p.
 1365-1370; 1992 Sep. Includes references.
 
 Language:  English
 
 Descriptors: Calcareous soils; Boron; Movement in soil;
 Transport processes; Simulation models; Mathematical models
 
 Abstract:  A model to predict B transport in calcareous soils
 is presented. The model considers one-dimensional, non-steady-
 state soil water flow, convective-dispersive solute transport
 of both noninteracting salt (i.e., Cl) and B. The model was
 designed to simulate field situations including infiltration,
 evaporation, transpiration, drainage, and water extraction by
 plant roots. Predictions were compared with field B profiles
 and column leaching studies. The model accurately simulated
 Bleaching from columns of B-contaminated soils under saturated
 and steady-state water flow conditions. Model simulations,
 Udder conditions of transient water flow and transient B
 concentrations in a column study, were in reasonable agreement
 with the measured values. Model predictions were also compared
 with evolving soil soluble-B profiles determined in a field
 study (5-7 yr) with repeated irrigation with saline, B-
 containing waters. Computed results of the B accumulation in
 the upper portion of the soil profile, and of the B front,
 were in good agreement with measured data.
 
 
 159                                  NAL Call. No.: TD172.J6
 Model simulation and regional pollution reduction strategies.
 Shirmohammadi, A.; Shoemaker, L.L.; Magette, W.L.
 New York, N.Y. : Marcel Dekker; 1992 Dec.
 Journal of environmental science and health : Part A :
 Environmental science and engineering v. 27 (8): p. 2319-2336;
 1992 Dec.  Includes references.
 
 Language:  English
 
 Descriptors: Maryland; Soil pollution; Groundwater pollution;
 Nitrogen; Losses; Erosion control; Coastal plains; Mountain
 areas; Plains; Tillage; Practice; Simulation models;
 Cultivation; Cropping systems; Fertilizers; Application
 methods
 
 
 160                                NAL Call. No.: 292.8 W295
 Modeling base flow soil water residence times from deuterium
 concentrations. Stewart, M.K.; McDonnell, J.J.
 Washington, D.C. : American Geophysical Union; 1991 Oct.
 Water resources research v. 27 (10): p. 2681-2693; 1991 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: New Zealand; Soil water; Transport processes;
 Rain; Water flow; Stream flow; Watersheds; Deuterium;
 Measurement; Mathematical models
 
 Abstract:  Three approaches to determining mean soil water
 residence times in a steep headwater catchment were
 investigated. The deuterium concentrations of soil water
 collected from 11 suction cup samplers at the Maimai M8
 catchment were determined weekly for 14 weeks and the results
 compared with those of rainfall in the same period. Deuterium
 variations in the suction samples were considerably delayed
 and diminished compared with the rainfall, indicating
 significant storage times and mixing with soil water. Soil
 matrix water at shallow levels (approximately 200 mm depth) in
 unsaturated soils was relatively responsive to fresh input,
 but deeper water and water near the stream subject to
 occasional water table rises showed much less variation.
 Steady state and non-steady state exponential models gave
 similar mean residence times, ranging from 12 to more than 100
 days for different locations. Three groups of soil water
 response were defined, comprising shallow, medium and deep
 (near-stream) soil locations based on the mean residence
 times. The nonsteady models revealed considerable week-to-week
 and longer variations in mean residence time for shallow soil
 (SL4), but indicated that steady state models could adequately
 represent the system in the overall period investigated. In
 the third approach, model types and parameters that gave the
 best fits to the soil water deuterium concentrations were
 determined. Exponential and especially dispersion models were
 the most satisfactory. Weighting the input (rainfall delta D)
 partially or fully with the amount of rainfall gave much worse
 fits than with the unweighted input, showing that much of the
 rainfall bypasses the soil matrix. The best fitting dispersion
 model (designated DM2) yielded the most accurate mean
 residence times: 13 days for shallow soil (SL4), 42 days for
 soil at 400 mm depth (SL5), both at midslope locations, and 63
 days for soil at 800 mm depth near the stream (SL2). Capillary
 flow was important for the unsaturated s
 
 
 161                      NAL Call. No.: KyUThesis 1991 Storm
 Modeling dynamic rill networks from random surfaces on
 moderate slopes. Storm, Daniel E.
 1991; 1991.
 2 v. : ill. ; 28 cm.  Includes vita and abstract.  Includes
 bibliographic refernces (l. 499-508).
 
 Language:  English
 
 Descriptors: Soil erosion; Drainage; Probabilities
 
 
 162                                NAL Call. No.: 292.8 W295
 Modeling infiltration for multistorm runoff events.
 Smith, R.E.; Corradini, C.; Melone, F.
 Washington, D.C. : American Geophysical Union; 1993 Jan.
 Water resources research v. 29 (1): p. 133-144; 1993 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Infiltration; Mathematical models; Soil water
 movement; Redistribution; Runoff; Soil water content; Rain;
 Storms; Simulation
 
 Abstract:  We present a relatively simple
 analytical/conceptual model for rainfall infiltration during
 complex storms. It is an approximate but physically based
 model which can treat intervals of either no rain, low rain,
 or evaporation. The infiltration model is based on the very
 general three-parameter analytic model of Parlange et al.
 (1982), extended to treat soils with very high initial water
 content. The redistribution model is based on profile
 extension with shape similarity. A wide range of soil types
 can be simulated. The model is tested by comparison with
 numerical solutions of Richards's equation carried out for a
 variety of events upon four selected soils. The model
 simulates the solution to Richards's equation quite
 accurately, provided basic soil retention relations are
 parametrically represented. It simulates redistribution
 particularly well for redistribution intervals up to 20 hours.
 The model usefulness in comparison with the common and simple
 approach which disregards soil water redistribution is also
 shown.
 
 
 163                                NAL Call. No.: 292.8 W295
 Modeling long-term solute transport in drained unsaturated
 zones. Kandil, H.; Miller, C.T.; Skaggs, R.W.
 Washington, D.C. : American Geophysical Union; 1992 Oct.
 Water resources research v. 28 (10): p. 2799-2809; 1992 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: Unsaturated flow; Transport processes; Solutes;
 Drained conditions; Soil water balance; Water table; Water
 quality; Prediction; Simulation; Mathematical models;
 Algorithms
 
 Abstract:  Long-term assessment of solute transport in the
 unsaturated zone is an important consideration for irrigation
 management, pesticide management, and subsurface contaminant
 restoration analysis and design. Mathematical models are often
 used to perform such analyses. Modeling fluid flow and solute
 transport in the unsaturated zone typically requires solution
 of the nonlinear Richards equation and an advective-dispersive
 equation for contaminant transport as a function of time. Such
 solutions are possible but computationally expensive. A
 simplified water balance approach to solve fluid flow in
 shallow, drained unsaturated zones has been developed and
 refined over the last 15 years. The objectives of this study
 were to use results from a water balance model to obtain
 solutions for solute transport in drained, shallow water table
 soils, and to compare the results with solutions based upon
 Richards' equation. Transient soil water flux rates computed
 with a water balance model were used as input to a Petrov-
 Galerkin advective-dispersive transport model to simulate
 solute transport in unsaturated soils. The transport model was
 checked for consistency by comparison with an analytical
 solution. Sample simulations showed good agreement between a
 Richards' equation-based transport model and a water balance-
 based transport model. Simulations were performed to show
 predicted trends in water quality over 1-year periods.
 
 
 164                                NAL Call. No.: 292.8 W295
 Modeling of carbon dioxide transport and production in soil.
 1. Model development.
 Simunek, J.; Suarez, D.L.
 Washington, D.C. : American Geophysical Union; 1993 Feb.
 Water resources research v. 29 (2): p. 487-497; 1993 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Carbon dioxide; Production; Transport processes;
 Spatial distribution; Water flow; Heat flow; Respiration; Soil
 biology; Soil chemistry; Prediction; Simulation models;
 Mathematical models
 
 Abstract:  Knowledge of the CO2 concentration in the
 unsaturated zone is essential for prediction of solution
 chemistry in the vadose zone and groundwater recharge as well
 as for quantifying carbon source/sink terms as part of the
 global CO2 mass balance. In this paper we present a predictive
 simulation model, SOILCO2, based on process-oriented
 relationships. The model includes one-dimensional water flow
 and multiphase transport of CO2 utilizing the Richards and the
 convection-dispersion equations, respectively, as well as heat
 flow and a CO2 production model. The transport of CO2 in the
 unsaturated zone can occur in both the liquid and gas phases.
 The gas transport equation accounts for production of CO2 and
 uptake of CO2 by plant roots associated with root water
 uptake. The CO2 production model considers both microbial and
 root respiration which is dependent on water content,
 temperature, growth, salinity and plant and soil
 characteristics. Heat flow is included, since some gas
 transport parameters, partitioning coefficients and production
 parameters are strongly temperature dependent. The resulting
 set of partial differential equations is solved numerically
 using the finite element and finite difference methods.
 
 
 165                                NAL Call. No.: 292.8 W295
 Modeling of carbon dioxide transport and production in soil.
 2. Parameter selection, sensitivity analysis, and comparison
 of model predictions to field data.
 Suarez, D.L.; Simunek, J.
 Washington, D.C. : American Geophysical Union; 1993 Feb.
 Water resources research v. 29 (2): p. 499-513; 1993 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: California; Missouri; Carbon dioxide; Production;
 Spatial distribution; Transport processes; Mathematical
 models; Simulation models; Prediction; Steady flow; Transient
 flow; Water flow; Heat flow; Triticum aestivum; Zea mays;
 Glycine max; Environmental factors
 
 Abstract:  In paper 1 of this two-paper series (Simunek and
 Suarez, this issue) we presented a description of the
 numerical model, SOILCO2, for CO2 transport and production in
 the unsaturated zone. In paper 2 the model sensitivity to
 various parameters is evaluated by both steady state and
 transient simulations, with a range in the parameter values
 typically found under field conditions. We also select
 parameter values for optimal plant and microbial CO2
 production and production dependence on temperature, water
 content, osmotic potential and gas composition for plant and
 microbial respiration, all based on literature review. The
 predictive capabilities of the SOILCO2 model are evaluated by
 comparing model simulations to published field data from
 Missouri for three different crops and two growing seasons
 under transient conditions as well as a data set collected in
 Riverside, California, under relatively constant water content
 at depth. The model provided good prediction of the CO2 flux
 to the atmosphere as well as the concentrations in the root
 zone for all data sets.
 
 
 166                          NAL Call. No.: TD1.E2 no.91/039
 Modeling of nonpoint source water quality in urban and non-
 urban areas. Donigian, Anthony S.; Huber, Wayne C.
 Environmental Research Laboratory (Athens, Ga.)
 Athens, Ga. : Environmental Research Laboratory, Office of
 Research and Development, U.S. Environmental Protection
 Agency,; 1991. vi, 72 p. : ill. (EPA/600/3 ; 91/039).  June
 1991.  Includes bibliographical references.
 
 Language:  English
 
 Descriptors: Water
 
 
 167                               NAL Call. No.: 290.9 AM32T
 Modeling pollutant transport in runoff and sediment.
 Ashraf, M.S.; Borah, D.K.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Nov. Transactions of the ASAE v. 35 (6): p.
 1789-1797; 1992 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Cyanazine; Nitrates;
 Phosphates; Pollutants; Rain; Runoff; Sediment; Simulation
 models
 
 Abstract:  A dynamic model was developed to simulate mixing of
 rainwater with soils containing agricultural nutrients and
 pesticides, entrainment of these pollutants to runoff, and
 their transport in runoff and sediment within a watershed and
 during a single storm event. The model is an advancement to
 the existing models in simulating chemical transport during
 individual storms. It routes infiltrating rainwater and
 solutes through the soil profile using concepts of complete
 mixing and piston displacement. When runoff begins, chemical
 exchange between runoff and a mixing soil layer of the soil
 profile, containing the chemicals in dissolved and adsorbed
 forms, are simulated using the concept of non-uniform mixing
 with respect to the soil layer depths. Entrained chemicals in
 runoff are routed along slope lengths in dissolved and
 adsorbed forms based on mass conservation. The basic model
 concepts and algorithms on chemical mixing and entrainment
 were tested for time varying concentrations of nitrate,
 phosphate, and cyanazine in runoff using a suitable laboratory
 data set found in the literature. A total of 15 model runs, 5
 for each pollutant, were made. Predicted concentrations were
 compared with the respective observed data. The comparisons
 showed that the concepts and the algorithms were valid and
 promising.
 
 
 168                                  NAL Call. No.: QH540.J6
 Modeling selenium transport in steady-state, unsaturated soil
 columns. Alemi, M.H.; Goldhamer, D.A.; Nielsen, D.R.
 Madison, Wis. : American Society of Agronomy; 1991 Jan.
 Journal of environmental quality v. 20 (1): p. 89-95; 1991
 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Selenium; Soil air; Soil chemistry; Soil flora;
 Soil sterilization; Transport processes; Adsorption; Leaching;
 Methodology; Microbial activities; Simulation models
 
 Abstract:  This study was conducted to characterize batch
 adsorption of selenate SeO4(2-), selenite (SeO4(2-), and
 selenomethionine (Se-CH2CH2CHNH2COOH)2 and transformations of
 Se in the presence of microbial activity in Panoche loam
 (fine-loamy, mixed, calcareous, thermic Typic Torriorthents).
 The effects of sterilization, enhanced microbial activity, and
 aerobic vs. anaerobic conditions on the transport of pulse-fed
 Se in soil columns were also investigated. Selenate was
 rapidly leached in the soil columns compared with
 selenomethionine and selenite both of which invaded the
 columns to only a limited extent. Adsorption was highest for
 selenite and least for selenate. Selenate was transformed to
 reduced and less mobile forms when soil was C-enriched,
 particularly with smaller water fluxes and under anaerobic
 conditions. Systems of partial differential equations (PDEs)
 involving equilibrium adsorption of Se are set up to simulate
 transport of selenate, selenite, and selenomethionine under
 sterilized conditions. The transport model is solved by an
 iterative procedure using a finite difference scheme.
 Experimentally determined adsorption parameters of selenite
 and selenomethionine did not produce a satisfactory fit when
 used in simulation of these Se species in column studies. The
 Se transport model adequately simulated Se concentrations in
 soil solution under sterilized conditions when the adsorption
 coefficients derived from batch experiments were adjusted. No
 transport modeling was considered for nonsterilized
 conditions.
 
 
 169                               NAL Call. No.: SB191.R5I59
 Modeling soil processes with N dynamics as an example.
 Kirk, G.J.D.; Rachhpal-Singh
 Manila : The Institute; 1991 Nov.
 IRRI research paper series - International Rice Research
 Institute (151): p. 39-42; 1991 Nov.  In the series analytic:
 Systems simulation at IRRI / edited by F.W.T. Penning de
 Vries, M.J. Kropff, P.S. Teng, and G.J.D. Kirk.  Includes
 references.
 
 Language:  English
 
 Descriptors: Urea fertilizers; Prediction; Transport
 processes; Volatilization; Simulation models; Computer
 simulation; Losses from soil systems; Nitrogen; Rhizosphere
 
 
 170                                NAL Call. No.: 292.8 W295
 Modeling solute transport influenced by multiprocess
 nonequilibrium and transformation reactions.
 Brusseau, M.L.; Jessup, R.E.; Rao, P.S.C.
 Washington, D.C. : American Geophysical Union; 1992 Jan.
 Water resources research v. 28 (1): p. 175-182; 1992 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Contaminants; Solutes; Transport processes;
 Sorption; Transformation; Degradation; Prediction; Simulation;
 Mathematical models
 
 Abstract:  We present an advective-dispersive solute transport
 model that explicitly accounts for multiple sources of
 nonequilibrium and transformation reactions during steady
 state flow in porous media. The multiprocess nonequilibrium
 with transformation (MPNET) model is formulated for cases
 where nonequilibrium, caused by a combination of transport-
 related and sorption-related processes, and abiotic/biotic
 transformations can be described as first-order processes. The
 impact of the coupling of nonequilibrium and transformation
 reactions on solute transport is examined using selected
 illustrative examples. The performance of the model is
 evaluated by comparing predictions obtained with the model,
 where values for all model parameters are obtained
 independently, to a data set obtained from the literature. The
 prediction obtained with the MPNET model matched the data very
 well, much better than did the predictions obtained with the
 MPNET model assuming no degradation and with a model that does
 not account for rate-limited sorption.
 
 
 171                                  NAL Call. No.: QH540.J6
 Modeling the influence of sorption and transformation on
 pesticide leaching and persistence.
 Boesten, J.J.T.I.; Linden, A.M.A. van der
 Madison, Wis. : American Society of Agronomy; 1991 Apr.
 Journal of environmental quality v. 20 (2): p. 425-435; 1991
 Apr.  Includes references.
 
 Language:  English
 
 Descriptors: Diuron; Aldicarb; Leaching; Persistence; Soil
 morphological features; Sandy soils; Mathematical models;
 Application date; Spring; Autumn; Continuous cropping; Zea
 mays; Water uptake; Water flow; Soil temperature;
 Precipitation; Evapotranspiration
 
 Abstract:  Pesticide leaching to ground water at 1 m depth and
 pesticide persistence in the plow layer were calculated with a
 mathematical model for a sandy soil continuously cropped with
 maize (Zea mays L.) and exposed to weather conditions in a
 temperate climate. The pesticide was applied in spring. In the
 model water flow was described by Darcy's law and water uptake
 by the crop was included. Daily averages of meteorological
 conditions (rainfall, evapotranspiration, soil temperature)
 were used as input. The model assumes first-order
 transformation, equilibrium sorption (Freundlich equation),
 and passive plant uptake. Pesticide leaching and persistence
 were calculated as a function of pesticide sorption
 (characterized by the organic-matter/water distribution
 coefficient, Kom) and of transformation rate. It was found
 that pesticide leaching is very sensitive to both Kom and the
 transformation rate: changing Kom or the transformation rate
 by a factor of 2 changes the fraction of the dose leached
 typically by about a factor of 10. Pesticide persistence in
 the plow layer was found to be sensitive to Kom at low
 transformation rates and sensitive to the transformation rate
 at high Kom values. Additional calculations showed that autumn
 application results in much higher leaching of nonsorbing
 pesticides with short half-lives than spring application
 (difference of two orders of magnitude).
 
 
 172                                NAL Call. No.: 292.8 W295
 Modeling the nonequilibrium transport of linearly interacting
 solutes in porous media: a review.
 Sardin, M.; Schweich, D.; Leij, F.J.; Van Genuchten, M.T.
 Washington, D.C. : American Geophysical Union; 1991 Sep.
 Water resources research v. 27 (9): p. 2287-2307; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Transport processes; Solutes; Aggregates;
 Porosity; Soil pore system; Time; Dynamics; Kinetics;
 Mathematical models
 
 Abstract:  The transport of linearly interacting solutes in
 porous media is investigated with the help of residence time
 distributions, transfer functions, methods of system dynamics,
 and time-moment analyses. The classical one-dimensional
 convection-dispersion equation is extended to two-region
 (mobile-immobile water) transport by including diffusional
 mass transfer limitations characteristic of aggregated soils.
 The two-region model is further revised by incorporating the
 effects of multiple retention sites (in parallel or in
 series), multiple porosity levels, and arbitrary but steady
 flow fields. It is shown that different physical situations
 can be represented by a relatively small number of transfer
 functions containing only two types of parameters:
 distribution coefficients to account for equilibrium
 properties and characteristic times reflecting kinetic
 processes. Relevant kinetic processes include convective
 transport, hydrodynamic dispersion, adsorption-desorption, and
 physical or chemical mass transfer limitations. In most
 situations, theoretical breakthrough curves are found to be
 relatively insensitive to the mathematical structure of the
 transfer function, irrespective of the physical interpretation
 of the distribution coefficients and the characteristic times
 in the model. This means that alternative physical and
 chemical interpretations of model parameters can lead to
 nearly identical breakthrough curves. Certain transfer time
 distributions can lead to quite unusual shapes in the
 breakthrough curves; these curves strongly depend on the
 characteristic times and a few operational variables. Results
 of this study show that the transfer time distribution is an
 extremely useful tool for explaining some unexpected
 experimental results in the solute transport literature.
 
 
 173                                  NAL Call. No.: 56.9 SO3
 Modeling the transport and retention of cadmium in soils:
 multireaction and muticomponent approaches.
 Selim, H.M.; Buchter, B.; Hinz, C.; Ma, L.
 Madison, Wis. : The Society; 1992 Jul.
 Soil Science Society of America journal v. 56 (4): p.
 1004-1015; 1992 Jul. Includes references.
 
 Language:  English
 
 Descriptors: Soil types (genetic); Cadmium; Transport
 processes; Heavy metals; Retention; Kinetics; Mathematical
 models; Simulation models; Ion exchange; Sorption
 
 Abstract:  A major challenge in modeling the mobility or
 solutes in soils is to take into account the time-dependent
 retention of reactive solutes in a transport model that can be
 evaluated by independent experiments. The kinetics of
 retention and transport or Cd in two soils were investigated
 in this study. Time-dependent batch experiments were carried
 out to describe the extent of Cd sorption by two soils.
 Miscible-displacement experiments were conducted to quantify
 Cd transport in soil columns that received single and multiple
 Cd pulses. A multi-reaction convective-dispersive transport
 model inadequately predicted effluent concentrations for both
 soils when independently measured parameters of retention-
 release rate coefficients were obtained from batch data sets.
 We developed a multicomponent approach that accounts for
 reversible and irreversible Cd retention during transport in
 soils. Retention mechanisms considered include instantaneous
 equilibrium ion exchange and a specific sorption process that
 was based on a second-order (Langmuir) kinetic reaction. The
 multicomponent model adequately predicted the observed
 breakthrough results. The use of kinetic ion exchange and
 specific sorption for irreversible retention provided improved
 overall predictions of the results. Parameter values used for
 the rates of specific sorption (kf) and that for kinetic ion
 exchange (alpha) which provided improved predictions for
 single-pulse applications, were similar to those used for
 multiple-pulse applications. This finding was consistent for
 both soils and was considered to add credence to our
 multicomponent model.
 
 
 174                                    NAL Call. No.: 30 AD9
 Modeling the transport and retention of inorganics in soils.
 Selim, H.M.
 San Diego, Calif. : Academic Press; 1992.
 Advances in agronomy v. 47: p. 331-384; 1992.  Literature
 review.  Includes references.
 
 Language:  English
 
 Descriptors: Soil chemistry; Solutes; Transport processes;
 Leaching; Movement in soil; Mathematical models; Literature
 reviews
 
 
 175                               NAL Call. No.: QH545.A1E58
 Modelling pesticide movement in forested watersheds: use of
 PRZM for evaluating pesticide options in loblolly pine stand
 management. Dowd, J.F.; Bush, P.B.; Neary, D.G.; Taylor, J.W.;
 Berisford, Y.C. Tarrytown, N.Y. : Pergamon Press; 1993 Mar.
 Environmental toxicology and chemistry v. 12 (3): p. 429-439;
 1993 Mar.  Paper presented at the "Symposium on Pesticides in
 Forest Management, 11th Annual Meeting of the Society of
 Environmental Toxicology and Chemistry," November 11-15, 1990,
 Arlington, Virginia.  Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Pesticides; Watersheds; Forests; Pinus
 taeda; Leaching; Profiles; Weather; Climatic factors; Soil
 water movement; Forest management; Simulation models;
 Prediction
 
 
 176                                 NAL Call. No.: 292.8 J82
 Modelling surface runoff contamination by soil chemicals under
 transient water infiltration.
 Wallach, R.; Shabtai, R.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Mar.
 Journal of hydrology v. 132 (1/4): p. 263-281; 1992 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Contamination; Soil
 water; Runoff; Overland flow; Rain; Solutes; Transport
 processes; Infiltration; Sloping land; Relationships;
 Prediction; Mathematical models
 
 Abstract:  A model was developed to predict the potential
 contamination of overland flow by chemicals removed from soil
 water by rainfall on sloping soil. The model accounts for
 transient water infiltration, overland flow and convective-
 dispersive solute transport in the soil. Solutes are assumed
 to be subjected to linear equilibrium sorption onto the soil's
 solid phase. Numerical simulations indicated that the value of
 the coefficient for soil chemical transfer to surface runoff
 does not affect the soil surface concentration when soil is
 initially dry, but is linearly related to the dissolved
 chemical flux to overland flow. This enables an approximate
 solution to the convective-dispersive equation for determining
 soil surface concentration, independent of its determination
 from rainfall-runoff relationships. Simulated dissolved
 chemical concentrations at the soil surface and in surface
 runoff were determined for different antecedent soil moistures
 and rainfall intensities. These concentrations were found to
 be lower when antecedent moisture was low, because ponding
 time for drier soils is longer and during this period soil
 solutes are therefore displaced downward by greater volumes of
 infiltrating water. For a specified initial soilwater content,
 higher rainfall rates cause higher dissolved chemical
 concentrations at the soil surface and in runoff water. The
 hydrological parameters (e.g. soil-surface slope, length and
 roughness) affecting the residence time of surface water on
 the field, greatly affect runoff concentration for a short
 time after the initiation of overland flow. The runoff
 concentration for longer periods is mainly affected by soil
 surface concentration, which is in turn controlled by the
 dispersion of the chemicals in the soil. The distribution
 coefficient between the liquid and solid phases of the soil
 controls the release of adsorbed chemicals to the soil
 solution and therefore affects the runoff concentration.
 
 
 177                                 NAL Call. No.: 56.8 J823
 Modelling water and solute transport in macroporous soil. I.
 Model description and sensitivity analysis.
 Jarvis, N.J.; Jansson, P.E.; Dik, P.E.; Messing, I.
 Oxford : Blackwell Scientific Publications; 1991 Mar.
 The Journal of soil science v. 42 (1): p. 59-70; 1991 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil physics; Macropore flow; Solutes;
 Macropores; Transport processes; Mathematical models;
 Diffusion models; Equations
 
 Abstract:  A detailed mechanistic model of water movement and
 transport of non-reactive solute in a macroporous soil is
 described. One important feature of the model is that it may
 be run in either one or two flow domains using the same values
 for the hydraulic properties characterizing the soil. Water
 and solute movement in the micropores is calculated with the
 Richards and convection-dispersion equations and, in two
 domains, this is coupled to fluxes of water and solute in the
 macropores by empirical interaction terms. These interaction
 terms are redundant in the one-domain model, which simply
 reduces to the non-steady state convection-dispersion
 equation. A sensitivity analysis is presented showing how it
 is possible to identify conditions under which a macropore
 flow domain may need to be considered. In part II (Jarvis et
 al., 1991), the model is evaluated under field conditions in
 chloride breakthrough experiments in soil monolith lysimeters.
 
 
 178                                 NAL Call. No.: 56.8 J823
 Modelling water and solute transport in macroporous soil. II.
 Chloride breakthrough under non-steady flow.
 Jarvis, N.J.; Bergstrom, L.; Dik, P.E.
 Oxford : Blackwell Scientific Publications; 1991 Mar.
 The Journal of soil science v. 42 (1): p. 71-81; 1991 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil physics; Macropore flow; Solutes; Chlorides;
 Leaching; Prediction; Topsoil; Hydraulic conductivity;
 Porosity; Clay soils; Mathematical models; Diffusion models
 
 Abstract:  A model of water and solute transport in
 macroporous soils (Jarvis et al., 1991) has been evaluated in
 column breakthrough experiments under field conditions.
 Hydraulic properties were first measured in replicate soil
 monolith lysimeters sampled from grass ley and continuous
 barley treatments in a clay soil. A pulse input of 0.05 M KCl
 was then supplied by drip irrigation and measurements made of
 the water discharge and chloride leaching resulting from the
 natural rainfall over a 1-month period. The results showed
 that the macropores constituted the dominant flow pathway
 (accounting for 80% of the total water outflow) and that
 diffusive exchange of chloride between the two flow domains
 was the main factor causing variability in leaching. Larger
 hydraulic conductivities and macroporosities in the lower
 topsoil and at plough depth in the grass ley monoliths were
 taken as evidence of structural amelioration. Less of the
 applied chloride was leached in the grass monoliths than in
 the barley (means of 20% and 31% respectively). This was
 mainly due to a smaller effective aggregate size and thus a
 more efficient diffusion-controlled retention.
 
 
 179                               NAL Call. No.: 290.9 AM32T
 Modification of EPIC to incorporate drainage systems.
 Sabbagh, G.J.; Bengtson, R.L.; Fouss, J.L.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Mar. Transactions of the ASAE v. 34 (2): p.
 467-472; 1991 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Louisiana; Drainage; Erosion; Evapotranspiration;
 Runoff; Simulation models; Water table; Watersheds; Zea mays;
 Crop production
 
 Abstract:  EPIC-WT is a modified verison of the Erosion
 Productivity Impact Calculator (EPIC). It is capable of
 determining the relationship between soil erosion and soil
 productivity, simulating the daily watertable fluctuations,
 and predicting the effect of subsurface drainage systems on
 the water budget components for shallow watertable soils.
 Validation of the performance of EPIC-WT in simulating surface
 and subsurface drained flows, daily watertable fluctuations,
 sediment loss, and crop yield was conducted over seven years
 (1981-1987) on a clay loam soil near Baton Rouge, LA.
 Satisfactory results were obtained.
 
 
 180                               NAL Call. No.: 290.9 AM32T
 Modification of Epic to simulate pesticide activities: EPIC-
 PST. Sabbagh, G.J.; Geleta, S.; Elliott, R.L.; Williams, J.R.;
 Griggs, R.H. St. Joseph, Mich. : American Society of
 Agricultural Engineers; 1991 Jul. Transactions of the ASAE v.
 34 (4): p. 1683-1692; 1991 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Louisiana; Atrazine; Metolachlor;
 Groundwater; Leaching; Mathematical models; Runoff; Water
 pollution
 
 Abstract:  The need for a mathematical model capable of
 simulating simultaneously the effects of different
 agricultural management practices on crop yield, and chemical
 (nutrients and pesticides) losses by surface runoff, sediment
 movement and leaching below the rootzone has prompted the
 development of EPIC-PST. This model was developed by using
 EPIC as a building block and adopting from the GLEAMS model
 the pesticide related subroutines. EPIC-PST was evaluated by
 a) validating the incorporation of GLEAMS pesticide
 subroutines into EPIC; b) comparing chemical losses by runoff
 and chemical concentration in the soil profile with observed
 data from Ben Hur Research Farm, near Baton Rouge, Louisiana;
 and c) comparing chemical concentration in the soil profile
 with observed data from Dorminey farm near Tifton, Georgia. It
 was concluded from the evaluation that the incorporation of
 GLEAMS pesticide-related subroutines was successfully
 accomplished. EPIC-PST overestimated total Atrazine loss in
 runoff by 7% and underestimated total Metolachlor loss in
 runoff by 8% when compared to the values observed at Ben Hur
 Research Farm. For both sites, comparison of observed and
 predicted pesticide concentrations in the soil profile has
 shown that the model is apparently simulating faster movement
 of chemical through the rootzone than that observed in the
 field. However, the patterns in the changes of chemical
 concentration with time were similar to the observed.
 
 
 181                                    NAL Call. No.: S1.S68
 Moisture transport in plastic coverings.
 Sariev, A.L.; Kotovich, I.N.; Kobylyanskii, G.V.; Shukurov,
 M.S. New York, N.Y. : Allerton Press; 1991.
 Soviet agricultural sciences (5): p. 53-57; 1991.  Translated
 from: Vsesoiuznaia akademiia sel'skokhoziaistvennykh nauk.
 Doklady, (5), p. 53-56. (20 AK1).  Includes references.
 
 Language:  English; Russian
 
 Descriptors: Greenhouses; Plastic cladding; Condensation;
 Runoff; Mathematical models; Equations
 
 
 182                                  NAL Call. No.: 56.9 SO3
 Moment method applied to solute transport with binary and
 ternary exchange. Leij, F.J.; Dane, J.H.
 Madison, Wis. : The Society; 1992 May.
 Soil Science Society of America journal v. 56 (3): p. 667-674;
 1992 May. Includes references.
 
 Language:  English
 
 Descriptors: Solutes; Movement in soil; Cation exchange;
 Transport processes; Mathematical models; Simulation models;
 Hydrodynamic dispersion
 
 Abstract:  When modeling transport of exchanging solutes in
 soils, it is sometimes conveniently assumed that the solutes
 interact linearly with the solid phase of the soil. In this
 study, an attempt was made to quantify the influence of
 nonlinear cation exchange on solute spreading with the moment
 method. Theoretical expressions for the first four moments
 were derived based on the equilibrium and physical
 nonequilibrium models of the advection-dispersion equation
 (ADE). Displacement experiments were conducted in which either
 a NaCl pulse (binary exchange) or a pulse of KBr and NaBr
 (ternary exchange) was applied to a CaBr2-saturated medium.
 Values for the transport parameters were determined with
 moment analysis and curve fitting. The observed breakthrough
 curves were somewhat better reproduced with parameters
 obtained from curve fitting than from the moment method.
 However, the curve-fitting program produced some unrealistic
 parameter estimates for the nonequilibrium model. A
 disadvantage of the moment method was that the fourth-order
 moment sometimes yielded unstable results for the
 nonequilibrium model. Parameters form the anion displacement
 were used to estimate the theoretical variance due to
 hydrodynamic dispersion and nonequilibrium spreading for the
 cation breakthrough curves. The difference between the
 variance of the observed cation breakthrough curve and these
 theoretical variances was used as an approximation of the
 variance due to nonlinear exchange. Particularly for the
 ternary exchange, the variance due to nonlinear exchange was
 often several times greater than predicted according to the
 transport model. The results enabled us to quantify errors in
 dispersion coefficient (D) values directly determined from
 cation-displacement experiments.
 
 
 183                          NAL Call. No.: 290.9 AM3PS (IR)
 Movement of nonpoint-source contaminants through heterogeneous
 soils. Tracy, J.C.
 New York, N.Y. : American Society of Civil Engineers; 1992
 Jan. Journal of irrigation and drainage engineering v. 118
 (1): p. 88-103; 1992 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: U.S.A.; Groundwater; Groundwater pollution;
 Pollutants; Movement in soil; Transport processes; Seepage;
 Soil water content; Simulation; Probabilistic models;
 Deterministic models; Comparisons
 
 
 184                                  NAL Call. No.: 56.8 AU7
 Movement of solutes associated with intermittent soil water
 flow. I. Tritium and bromide.
 Scotter, D.R.; Tilman, R.W.
 East Melbourne : Commonwealth Scientific and Industrial
 Research Organization; 1991.
 Australian journal of soil research v. 29 (2): p. 175-183;
 1991.  Includes references.
 
 Language:  English
 
 Descriptors: Silt loam soils; Potassium bromide; Tritiated
 water; Soil water movement; Solutes; Movement in soil;
 Leaching; Diffusion; Equations; Hydrodynamic dispersion;
 Diffusion models
 
 
 185                                NAL Call. No.: 292.9 AM34
 Multicriterion analysis of groundwater contamination
 management. Shafike, N.G.; Duckstein, L.; Maddock, T. III
 Bethesda, Md. : American Water Resources Association; 1992
 Jan. Water resources bulletin v. 28 (1): p. 33-43; 1992 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Groundwater; Water
 management; Decision making; Water supply; Wastes; Costs;
 Mathematical models
 
 Abstract:  Multicriterion decision making (MCDM) techniques
 were used to analyze a groundwater contamination management
 problem from the viewpoint of conflicting multiple objectives.
 The groundwater management model was used to find a compromise
 strategy for trading off fresh water supply, containment of
 the waste, and total pumping cost in a hypothetical confined
 aquifer affected by previous waste disposal action. A
 groundwater flow model was used to formulate the hydraulic
 constraints. A linear system model was used to describe
 drawdown and velocity as functions of the decision variables
 which were pumping rates. The model determines the pumping
 location and rates. A modified epsilon-constraint method was
 used to generate the set of nondominated solutions which were
 the alternative compromise strategies. Three different MCDM
 techniques, Compromise programming (CP), ELECTRA II and MCQA
 II, were used to select a "satisficing" alternative. Analysis
 of the results showed that, although these techniques follow
 different principles, the same preferred strategies were
 reached. Also, it was noticed that maintaining high
 groundwater velocities is expensive and difficult. In order to
 meet a two year target date, large amounts of water had to be
 pumped. Therefore, rapid restoration results in large pumping
 volumes and high costs.
 
 
 186                                    NAL Call. No.: HD1.A3 A
 multi-objective dynamic programming model for evaluation of
 agricultural management systems in Richmond County, Virginia.
 Zhu, M.; Taylor, D.B.; Sarin, S.C.
 Essex : Elsevier Applied Science Publishers; 1993.
 Agricultural systems v. 42 (1/2): p. 127-152; 1993.  In the
 special issue: Application of dynamic optimization techniques
 to agricultural problems / edited by C.R. Taylor.  Includes
 references.
 
 Language:  English
 
 Descriptors: Virginia; Legumes; Farm management; Farming
 systems; Dynamic programming; Simulation models; Economic
 impact; Environmental impact; Nitrogen fertilizers
 
 
 187                               NAL Call. No.: 290.9 AM32T
 Multiobjective parameter estimation for hydrologic models--
 multiobjective programming.
 Yan, J.; Haan, C.T.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 May. Transactions of the ASAE v. 34 (3): p.
 848-856; 1991 May.  Includes references.
 
 Language:  English
 
 Descriptors: Oklahoma; Hydrology; Precipitation; Problem
 solving; Programming; Runoff; Simulation models; Watershed
 management
 
 Abstract:  A procedure for parameter estimation in
 multipurpose hydrologic models based on multiobjective
 programming is developed. The procedure helps overcome a
 problem which often occurs using traditional parameter
 estimation techniques-producing parameters that are good with
 respect to one objective but poor in terms of other
 objectives. The proposed method was tested using a
 precipitation runoff modeling system. The multiobjective
 function used had three objectives for estimating four
 parameters. It is shown that substantial improvement in
 parameter estimates can be obtained using the tested method.
 
 
 188                                  NAL Call. No.: QH540.N3
 Multiphase contaminants in natural permeable media: various
 modeling approaches.
 Corapcioglu, M.Y.; Panday, S.
 Berlin, W. Ger. : Springer-Verlag; 1993.
 NATO ASI series : Series G : Ecological sciences v. 32: p.
 191-220; 1993.  In the series analytic: Migration and fate of
 pollutants in soils and subsoils / edited by D. Petruzzelli
 and F.G. Helfferich. Proceedings of the NATO Advanced Study
 Institute, May 24-June 5, 1992, Maratea, Italy.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution;
 Pollutants; Transport processes; Mathematical models;
 Equations; Organic compounds; Groundwater flow; Soil water
 movement
 
 
 189                                  NAL Call. No.: HD101.S6
 Multiproduct production choices and pesticide regulation in
 Georgia. McIntosh, C.S.; Williams, A.A.
 Experiment, Ga. : The Association; 1992 Jul.
 Southern journal of agricultural economics - Southern
 Agricultural Economics Association v. 24 (1): p. 135-144; 1992
 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Pesticides; Uses; Groundwater pollution;
 Regulations; Agricultural production; Supply response; Profit
 functions; Econometric models; Economic impact; Taxes
 
 Abstract:  An increasing emphasis on surface and groundwater
 quality and food safety may result in some form of pesticide
 regulations. A restricted profit function model of Georgia
 agriculture is used to examine the short-run effects of 2 and
 5 percent reductions in all pesticides. Point estimates of
 short-run impacts, along with their 90 percent confidence
 intervals are presented.
 
 
 190                                NAL Call. No.: SF85.A1R32
 National rangeland hydrology study.
 Flanagan, M.
 Denver, Colo. : Society for Range Management; 1992 Aug.
 Rangelands v. 14 (4): p. 217-218; 1992 Aug.
 
 Language:  English
 
 Descriptors: Nebraska; Texas; Kansas; Wyoming; Colorado;
 Rangelands; Watersheds; Water quality; Vegetation; Erosion;
 Runoff; Models; Databases; Data analysis; Hydrological data;
 Plant communities
 
 
 191                                  NAL Call. No.: QH540.N3
 Nitrate ground-water modeling for agricultural and other
 nonpoint sources. Kelly, W.E.; Curtis, B.; Adelman, D.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 30: p.
 97-113; 1991.  In the series analytic: Nitrate contamination:
 Exposure, consequence, and control / edited by I. Bogardi and
 R.D. Kuzelka. Proceedings of the NATO Advanced Research
 Workshop on Nitrate Contamination: Exposure, Consequences, and
 Control, September 9-14, 1990, Lincoln, Nebraska.  Includes
 references.
 
 Language:  English
 
 Descriptors: Nebraska; Nitrate; Nitrate fertilizers;
 Groundwater pollution; Groundwater recharge; Farmland;
 Simulation models
 
 
 192                                    NAL Call. No.: QE1.E5
 Nitrate pollution of groundwater in the Alsatian Plain
 (France)--a multidisciplinary study of an agricultural area:
 the Central Ried of the Ill River.
 Bernhard, C.; Carbiener, R.; Cloots, A.R.; Froehlicher, R.;
 Schenck, C.; Zilliox, L.
 New York, N.Y. : Springer; 1992 Sep.
 Environmental geology and water sciences v. 20 (2): p.
 125-137; 1992 Sep. Includes references.
 
 Language:  English
 
 Descriptors: France; Groundwater pollution; Nitrates; Maize;
 Grain crops; Intensive cropping; Hydromorphic soils; Problem
 solving; Grasslands; Geomorphology; Soil types; Agricultural
 development; Land use; Models
 
 
 193                                NAL Call. No.: 292.8 W295
 Nitrate reduction in an unconfined sandy aquifer: water
 chemistry, reduction proceses, and geochemical modeling.
 Postma, D.; Boesen, C.; Kristiansen, H.; Larsen, F.
 Washington, D.C. : American Geophysical Union; 1991 Aug.
 Water resources research v. 27 (8): p. 2027-2045; 1991 Aug. 
 Includes references.
 
 Language:  English
 
 Descriptors: Nitrates; Soil pollution; Groundwater pollution;
 Aquifers; Arable land; Heathland; Coniferous forests; Land
 use; Transport processes; Reduction; Geochemistry; Models
 
 Abstract:  Nitrate distribution and reduction processes were
 investigated in an unconfined sandy aquifer of Quaternary age.
 Groundwater chemistry was studied in a series of eight
 multilevel samplers along a flow line, deriving water from
 both arable and forested land. Results show that plumes of
 nitrate-contaminated groundwater emanate from the agricultural
 areas and spread through the aquifer. The aquifer can be
 subdivided into an upper 10- to 15-m thick oxic zone that
 contains O2 and NO3(-), and a lower anoxic zone characterized
 by Fe2+-rich waters. The redox boundary is very sharp, which
 suggests that reduction processes of O2 and NO3(-) occur at
 rates that are fast compared to the rate of downward water
 transport. Nitrate-contaminated groundwater contains total
 contents of dissolved ions that are two to four times higher
 than in groundwater derived from the forested area. The
 persistence of the high content of total dissolved ions in the
 NO3(-) free anoxic zone indicates the downward migration of
 contaminants and that active nitrate reduction is taking
 place. Nitrate is apparently reduced to N2 because both
 nitrite and ammonia are absent or found at very low
 concentrations. Possible electron donors in the reduced zone
 of the aquifer are organic matter, present as reworked brown
 coal fragments from the underlying Miocene. and small amounts
 of pyrite at an average concentration of 3.6 mmol/kg. Electron
 balances across the redoxcline, based on concentrations of O2,
 NO3(-), SO4(2-) and total inorganic carbon (TIC), indicate
 that pyrite is by far the dominant electron donor even though
 organic matter is much more abundant. Groundwater transport
 and chemical reactions were modeled using the code PHREEQM,
 which combines a chemical equilibrium model with a one-
 dimensional mixing cell transport model. Only the vertical
 component of the water transport was modeled since, in
 contrast to rates along flow lines, the vertical rates are
 close to constant as required by the one-dimensio
 
 
 194                                 NAL Call. No.: 56.8 J822
 Nitrogen leaching sensitivity to evapotranspiration and soil
 water storage estimates in EPIC.
 Benson, V.W.; Potter, K.N.; Bogusch, H.C.; Goss, D.; Williams,
 J.R. Ankeny, Iowa : Soil and Water Conservation Society of
 America; 1992 Jul. Journal of soil and water conservation v.
 47 (4): p. 334-337; 1992 Jul. Includes references.
 
 Language:  English
 
 Descriptors: U.S.A.; Water quality; Nitrogen; Leaching;
 Movement in soil; Percolation; Soil water balance;
 Evapotranspiration; Soil water; Storage; Estimation;
 Methodology; Comparisons; Simulation models; Climatic zones;
 Meteorological factors; Geographical distribution; Spatial
 variation; Soil variability; Crop growth stage; Crop
 management
 
 
 195                                  NAL Call. No.: QH540.N3
 Nitrogen modeling on a regional scale.
 Rijtema, P.E.; Kroes, J.G.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 30: p.
 81-95; 1991.  In the series analytic: Nitrate contamination:
 Exposure, consequence, and control / edited by I. Bogardi and
 R.D. Kuzelka. Proceedings of the NATO Advanced Research
 Workshop on Nitrate Contamination: Exposure, Consequences, and
 Control, September 9-14, 1990, Lincoln, Nebraska.  Includes
 references.
 
 Language:  English
 
 Descriptors: Netherlands; Nitrate; Nitrate fertilizers; Water
 pollution; Groundwater pollution; Simulation models; Computer
 simulation; Runoff; Drainage; Farmland; Groundwater recharge
 
 
 196                                 NAL Call. No.: TD419.R47
 Nonpoint sources.
 Line, D.E.; Arnold, J.A.; Osmond, D.L.; Coffey, S.W.; Gale,
 J.A.; Spooner, J.; Jennings, G.D.
 Alexandria, Va. : The Federation; 1993 Jun.
 Water environment research v. 65 (4): p. 558-571; 1993 Jun. 
 Literature review.  Includes references.
 
 Language:  English
 
 Descriptors: Agricultural production; Agricultural chemicals;
 Water pollution; Models
 
 
 197                                 NAL Call. No.: TD419.R47
 Nonpoint sources.
 Spooner, J.; Coffey, S.W.; Brichford, S.L.; Arnold, J.A.;
 Smolen, M.D.; Jennings, G.D.; Gale, J.A.
 Alexandria, Va. : The Federation; 1991 Jun.
 Research journal of the Water Pollution Control Federation v.
 63 (4): p. 527-536; 1991 Jun.  Literature review.  Includes
 references.
 
 Language:  English
 
 Descriptors: Water pollution; Groundwater; Surface water; Land
 use; Activity; Agricultural land; Forest soils; Urban areas;
 Economics; Planning; Water quality; Water resources; Models;
 Reviews
 
 
 198                                  NAL Call. No.: QH540.N3
 Numerical modeling of contaminant transport in groundwater.
 Gambolati, G.; Paniconi, C.; Putti, M.
 Berlin, W. Ger. : Springer-Verlag; 1993.
 NATO ASI series : Series G : Ecological sciences v. 32: p.
 381-410; 1993.  In the series analytic: Migration and fate of
 pollutants in soils and subsoils / edited by D. Petruzzelli
 and F.G. Helfferich. Proceedings of the NATO Advanced Study
 Institute, May 24-June 5, 1992, Maratea, Italy.  Includes
 references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Pollutants; Transport
 processes; Groundwater flow; Soil water movement; Equations;
 Mathematical models
 
 
 199                                 NAL Call. No.: 292.8 J82
 Numerical simulation of infiltration and solute transport in
 an S-shaped model basin by a boundary-fitted grid system.
 Kinouchi, T.; Kanda, M.; Hino, M.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Jan.
 Journal of hydrology v. 122 (1/4): p. 373-406; 1991 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Subsurface layers; Soil water movement; Solutes;
 Transport processes; Rain; Simulation; Water; Discharge; Water
 distribution; Velocity; Unsaturated flow; Capillary fringe;
 Overland flow; Runoff; Groundwater; Mathematical models;
 Simulation models
 
 Abstract:  The boundary-fitted grid method, which transforms a
 complicated computational domain into a rectangular domain, is
 applied for the moisture and solute transport problems in the
 unsaturated soil layer of an S-shaped model hillslope. In the
 transformed domain, the fundamental equations of moisture and
 solute transport (i.e. the Richards equation and the Fickian
 equation) can be easily discretized into the finite-difference
 form. For three types of rainfall pattern (a unit rainfall,
 two-unit successive rainfalls and two unit rainfalls with a
 lag between them), hydrographs of total (pre-event and event
 water) and event water discharges, contour lines of soil
 moisture, pressure and total hydraulic head distributions, and
 flow velocity vectors are compared. For a relatively thick
 soil layer or for a relatively light rainfall, the capillary
 fringe effect plays an important role, whereas for a
 relatively thin soil layer or for a relatively heavy rainfall,
 overland flow from a variable source area is superimposed on
 the capillary-fringe-type runoff.
 
 
 200                                   NAL Call. No.: 10 J822
 Nutrient cycling and losses based on a mass-balance model in
 grazed pastures receiving long-term superphosphate
 applications in New Zealand. 1. Phosphorus. Nguyen, M.L.; Goh,
 K.M.
 Cambridge : Cambridge University Press; 1992 Aug.
 The Journal of agricultural science v. 119 (pt.1): p. 89-106;
 1992 Aug. Literature review.  Includes references.
 
 Language:  English
 
 Descriptors: New Zealand; Pastures; Phosphorus;
 Superphosphates; Cycling; Leaching; Grazing effects; Nutrient
 intake; Sheep; Simulation models; Literature reviews
 
 
 201                                   NAL Call. No.: 10 J822
 Nutrient cycling and losses based on a mass-balance model in
 grazed pastures receiving long-term superphosphate
 applications in New Zealand. 2. Sulphur. Nguyen, M.L.; Goh,
 K.M.
 Cambridge : Cambridge University Press; 1992 Aug.
 The Journal of agricultural science v. 119 (pt.1): p. 107-122;
 1992 Aug. Literature review.  Includes references.
 
 Language:  English
 
 Descriptors: New Zealand; Pastures; Fertilizer requirement
 determination; Sulfur; Superphosphates; Cycling; Grazing
 effects; Irrigated conditions; Leaching; Nutrient intake;
 Sheep; Simulation models; Literature reviews
 
 
 202                                   NAL Call. No.: 26 T754
 Nutrient leaching loss from two contrasting cropping systems
 in the humid tropics.
 Seyfried, M.S.; Rao, P.S.C.
 Guildford : Butterworth Scientific; 1991 Jan.
 Tropical agriculture v. 68 (1): p. 9-18; 1991 Jan.  Includes
 references.
 
 Language:  English
 
 Descriptors: Costa Rica; Cropping systems; Fertilizers;
 Leaching; Losses from soil systems; Nutrients; Soil fertility;
 Soil water balance; Simulation models; Humid tropics
 
 
 203                                 NAL Call. No.: TD426.J68
 One-dimensional immiscible displacement experiments.
 Thomson, N.R.; Graham, D.N.; Farquhar, G.J.
 Amsterdam : Elsevier; 1992 Aug.
 Journal of contaminant hydrology v. 10 (3): p. 197-223; 1992
 Aug.  Includes references.
 
 Language:  English
 
 Descriptors: Soil pollution; Immiscible displacement;
 Prediction; Models; Groundwater pollution; Water table
 
 
 204                                 NAL Call. No.: 292.8 J82
 One-dimensional solute transport modelling in aggregated
 porous media. 1. Model description and numerical solution.
 Lafolie, F.; Hayot, C.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 Mar01.
 Journal of hydrology v. 143 (1/2): p. 63-83; 1993 Mar01. 
 Special Issue: Modelling Flow and Transport in the Unsaturated
 Zone: Scale Problems and Spatial Variability.  Includes
 references.
 
 Language:  English
 
 Descriptors: Aggregates; Porosity; Macropores; Transport
 processes; Particle size distribution; Simulation models
 
 Abstract:  A model for the simulation of solute transport in
 aggregated porous media is presented. Transport by convection
 and dispersion in the mobile phase, diffusion of solute inside
 aggregates of arbitrary shapes and sizes, external mass
 transfer resistance and linear adsorption are considered.
 Depth-dependent properties of porous media and size
 distribution of aggregates are accounted for. The problem of
 solute diffusion inside arbitrarily shaped aggregates is
 rigorously and easily treated by application of the Laplace
 transformation and by introduction of an 'aggregate shape
 function'. The whole system of equations is solved by: (1)
 application of the Laplace transformation; (2) introduction of
 the 'aggregate shape function' to reduce the transport problem
 to a single ordinary differential equation whatever the
 geometry of aggregates and the phenomena accounted for
 (kinetic or instantaneous adsorption, external mass transfer
 resistance); (3) finite-difference numerical solution of this
 differential equation; (4) numerical inversion of the solution
 obtained in the Laplace space. The main advantages of this
 model are: (1) it incorporates, in a unique frame, the whole
 variety of models so far proposed for transport modelling in
 aggregated porous media (zero-, first- and higher order
 approaches); (2) it simplifies the numerical treatment so that
 there is no need to make simplifying assumptions about the
 phenomena; (3) it provides an accurate solution using very
 little computer time. The model is compared with previous
 solutions, analytical or numerical, obtained for simple
 aggregate geometries.
 
 
 205                                 NAL Call. No.: 292.8 J82
 One-dimensional solute transport modelling in aggregated
 porous media. 2. Effects of aggregate size distribution.
 Hayot, C.; Lafolie, F.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 Mar01.
 Journal of hydrology v. 143 (1/2): p. 85-107; 1993 Mar01. 
 Special Issue: Modelling Flow and Transport in the Unsaturated
 Zone: Scale Problems and Spatial Variability.  Includes
 references.
 
 Language:  English
 
 Descriptors: Aggregates; Porosity; Particle size distribution;
 Particle velocity; Transport processes; Diffusion;
 Mathematical models
 
 Abstract:  The influence of various aggregate size
 distributions on solute transport is analysed from a
 quantitative and qualitative point of view. Uniform, normal,
 log-normal and discrete aggregate size distributions are
 considered. The model described in Part 1 is used to calculate
 the breakthrough curves. The second-order moments and the sum
 of squared differences are used to compare the responses
 calculated with the distributions and with the mean radius.
 The influence of a distribution depends on the velocity, and
 consequently on the proportion of aggregates in situations of
 local equilibrium or physical non-equilibrium. Breakthrough
 curves calculated from normal distributions, whatever their
 spread, do not differ significantly from those calculated
 using the mean radii, while slightly skewed narrow
 distributions generate significant differences. Thus, the
 skewness and not only the spreading of the distribution seem
 to modify the spreading of solute. The problem of using a
 unique 'mean radius' instead of a distribution is also
 considered. It is shown that the problem does not have a
 simple answer. For a given distribution, the existence of an
 acceptable mean radius depends strongly on the contrast
 between the mobile phase residence time and the distribution
 of characteristic diffusion times. Also, intuitively,
 acceptable mean radii are more easily found for narrow
 distributions. In most cases, it appears that a mean radius
 cannot be used instead of the distribution. The analysis of
 the way the distributions modify the breakthrough curves
 suggests that simple bimodal distributions presenting fast-
 and slow-reacting sites could be used in lieu of complete
 distributions.
 
 
 206                                NAL Call. No.: 280.8 J822
 The on-farm costs of reducing groundwater pollution.
 Johnson, S.L.; Adams, R.M.; Perry, G.M.
 Ames, Iowa : American Agricultural Economics Association; 1991
 Nov. American journal of agricultural economics v. 73 (4): p.
 1063-1073; 1991 Nov. Includes references.
 
 Language:  English
 
 Descriptors: Oregon; Groundwater pollution; Nitrates; Economic
 impact; Farm management; Crop yield; Simulation models; Farm
 income; Costs; Farm inputs; Taxes; Dynamic models
 
 Abstract:  Agricultural chemicals are a source of groundwater
 pollution in some areas. Regulatory options to reduce such
 nonpoint pollution imply costs to producers. By integrating
 plant simulation, hydrologic, and economic models of farm-
 level processes, this study evaluates on-farm costs of
 strategies to reduce nitrate groundwater pollution. The
 empirical focus is on intensively managed, irrigated farms in
 the Columbia Basin of Oregon. Results suggest that changes in
 timing and application rates of nitrogen and water reduce
 nitrate pollution with little loss in profits. Once such
 practices are adopted, further reductions in nitrates can be
 achieved only at increasing costs to producers.
 
 
 207                                NAL Call. No.: 292.8 W295
 Optimal data acquisition strategy for the development of a
 transport model for groundwater remediation.
 Tucciarelli, T.; Pinder, G.
 Washington, D.C. : American Geophysical Union; 1991 Apr.
 Water resources research v. 27 (4): p. 577-588; 1991 Apr. 
 Includes references.
 
 Language:  English
 
 Descriptors: Groundwater; Water quality; Water management;
 Costs; Measurement; Stochastic models; Simulation models
 
 Abstract:  The reliability of groundwater quality management
 algorithms is limited in large part by the uncertainty present
 in the model parameters. Because the field parameter
 measurement costs and the remediation costs must be supplied
 by the same financial source, the classical optimization
 procedure does not minimize the real total remediation
 investment. This research presents an algorithm able to find
 the total minimum for the sum of both the measurement and the
 pumping costs. A chance-constrained technique is used to cast
 the optimization problem in stochastic form, relating the
 concentration covariance matrix to the log-transmissivity
 covariance matrix by means of the transport equations and a
 first-order approximation for the uncertainty. The simulation
 model solves the steady state flow equations on a finite
 element triangular mesh and the transport equations using the
 backward method of characteristics. The resulting nonlinearly
 constrained optimization problem is solved using the quasi-
 linearity algorithm; this algorithm is designed to find a good
 initial point for the local minimum search when the feasible
 domain is not convex.
 
 
 208                                NAL Call. No.: aS21.R44A7
 Opus: an integrated simulation model for transport of
 nonpoint-source pollutants at the field scale: volume I.
 Documentation.
 Smith, R.E.
 Beltsville, Md. : The Service; 1992 Jul.
 ARS - U.S. Department of Agriculture, Agricultural Research
 Service (98): 135 p.; 1992 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Pollution; Pollutants; Transport processes;
 Movement in soil; Hydrology; Computer simulation; Simulation
 models; Water flow; Meteorological factors; Growth models
 
 
 209                                NAL Call. No.: 292.8 W295 A
 partial contributing area model for linking rainfall
 simulation data with hydrographs of a small arid watershed.
 Ben-Asher, J.; Humborg, G.
 Washington, D.C. : American Geophysical Union; 1992 Aug.
 Water resources research v. 28 (8): p. 2041-2047; 1992 Aug. 
 Includes references.
 
 Language:  English
 
 Descriptors: Mali; Watersheds; Runoff water; Rain; Water
 harvesting; Measurement; Prediction; Simulation; Satellite
 imagery; Remote sensing; Catchment hydrology; Semiarid zones
 
 Abstract:  Four years of runoff measurement (29 events) in
 Kangussano, Mali, were analyzed on the basis of the partial
 area contribution concept. The study region is semiarid and
 the use of runoff water to satisfy crop consumption is of high
 importance. A first-order basin which included two flow
 channels draining an area of 1.14 X 10(6) ha (1.14 km(2)) was
 used for this purpose. The objective of this study was to
 develop and test a conceptual model to predict runoff on
 natural catchments of about this size. The model assumes that
 a basin is composed of a large number of pixels (satellite
 picture elements). Each pixel covers an area of 900 m(2). The
 hydraulic properties of a representative pixel are determined
 by runoff simulation experiments. The model calculates the
 number of runoff generating pixels at a given time and rain
 depth. The areal runoff is a product of these two factors.
 Analysis of satellite images from LANDSAT and SPOT indicated
 similarities of soil cover complexes between the study area
 and an experimental area in Upper Volta. Results of runoff
 simulation from this area were adapted for the study area and
 used for the calculations. A good agreement between predicted
 and measured contributing area was obtained when the number of
 runoff generating pixels was 80 pixels/mm effective rain.
 Predicted and measured hydrographs were also in good
 agreement. It was therefore concluded that the model can
 satisfactorily predict actual hydrographs from data generated
 by rainfall-runoff simulators. Dividing the watershed to
 surface elements of pixel's size makes the model capable of
 linking remote sensing information with simulation data in
 order to predict areal runoff.
 
 
 210                                NAL Call. No.: 292.8 W295
 Partitioning solute transport between infiltration and
 overland flow under rainfall.
 Havis, R.N.; Smith, R.E.; Adrian, D.D.
 Washington, D.C. : American Geophysical Union; 1992 Oct.
 Water resources research v. 28 (10): p. 2569-2580; 1992 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: Pollutants; Solutes; Transport processes;
 Infiltration; Overland flow; Rain; Surface water; Soil depth;
 Interactions; Mathematical models; Field experimentation
 
 Abstract:  Solute transport from soil to overland flow is an
 important source of nonpoint pollution and was investigated
 through tracer studies in the laboratory and at an outdoor
 laboratory catchment. The depth of surface water interaction
 with soil, defined as the mixing zone is a useful value for
 approximate estimation of potential solute transport into
 surface water under rainfall. It was measured in the
 laboratory for a noninfiltration case (0.90 to 1.0 cm) and
 estimated through mass balance modeling for an infiltration
 case (0.52 and 0.73 cm). At an outdoor laboratory catchment,
 mixing zones were calculated through calibration of a
 numerical model that describes unsteady, uniform, infiltration
 and chemical transport. Overland flow was simulated using
 kinematic wave theory. Mixing zone depths ranged from 0.47 to
 1.02 cm and were a linear function of rainfall intensity.
 Also, the fraction of solute present in the mixing zone at the
 time of ponding which was extracted into overland flow was a
 linear function of the initial soil moisture content. A steady
 state analytical approximation of the solute transport model
 was also developed which overpredicted solute transport into
 overland flow by 1 to 60%.
 
 
 211                               NAL Call. No.: 290.9 AM32T
 PATS: pesticide availability and transfer simualtor.
 Kenimer, A.L.; Mitchell, J.K.; Bode, L.E.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 May. Transactions of the ASAE v. 35 (3): p.
 841-853; 1992 May.  Includes references.
 
 Language:  English
 
 Descriptors: Alachlor; Terbufos; Pesticides; Absorption;
 Availability; Computer software; Losses from soil systems;
 Runoff; Simulation models
 
 Abstract:  A computer model was developed to simulate the
 availability of pesticides in the soil matrix and uptake of
 these pesticides into overland flow. The Pesticide
 Availability and Transfer Simulator, PATS, accounts for the
 distribution of chemical within soil, adsorption kinetics, and
 chemical release from soil to overland flow. PLIERS, Pesticide
 Losses In Erosion and Runoff Simulator, was used to simulate
 surface transport of pesticides. Hydrologic data required by
 PATS and PLIERS were generated by the distributed parameter
 hydrologic model ANSWERS. PLIERS was enhanced through the
 incorporation of PATS. Performance of enhanced model was
 evaluated by comparing model predictions to observed data.
 PATS-enhanced PLIERS dissolved pesticide loss predictions were
 similar to predictions made with PLIERS alone and were in
 reasonably good agreement with observed data. PATS-enhanced
 PLIERS adsorbed pesticide loss predictions were frequently
 lower than observed losses, but were generally closer to
 observed losses than were PLIERS adsorbed pesticide loss
 predictions.
 
 
 212                              NAL Call. No.: 100 SO82 (3)
 Pesticide, nutrient and salt movement through the root zone.
 Carlson, C.G.
 Brookings, S.D. : The Station; 1991.
 TB - Agricultural Experiment Station, South Dakota State
 University (97): 6 p. (soil PR 90-41); 1991.  Includes
 references.
 
 Language:  English
 
 Descriptors: South Dakota; Pesticides; Nutrients; Root zone
 flux; Groundwater pollution; Models
 
 
 213                                 NAL Call. No.: SB610.W39
 Pesticide runoff simulations: long-term annual means vs. event
 extremes?. Leonard, R.A.; Truman, C.C.; Knisel, W.G.; Davis,
 F.M.
 Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 725-730; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Simulation models; Pesticides; Runoff; Losses
 from soil; Rain; Simulation
 
 
 214                                  NAL Call. No.: QD241.T6
 Pesticide transport modelling in soil for risk assessment of
 groundwater contamination.
 Matthies, M.; Behrendt, H.
 London : Gordon and Breach Science Publishers; 1991.
 Toxicological and environmental chemistry v. 31/32: p.
 357-365; 1991. Includes references.
 
 Language:  English
 
 Descriptors: 2,4,5-t; Pesticide residues; Movement in soil;
 Soil water movement; Groundwater pollution
 
 Abstract:  The risk of groundwater contamination with
 pesticides applied to soil surface depends on the soil
 properties, the agricultural practices, the climatic
 influences, and on the properties of the pesticides
 themselves. The EXSOL model was developed for the simulation
 of the transport and fate of pesticides and organic in soils.
 The dynamics of mobility, accumulation and degradation can be
 studied under various soil and climatic conditions. Transient
 water flow is provided from a simulation model of the field
 water balance. The percentages of the herbicide 2,4-5-
 trichlorophenoxyacetic acid in a luvisol soil after a single
 application in summer are compared with model calculations
 using sorption coefficients from laboratory column studies.
 The calculated percentages lie within the measured range,
 except for those in the deeper soil layer. The underestimation
 can be explained with preferential flow in macropores which
 may have occurred during the heavy rainfall six days after
 application.
 
 
 215                               NAL Call. No.: HD1773.A2N6
 Physical and economic model integration for measurement of the
 environmental impacts of agricultural chemical use.
 Antle, J.M.; Capalbo, S.M.
 Morgantown, W.Va. : The Northeastern Agricultural and Resource
 Economics Association; 1991 Apr.
 Northeastern journal of agricultural and resource economics v.
 20 (1): p. 68-82; 1991 Apr.  Paper submitted in response to
 call for papers on the theme "The Effects of Agricultural
 Production on Environmental Quality.".  Includes references.
 
 Language:  English
 
 Descriptors: Groundwater; Surface water; Water quality;
 Agricultural chemicals; Usage; Environmental impact;
 Measurement; Agricultural production; Cost benefit analysis;
 Models
 
 
 216                                  NAL Call. No.: S601.A34
 Potential contribution of ploughed grassland to nitrate
 leaching. Whitmore, A.P.; Bradbury, N.J.; Johnson, P.A.
 Amsterdam : Elsevier; 1992 Apr.
 Agriculture, ecosystems and environment v. 39 (3/4): p.
 221-233; 1992 Apr. Includes references.
 
 Language:  English
 
 Descriptors: England; Wales; Leaching; Nitrate nitrogen;
 Nitrogen; Plowing; Grassland soils; Soil organic matter;
 Losses from soil systems; Runoff water; Drinking water;
 Mathematical models
 
 
 217                                   NAL Call. No.: QD1.A45
 Potential leaching of herbicides applied to golf course
 greens. Smith, A.E.; Tillotson, W.R.
 Washington, D.C. : The Society; 1993.
 ACS Symposium series - American Chemical Society (522): p.
 168-181; 1993.  In the series analytic: Pesticides in urban
 environments: Fate and significance / edited by K.D. Racke and
 A.R. Leslie. Paper presented at the 203rd National Meeting of
 the American Chemical Society, April 5-10, 1992, San
 Francisco, California.  Includes references.
 
 Language:  English
 
 Descriptors: 2,4-d; Herbicide residues; Leaching; Golf
 courses; Golf green soils; Cynodon dactylon; Mathematical
 models; Simulation models
 
 Abstract:  A critical issue facing the turfgrass industry is
 the environmental fate and safety of pesticides used in the
 management of national facilities. The purpose of our research
 program was to develop a data base for the determination of
 the potential movement of pesticides from golf course greens
 into potable aquifers. Lysimeters were developed, in the
 greenhouse, for the measurement of herbicide leaching from
 simulated greens. Data were obtained from lysimeters
 containing 'Tifdwarf' bermudagrass maintained as simulated
 greens and receiving treatments of the dimethylamine salt of
 2,4-D as a split application at rates of 0.56 + 0.56 kg ae
 ha-1 on a two week interval. Only minute quantities of 2,4-D
 were detected in the effluent from the lysimeters containing
 two mixtures of rooting media. These data were compared to the
 estimated values obtained from the GLEAMS mathematical model
 simulations using parameters independently determined to
 describe the lysimeter system. The GLEAMS model overestimated
 the actual data-values received from the lysimeter experiments
 on the potential for 2,4-D to leach through both rooting-media
 profiles.
 
 
 218                                 NAL Call. No.: TC401.W27
 The potential of runoff-farming in the Sahel region:
 developing a methodology to identifiy suitable areas.
 Tauer, W.; Prinz, D.; Vogtle, T.
 Hingham, Mass. : Kluwer Academic Publishers; 1991.
 Water resources management v. 5 (3/4): p. 281-287; 1991. 
 Includes references.
 
 Language:  English
 
 Descriptors: West  Africa; Runoff farming; Runoff irrigation;
 Site selection; Crops; Water requirements; Soil; Water
 storage; Capacity; Models
 
 
 219                               NAL Call. No.: 290.9 AM32T
 Potential runoff quality effects of poultry manure slurry
 applied to fescue plots.
 Edwards, D.R.; Daniel, T.C.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Nov. Transactions of the ASAE v. 35 (6): p.
 1827-1832; 1992 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Arkansas; Poultry manure; Runoff; Soil
 amendments; Water quality; Simulation models
 
 Abstract:  A 3 X 2 factorial experiment was conducted to
 determine how quality of runoff from grassed areas amended
 with poultry manure slurry is affected by slurry application
 rate and rainfall intensity for storms occurring one day
 following application. Poultry manure slurry was applied at
 rates of 0, 220, and 879 kg N ha-1 to plots established with
 fescue grass on a Captina silt loam soil. Simulated rainfall
 was applied 24 h following slurry application at intensities
 of 5 and 10 cm h-1 until runoff had occurred for a duration of
 0.5 h. Flow-weighted composite runoff samples were collected
 and analyzed for total Kjeldahl N, ammonia N, nitrate N, total
 P, dissolved reactive P, chemical oxygen demand, total
 suspended solids, and electrical conductivity. Effects of the
 experimental variables on both runoff concentrations and mass
 losses of slurry constituents were assessed by analyses of
 variance. Increasing slurry application rate significantly
 increased runoff concentrations of all slurry constituents
 investigated except nitrate N. For the affected slurry
 constituents, the relationships between runoff concentration
 of the constituent and slurry application rate appeared to be
 linear over the range of application rates used. Mass losses
 of all slurry constituents except nitrate N significantly
 increased with increases in both slurry application rate and
 rainfall intensity. Relationships between mass losses and
 slurry application rate also appeared to be linear for the
 range of application rates used in the study.
 
 
 220                          NAL Call. No.: 290.9 AM3PS (IR)
 Precipitation distributions and Green-Ampt runoff.
 Van Mullem, J.A.
 New York, N.Y. : American Society of Civil Engineers; 1991
 Nov. Journal of irrigation and drainage engineering v. 117
 (6): p. 944-959; 1991 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Montana; Drainage; Runoff; Water distribution;
 Precipitation; Storms; Flow; Green and ampt equation;
 Infiltration; Prediction; Models
 
 
 221                                  NAL Call. No.: 56.9 SO3
 Predicting cation mobility in kaolinitic media based on
 exchange selectivities of kaolinite.
 Gaston, L.A.; Selim, H.M.
 Madison, Wis. : The Society; 1991 Sep.
 Soil Science Society of America journal v. 55 (5): p.
 1255-1261; 1991 Sep. Includes references.
 
 Language:  English
 
 Descriptors: Louisiana; Hapludults; Kaolinite; Sand; Subsoil;
 Cation exchange; Cation exchange capacity; Exchangeable
 cations; Calcium; Magnesium; Exchangeable sodium; Spatial
 distribution; Movement in soil; Transport processes;
 Mathematical models; Adsorption; Soil solution; Soil water;
 Potassium; Pores; Physicochemical properties; Prediction
 
 Abstract:  Predictive modeling of cation transport in soils
 requires knowledge of the distribution of exchangeable species
 between solution and adsorbed phases. Such distribution of
 exchangeable species may be described with an exchange
 selectivity coefficient. Typically, the selectivity
 coefficient for any cation-exchange pair varies among soils.
 If the exchange complex of a soil is dominated by one type of
 exchanger, however, then the selectivity coefficient for that
 soil may be similar in magnitude to that for the principal
 mineral (or organic) constituent. Therefore, reasonably
 accurate predictions of cation transport in that soil might be
 obtained using exchange data for the dominant exchange
 material. This study was undertaken to determine whether
 exchange data for kaolinite could be successfully used in
 predicting Ca, Mg, and Na retention during movement in a Mahan
 series soil (clayey, kaolinitic, thermic Typic Hapludult).
 Binary-exchange isotherms for Ca-Mg, Ca-Na, and Mg-Na were
 generated for Ga-1 kaotinite (well crystallized). Selectivity
 coefficients derived from these data were used to describe
 cation exchange during miscible displacement through columns
 of (i) kaolinite admixed with acid-washed sand and (ii) Mahan
 soil. Use of the selectivity coefficients for kaotinite
 provided good predictions of cation transport in the
 kaolinite/sand mixture. Predictions for the kaolinitic Mahan
 soil were not as good. The presence of small amounts of 2:1
 minerals may have influenced the overall exchange behavior of
 the Mahan soil. When the uncertainty in values for selectivity
 coefficients and other exchange or transport parameters was
 considered, however, the exchange selectivity data for
 kaolinite could adequately describe cation transport in the
 Mahan soil.
 
 
 222                                  NAL Call. No.: 56.8 AU7
 Predicting exchangeable cation distributions in soil by using
 exchange coefficients and solution activity ratios.
 Phillips, I.R.; Black, A.S.
 East Melbourne : Commonwealth Scientific and Industrial
 Research Organization; 1991.
 Australian journal of soil research v. 29 (3): p. 403-414;
 1991.  Includes references.
 
 Language:  English
 
 Descriptors: Exchangeable cations; Potassium; Magnesium;
 Movement in soil; Distribution; Leaching; Prediction; Models;
 Equilibrium; Soil solution; Soil water content
 
 
 223                               NAL Call. No.: 290.9 AM32T
 Predicting runoff of water, sediment, and nutrients from a New
 Zealand grazed pasture using CREAMS.
 Cooper, A.B.; Smith, C.M.; Bottcher, A.B.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Jan. Transactions of the ASAE v. 35 (1): p.
 105-112; 1992 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: New Zealand; Grassland management; Grazing
 effects; Hydraulic conductivity; Losses from soil systems;
 Prediction; Runoff; Water quality; Computers; Simulation
 models
 
 Abstract:  The ability of the CREAMS model to predict loadings
 of runoff, sediment and nutrients from a New Zealand grazed
 pasture was evaluated. Before use, CREAMS was adapted to
 better represent N and P cycling in grazed pastures and the
 seasonal variation in hydraulic conductivity observed at the
 site. There was a moderately strong relationship (r2 = 0.81)
 between daily surface runoff volumes predicted by this
 modified model and volumes measured at the site for 62 events
 over a three and one half year period. Although the ability of
 the model to predict daily losses of sediment and nutrients
 was considerably less (r2 < 0.45), the model was always an
 unbiased predictor. This unbiased predictive ability provides
 good estimates of losses over longer time scales (e.g.,
 seasonal) which is often sufficient when evaluating the
 impacts of land use practices on water quality. The adapted
 CREAMS model successfully simulated measured reductions in
 edge-of-field losses of sediment and nutrient upon
 installation of a vegetated filter strip. We conclude that
 although CREAMS has limitations in representing the dynamics
 of grazed pastures, it shows potential as a water quality
 management tool in pastoral watersheds.
 
 
 224                               NAL Call. No.: QH545.A1E52
 Predicting stream-water quality using catchment and soil
 chemical characteristics.
 Billett, M.F.; Cresser, M.S.
 Essex : Elsevier Applied Science; 1992.
 Environmental pollution v. 77 (2/3): p. 263-268; 1992.  In the
 special issue: Effects of acidic pollutants on the chemistry
 of freshwater streams and lakes / edited by R. Harriman. Paper
 presented at the "Fourth International Conference on Acidic
 Deposition: Its Nature and Impacts," September 16-21, 1990,
 Glasgow, Scotland.  Includes references.
 
 Language:  English
 
 Descriptors: Northern scotland; Eastern scotland; Soil
 chemistry; Cation exchange; Prediction; Water quality;
 Hydrogen ions; Acidity; Calcium ions; Streams; Watersheds;
 Horizons; Simulation; Simulation models
 
 
 225                                NAL Call. No.: 292.8 W295
 Prediction uncertainty in solute flux through heterogeneous
 soil. Destouni, G.
 Washington, D.C. : American Geophysical Union; 1992 Mar.
 Water resources research v. 28 (3): p. 793-801; 1992 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Solutes; Transport processes; Unsaturated flow;
 Degradation; Surface layers; Soil depth; Hydraulic
 conductivity; Soil zonation; Mathematical models
 
 Abstract:  The Lagrangian framework presented by Dagan et al.
 (1992a) is used to analyze the uncertainty in predictions of
 the field scale mass flux of solute through the unsaturated
 zone. Transport of both nonreactive and degradable solutes is
 investigated for input sources that are located at the soil
 surface of fields with spatially variable hydraulic
 conductivity at saturation. The variances of the solute flux
 and accumulated mass, which quantify the corresponding
 prediction uncertainties, are illustrated at an arbitrary
 depth below the soil surface for different sizes and shapes of
 the input domain, and for different flow and degradation
 conditions. The greatest solute flux variances arise when the
 expected breakthrough curve has a steep slope. The coefficient
 of variation for the solute flux is minimum at the peak
 arrival time of the expected breakthrough curve; this minimum
 value is relatively insensitive to the assumed distribution
 for solute travel time and to the loss rate coefficient for
 degradable solute. The prediction uncertainty decreases with
 increasing size of the input domain and is smaller for a
 planar source than for a linear one. The relative uncertainty
 in the total leached mass of degradable solute increases with
 increasing loss rate coefficient.
 
 
 226                               NAL Call. No.: 290.9 AM32T
 Predictive capabilities of erosion models for different storm
 sizes. Bingner, R.L.; Mutchler, C.K.; Murphree, C.E.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 Mar. Transactions of the ASAE v. 35 (2): p.
 505-513; 1992 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Mississippi; Erosion; Rain; Runoff; Sediment
 yield; Simulation models; Slopes; Storms; Watersheds
 
 Abstract:  When conservation practices are evaluated for
 erosion control effectiveness, the erosion or sediment yield
 produced by all the various storms that occur throughout the
 year should he considered. The Universal Soil Loss Equation
 neglects storms less than 13 mm unless the storm includes
 excessive rainfall intensities. Other erosion models have been
 developed that can easily consider all sizes of storms. This
 study evaluates the capability of several erosion models
 (CREAMS, SWRRB, EPIC, ANSWERS, and AGNPS) to predict runoff
 and erosion from rainfall events of 0 to 13, 13 to 25, 25 to
 50, 50 to 75, and greater than 75 mm. Runoff and erosion were
 simulated on three watersheds in Mississippi: a sloping upland
 watershed, a flatland watershed, and a terraced watershed with
 underground outlets. Results show that the models predicted a
 linear relation of runoff and erosion with rainfall. However,
 the slope of the model regressions varied widely from data
 values. Only CREAMS and SWRRB were successful in predicting
 annual average runoff and sediment yield within 20% of
 measured amounts from the upland watershed and only SWRRB and
 AGNPS were successful in prediction for the flatland
 watershed. None of the models predicted within 20% of measured
 amounts from the terraced watershed. In all cases, errors were
 greatest for the larger storms.
 
 
 227                     NAL Call. No.: GB701.W375 no.92-4108
 Preliminary results of the simulation of Oregon coastal basins
 using Precipitation-Runoff Modeling System (PRMS).
 Allen, Roderick L.; Laenen, Antonius
 United States, Bureau of Land Management, Geological Survey
 (U.S.) Portland, Or. : U.S. Dept. of the Interior, U.S.
 Geological Survey ; Denver, CO : Books and Open-File Reports
 Section [distributor],; 1993; I 19.42/4:92-4108.
 vi, 99 p. : ill., maps ; 28 cm. (Water-resources
 investigations report ; 92-4108).  Shipping list no.: 93-0315-
 P.  Includes bibliographical references (p. 43-44).
 
 Language:  English; English
 
 Descriptors: Hydrologic models; Runoff; Coasts
 
 
 228                                 NAL Call. No.: 60.18 J82
 Rangeland experiments to parameterize the water erosion
 prediction project model: vegetation canopy cover effects.
 Simanton, J.R.; Weltz, M.A.; Larsen, H.D.
 Denver, Colo. : Society for Range Management; 1991 May.
 Journal of range management v. 44 (3): p. 276-282; 1991 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Rangelands; Water erosion; Prediction; Simulation
 models; Rain; Interception; Canopy; Ground vegetation;
 Infiltration; Runoff; Losses from soil systems; Prairies;
 Steppes; Soil types; Edaphic factors; Site factors
 
 Abstract:  The Water Erosion Prediction Project (WEPP) is a
 new water erosion prediction technology being developed by the
 USDA-Agricultural Research Service to replace the Universal
 Soil Loss Equation. Rangeland field experiments were designed
 to parameterize the WEPP rangeland erosion model. Included in
 the field experiments were plot treatments designed to
 separate direct from indirect effects of vegetation canopy on
 runoff and soil erosion. Nine rangeland sites from a wide
 range of soil and vegetation types were evaluated using
 rainfall simulation techniques. Natural versus clipped
 treatment surface characteristics and runoff and erosion
 responses were compared using regression analyses. These
 analyses showed that there were no significant differences
 between natural and clipped plot surface characteristics,
 runoff ratios, final infiltration rates, or initial rainfall
 abstractions. Erosion rates were different between treatments
 with the clipped plots having slightly less erosion than the
 natural plots. Results indicated that, under the rainfall
 conditions simulated, canopy cover was not directly
 contributing to initial abstractions through rainfall
 interception loss or significantly affecting runoff or
 erosion.
 
 
 229                                  NAL Call. No.: QD241.T6
 Regression models for some solute distribution equilibria in
 the terrestrial environment.
 Noegrohati, S.; Hammers, W.E.
 Reading : Gordon and Breach Science Publishers; 1992.
 Toxicological and environmental chemistry v. 34 (2/4): p.
 175-185; 1992. Includes references.
 
 Language:  English
 
 Descriptors: Organochlorine insecticides; Soil; Sorption;
 Solvents; Leaching; Regression analysis
 
 Abstract:  Sorption coefficients (K(p)) of several
 organochlorine insecticides (OCs) in volcanic ash silt from
 Central Java are presented. Selected experimental and
 estimated octanol-water partition coefficient (P) values are
 used to study log-log regressions with K(p) data collected
 from the literature (PAHs, chlorophenols, phenylureas, chloro-
 s-triazines, carbamates and organophosphorus insecticides) and
 those of the OCs determined in the present study. Leaching
 distances and bioactivities in soil are correlated with the
 K(p) values of the pesticides, and with the organic matter and
 the water content of the soil.
 
 
 230                                NAL Call. No.: HC79.P55J6
 Regulating agricultural contamination of groundwater through
 strict liability and negligence legislation.
 Wetzstein, M.E.; Centner, T.J.
 Orlando, Fla. : Academic Press; 1992 Jan.
 Journal of environmental economics and management v. 22 (1):
 p. 1-11; 1992 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Idaho; Iowa; Minnesota; Vermont;
 Groundwater pollution; Environmental legislation; Regulations;
 Legal liability; Game theory; Dynamic models; Agricultural
 chemicals
 
 Abstract:  New state and national legislation attempts to
 limit the liability of agricultural chemical users by
 emasculating existing strict liability standards and replacing
 them with negligence standards. The allocation of
 contamination costs and precaution level between producers and
 victims of contamination associated with these alternative
 legislative standards is investigated. The analysis employed
 is a dynamic game theoretic framework considering moral
 hazard. Based on this analysis, a new institutional response
 is recommended to assign property rights based upon propensity
 and severity of injury and to require victim precaution.
 
 
 231                                NAL Call. No.: 292.8 W295
 The regulation of groundwater quality with delayed responses.
 Kim, C.S.; Hostetler, J.; Amacher, G.
 Washington, D.C. : American Geophysical Union; 1993 May.
 Water resources research v. 29 (5): p. 1369-1377; 1993 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Pollution control;
 Groundwater; Water quality; Regulations; Dynamic models;
 Algorithms; Nitrogen fertilizers; Farm inputs; Leachates;
 Nitrates; Usage; Costs; Agricultural policy
 
 Abstract:  This research develops a dynamic model of input
 regulation in the presence of externalities that do not occur
 simultaneously with input use. The model is formulated to
 study the regulation of firms that apply fertilizer, where
 leachate from the application of fertilizer accumulates in
 groundwater over time. In the model we show the derivation of
 an optimal nitrogen user fee and the consequences of
 regulatory design when time lags between nitrogen application
 and nitrate contamination are present. This research also
 responds to the need of developing a general solution
 algorithm for an optimal control model when the control
 variable exhibits a delayed response. A multistage solution
 algorithm presented in this paper is different from other
 studies in that a typical relationship is not assumed for the
 state and adjoint variables.
 
 
 232                                NAL Call. No.: HC79.P55J6
 The regulation of non-point source pollution under imperfect
 and asymmetric information.
 Cabe, R.; Herriges, J.A.
 Orlando, Fla. : Academic Press; 1992 Mar.
 Journal of environmental economics and management v. 22 (2):
 p. 134-146; 1992 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Pollution; Control methods; Agricultural
 chemicals; Information; Costs; Reliability; Bayesian theory;
 Regulations; Taxes; Farmers' attitudes; Beliefs; Mathematical
 models
 
 Abstract:  This paper develops a Bayesian framework for
 discussing the role of information in the design of non-point-
 source pollution control mechanisms. An ambient concentration
 tax is examined, allowing for spatial transport among multiple
 zones. Imposition of the tax requires costly measurement of
 concentrations in selected zones, and the selection of zones
 for measurement must be undertaken without perfect information
 regarding several parameters of the problem. Potentially
 crucial information issues discussed include: (a) the impact
 of asymmetric priors regarding fate and transport. (b) the
 cost of measuring ambient concentration, and (c) the optimal
 acquisition of information regarding fate and transport.
 
 
 233                                   NAL Call. No.: 10 J822
 Relating the nitrogen fertilizer needs of winter wheat crops
 to the soil's mineral nitrogen. Influence of the downward
 movement of nitrate during winter and spring.
 Addiscott, T.M.; Darby, R.J.
 Cambridge : Cambridge University Press; 1991 Oct.
 The Journal of agricultural science v. 117 (pt.2): p. 241-249;
 1991 Oct. Includes references.
 
 Language:  English
 
 Descriptors: Triticum aestivum; Fertilizer requirement
 determination; Leaching; Mineralization; Nitrates; Nitrogen
 fertilizers; Simulation models; Soil fertility
 
 
 234                                  NAL Call. No.: QH540.N3
 Risk analysis for water supply from a river polluted by
 nitrate runoff. Plate, E.J.; Duckstein, L.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 30: p.
 67-79; 1991.  In the series analytic: Nitrate contamination:
 Exposure, consequence, and control / edited by I. Bogardi and
 R.D. Kuzelka. Proceedings of the NATO Advanced Research
 Workshop on Nitrate Contamination: Exposure, Consequences, and
 Control, September 9-14, 1990, Lincoln, Nebraska.  Includes
 references.
 
 Language:  English
 
 Descriptors: German federal republic; Nitrate; Nitrate
 fertilizers; Water pollution; Rivers; Runoff; Water quality;
 Risk; Drainage; Farmland; Stochastic models
 
 
 235                                  NAL Call. No.: QH540.N3
 Risk analysis of groundwater contamination.
 Ganoulis, J.
 Berlin, W. Ger. : Springer-Verlag; 1993.
 NATO ASI series : Series G : Ecological sciences v. 32: p.
 455-474; 1993.  In the series analytic: Migration and fate of
 pollutants in soils and subsoils / edited by D. Petruzzelli
 and F.G. Helfferich. Proceedings of the NATO Advanced Study
 Institute, May 24-June 5, 1992, Maratea, Italy.  Includes
 references.
 
 Language:  English
 
 Descriptors: Victoria; Groundwater pollution; Pollutants;
 Hydrodynamics; Transport processes; Groundwater flow;
 Aquifers; Mathematical models; Risk; Saline water; Irrigation
 water
 
 
 236                                  NAL Call. No.: QH540.N3 A
 river water quality management model for Canal de Isabel. II.
 Comunidad de Madrid.
 Cubillo, F.; Rodriguez, B.
 Berlin, W. Ger. : Springer-Verlag; 1991.
 NATO ASI series : Series G : Ecological sciences v. 26: p.
 375-385; 1991.  In the series analytic: Decision support
 systems: Water resources planning / edited by D.P. Loucks and
 J.R. da Costa. Proceedings of the NATO Advanced Research
 Workshop on Computer-Aided Support Systems for Water
 Resources, Research and Management, September 24-28, 1990,
 Ericeira, Portugal.  Includes references.
 
 Language:  English
 
 Descriptors: Spain; Water management; Rivers; Water quality;
 Water pollution; Waste water treatment; Simulation models;
 Computer simulation; Computer software
 
 
 237                                 NAL Call. No.: SB610.W39
 The role of sensitivity analysis in groundwater risk modeling
 for pesticides. Fontaine, D.D.; Havens, P.L.; Blau, G.E.;
 Tillotson, P.M. Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 716-724; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Simulation models; Pesticides; Leaching;
 Groundwater; Methodology
 
 
 238                                 NAL Call. No.: 56.8 J822
 Runoff characteristics of sagebrush rangelands: modeling
 implications. Wilcox, B.P.; Seyfried, M.S.; Cooley, K.R.;
 Hanson, C.L.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1991 Mar. Journal of soil and water conservation v. 46 (2): p.
 153-158; 1991 Mar. Includes references.
 
 Language:  English
 
 Descriptors: Rangelands; Runoff; Computer simulation;
 Prediction; Watersheds; Precipitation
 
 
 239                                NAL Call. No.: 292.8 W295
 Runoff contamination by soil chemicals: time scale approach.
 Wallach, R.
 Washington, D.C. : American Geophysical Union; 1991 Feb.
 Water resources research v. 27 (2): p. 215-223; 1991 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Runoff; Runoff water; Chemicals; Contamination;
 Overland flow; Soil solution; Transport processes; Profiles;
 Mathematical models
 
 Abstract:  Two mass balance equations were used to model the
 transfer of dissolved chemicals from the soil solution to the
 surface runoff water and transport of these chemicals to the
 field outlet end. One mass balance equation is written for the
 chemicals dissolved in the overland water, and the other for
 the chemicals within the soil profile. The chemical input into
 the surface runoff water is by the rate-limited convective
 mass transfer process. Two time scales are isolated: the slow
 time scale represents the diffusion-based mass transfer
 process and the fast time scale represents the convective
 transport of dissolved chemicals by overland flow. Scaling the
 mass balance equations for the slow time scale yields a small
 parameter, which multiplies the time derivative of the mass
 balance equation written for the overland flow, providing a
 singular perturbation problem. By using the method of matched
 asymptotic expansion, an inner and outer problem is formulated
 and solved for each order of approximation. A single composite
 expansion, uniformly valid over the entire domain, is derived
 analytically. This approximated solution was compared with an
 exact analytical solution for the case in which chemicals are
 initially uniformly distributed throughout a semi-infinite
 soil profile. The time scale method was then used to solve a
 more complicated problem in which chemicals are initially
 distributed within a certain soil surface layer of a semi-
 infinite soil profile.
 
 
 240                               NAL Call. No.: 290.9 AM32T
 Runoff curve numbers determined by three methods under
 conventional and conservation tillages.
 Yoo, K.H.; Yoon, K.S.; Soileau, J.M.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1993 Jan. Transactions of the ASAE v. 36 (1): p.
 57-63; 1993 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Alabama; Runoff; Tillage; Traditional farming;
 Conservation tillage; Gossypium; Mathematical models
 
 Abstract:  Event-based rainfall and the associated runoff data
 collected from a small watershed planted to cotton were
 analyzed to determine effects of two tillage systems on SCS
 runoff curve numbers. A tillage study was conducted for six
 years on a 3.8 ha watershed planted to cotton in the Limestone
 Valley region of northern Alabama. The tillage included three
 years of conventional (CvT), followed by three years of
 conservation tillage (CsT). Soils of the watershed are Decatur
 (clayey, kaolinitic, thermic Rhodic Paleudults) and Emory silt
 loam (fine-silty, siliceous, thermic Fluventic Umbric
 Dystrochrepts) which are classified in Hydrologic Soil Group
 B. Curve numbers (CN) were determined by the SCS method and a
 method developed assuming a log-normal probability
 distribution of potential maximum retention, S. The published
 CN of the average soil moisture condition or antecedent
 moisture condition II (AMC II) for the study site are 78 and
 75 for CvT and CsT, respectively, which are recommended in
 many watershed/water quality computer simulation models such
 as CREAMS and AGNPS. The results showed that CN of AMC II (CN-
 II) calculated by the log-normal method were 83 and 88 for CvT
 and CsT, respectively. These were slightly higher than those
 calculated by the SCS method which were 82 for CvT and 86 for
 CsT. The calculated CN-II values were higher than the
 published CN-II values but the order of magnitude was
 reversed.
 
 
 241                               NAL Call. No.: 290.9 AM32T
 Runoff curve numbers for the southern High Plains.
 Hauser, V.L.; Jones, O.R.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Jan. Transactions of the ASAE v. 34 (1): p.
 142-148; 1991 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Southern plains states of U.S.A.; Runoff; Surface
 water; Water erosion; Water quality; Watersheds; Mathematical
 models; Rain; Soil conservation
 
 Abstract:  Rainfall produces significant amounts of surface
 runoff from cultivated drylands of the western Great Plains.
 Currently, engineers must extrapolate runoff data from more
 humid regions to estimate runoff from farm fields. Runoff data
 are now available from a 32-year record in the semiarid,
 western Great Plains. We derived curve numbers (CN) for the
 Soil Conservation Service curve number method for three field-
 sized watersheds that were dryland-farmed in a wheat-sorghum-
 fallow crop sequence. The watershed soils are classified in
 hydrologic group D. The CNs for wheat and sorghum should be 79
 and 82, respectively (handbook CN are both 80). The single
 handbook CN for fallow (90) is too high; it should be 77 for
 fallow after wheat and 82 for fallow after sorghum. These new
 CNs should improve computer model predictions of runoff,
 erosion and water quality, and provide more accurate estimates
 of runoff volume for use in designing conservation structures,
 water supply, flood control, and numerous other uses.
 
 
 242                                 NAL Call. No.: 60.18 J82
 Runoff prediction from sagebrush rangelands using water
 erosion prediction project (WEPP) technology.
 Wilcox, B.P.; Sbaa, M.; Blackburn, W.H.; Milligan, J.H.
 Denver, Colo. : Society for Range Management; 1992 Sep.
 Journal of range management v. 45 (5): p. 470-474; 1992 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Artemisia tridentata; Rangelands; Grassland
 management; Water erosion; Erosion control; Runoff;
 Prediction; Simulation models; Mathematical models
 
 Abstract:  Runoff prediction is an important component of any
 process-based soil erosion model. In this paper we evaluate
 the runoff prediction capabilities of a new soil erosion
 model, WEPP, on sagebrush rangelands. Particular attention was
 given to the parameter estimation techniques used in WEPP to
 predict infiltration. Runoff volume predicted by WEPP is based
 on the Green and Ampt infiltration equation. Predicted runoff
 was compared to observed runoff from 90 large plot rainfall
 simulation experiments on sagebrush rangelands. There was a
 poor correlation between predicted and observed runoff when
 the Green and Ampt parameters were estimated using the
 parameter estimation techniques. Runoff prediction was
 improved when parameters were determined from field
 measurements. Additional refinement of the Green and Ampt
 parameterization techniques is needed for continued
 improvement of WEPP.
 
 
 243                                  NAL Call. No.: 56.8 SO3
 Saline and sodic-saline soil reclamation: first order kinetic
 model. Selassie, T.G.; Jurinak, J.J.; Dudley, L.M.
 Baltimore, Md. : Williams & Wilkins; 1992 Jul.
 Soil science v. 154 (1): p. 1-7; 1992 Jul.  Includes
 references.
 
 Language:  English
 
 Descriptors: Saline sodic soils; Saline soils; Reclamation;
 Leaching; Kinetics; Soil water movement; Saturated conditions;
 Drained conditions; Salts in soil; Sodium; Solutes; Movement
 in soil; Electrical conductivity; Exchangeable sodium;
 Adsorption; Ratios; Ion exchange; Diffusion
 
 
 244                                  NAL Call. No.: 56.8 SO3 A
 scaled sorption model validated at the column scale to predict
 cadmium contents in a spatially variable field soil.
 Boekhold, A.E.; Zee, S.E.A.T.M. van der
 Baltimore, Md. : Williams & Wilkins; 1992 Aug.
 Soil science v. 154 (2): p. 105-112; 1992 Aug.  Includes
 references.
 
 Language:  English
 
 Descriptors: Netherlands; Spodosols; Arable soils; Polluted
 soils; Cadmium; Sorption; Mathematical models; Validity; Soil
 ph; Soil organic matter; Soil variability; Spatial variation;
 Soil solution; Sorption isotherms; Transport processes
 
 
 245                                 NAL Call. No.: SB610.W39
 Screening procedure for soils and pesticides for potential
 water quality impacts.
 Goss, D.W.
 Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 701-708; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Pesticides; Losses from soil; Leaching; Water
 quality; Groundwater pollution; Simulation models
 
 
 246                                 NAL Call. No.: 292.8 J82
 The seasonal variation of streamwater chemistry in three
 forested Mediterranean catchments.
 Pinol, J.; Avila, A.; Roda, F.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Dec.
 Journal of hydrology v. 140 (1/4): p. 119-141; 1992 Dec. 
 Includes references.
 
 Language:  English
 
 Descriptors: Spain; Watersheds; Broadleaved evergreen forests;
 Streams; Water quality; Water content; Chemical properties;
 Stream flow; Seasonal variation; Discharge; Solutes; Ions;
 Soil water; Groundwater; Temperature; Catchment hydrology;
 Mediterranean climate; Mathematical models
 
 Abstract:  Streamwater chemistry is described for three
 streams draining undisturbed, evergreen broad-leaved forested
 catchments on phyllites in NE Spain: two streams with no or
 negligible flow in summer are located in the Prades massif,
 and one perennial stream is in the wetter Montseny mountains.
 Weekly data for a study period of 24 years are provided to (1)
 describe the seasonal variations in streamwater chemistry, (2)
 analyse the relationship between stream discharge and solute
 concentrations using a two-component mixing model and (3)
 search for patterns of temporal variation in stream solute
 concentrations after discounting the effects of discharge. At
 Prades, concentrations of all analysed ions, except NO3(-1),
 showed marked seasonal variations in stream water, whereas at
 Montseny only ions related to mineral weathering (HCO3(-1),
 Na+, Ca2+ and Mg2+) showed strong seasonality. Ion
 concentrations were more closely dependent on instantaneous
 discharge at Montseny than at Prades. The residuals of the
 relationship between solute concentrations and discharge
 retained a strong seasonality at Prades, but not at Montseny.
 These differences are related to the major hydrochemical
 processes that determine the streamwater chemistry at each
 site. The same processes are probably operative in the three
 catchments, but are of varying relative importance. At
 Montseny, the mixing of waters of different chemical
 composition seems to be the major process controlling
 streamwater chemistry, although the soilwater end-member
 composition predicted by the mixing model applied did not
 match the measured soilwater chemistry. In the drier Prades
 catchments, the two major hydrochemical processes determining
 the seasonal variation of streamwater chemistry are (1) the
 restart of flow after the summer drought, which flushes out
 the solutes accumulated during the dry period, and (2) the
 seasonal changes in groundwater chemistry that result from the
 interplay of water residence time, temperature and CO
 
 
 247                                NAL Call. No.: 292.8 W295
 The second Las Cruces Trench experiment: experimental results
 and two-dimensional flow predictions.
 Hills, R.G.; Wierenga, P.J.; Hudson, D.B.; Kirkland, M.R.
 Washington, D.C. : American Geophysical Union; 1991 Oct.
 Water resources research v. 27 (10): p. 2707-2718; 1991 Oct. 
 Includes references.
 
 Language:  English
 
 Descriptors: New Mexico; Soil water; Water flow; Tritium;
 Bromide; Solutes; Transport processes; Infiltration;
 Redistribution; Semiarid soils; Soil variability; Measurement;
 Deterministic models; Prediction
 
 Abstract:  As part of a comprehensive field study designed to
 provide data to test stochastic and deterministic models of
 water flow and contaminant transport in the vadose zone,
 several trench experiments were performed in the semiarid
 region of southern New Mexico. The first trench experiment is
 discussed by Wierenga et al. (this issue). During the second
 trench experiment, a 1.2 m wide by 12 m long area on the north
 side of and parallel to a 26.4 m long by 4.8 m wide by 6 m
 deep trench was irrigated with water containing tracers using
 a carefully controlled drip irrigation system. The irrigated
 area was heavily instrumented with tensiometers and neutron
 probe access tubes to monitor water movement, and with suction
 samplers to monitor solute transport. Water containing tritium
 and bromide was applied during the first 11.5 days of the
 study. Thereafter, water was applied without tracers for an
 additional 64 days. Both water movement and tracer movement
 were monitored in the subsoil during infiltration and
 redistribution. The experimental results indicate that water
 and bromide moved fairly uniformly during infiltration and the
 bromide moved ahead of the tritium due to anion exclusion
 during redistribution. Comparisons between measurements and
 predictions made with a two-dimensional model show qualitative
 agreement for two of the three water content measurement
 planes. Model predictions of tritium and bromide transport
 were not as satisfactory. Measurements of both tritium and
 bromide show localized areas of high relative concentrations
 and a large downward motion of bromide relative to tritium
 during redistribution. While the simple deterministic model
 does show larger downward motions for bromide than for tritium
 during redistribution, it does not predict the high
 concentrations of solute observed during infiltration, nor can
 it predict the heterogeneous behavior observed for tritium
 during infiltration and for bromide during redistribution.
 
 
 248                             NAL Call. No.: QE581.F4 1991
 Sediment-nutrient transport during severe storms.
 Smith, S.J.; Sharpley, A.N.; Williams, J.R.; Berg, W.A.;
 Coleman, G.A. Washington, D.C.? : Federal Energy Regulatory
 Commission; 1991. Proceedings of the Fifth Federal Interagency
 Sedimentation Conference, 1991 / edited by Shou-Shan Fan and
 Yung-Huang Kuo ; sponsored by Subcommittee on Sedimentation of
 the Interagency Advisory Committee on Water Data. p. PS/48-
 PS/55; 1991.  Includes references.
 
 Language:  English
 
 Descriptors: Oklahoma; Texas; Runoff; Geological
 sedimentation; Storms; Mathematical models; Prediction
 
 
 249                                  NAL Call. No.: 56.9 SO3
 Selenium mobility and distribution in irrigated and
 nonirrigated alluvial soils.
 Fio, J.L.; Fujii, R.; Deverel, S.J.
 Madison, Wis. : The Society; 1991 Sep.
 Soil Science Society of America journal v. 55 (5): p.
 1313-1320; 1991 Sep. Includes references.
 
 Language:  English
 
 Descriptors: California; Selenium; Salts in soil; Movement in
 soil; Alluvial soils; Irrigated soils; Alkaline soils;
 Solutes; Transport processes; Adsorption; Desorption;
 Irrigation; Drainage; Irrigation water; Drainage water;
 Dispersion; Mathematical models; Dissolving; Leaching;
 Groundwater; Oxidation; Saturated conditions; Spatial
 distribution; Soil depth; Gypsum; Hysteresis; Time lag;
 Physicochemical properties
 
 Abstract:  Dissolution and leaching of soil salts by
 irrigation water is a primary source of Se to shallow
 groundwater in the western San Joaquin Valley, California. In
 this study, the mobility and distribution of selenite and
 selenate in soils with different irrigation and drainage
 histories was evaluated using sorption experiments and an
 advection-dispersion model. The sorption studies showed that
 selenate (15-12 400 micrograms Se L-1) is not adsorbed to soil
 whereas selenite (10-5000 micrograms Se L-1) is rapidly
 adsorbed. The time lag between adsorption and desorption of
 selenite is considerable, indicating a dependence of reaction
 rate on reaction direction (hysteresis). Selenite adsorption
 and desorption isotherms were different, and both were
 described with the Freundlich equation. Model results and
 chemical analyses of extracts from the soil samples showed
 that selenite is resistant to leaching and therefore can
 represent a potential long-term source of Se to groundwater.
 In contrast, selenate behaves as a conservative constituent
 under alkaline and oxidized conditions and is easily leached
 from soil.
 
 
 250                                NAL Call. No.: 292.8 W295 A
 semidiscrete model for water and solute movement in tile-
 drained soils. 1. Governing equations and solution.
 Kamra, S.K.; Singh, S.R.; Rao, K.V.G.K.; Van Genuchten, M.T.
 Washington, D.C. : American Geophysical Union; 1991 Sep.
 Water resources research v. 27 (9): p. 2439-2447; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: Drainage water; Solutes; Water flow; Movement in
 soil; Transport processes; Aquifers; Tile drainage;
 Prediction; Mathematical models
 
 Abstract:  A finite element model has been developed to
 simulate solute transport in tile-drained soil-aquifer
 systems. Water flow in the unsaturated zone and to drains in
 the saturated zone was assumed to be at steady state. The
 model considers the transport of nonreactive solutes, as well
 as of reactive solutes whose behavior can be described by a
 distribution coefficient. The exact-in-time numerical solution
 yields explicit expressions for the concentration field at any
 future point in time without having to compute concentrations
 at intermediate times. The semidiscrete method involves the
 determination of an eigensystem of eigenvalues and
 eigenvectors of the coefficient matrix. The eigensystem may be
 complex (i.e., it may have imaginary components) due to
 asymmetry created by the convection term in the governing
 convection-dispersion equation. The proposed approach
 facilitates long-term predictions of concentrations in
 drainage effluents and of salt distributions in soil and
 groundwater. The accuracy of the model was verified by
 comparing model results with those based on an analytical
 solution for two-dimensional solute transport in groundwater.
 
 
 251                                NAL Call. No.: 292.8 W295 A
 semidiscrete model for water and solute movement in tile-
 drained soils. 2. Field validation and applications.
 Kamra, S.K.; Singh, S.R.; Rao, K.V.G.K.; Van Genuchten, M.T.
 Washington, D.C. : American Geophysical Union; 1991 Sep.
 Water resources research v. 27 (9): p. 2449-2456; 1991 Sep. 
 Includes references.
 
 Language:  English
 
 Descriptors: India; Drainage water; Solutes; Movement in soil;
 Tile drainage; Subsurface drainage; Depth; Spacing; Soil
 salinity; Water table; Effluents; Water quality; Aquifers;
 Simulation; Prediction; Mathematical models
 
 Abstract:  An exact-in-time two-dimensional finite element
 model for simulating convective-dispersive solute transport in
 a tile-drained field is validated against observed data from a
 subsurface drainage experiment. The model is capable of
 predicting the long-term effects of different irrigation and
 drainage practices on the salt distribution in an artificially
 drained soil-aquifer system. The model was used to predict
 transient changes in the salinity of the soil, the shallow
 groundwater table, and the drain effluent. Results are also
 presented on the effects of imposing alternative drain
 spacing-depth combinations, initial groundwater salinities,
 solute distribution coefficients, and different types of
 layering of the aquifer, on the computed salinity
 distributions in the unsaturated zone, the groundwater, and
 the drain effluent.
 
 
 252                                 NAL Call. No.: SB951.P47
 Sensitivity analysis of a mathematical model for pesticide
 leaching to groundwater.
 Boesten, J.J.T.I.
 Essex : Elsevier Applied Science Publishers; 1991.
 Pesticide science v. 31 (3): p. 375-388; 1991.  Includes
 references.
 
 Language:  English
 
 Descriptors: Netherlands; Pesticides; Groundwater; Leaching;
 Mathematical models; Meteorological factors; Plants; Uptake;
 Water pollution; Soil properties; Zea mays; Sandy soils
 
 Abstract:  The sensitivity of pesticide leaching to
 pesticide/soil properties and to meteorological conditions was
 assessed by calculations with an existing convection-
 dispersion model. The model assumes equilibrium sorption
 (Freundlich equation), first-order transformation kinetics and
 passive plant uptake. The extent of pesticide leaching was
 characterized by the percentage of the dose leached below 1 m
 depth. The calculations were carried out for a humic sand soil
 cropped with maize and exposed to Dutch weather conditions. In
 general, the percentage leached was found to be very sensitive
 to the sorption coefficient, the Freundlich exponent
 (describing the curvature of the isotherm) and the
 transformation rate. The percentage leached was moderately
 sensitive to weather conditions (wet/dry years), long-term
 sorption equilibration and the relationship between
 transformation rate and temperature. Sensitivity to the extent
 of plant uptake was only significant for pesticides with low
 sorption coefficients. Sensitivity to soil hydraulic
 properties was small. The effect of application in autumn
 instead of in spring was found to be very large for non-
 sorbing pesticides with short half-lives. The sensitivity to
 spatial variability in sorption coefficient and transformation
 rate was found to be substantial at low percentages leached.
 
 
 253                                  NAL Call. No.: TD403.G7 A
 simple analytical approach for predicting nitrate
 concentrations in pumped ground water.
 Lerner, D.N.; Papatolios, K.T.
 Dublin, Ohio : Ground Water Pub. Co; 1993 May.
 Ground water v. 31 (3): p. 37-375; 1993 May.  Includes
 references.
 
 Language:  English
 
 Descriptors: England; Groundwater pollution; Pollutants;
 Nitrates; Wells; Groundwater recharge; Concentration;
 Prediction; Models; Aquifers
 
 Abstract:  A simple analytical expression is presented which
 predicts how solute concentrations evolve with time in a
 pumped well. The basic expression is for uniform recharge and
 uniform concentration of a conservative solute (e.g. nitrate)
 in the recharge. It shows that pumped concentrations are
 independent of pumping rates. The expression can be developed
 to allow for more complex patterns of recharge and solute
 loading, and an example is given with three zones of recharge
 and concentrations, induced river recharge, and a cross-
 boundary inflow. Predictions are made for Edgmond Bridge, a
 new pumping station which lies in a drift-filled valley in the
 Triassic sandstone aquifer of Shropshire, UK. The model
 predicts that concentrations of nitrate will stay below the
 drinking water limit for 78 years, although this would be
 substantially reduced if the aquifer were significantly
 layered or if nitrate loads from agriculture increased.
 Predictions were reevaluated after two years and found to be
 consistent with observed patterns once actual, rather than
 expected, conditions were incorporated in the model.
 
 
 254                                  NAL Call. No.: 56.8 SO3 A
 simple, inverse model for estimating nitrogen reaction rates
 from soil column leaching experiments at steady water flow.
 Yamaguchi, T.; Moldrup, P.; Rolston, D.E.; Hansen, J.A.
 Baltimore, Md. : Williams & Wilkins; 1992 Dec.
 Soil science v. 154 (6): p. 490-496; 1992 Dec.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil analysis; Nitrification; Denitrification;
 Nitrogen; Transport processes; Movement in soil; Soil water
 movement; Leaching; Mathematical models
 
 
 255                                  NAL Call. No.: S590.C63
 Simple techniques for monitoring and predicting the movement
 of chemicals in a field soil.
 Phillips, I.R.
 New York, N.Y. : Marcel Dekker; 1992.
 Communications in soil science and plant analysis v. 23
 (9/10): p. 965-980; 1992.  Includes references.
 
 Language:  English
 
 Descriptors: Leaching; Chemicals; Podzolic soils; Movement in
 soil; Soil water movement; Exchangeable sodium; Sodium;
 Calcium; Magnesium; Potassium; Bromide; Chloride; Soil
 solution; Cation exchange; Anion exchange; Soil depth;
 Mathematical models
 
 
 256                                 NAL Call. No.: aZ5071.N3
 Simulation models, GIS and nonpoint-source pollution--January
 1988-June 1992. Holloway, D.; Makuch, J.
 Beltsville, Md. : The Library; 1992 Sep.
 Quick bibliography series - U.S. Department of Agriculture,
 National Agricultural Library (U.S.). (92-69): 43 p.; 1992
 Sep.  Bibliography.
 
 Language:  English
 
 Descriptors: Simulation models; Information systems;
 Groundwater pollution; Agricultural chemicals; Bibliographies
 
 
 257                                NAL Call. No.: 292.8 W295
 Simulation of a two-pollutant, two-season pollution offset
 system for the Colorado River of Texas below Austin.
 Letson, D.
 Washington, D.C. : American Geophysical Union; 1992 May.
 Water resources research v. 28 (5): p. 1311-1318; 1992 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Texas; River water; Water pollution; Pollutants;
 Water quality; Environmental impact; Seasonal variation;
 Simulation models; Mathematical models
 
 Abstract:  A pollution offset system is a discharge permit
 system in which transfers are made subject to a restriction
 that no violations of water quality standards occur at any
 location. Simulation of a pollution offset system with
 seasonal variation and multiple pollutants allows for
 comparison of the savings possible from these design features.
 A simulation model (Qual-TX) developed by the Texas Water
 Commission is applied to a case study region near Austin,
 Texas, yielding impact coefficients for an economic
 optimization model without investment whose least cost
 solution represents the theoretical equilibrium of a pollution
 offset system. The optimization model finds short-run savings
 of 17.5% for a pollution offset system, as compared to a
 command and control policy that would also achieve the
 dissolved oxygen standard. Seasonalvariation in permit design
 produces minimal effects; virtually all savings come from
 allowing pollution offsets for the two different pollutants.
 
 
 258                                 NAL Call. No.: TD426.J68
 Simulation of nitrogen dynamics and leaching from arable
 soils. Lotse, E.G.; Jabro, J.D.; Simmons, K.E.; Baker, D.E.
 Amsterdam : Elsevier; 1992 Aug.
 Journal of contaminant hydrology v. 10 (3): p. 183-196; 1992
 Aug.  Includes references.
 
 Language:  English
 
 Descriptors: Pennsylvania; Arable soils; Soil chemistry;
 Nitrogen balance; Nitrogen; Uptake; Nitrate nitrogen; Storage;
 Profiles; Mineralization; Nitrification; Leaching; Simulation
 models; Water pollution
 
 
 259                                  NAL Call. No.: 56.8 SO3
 Simulation of one-dimensional nitrate transport through soil
 and concomitant nitrate diminution.
 Sadeghi, A.M.; Kunishi, H.M.
 Baltimore, Md. : Williams & Wilkins; 1991 Nov.
 Soil science v. 152 (5): p. 333-339; 1991 Nov.  Includes
 references.
 
 Language:  English
 
 Descriptors: Maryland; Sandy loam soils; Clay loam soils;
 Nitrate; Ion transport; Movement in soil; Losses from soil
 systems; Leaching; Laboratory methods; Undisturbed sampling;
 Horizontal flow; Velocity; Dispersion; Sorption; Mathematical
 models; Simulation; Nitrate nitrogen; Potassium nitrate;
 Carbon; Phthalates; Nutrient sources; Hydrology; Watershed
 management; Denitrification
 
 
 260                                NAL Call. No.: 292.9 AM34
 Simulation of sediment and plant nutrient losses by the CREAMS
 water quality model.
 Yoon, K.S.; Yoo, K.H.; Soileau, J.M.; Touchton, J.T.
 Bethesda, Md. : American Water Resources Association; 1992
 Nov. Water resources bulletin v. 28 (6): p. 1013-1021; 1992
 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Alabama; Gossypium hirsutum; Conservation
 tillage; Tillage; Erosion; Runoff; Nitrogen; Phosphorus;
 Losses from soil; Water quality; Water pollution; Catchment
 hydrology; Simulation models; Prediction
 
 Abstract:  CREAMS was applied to a field-sized watershed
 planted to cotton in the Limestone Valley region of northern
 Alabama. The field was cultivated for three years with
 conventional tillage (CvT) followed by three years or
 conservation tillage (CsT). CREAMS is composed of three
 components: hydrology, erosion, and chemistry. Surface runoff
 and losses of sediment, N and P were simulated and results
 were compared with the observed data from the watershed. Curve
 numbers recommended in the CREAMS user's guide were not
 adequate for the watershed conditions. The hydrology submodel
 improved runoff simulation from CvT and CsT when field-data
 based curve numbers were used. The erosion submodel
 demonstrated that CsT reduced sediment loss more than CvT,
 even though CsT had higher runoff than CvT. The nutrient
 submodel based on the simulated runoff and sediment
 underpredicted N loss for both CvT and CsT. This submodel,
 however, accurately predicted P loss for CvT, but
 underpredicted for CsT (50 percent lower than the observed).
 The results of CREAMS simulation generally matched the
 observed order of magnitude for higher runoff, lower sediment,
 and higher N and P losses from CsT than from CvT.
 
 
 261                                 NAL Call. No.: 292.8 J82
 Simulation of water and chemicals in macropore soils. 2.
 Application of linear filter theory.
 Chen, C.; Wagenet, R.J.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Jan.
 Journal of hydrology v. 130 (1/4): p. 127-149; 1992 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Macropores; Macropore flow; Water flow; Hydraulic
 conductivity; Soil water content; Transport processes; Linear
 models; Simulation
 
 Abstract:  Description of flow in soils with macropores is
 difficult, yet quite important in describing the dynamics of
 field soils. Recognizing the two structural domains of the
 macropore and matrix, and possible water-flow situations,
 three flow regions have been suggested: matrix, macropore, and
 transaction. The matrix and the macropore are the two domains,
 and the transaction represents the exchange of water between
 the matrix and the macropore. As a beginning point for the
 description of such systems, linear filter theory is applied
 to the Richards equation to obtain a general set of analytical
 solutions for water and contaminant movement in unsaturated
 soil in which there are no macropores. To develop these
 solutions, it unique relationship between water flux (q) and
 water content (0) is demonstrated by executing a numerical
 simulation based on the Richards equation. By piece-wise curve
 fitting of q(0), it is possible to establish and obtain a set
 of equations which describe water flow and chemical movement
 in soil, and which take the form of linear filter systems,
 providing analytical solutions by convolution. A two-domain
 approach applies equations for homogeneous soil to describe
 the matrix domain, with the macropore domain described with
 coefficients obtained by applying the Poiseuille and Chezy
 equations. These equations are analytically solved in
 correspondence with the three flow situations, resulting in a
 model. LASOMS (linear analytical solutions of macropore
 soils). Simulations, data and model comparisons of LASOMS have
 shown the above solutions to be reasonable under several
 conditions.
 
 
 262                                 NAL Call. No.: 292.8 J82
 Simulation of water and chemicals in macropore soils. 2.
 Application of linear filter theory.
 Chen, C.; Wagenet, R.J.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Jan.
 Journal of hydrology v. 130 (1/4): p. 127-149; 1992 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Macropores; Macropore flow; Water flow; Hydraulic
 conductivity; Soil water content; Transport processes; Linear
 models; Simulation
 
 Abstract:  Description of flow in soils with macropores is
 difficult, yet quite important in describing the dynamics of
 field soils. Recognizing the two structural domains of the
 macropore and matrix, and possible water-flow situations,
 three flow regions have been suggested: matrix, macropore, and
 transaction. The matrix and the macropore are the two domains,
 and the transaction represents the exchange of water between
 the matrix and the macropore. As a beginning point for the
 description of such systems, linear filter theory is applied
 to the Richards equation to obtain a general set of analytical
 solutions for water and contaminant movement in unsaturated
 soil in which there are no macropores. To develop these
 solutions, it unique relationship between water flux (q) and
 water content (0) is demonstrated by executing a numerical
 simulation based on the Richards equation. By piece-wise curve
 fitting of q(0), it is possible to establish and obtain a set
 of equations which describe water flow and chemical movement
 in soil, and which take the form of linear filter systems,
 providing analytical solutions by convolution. A two-domain
 approach applies equations for homogeneous soil to describe
 the matrix domain, with the macropore domain described with
 coefficients obtained by applying the Poiseuille and Chezy
 equations. These equations are analytically solved in
 correspondence with the three flow situations, resulting in a
 model. LASOMS (linear analytical solutions of macropore
 soils). Simulations, data and model comparisons of LASOMS have
 shown the above solutions to be reasonable under several
 conditions.
 
 
 263                                 NAL Call. No.: SB610.W39
 Site-specific pesticide recommendations: the final step in
 environmental impact prevention.
 Hornsby, A.G.
 Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 736-742; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Florida; Pesticides; Environmental impact;
 Leaching; Runoff; Toxicology; Soil properties; Water quality;
 Water pollution; Decision making; Methodology; Simulation
 models; Geographical information systems; Risk; Cooperative
 extension service
 
 
 264                             NAL Call. No.: S623.O94 1992
 Soil erosion and sediment yield modeling, simulation and
 prediction. Overton, Donald E.,
 Knoxville, TN : Stormwater Publications,; 1992.
 197 p. : ill. (some col.) ; 23 cm.  Includes bibliographical
 references and indexes.
 
 Language:  English
 
 Descriptors: Runoff; Soil erosion; Sediment transport
 
 
 265                                 NAL Call. No.: 292.8 J82
 Soil water content at R-5. 2. Impact of antecedent conditions
 on rainfall-runoff simulations.
 Loague, K.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Nov.
 Journal of hydrology v. 139 (1/4): p. 253-261; 1992 Nov. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil water content; Simulation models; Rain;
 Runoff; Watersheds; Spatial variation; Topsoil; Subsoil; Soil
 depth; Estimation
 
 Abstract:  In this paper, the second part of a two-part
 series, the performance of a quasi-physically based rainfall-
 runoff model (QPBRRM) is evaluated for a set of 39 events from
 a small rangeland catchment (R-5) using a suite of alternative
 antecedent soil water content estimates. The data set used to
 glean antecedent conditions for the R-5 events, described in
 the companion paper contains 22 848 observations of soil water
 content made over a 4 year period. The performance of the
 model is improved by using estimates of antecedent soil water
 content that include consideration of spatial variability.
 
 
 266                                  NAL Call. No.: 56.9 SO3
 Soil water movement in response to temperature graidents:
 experimental measurements and model evaluation.
 Bach, L.B.
 Madison, Wis. : The Society; 1992 Jan.
 Soil Science Society of America journal v. 56 (1): p. 37-46;
 1992 Jan. Includes references.
 
 Language:  English
 
 Descriptors: Sandy loam soils; Soil water movement; Transport
 processes; Soil water; Spatial distribution; Soil temperature;
 Spatial variation; Laboratory methods; Measurement;
 Comparisons; Simulation models; Mathematical models; Soil
 water content; Heat flow; Thermal conductivity; Thermal
 diffusivity; Water vapor; Matric potential; Soil water
 retention
 
 Abstract:  Temperature gradients may have a significant effect
 on soil water movement under certain conditions, but inclusion
 of these effects adds complexity to the flow analysis. This
 study was conducted to help clarify the significance of
 nonisothermal water flow, and to examine theoretical and
 numerical descriptions of the transport processes. At initial
 water contents of 0.00, 0.049, 0.099, 0.151, and 0.282 m3 m-3
 isothermal and nonisothermal laboratory experiments were
 conducted to provide direct information on soil water movement
 in response to temperature gradients. These data were used to
 evaluate the numerical simulation model SPLaSHWaTr2, and to
 examine calculation of the thermal conductivity, the thermal
 vapor diffusivity, and the temperature coefficient of the
 matric potential, based on modifications to a theory proposed
 by Philip and de Vries in 1957. A statistically significant
 effect of the temperature gradient was found at an initial
 water content of 0.151 m3 m-3, which corresponds to a pressure
 head of approximately -1.2 m of H2O. No effect of the
 temperature gradient was found at initial water contents of
 0.00, 0.049, 0.099, or 0.282 m3 m-3. Under isothermal
 conditions, the model provided simulated water-content
 profiles that were in good agreement with measured profiles.
 Under nonisothermal conditions, profiles simulated by the
 model were in poor agreement with the measured data, using the
 original values of thermal conductivity, thermal vapor
 diffusivity and the temperature coefficient of the matric
 potential. Sensitivity analysis showed that thermal
 conductivity and thermal vapor diffusivity had a negligible
 influence on nonisothermal water movement. On the other hand,
 the temperature coefficient of the matric potential had a
 significant influence on nonisothermal water movement.
 Adjusting the temperature coefficient of the matric potential
 from the original value of -0.0068 K-1 to the value suggested
 by Philip and de Vries, -0.00209 K-1, improved the a
 
 
 267                                  NAL Call. No.: 56.9 SO3
 Solute transport in a two-layer medium investigated with time
 moments. Leij, F.J.; Dane, J.H.
 Madison, Wis. : The Society; 1991 Nov.
 Soil Science Society of America journal v. 55 (6): p.
 1529-1535; 1991 Nov. Includes references.
 
 Language:  English
 
 Descriptors: Layered soils; Transport processes; Solutes;
 Movement in soil; Statistical methods; Mathematical models;
 Soil boundaries; Interface; Soil water movement; Variance;
 Models; Spreading
 
 Abstract:  The study of solute transport in porous media
 requires knowledge of the transport parameters. These
 transport parameters can be determined from data collected
 during displacement experiments using a number of mathematical
 procedures, among them the moment method. An advantage of this
 method is that it can also be used to theoretically analyze,
 and therefore enhance our understanding of, transport
 problems. We present theoretical time moments as derived from
 analytical solutions of the advection-dispersion equation in
 the Laplace domain for a step- and pulse-type solute input
 applied to a two-layer soil with steady flow transverse to
 layering. These moments were used for investigating the mean
 breakthrough time, u1, and variance, u2. It was shown that,
 theoretically, more retardation and spreading occurs for a
 third- than for a first-type boundary condition, but that the
 presence of the interface, as such, does not affect spreading
 for either boundary condition.
 
 
 268                                  NAL Call. No.: 56.8 SO3
 Solute transport through hard pans of paddy fields. 2. Cation
 exchange processess.
 Ishiguro, M.
 Baltimore, Md. : Williams & Wilkins; 1992 Jan.
 Soil science v. 153 (1): p. 42-47; 1992 Jan.  Includes
 references.
 
 Language:  English
 
 Descriptors: Paddy soils; Compact soils; Pans; Disturbed
 soils; Solutes; Transport processes; Exchangeable cations;
 Movement in soil; Calcium ions; Strontium; Bromide; Simulation
 models; Laboratory methods; Mathematical models; Cation
 exchange; Cation exchange capacity; Adsorption; Equilibrium;
 Diffusivity; Roots; Pores; Pore volume
 
 
 269                                  NAL Call. No.: 56.8 SO3
 Solute transport through hard pans of paddy fields. I. Effect
 of vertical tubular pores made by rice roots on solute
 transport.
 Ishiguro, M.
 Baltimore, Md. : Williams & Wilkins; 1991 Dec.
 Soil science v. 152 (6): p. 432-439; 1991 Dec.  Includes
 references.
 
 Language:  English
 
 Descriptors: Oryza sativa; Paddy soils; Gley soils; Andosols;
 Lowland areas; Subsoil; Soil compaction; Transport processes;
 Bromine; Movement in soil; Macropores; Roots; Simulation;
 Measurement; Calculation; Mathematical models; Convection;
 Diffusion; Velocity; Pore volume
 
 
 270                                  NAL Call. No.: QH540.J6
 Sorptive reversibility of atrazine and metolachlor residues in
 field soil samples.
 Pignatello, J.J.; Huang, L.Q.
 Madison, Wis. : American Society of Agronomy; 1991 Jan.
 Journal of environmental quality v. 20 (1): p. 222-228; 1991
 Jan.  Includes references.
 
 Language:  English
 
 Descriptors: Atrazine; Metolachlor; Herbicide residues;
 Measurement; Samples; Soil pollution; Sorption; Theory;
 Transport processes; Leaching; Mathematical models
 
 Abstract:  Predictions of the fate and transport of organic
 compounds in soils depend on sound sorption models. The
 impacts of slowly reversible (nonequilibrium) sorption on
 compound fate are not well quantified. Soil samples containing
 residues of the herbicides atrazine (2-chloro-4-ethylamino-6-
 isopropyl-1,3,5-triazine) and metolachlor (2-chloro-N-[2-
 ethyl-5-methylphenyl]-N-[2-methoxy-1-methylethyl]-acetamide)
 were collected from fields 2 to 15 mo after their last
 application to assess the sorptive reversibility of these
 residues. The apparent sorption constant of the native
 herbicide, Kapp was determined from the sorbed and solution
 concentrations after suspension of the sample in water for 24
 h. The "equilibrium" sorption constant, Kd, was determined in
 the same samples from 24 h sorption isotherms of freshly added
 herbicide, taking into account the fraction of labile native
 herbicide (fL). The ratio Kapp/Kd varied from 2.3 to 42 and
 was directly related to the "age" of the residue (i.e, time
 between sampling and last application). The value of fL ranged
 from 0.056 to 0.60 and was inversely related to the age of the
 residue. The results indicate that contaminated samples
 collected from the field can contain a large fraction of
 contaminant in a slowly reversible sorbed state, and that this
 fraction increase with time.
 
 
 271                                  NAL Call. No.: 501 L84B
 Spatio-temporal pattern formation in nonlinear non-equilibrium
 plankton dynamics.
 Malchow, H.
 London : The Society; 1993 Feb22.
 Proceedings of the Royal Society of London : Series B :
 Biological sciences v. 251 (1331): p. 103-109; 1993 Feb22. 
 Includes references.
 
 Language:  English
 
 Descriptors: Algae; Phytoplankton; Zooplankton; Aquatic
 communities; Indicator plants; Indicator species; Spatial
 distribution; Temporal variation; Water quality; Mathematical
 models
 
 
 272                                 NAL Call. No.: 56.8 J822
 Statewide GIS-based ranking of watersheds for agricultural
 pollution prevention.
 Hamlett, J.M.; Miller, D.A.; Day, R.L.; Peterson, G.W.;
 Baumer, G.M.; Russo, J.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1992 Sep. Journal of soil and water conservation v. 47 (5): p.
 399-404; 1992 Sep. Includes references.
 
 Language:  English
 
 Descriptors: Pollution; Watersheds; Ranking; Computer
 techniques; Models; Databases; Geography
 
 
 273                                NAL Call. No.: 292.8 W295
 Statistical analysis of spatial variability in unsaturated
 flow parameters. Russo, D.; Bouton, M.
 Washington, D.C. : American Geophysical Union; 1992 Jul.
 Water resources research v. 28 (7): p. 1911-1925; 1992 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Sandy loam soils; Unsaturated flow; Leaching;
 Soil properties; Hydraulic conductivity; Soil water retention;
 Spatial variation; Stochastic models; Statistical analysis;
 Autocorrelation; Prediction
 
 Abstract:  Core scale estimates of soil parameters of the
 Gardner-Russo and van Genuchten models of the hydraulic
 conductivity and water retention functions were obtained for
 417 undisturbed soil cores taken from a wall of a trench (20 m
 long, 2.5 m deep), using a procedure based on inverse problem
 methodology. These estimates were used to evaluate the first
 two statistical moments of the underlying random space
 functions (RSFs), using the restricted maximum likelihood
 estimation procedure, coupled with the weighted least squares
 procedure, to estimate parameters of models of the covariance
 and the drift functions of the pertinent RSFs. The fitted
 models were used to evaluate the mean and covariance functions
 of the hydraulic conductivity and water retention functions
 for given water saturations. Covariance functions of log-
 saturated conductivity (log Ks) and the "shape" parameters of
 the Gardner-Russo and van Genuchten models exhibited
 statistical anisotropy characterized by aspect ratios that
 vary between 3 to 4. Correlation scales of log Ks were larger
 than those of the "shape" parameters. Consequently, the
 product of the variance of log unsaturated conductivity and
 its correlation scale remained essentially invariant for a
 considerable range of water saturation. The implications of
 these results regarding stochastic modeling of transport in
 heterogeneous porous formations and possible applications of
 the results of this study are discussed briefly.
 
 
 274                                 NAL Call. No.: TD426.J68
 Statistical and graphical methods for evaluating solute
 transport models: Overview and application.
 Loague, K.; Green, R.E.
 Amsterdam : Elsevier; 1991 Jan.
 Journal of contaminant hydrology v. 7 (1/2): p. 51-73. maps;
 1991 Jan. Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Pollutants; Persistence;
 Prediction; Mathematical models; Pesticides; Leaching
 
 
 275                                NAL Call. No.: 292.8 W295
 Stochastic analysis of simulated vadose zone solute transport
 in a vertical cross section of heterogeneous soil during
 nonsteady water flow. Russo, D.
 Washington, D.C. : American Geophysical Union; 1991 Mar.
 Water resources research v. 27 (3): p. 267-283; 1991 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil water; Solutes; Water flow; Unsaturated
 flow; Horizontal flow; Vertical movement; Transport processes;
 Hydraulic conductivity; Spatial variation; Stochastic models;
 Simulation
 
 Abstract:  The problem of transport of a conservative
 nonreactive solute in a vertical cross section of a
 hypothetical partially saturated, scale-heterogeneous soil
 under transient water flow was analyzed here. It was assumed
 that locally the water flow and the solute transport can be
 described by the Richards' equation and by the one-component
 convection dispersion equation, respectively. The simulated
 water content and the solute concentration distributions in
 the vertical cross section of the soil at different elapsed
 times were quantified in terms of space averages and two-point
 autocorrelation functions. The time evolution of the solute
 plume was quantified in terms of its first two normalized
 spatial moments, from which the time dependence of the
 longitudinal and the transverse components of the solute
 velocity vector, and the spatial covariance tensor, were
 estimated. The results of this study, which are relevant to
 solute transport at the local or the plume scale, demonstrated
 the considerable variability in the solute concentration in
 space and time, due to the complex heterogeneity of the soil
 hydraulic properties in both the vertical and the horizontal
 directions. Consequently, the movement of the solute plume was
 characterized by a compression-expansion phenomenon,
 attributed to the decrease in the effective solute velocity
 through the zones of relatively fine-textured soil material.
 It was concluded that existing stochastic vadose zone
 transport models may be applicable to shallow depths but may
 fail to describe the actual spread of a solute plume when the
 transport takes place at relatively large depths, mainly
 because of the neglect of the significant vertical
 heterogeneity in the soil hydraulic properties.
 
 
 276                                 NAL Call. No.: 292.8 J82
 Stochastic modelling of solute flux in the unsaturated zone at
 the field scale.
 Destouni, G.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1993 Mar01.
 Journal of hydrology v. 143 (1/2): p. 46-61; 1993 Mar01. 
 Special Issue: Modelling Flow and Transport in the Unsaturated
 Zone: Scale Problems and Spatial Variability.  Includes
 references.
 
 Language:  English
 
 Descriptors: Solutes; Unsaturated flow; Transport processes;
 Spatial variation; Saturated hydraulic conductivity; Pore size
 distribution; Mathematical models
 
 Abstract:  Spatial variability in both the saturated hydraulic
 conductivity and the pore-size distribution is incorporated in
 a stochastic model of field-scale solute transport through the
 unsaturated zone. The transport model considered is based on a
 Lagrangian framework, in which the expected field-scale solute
 flux and the associated uncertainty in predictions are defined
 from distributions of solute travel time. Expressions for such
 travel time distributions are derived from statistical
 information on measurable soil hydraulic properties and are
 used to analyze the statistics of the field-scale solute flux
 in heterogeneous soil. The spatial variability in the
 saturated hydraulic conductivity and in the pore-size
 distribution has a similar effect on the prediction
 uncertainty, quantified by the variance of the solute flux, as
 on the expected breakthrough curve. The effect on the relative
 prediction uncertainty, quantified by the coefficient of
 variation for the solute flux, is therefore small. Both the
 solute flux variance and the coefficient of variation decrease
 rapidly with increasing size of the input domain and are
 considerably smaller for a planar source than for a linear
 one.
 
 
 277                                   NAL Call. No.: QD1.A45
 Study design to investigate and simulate agrochemical movement
 and fate in groundwater recharge.
 Asmussen, L.E.; Smith, C.N.
 Washington, D.C. : The Society; 1991.
 ACS Symposium series - American Chemical Society (465): p.
 150-164; 1991.  In the series analytic: Groundwater residue
 sampling design / edited by R.G. Nash and A.R. Leslie. 
 Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Groundwater; Agricultural chemicals;
 Water quality; Water pollution; Sampling; Mathematical models
 
 Abstract:  The vulnerability of aquifers to contamination by
 agrochemicals is relatively high in the southeastern Coastal
 Plain. Transport and fate of agrochemicals in either the root,
 unsaturated, or saturated zones can be simulated by existing
 mathematical models. However, a linked mathematical model is
 needed to simulate the movement and degradation from the point
 of application through the unsaturated zone, and into
 groundwater. The United States Geological Survey and
 Agricultural Research Service initiated a cooperative
 investigation in 1986. In 1988, the United States
 Environmental Protection Agency joined the research
 investigation. These agencies are sharing technical expertise
 and resources to develop an understanding of physical,
 chemical, and biological processes and to evaluate their
 spatial and temporal variability; and to develop and validate
 linked model(s) that would describe chemical transport and
 fate. Study sites have been selected in the Fall Line Hills
 district of the Coastal Plain province. The Claiborne aquifer
 recharge area is located in this district near Plains,
 Georgia. Instrumentation to measure water and chemical
 transport has been installed.
 
 
 278                        NAL Call. No.: TD899.P3N34 no.618
 Supplemental user's guide for applying the WASP4 model
 program. National Council of the Paper Industry for Air and
 Stream Improvement (U.S.) New York, N.Y. : National Council of
 the Paper Industry for Air and Stream Improvement,; 1991.
 2 v. : ill. ; 28 cm. (Technical bulletin (National Council of
 the Paper Industry for Air and Stream Improvement (U.S.) :
 1981) ; no. 618.).  Cover title.  "September 1991"--Cover. 
 Includes bibliographical references.
 
 Language:  English
 
 Descriptors: Water quality; Information storage and retrieval
 systems
 
 
 279                                 NAL Call. No.: 292.8 J82
 Surface runoff and soil water percolation as affected by snow
 and soil frost. Johnsson, H.; Lundin, L.C.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Jan.
 Journal of hydrology v. 122 (1/4): p. 141-159; 1991 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Arable soils; Frost; Snow; Spatial variation;
 Infiltration; Water flow; Drainage; Soil water content;
 Unfrozen water; Soil temperature; Frozen conditions; Soil
 depth; Soil pore system; Simulation models
 
 Abstract:  A coupled soil water and heat model was used to
 study the influence of soil frost and snow on infiltration and
 drainage flow in an agricultural field in central Sweden. An
 analogy between freezing/thawing and drying/wetting was
 assumed for the soil frost submodel. Model simulations were
 evaluated against measurements of total soil water content,
 unfrozen water content, soil temperature and drainage water-
 flow. The influences of soil frost and spatial variation in
 snow cover were studied by simulation of possible extreme
 situations in the field. The model accurately described the
 dynamics of soil temperature and water contents; however,
 infiltration and field drainage flow were considerably
 underestimated and delayed by about three weeks under frozen
 conditions. A model simulation, discounting the effects of
 soil frost, overestimated the drain response. An attempt at
 simulating the field variation in snow cover by assuming
 possible 'sink points' for snowmelt, explained part of the
 deviations between simulated and measured drain flows. A basis
 for a new model formulation of the infiltration and
 percolation processes in frozen soil is proposed in which two
 water-flow domains are assumed, one low-flow domain in the
 fine pores. smaller than those filled with ice, and one high-
 flow domain in the large air-filled pores. This allows the
 simulation of rapid infiltration in large ice-free pores and
 drainage flow under frozen conditions as well as the resulting
 redistribution of ice from smaller to larger pores.
 
 
 280                                NAL Call. No.: 292.8 W295
 Surface runoff contamination by chemicals initially
 incorporated below the soil surface.
 Wallach, R.; Shabtai, R.
 Washington, D.C. : American Geophysical Union; 1993 Mar.
 Water resources research v. 29 (3): p. 697-704; 1993 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Runoff; Overland flow; Agricultural chemicals;
 Contamination; Clay soils; Silt loam soils; Incorporation;
 Soil depth; Mathematical models; Prediction
 
 Abstract:  One method of reducing the contamination of
 overland flow by soil chemicals (e.g., nutrients, pesticides)
 is to reduce their concentration at the immediate soil
 surface. This can be done by incorporating the chemicals at
 lower depths, by either tilling the soil or by irrigating
 shortly after chemical application. A mathematical model
 designed to predict the runoff concentration of chemicals
 initially, located at different depths below the soil surface
 is presented. The model accounts for transient water
 infiltration and convective-dispersive solute transport in the
 soil, and also considers rate-limited mass transfer through a
 laminar boundary layer at the soil surface/runoff water
 interface. Sorption-desorption interactions between soil and
 chemicals are assumed to be subject to linear isotherms or to
 first-order kinetics. The dissolved chemical concentrations at
 the soil surface and in the surface runoff were simulated for
 coarse and fine soils at different antecedent soil moistures
 and rainfall intensities. The simulation indicated that the
 initial depth of chemical incorporation below the soil surface
 is negatively correlated to the dissolved chemical
 concentration at the soil surface and in runoff water. A basic
 and characteristic difference between the chemical whose
 retention by the soil solids is expressed by an equilibrium
 model and the one whose retention is expressed by a kinetic
 model is soil surface concentration during water and chemical
 redistribution following the termination of rainfall and
 runoff. Contrary, to the instantaneous equilibrium-type
 chemicals, the dissolved concentration of the kinetic-type
 chemicals increases sharply to its final value. For the
 coarser soil with higher saturated hydraulic conductivity, the
 relative chemical concentrations in surface runoff are lower
 than for the finer soil, when similar values of initial
 pressure head psi (0) and rainfall intensities (three times
 the saturated hydraulic conductivity of each soil) are
 
 
 281                                NAL Call. No.: 292.8 W295
 Surface runoff contamination by soil chemicals: simulations
 for equilibrium and first-order kinetics.
 Wallach, R.; Shabtai, R.
 Washington, D.C. : American Geophysical Union; 1992 Jan.
 Water resources research v. 28 (1): p. 167-173; 1992 Jan. 
 Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Solutes; Runoff; Overland
 flow; Contamination; Soil water content; Rain; Sloping land;
 Infiltration; Transport processes; Sorption; Desorption;
 Kinetics; Prediction; Mathematical models
 
 Abstract:  A model was developed to predict the potential
 contamination of overland flow by chemicals removed from soil
 water by rainfall on sloping soil. The model accounts for
 transient water infiltration and convective-dispersive solute
 transport in the soil and also considers rate-limited mass
 transfer through a laminar boundary layer at the soil
 surface/runoff water interface. Sorption-desorption
 interactions between soil and chemicals are assumed to be
 subject to linear and nonlinear isotherms or to first-order
 kinetics. The dissolved-chemical concentrations at the soil
 surface and in the surface runoff were determined for
 different antecedent soil moistures and rainfall intensities.
 These concentrations are lower when the antecedent moisture is
 low because the time of ponding for drier soil is longer and
 because during that period soil solutes are displaced by
 greater volumes of infiltrating water. For a specified initial
 soil water content, higher rainfall rates cause higher
 dissolved-chemical concentrations at the soil surface. The
 degree of nonlinearity of the equilibrium isotherm greatly
 affects the transient dissolved-chemical concentrations and
 the linear isotherm cannot always be used as an alternative.
 These concentrations are also greatly affected by the value of
 the kinetics rate coefficient. In the first-order kinetics
 model there is a recovery of the dissolved-chemical
 concentration at the soil surface during the period between
 rainstorms. As a result, the initial concentration at the soil
 surface for the subsequent rainstorm is higher than that
 expected when equilibrium is assumed.
 
 
 282                                  NAL Call. No.: Q320.B56
 Surface transport of microorganisms by water.
 Moore, J.A.
 Stoneham, Mass. : Butterworth Publishers; 1991.
 Biotechnology (15): p. 41-55; 1991.  In the Series Analytic:
 Assessing Ecological Risks of Biotechnology / edited by Lev R.
 Ginzburg.  Includes references.
 
 Language:  English
 
 Descriptors: Contaminants; Microbial contamination; Movement;
 Water transport; Runoff water; Models
 
 
 283                                NAL Call. No.: TD420.A1P7
 System modeling approach for solute transport through upper
 soils. Liu, C.C.K.; Feng, J.S.; Chen, W.
 Oxford : Pergamon Press; 1991.
 Water science and technology : a journal of the International
 Association on Water Pollution Research and Control v. 24 (6):
 p. 67-72; 1991.  In the series analytic: Watermatex '91 /
 edited by T.O. Barnwell, P.J. Ossenbruggen and M.B. Beck.
 Proceedings of the "Second International Conference on Systems
 Analysis in Water Quality Management," June 3-6, 1991, Durham,
 New Hampshire.  Includes references.
 
 Language:  English
 
 Descriptors: Hawaii; Soil; Surface layers; Solutes; Movement
 in soil; Agricultural chemicals; Groundwater pollution;
 Physical models; Simulation models; Systems approach; Case
 studies; Fenamiphos; Transport processes
 
 
 284                                  NAL Call. No.: S671.A66
 Targeting animal waste pollution potential using a geographic
 information system.
 Heatwole, C.D.; Shanholtz, V.O.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Nov. Applied engineering in agriculture v. 7
 (6): p. 692-698; 1991 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Virginia; Water pollution; Animal wastes; Site
 factors; Geography; Environmental impact; Models; Screening;
 Indexes; Ranking
 
 Abstract:  Data on livestock operations were added as a data
 layer and corresponding attribute table to the Virginia
 Geographic Information System (VirGIS) for seven counties in
 Virginia. A simple model calculates an animal waste pollution
 index (AWPI) which rates each site based on waste load, slope,
 and distance-to-stream. These factors are considered both for
 the facility as well as for the potential land application
 area surrounding the farm site. The geographic information
 system (GIS) database and model were used to produce maps and
 corresponding tables of facilities ranked by AWPI. Outputs
 were used as a screening tool to identify high-risk sites.
 Model evaluation based on 1253 farm sites in Rockingham County
 and 311 sites in Augusta County indicate a balance in site
 versus application area contribution to AWPI. For these two
 counties, the distribution of AWPI ratings is conducive to
 effective targeting. No relationship between animal type and
 AWPI was evident.
 
 
 285                                 NAL Call. No.: 56.8 J822
 Teaching land management with a microcomputer-based model.
 Ross, D.; Nash, T.; Harbor, J.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1992 May. Journal of soil and water conservation v. 47 (3): p.
 226-230; 1992 May. Includes references.
 
 Language:  English
 
 Descriptors: Land management; Soil conservation; Teaching
 methods; Land use; Computer assisted instruction;
 Microcomputers; Computer simulation; Simulation models;
 Universal soil loss equation; Water erosion; Runoff;
 Measurement; Erosion control; Sediment; Geological
 sedimentation; Gully erosion; Land types
 
 
 286                     NAL Call. No.: GB701.W375 no.91-4068
 Techniques for estimating selected parameters of the U.S.
 Geological Survey's Precipitation-Runoff Modeling System in
 eastern Montana and northeastern Wyoming.
 Cary, Lawrence E.
 United States, Bureau of Land Management, Geological Survey
 (U.S.) Helena, Mont. : U.S. Dept. of the Interior, U.S.
 Geological Survey ; Denver, CO : Books and Open-File Reports
 Section [distributor,; 1991; I 19.42/4:91-4068.
 iv, 39 p. : ill., maps ; 28 cm. (Water-resources
 investigations report ; 91-4068).  Shipping list no.: 92-047-
 P.  November 1991.  Includes bibliographical references (p.
 36-39).
 
 Language:  English; English
 
 Descriptors: Precipitation (Meteorology); Hydrologic cycle;
 Watersheds
 
 
 287                                 NAL Call. No.: 56.8 J822
 Terrain analysis: integration into the agricultural nonpoint
 source (AGNPS) pollution model.
 Panuska, J.C.; Moore, I.D.; Kramer, L.A.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1991 Jan. Journal of soil and water conservation v. 46 (1): p.
 59-64; 1991 Jan. Includes references.
 
 Language:  English
 
 Descriptors: Terrain; Pollution; Water quality; Erosion;
 Computer simulation
 
 
 288                                  NAL Call. No.: 56.9 SO3 A
 test of the local equilibrium assumption for adsorption and
 transport of picloram.
 Gaber, H.M.; Comfort, S.D.; Inskeep, W.P.; El-Attar, H.A.
 Madison, Wis. : The Society; 1992 Sep.
 Soil Science Society of America journal v. 56 (5): p.
 1392-1400; 1992 Sep. Includes references.
 
 Language:  English
 
 Descriptors: Silt loam soils; Picloram; Movement in soil;
 Equilibrium; Transport processes; Adsorption; Sorption
 isotherms; Soil water; Soil pore system; Soil water movement;
 Velocity; Kinetics; Mathematical models; Bromine
 
 Abstract:  The inability of transport models that use a local
 equilibrium assumption (LEA) to describe contaminant transport
 under certain conditions has led to the development of various
 criteria for assessing LEA applicability. Our objectives were
 to determine the influence of pore water velocity on the
 adsorption and transport of picloram
 (4-amino-3,5,6-trichloropicolinic acid) and evaluate the use
 of dimensionless Damkohler numbers for identifying
 experimental conditions conducive to nonequilibrium transport.
 Three sets of transport experiments were conducted to study
 the movement of Br- and picloram through an Amsterdam silt
 loam soil (fine-silty, mixed Typic Haploboroll). Experiments
 were performed by displacing a 100-mL Br-14C-labeled picloram
 pulse through disturbed soil columns (5.1-cm diam, 30-cm
 length) at pore water velocities of 4.1, 40.6, and 200.1 cm
 d-1. The kinetic parameters of picloram adsorption and
 desorption were obtained independently. Results indicated that
 Br- breakthrough curves (BTCs) were symmetrical at each pore
 water velocity. In contrast, picloram BTCs were shifted to the
 left on a pore-volume basis and demonstrated increased tailing
 with increasing pore water velocities. The use of LEA with a
 batch-determined distribution coefficient (Kd) in the
 convection-dispersion equation adequately described picloram
 BTCs at the 4.1 cm d-1 pore water velocity, but overestimated
 the elution time at faster pore water velocities. These
 observations were consistent with conclusions derived from
 criteria used to assess LEA applicability and indicate that
 knowledge of reaction kinetics and convective velocities can
 be easily used to identity conditions conducive to
 nonequilibrium transport.
 
 
 289                                  NAL Call. No.: QH540.J6
 Tests of the pesticide root zone model and the aggregate model
 for transport and transformation of aldicarb, metolachlor, and
 bromide. Parrish, R.S.; Smith, C.N.; Fong, F.K.
 Madison, Wis. : American Society of Agronomy; 1992 Oct.
 Journal of environmental quality v. 21 (4): p. 685-697; 1992
 Oct.  Includes references.
 
 Language:  English
 
 Descriptors: Aldicarb; Metolachlor; Bromide; Tracers;
 Profiles; Leaching; Vertical movement; Pesticide residues;
 Soil water movement; Sorption; Soil depth; Velocity;
 Dispersion; Mathematical models; Simulation models; Prediction
 
 Abstract:  Mathematical models are widely used to predict
 leaching of pesticides and nutrients in agricultural systems.
 This work was conducted to investigate the predictive
 capability of the Pesticide Root Zone Model (PRZM) and the
 Aggregate model (AGGR) for the pesticides aldicarb [2-
 methyl-2-(methylthio)propionaldehyde O-
 (methylcarbamoyl)oxime], metolachlor [2-chloro-N-(2-ethyl-6-
 methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide], and for
 a bromide tracer. Model predictions were compared with data
 collected during 1984 to 1987 in the Dougherty Plain area of
 southwestern Georgia. Field data were used to estimate mean
 concentrations of pesticide and bromide residues in the soil
 profile on various dates after application in each of four
 growing seasons. Both models tended to predict rates of
 movement of bromide tracer compounds in excess of that
 observed. For metolachlor, a pesticide with a sorption-
 partition coefficient that is higher than for other compounds
 in the study, both models provided reasonably accurate
 predictions within the upper 30-cm zone. For the pesticide
 aldicarb, results were more variable. The results suggest that
 the hydrologic components of both models are more accurate for
 the upper zones, but they are imprecise in deeper zones,
 underpredicting vertical dispersion and overpredicting
 transport velocity.
 
 
 290                                  NAL Call. No.: SB249.N6
 Theoretical background and validation of CPM, A new cotton
 simulation model. Sequeira, R.A.; Olson, R.L.
 Memphis, Tenn. : National Cotton Council of America; 1993.
 Proceedings - Beltwide Cotton Conferences. p. 543-549; 1993. 
 Meeting held January 10-14, 1993, New Orleans, Louisiana. 
 Includes references.
 
 Language:  English
 
 Descriptors: Cotton; Simulation models; Validity; Theory
 
 
 291                                NAL Call. No.: 292.8 W295
 Theoretical study of the significance of nonequilibrium
 dissolution of nonaqueous phase liquids in subsurface systems.
 Powers, S.E.; Loureiro, C.O.; Abriola, L.M.; Weber, W.J. Jr
 Washington, D.C. : American Geophysical Union; 1991 Apr.
 Water resources research v. 27 (4): p. 463-477; 1991 Apr. 
 Includes references.
 
 Language:  English
 
 Descriptors: Groundwater pollution; Soil pollution; Subsurface
 layers; Aquifers; Pollutants; Mass transfer; Movement in soil;
 Mathematical models
 
 Abstract:  The objective of this work is to assess the
 potential significance of deviations from local equilibrium
 for the exchange of mass between residual nonaqueous phase
 liquids and the aqueous phase in the saturated groundwater
 zone. A one-dimensional convection-dispersion mass balance
 equation incorporating a first-order interphase mass transfer
 rate relationship and temporal changes in blob configuration
 is used to model this system. Analytical and numerical methods
 are employed to examine the steady state and transient
 behavior of the system under a variety of hypothetical aquifer
 conditions and pumping remediation schemes. Sensitivity of the
 model to several parameters including mass transfer
 coefficient, blob size and shape, and Darcy velocity is
 explored. Results of the theoretical assessment indicate that
 nonequilibrium effects could play a significant role in some
 contamination scenarios, primarily for large blob sizes and
 relatively high velocities. Design of soil flushing techniques
 will be impacted by these conclusions. Uncertainty in several
 parameter values used in this analysis indicate the need for
 further experimental investigation of this process.
 
 
 292                         NAL Call. No.: HC110.W43T48 1993
 Theory, modeling, and experience in the management of
 nonpoint-source pollution.
 Russell, Clifford S.; Shogren, Jason F.
 Boston : Kluwer Academic Publishers,; 1993.
 xvii, 345 p. : ill., maps ; 24 cm. (Natural resource
 management and policy). Papers presented at a workshop
 sponsored by the Association of Environmental and Resource
 Economists and held at the University of Kentucky, Lexington,
 KY, in June 1991.  Includes bibliographical references.
 
 Language:  English; English
 
 Descriptors: Water; Agricultural pollution; Water quality
 management
 
 
 293                                NAL Call. No.: 292.8 W295 A
 three-dimensional field study of solute transport through
 unsaturated, layered, porous media. 2. Characterization of
 vertical dispersion. Ellsworth, T.R.; Jury, W.A.
 Washington, D.C. : American Geophysical Union; 1991 May.
 Water resources research v. 27 (5): p. 967-981; 1991 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Transport processes; Vertical movement;
 Dispersion; Solutes; Soil types; Prediction; Mathematical
 models; Transformation
 
 Abstract:  Solute plumes were created in an unsaturated field
 soil with either flux application or by leaching an initial
 resident distribution (see Ellsworth et al., this issue). The
 spatial variance of the plumes initially increased with time
 between the soil surface and a depth of 2.5 m, within which
 the soil was a nearly structureless loamy sand. Below this
 depth, the plumes were observed to compress in the vertical
 direction as they moved into, and through, a region of
 subangular blocky structure and loam texture (between 2.5 and
 4.0 m depth). As the solute moved below the layer of fine
 texture, the plume variance again increased with time. Using a
 transformed advection-dispersion equation description, two
 constant, field-averaged transport coefficients, V and D zz,
 were determined in a scaled coordinate system from the moment
 equations. These two constant parameters were then used to
 predict the observed local, or plot scale, transport. Results
 indicate that the two constant parameters describe transport
 reasonably well at each plot site and over all sampling
 depths.
 
 
 294                                NAL Call. No.: 292.8 W295 A
 three-dimensional field study of solute transport through
 unsaturated, layered, porous media. I. Methodology, mass
 recovery, and mean transport. Ellsworth, T.R.; Jury, W.A.;
 Ernst, F.F.; Shouse, P.J.
 Washington, D.C. : American Geophysical Union; 1991 May.
 Water resources research v. 27 (5): p. 951-965; 1991 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: California; Transport processes; Solutes; Soil
 types; Physicochemical properties; Prediction; Mathematical
 models
 
 Abstract:  A field experiment is reported which monitored the
 three-dimensional movement of cubic solute plumes through an
 unsaturated, loamy sand soil. The plumes were created with one
 of two methods, a two-dimensional flux application and an
 initial resident distribution. Soil coring was used to sample
 resident concentrations for the three solutes studied. The
 data were analyzed using the method of moments. In addition to
 the solute transport experiments, a detailed set of physical
 properties of the field was obtained by excavating three pits
 to a depth of 5.0 m and also by taking soil cores throughout
 the study area. This paper explains the experimental
 methodology, summarizes the relevant site characteristics, and
 describes the observed transport based on the zeroth and first
 order spatial moments. Mass balance varied between 78 and
 138%. The field-averaged gravimetric water content and dry
 bulk density were used to accurately predict the mean vertical
 plume displacements. The plumes spread relatively little in
 the horizontal direction.
 
 
 295                                NAL Call. No.: TD420.A1P7
 Trace metal soil quality criteria to protect groundwater. Lee,
 J.; Chen, B.; Allen, H.E.; Huang, C.P.; Sparks, D.L.; Sanders,
 P. Oxford : Pergamon Press; 1992.
 Water science and technology : a journal of the International
 Association on Water Pollution Research and Control v. 26
 (9/11): p. 2327-2329; 1992.  In the series analytic: Water
 Quality International '92. Part 5 / edited by M. Suzuki,
 et.al. Proceedings of the Sixteenth Biennial Conference of the
 International Association on Water Pollution Research and
 Control held May 24-30, 1992, Washington, D.C.
 
 Language:  English
 
 Descriptors: New Jersey; Soil pollution; Pollutants;
 Standards; Metals; Groundwater pollution; Soil; Adsorption;
 Soil ph; Mathematical models
 
 
 296                                  NAL Call. No.: TD403.G7
 Tracer test evaluation of a drainage ditch capture zone.
 Chambers, L.W.; Bahr, J.M.
 Dublin, Ohio : Ground Water Pub. Co; 1992 Sep.
 Ground water v. 30 (5): p. 667-675; 1992 Sep.  Includes
 references.
 
 Language:  English
 
 Descriptors: Wisconsin; Groundwater pollution; Agricultural
 chemicals; Spread; Prevention; Drainage; Ditches; Tracers;
 Iodide; Bromide; Tests; Prediction; Capacity; Analytical
 methods; Models; Movement in soil
 
 
 297                                  NAL Call. No.: TD403.G7
 Transient and steady-state solute transport through a large
 unsaturated soil column.
 Porro, I.; Wierenga, P.J.
 Dublin, Ohio : Ground Water Pub. Co; 1993 Mar.
 Ground water v. 31 (2): p. 193-200; 1993 Mar.  Includes
 references.
 
 Language:  English
 
 Descriptors: Soil pollution; Groundwater pollution;
 Pollutants; Solutes; Movement in soil; Transient flow; Steady
 flow; Unsaturated flow; Prediction; Models
 
 Abstract:  The use of steady-state models can sometimes reduce
 the computational resources and input data required for
 solution of transient transport problems. A large column
 experiment was performed to test whether solute transport
 parameters determined from a steady flow experiment may be
 used in transient, unsaturated flow and transport model
 predictions. Tritiated water and bromide were applied at a
 steady rate to the top of a 0.95 m diameter by 6 m deep soil
 column containing unsaturated soil. After 10 days, tracers
 were eliminated from the irrigation water. When the soil
 moisture content within the column ceased to change, another
 10-day pulse of tritiated water and bromide was applied,
 followed by water without tracers. Transport model parameters
 were determined through optimization, using breakthrough
 curves observed at various depths. The tritiated water and
 bromide pulses lagged behind the wetting front during
 infiltration into the relatively dry soil. The bromide pulse
 moved 17-20% faster than the tritiated water pulse, because of
 anion exclusion. Breakthrough curves for the transient and
 steady-state experiments were similar. Because the solute
 fronts lagged significantly behind the moisture fronts,
 steady-state transport parameters, when used in a fully
 transient numerical model, fairly described the transport
 under transient conditions.
 
 
 298                                  NAL Call. No.: 56.9 SO3
 Transport in a horizontal flow chamber.
 Sadeghi, A.M.; Starr, J.L.
 Madison, Wis. : The Society; 1992 Mar.
 Soil Science Society of America journal v. 56 (2): p. 600-603;
 1992 Mar. Includes references.
 
 Language:  English
 
 Descriptors: Groundwater flow; Horizontal flow; Transport
 processes; Laboratory methods; Simulation models; Soil water;
 Soil pore system; Velocity; Hydrodynamic dispersion
 
 Abstract:  A better understanding is needed of the factors
 that control the rate of chemicals that move laterally in
 shallow groundwater within fields to tile lines and drainage
 ditches and from fields to nearby streams or estuaries. A
 chamber was designed and used to simulate shallow groundwater
 flow in the field. The chamber, made of Plexiglas with
 dimensions 120 by 60 by 60 cm, was filled to a depth of 30 cm
 with sand. A multiport arrangement of 10-mm-diam. holes on a 5
 by 5 cm grid on both end walls of the chamber provided a
 combination for quite uniform solute application at the inlet
 side, and allowed sampling simultaneously from all ports at
 the outlet side. As a first approximation, the flow and
 transport were assumed to be one dimensional, and a
 convective-dispersive solute-transport model was applied to
 the Cl breakthrough data of each of the 50 outlet ports in
 order to quantify the spatial distribution of the dispersion-
 coefficient values at the outlet plate. Based on the
 inconsistency observed between measured and estimated pore-
 water velocities and dispersion coefficients of each of the 50
 outlet ports, it appears that the one-dimensional model is not
 appropriate to adequately characterize transport parameter in
 this horizontal flow system.
 
 
 299                              NAL Call. No.: RA1270.P35A1
 Transport of a BTX mixture in a groundwater aquifer material.
 Uchrin, C.G.; Katz, J.
 New York, N.Y. : Springer-Verlag; 1991 Apr.
 Bulletin of environmental contamination and toxicology v. 46
 (4): p. 534-541; 1991 Apr.  Includes references.
 
 Language:  English
 
 Descriptors: New Jersey; Petroleum; Benzene; Toluene; Xylene;
 Flow; Leaching; Aquifers; Groundwater; Mathematical models
 
 
 300                                    NAL Call. No.: 30 AD9
 Transport of chemicals through soil: mechanisms, models, and
 field applications.
 Jury, W.A.; Fluhler, H.
 San Diego, Calif. : Academic Press; 1992.
 Advances in agronomy v. 47: p. 141-210; 1992.  Literature
 review.  Includes references.
 
 Language:  English
 
 Descriptors: Soil chemistry; Movement in soil; Solutes;
 Transport processes; Literature reviews; Mathematical models
 
 
 301                                  NAL Call. No.: QH540.N3
 Transport of linearly reactive solutes in porous media. Basic
 models and concepts.
 Schweich, D.
 Berlin, W. Ger. : Springer-Verlag; 1993.
 NATO ASI series : Series G : Ecological sciences v. 32: p.
 221-245; 1993.  In the series analytic: Migration and fate of
 pollutants in soils and subsoils / edited by D. Petruzzelli
 and F.G. Helfferich. Proceedings of the NATO Advanced Study
 Institute, May 24-June 5, 1992, Maratea, Italy.  Includes
 references.
 
 Language:  English
 Descriptors: Soil pollution; Pollutants; Transport processes;
 Equations; Mathematical models; Soil water movement;
 Groundwater flow
 
 
 302                                 NAL Call. No.: 56.8 J823
 Two models for the leaching of a non-reactive solute to a mole
 drain. Scotter, D.R.; Heng, L.K.; White, R.E.
 Oxford : Blackwell Scientific Publications; 1991 Dec.
 The Journal of soil science v. 42 (4): p. 565-576; 1991 Dec. 
 Includes references.
 
 Language:  English
 
 Descriptors: Mole drainage; Solutes; Losses from soil;
 Simulation models; Mathematical models; Silt loam soils;
 Potassium chloride; Chloride; Leaching
 
 Abstract:  Two models of solute leaching to a mole-pipe
 drainage system are described. The first model is research-
 oriented. It simplifies two-dimensional water and solute flow
 to a mole drain by dividing the soil between the mid-mole
 plane and the mole into notional compartments. Solute movement
 between compartments is assumed to occur by convection and
 mechanical dispersion. Within each compartment a mobile and
 immobile solute phase is defined, with diffusion occurring
 between them. Rainfall intensity (over approximately hourly,
 intervals) and basic soil hydraulic data are needed as inputs.
 An explicit finite-difference solution to the water and solute
 mass-balance and flux equations is used. The second simpler
 model is management-oriented. It uses daily time steps, and
 assumes the soil solution behaves as if it were a well-mixed
 system. It requires only-daily rainfall and evaporation data,
 the drainage coefficient of the mole-pipe system, and the soil
 macroporosity as inputs. In both models a source/sink term
 accounts for additions of solute in rainfall and fertilizer,
 and extraction by plant uptake. The models were used to
 simulate leaching, losses of chloride to a mole-pipe drainage
 system in a silt loam under pasture, following the application
 of potassium chloride to the soil surface. The first model
 simulated leaching better immediately after fertilizer
 application, and during bypass flow, induced by heavy rain.
 However both models were able to simulate the measured losses
 over a 2-year period equally well.
 
 
 303                                 NAL Call. No.: TC401.W27
 Two new characteristic parameters for runoff computation. Leu,
 J.M.; Liu, C.L.
 Dordrecht : Kluwer Academic Publishers; 1992.
 Water resources management v. 6 (1): p. 165-184; 1992. 
 Includes references.
 
 Language:  English
 
 Descriptors: Taiwan; Rain; Runoff; Watersheds; Models
 
 
 304                               NAL Call. No.: 290.9 AM32T
 Uncertainty analysis of the WEPP soil erosion model.
 Chasves, H.M.L.; Nearing, M.A.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Nov. Transactions of the ASAE v. 34 (6): p.
 2437-2444; 1991 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Water erosion; Prediction; Losses from soil
 systems; Simulation models
 
 Abstract:  Predictions from hydrologic and erosion models
 contain a large degree of uncertainty. The Modified Point
 Estimate Method (Harr, 1989) used in conjunction with a
 response surface exploration technique (Brooks, 1958) provides
 a simple, computationally efficient, and powerful tool for
 evaluating uncertainty of predictions by natural-resource
 models. The method allows analysis of models with a large
 number of input parameters which may be correlated and for
 which the exact input parameter distribution is unknown. The
 method was applied to the Water Erosion Prediction Project
 single rainfall-event erosion model. Sixty treatment
 combinations were selected to determine WEPP output
 uncertainties for a wide range of soil, crop, management,
 topographic, and storm conditions. The levels of the treatment
 combinations were randomly selected to span the entire
 factorial space of the 28 WEPP inputs, but with a finite
 number of treatment combinations. Five WEPP outputs were
 studied: peak runoff rate, average soil loss, average
 deposition, sediment yield, and sediment specific surface
 enrichment ratio. Maximum and average output uncertainties,
 given by the coefficient of variation, were determined for
 each output of the 60 treatments. Maximum coefficients of
 variation for peak runoff rate, soil loss, sediment yield, and
 sediment enrichment ratio were 196, 267, 323, and 47%,
 respectively. Average coefficients of variation for the same
 set of variables were 65, 99, 106, and 13%, respectively.
 Coefficient of variation was less for larger runoff and
 erosion events, which account for a large percentage of the
 total soil loss at a location over extended time periods.
 Significant, positive correlations existed between the
 coefficients of variation of peak runoff average soil loss,
 and average soil loss and sediment yield, indicating that the
 uncertainty in average soil loss and in sediment yield may be
 directly related to the uncertainty in peak runoff rate.
 
 
 305                                  NAL Call. No.: 56.8 SO3
 Unsaturated hydraulic characteristics of composted
 agricultural wastes, tuff, and their mixtures.
 Wallace, R.; Silva, F.F. da; Chen, Y.
 Baltimore, Md. : Williams & Wilkins; 1992 Jun.
 Soil science v. 153 (6): p. 434-441; 1992 Jun.  Includes
 references.
 
 Language:  English
 
 Descriptors: Composts; Grape marc; Volcanic ash; Mixtures;
 Culture media; Pot culture; Unsaturated hydraulic
 conductivity; Determination; Mathematical models; Soil water
 retention; Soil water potential; Saturated hydraulic
 conductivity; Hysteresis; Crop management; Fertilizers;
 Irrigation
 
 
 306                                  NAL Call. No.: 56.9 SO3
 Urea transformations in flooded soil columns. II. Derivation
 of model and implications to ammonia volatilization.
 Bouldin, D.R.; Hongprayoon, C.; Lindau, C.W.; Patrick, W.H. Jr
 Madison, Wis. : The Society; 1991 Jul.
 Soil Science Society of America journal v. 55 (4): p.
 1135-1142; 1991 Jul. Includes references.
 
 Language:  English
 
 Descriptors: Oryza sativa; Silt loam soils; Urea; Transport
 processes; Volatilization; Ammonia; Losses from soil systems;
 Diffusion; Hydrolysis; Sorption; Ammonium nitrogen;
 Diffusivity; Mathematical models; Soil management;
 Incorporation; Depth; Ph; Temperature; Flooded rice; Paddy
 soils; Laboratory methods
 
 Abstract:  Ammonia volatilization from rice (Oryza sativa L.)
 paddies following urea application reduces the effectiveness
 of the urea-N. The objectives of this study were to: (i)
 derive, for flooded soils, a model describing hydrolysis and
 diffusion of urea and diffusion of ammoniacal N; (ii) derive
 the necessary parameters from experimental data, and (iii) use
 the model to study implications of hydrolysis/transport sport
 parameters and management variables to NH3 volatilization. The
 parameters are diffusion coefficients of urea and NH4, in soil
 hydrolysis coefficients of urea in the soil and overlying
 floodwater, and the sorption coefficient for NH4 on the soil.
 The effects on potential for NH3 volatilization of variation
 in these parameters and the management factors of depth of
 flood water and depth of fertilizer incorporation were
 calculated. The results illustrate that urea-hydrolysis rates
 in the floodwater and soil are the most important factors
 influencing the potential for NH3 volatilization. If urea-
 hydrolysis rates are very high, incorporation and shallow
 floodwater are the indicated management while, with low
 hydrolysis rates, deep floodwater and no incorporation are the
 indicated management.
 
 
 307                                 NAL Call. No.: 56.8 J822
 Use of a geographic information system for selection of sites
 for land application of sewage waste.
 Hendrix, W.G.; Buckley, D.J.A.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1992 May. Journal of soil and water conservation v. 47 (3): p.
 271-275; 1992 May. Includes references.
 
 Language:  English
 
 Descriptors: Vermont; Agricultural land; Forests; Land types;
 Sewage effluent; Sewage effluent disposal; Waste disposal
 sites; Selection methods; Information systems; Geography;
 Computer techniques; Site factors; Soil variability; Soil
 physical properties; Land use; Topography; Social values;
 Environmental legislation; Models
 
 
 308                     NAL Call. No.: GB701.W375 no.90-4140
 Use of a geographic information system to assess risk to
 ground-water quality at public-supply wells, Cape Cod,
 Massachusetts.
 Olimpio, Julio C.
 Massachusetts, Division of Water Pollution Control, Geological
 Survey (U.S.) Boston, Mass. : U.S. Dept. of the Interior, U.S.
 Geological Survey ; Denver, CO : Books and Open-File Reports
 Section [distributor],; 1991; I 19.42/4:90-4140.
 v, 35, 10 p. : ill., maps (some col.) ; 28 cm. (Water-
 resources investigations report ; 90-4140).  Shipping list
 no.: 91-790-P.  Includes bibliographical references (p. 35).
 
 Language:  English
 
 Descriptors: Water quality; Geographic information systems;
 Water, Underground
 
 
 309                               NAL Call. No.: QH545.A1E58
 Use of gleams to predict insecticide losses from pine seed
 orchards. Nutter, W.L.; Knisel, W.G. Jr; Bush, P.B.; Taylor,
 J.W.
 Tarrytown, Y. : Pergamon Press; 1993 Mar.
 Environmental toxicology and chemistry v. 12 (3): p. 441-452;
 1993 Mar.  Paper presented at the "Symposium on Pesticides in
 Forest Management, 11th Annual Meeting of the Society of
 Environmental Toxicology and Chemistry," November 11-15, 1990,
 Arlington, Virginia.  Includes references.
 
 Language:  English
 
 Descriptors: Southern states of U.S.A.; Carbofuran; Azinphos-
 methyl; Fenvalerate; Permethrin; Leaching; Groundwater;
 Runoff; Vertical movement; Surface water; Seed orchards;
 Simulation models; Prediction
 
 
 310                                  NAL Call. No.: S671.A66
 The use of graphics to present the results of erosion models.
 Bingner, R.L.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Mar. Applied engineering in agriculture v. 7
 (2): p. 193-197; 1991 Mar.  Includes references.
 
 Language:  English
 
 Descriptors: Erosion; Models; Watersheds; Computer software;
 Graphic arts; Runoff
 
 Abstract:  This study shows how graphical representations of a
 watershed system can be used to analyze the runoff and
 sediment yield. Combining output data from an erosion model,
 such as runoff, sediment yield, and particle size distribution
 of the eroded sediment, onto a single screen on a computer
 monitor, permits immediate analysis as a rainfall event
 occurs. This study shows how the erosion models CREAMS and
 ANSWERS can be modified for simulations on small and large
 watersheds, using graphics to enhance the results.
 
 
 311                                 NAL Call. No.: SB610.W39
 Use of modeling in developing label restrictions for
 agricultural chemicals. Jones, R.L.
 Champaign, Ill. : The Society; 1992 Jul.
 Weed technology : a journal of the Weed Science Society of
 America v. 6 (3): p. 683-687; 1992 Jul.  Paper presented at a
 Symposium on the, "Role of Modeling in Regulatory Affairs," at
 the Weed Science Society of America, February 4, 1991,
 Louisville, Kentucky.  Includes references.
 
 Language:  English
 
 Descriptors: Agricultural chemicals; Pesticides; Simulation
 models; Regulations; Labeling; Groundwater; Drinking water;
 Water quality
 
 
 312                                 NAL Call. No.: 60.18 J82
 Use of stochastically generated weather records with rangeland
 simulation models.
 Wight, J.R.; Hanson, C.L.
 Denver, Colo. : Society for Range Management; 1991 May.
 Journal of range management v. 44 (3): p. 282-285; 1991 May. 
 Includes references.
 
 Language:  English
 
 Descriptors: Rangelands; Herbage; Crop yield; Prediction;
 Simulation models; Weather data; Runoff; Precipitation; Air
 temperature; Solar radiation; Stochastic models; Yield
 forecasting; Hydrological data
 
 Abstract:  We compared long-term historical and stochastically
 generated weather records in terms of their statistical
 attributes and effects on herbage yield and runoff forecasts
 calculated from model simulations. The historical and
 synthetic air temperature and solar radiation records were in
 good agreement in terms of monthly means and extremes. The
 synthetic precipitation record failed to simulate extreme
 precipitation events which significantly reduced forecasted
 runoff values. Yield forecasts were similar using either
 historical or synthetic weather records.
 
 
 313                                 NAL Call. No.: HC79.E5E5
 Use of wetlands for water quality improvement under USEPA
 Region V Clean Lakes Programs.
 Landers, J.C.; Knuth, B.A.
 New York, N.Y. : Springer-Verlag; 1991 Mar.
 Environmental management v. 15 (2): p. 151-162; 1991 Mar. 
 Includes references.
 
 Language:  English
 
 Descriptors: Minnesota; Wisconsin; Indiana; Wetlands; Lakes;
 Water quality; Environmental protection; Runoff water; Land
 management; Program evaluation; Models; Land diversion;
 Federal programs
 
 
 314                          NAL Call. No.: SD421.37.C6 1991
 Using a GIS to document relationships between disturbance and
 sedimentation following salvage logging.
 Wells, W.G. II; Napoleon, E.J.; Wohlgemuth, P.M.
 Bethesda, Md. : Society of American Foresters; 1991.
 Proceedings of the 11th Conference on Fire and Forest
 Meteorology, April 16-19, 1991, Missoula, Montana / sponsored
 by the Society of American Foresters and American
 Meteorological Soc. ; editors, P.L. Andrews and D.F. Potts. p.
 405-411; 1991.  This record corrects IND 92025711 which was
 entered incorrectly under call number SD143.S64.  Includes
 references.
 
 Language:  English
 
 Descriptors: California; Salvage felling and logging; Erosion;
 Sediment
 
 
 315                                NAL Call. No.: 60.18 UN33
 Using computer situations to predict the fate and
 environmental impact of applied pesticides.
 Franke, K.J.
 Far Hills, N.J. : United States Golf Association; 1992 Mar.
 USGA Green Section record v. 30 (2): p. 17-21; 1992 Mar.
 
 Language:  English
 
 Descriptors: Lawns and turf; Golf courses; Pesticides;
 Integrated pest management; Environmental impact; Computer
 simulation
 
 
 316                                    NAL Call. No.: 10 OU8
 Using crop models for sustainability and environmental quality
 assessment. Singh, U.; Thornton, P.K.
 Oxon : C.A.B. International; 1992.
 Outlook on agriculture v. 21 (3): p. 209-218; 1992.  Includes
 references.
 
 Language:  English
 
 Descriptors: Crop production; Environmental impact; Leaching;
 Nitrogen fertilizers; Pollution; Simulation models;
 Sustainability
 
 
 317                                 NAL Call. No.: 56.9 SO32
 Using geographic information systems in a well permitting
 program. Myhre, B.E.; Shih, S.F.
 S.l. : The Society; 1991.
 Proceedings - Soil and Crop Science Society of Florida v. 50:
 p. 102-105; 1991.  Paper presented at the "Symposium on
 Reality of Sustainable Agriculture in Florida, September
 26-28, 1990, Daytona Beach, FLorida.  Includes references.
 
 Language:  English
 
 Descriptors: Florida; Groundwater; Water quality; Wells;
 Geographical distribution
 
 
 318                                 NAL Call. No.: 56.9 SO32
 Using landsat data and geographic information system for
 wetland assessment in water-quality management.
 Still, D.A.; Shih, S.F.
 S.l. : The Society; 1991.
 Proceedings - Soil and Crop Science Society of Florida v. 50:
 p. 98-102; 1991.  Paper presented at the "Symposium on Reality
 of Sustainable Agriculture in Florida, September 26-28, 1990,
 Daytona Beach, FLorida.  Includes references.
 
 Language:  English
 
 Descriptors: Florida; Wetlands; Water quality; Assessment;
 Landsat
 
 
 319                                NAL Call. No.: 292.9 AM34
 Using soil texture to estimate saturated hydraulic
 conductivity and the impact on rainfall-runoff simulations.
 Loague, K.
 Bethesda, Md. : American Water Resources Association; 1992
 Jul. Water resources bulletin v. 28 (4): p. 687-693; 1992 Jul. 
 Includes references.
 
 Language:  English
 
 Descriptors: Rangelands; Rangeland soils; Soil texture;
 Saturated hydraulic conductivity; Infiltration; Rain; Runoff;
 Simulation models; Mathematical models
 
 Abstract:  In this paper a new set of soil texture data is
 used to estimate the spatial distribution or saturated
 hydraulic conductivity values for a small rangeland catchment.
 The estimates of conductivity are used to re-excite and re-
 evaluate a quasi-physically based rainfall-runoff model. The
 performance or the model is significantly reduced with
 conductivity estimates gleaned from soil texture data rather
 than the infiltration data used in our previous efforts.
 
 
 320                               NAL Call. No.: 290.9 AM32T
 Using the ANSWERS model to predict runoff and soil loss in
 southwestern Quebec.
 Montas, H.J.; Madramootoo, C.A.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Jul. Transactions of the ASAE v. 34 (4): p.
 1754-1762; 1991 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Quebec; Losses from soil systems; Runoff;
 Sediment; Computer simulation; Erosion; Watersheds
 
 Abstract:  The distributed parameter model ANSWERS was used to
 predict runoff and soil loss for two small agricultural
 watersheds in southwestern Quebec. Runoff predictions were
 compared for 24 observed events. Peak flow was generally
 underpredicted and time to peak was overpredicted. A seasonal
 adjustment of infiltration parameters was derived to account
 for crusting and sealing of the soils in the spring and fall.
 Runoff predictions with adjusted parameters were better than
 those with measured parameters. Predictions of sediment
 concentration and yield, with adjusted infiltration
 parameters, were compared with seven observed storm events.
 ANSWERS underpredicted sediment yield for all events.
 
 
 321                               NAL Call. No.: 290.9 AM32T
 Validating GLEAMS with pesticide field data on a Clermont silt
 loam soil. Sichani, S.A.; Engel, B.A.; Monke, E.J.; Eigel,
 J.D.; Kladivko, E.J. St. Joseph, Mich. : American Society of
 Agricultural Engineers; 1991 Jul. Transactions of the ASAE v.
 34 (4): p. 1732-1737; 1991 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: Indiana; Alachlor; Atrazine; Cyanazine;
 Carbofuran; Chlorpyrifos; Groundwater; Leaching; Simulation
 models; Water pollution
 
 Abstract:  The GLEAMS (Groundwater Loading Effects of
 Agricultural Management Systems) model was used to simulate
 the appearances of pesticides in outflow of an experimental
 drainage field at the South East Purdue Agricultural Center
 (SEPAC) in southeastern Indiana. This article presents the
 comparison of simulated and observed loading of Alachlor,
 Atrazine, Cyanazine, Carbofuran, and Chlorpyrifos in tile
 outflows for 1985 through 1989. Me results of the simulation
 were close to field observations for total masses of
 pesticides leached from the root zone and for the overall
 timing of pesticide appearance in tile flows. However, the
 simulation of the watershed did not predict the observed
 arrival of pesticides in the drain during the first storm
 event after pesticide application. To compare the simulated
 results from on-site weather data and the data from nearby
 locations, long-term mean monthly solar radiation data for
 SEPAC and Indianapolis, Indiana were evaluated.
 
 
 322                                NAL Call. No.: FICHE S-72
 Validation of WEPP 91.2 with erosion plot data.
 Kramer, L.A.; Alberts, E.E.; Ghidey, F.
 St. Joseph, Mich. : The Society; 1991.
 American Society of Agricultural Engineers (Microfiche
 collection) (fiche no. 91-2079): 16 p.; 1991.  Paper presented
 at the 1991 Summer Meeting of the American Society of
 Agricultural Engineers held June 23-26, 1991, Albuquerque, New
 Mexico.  Includes references.
 
 Language:  English
 
 Descriptors: Water erosion; Prediction; Simulation models;
 Runoff; Losses from soil systems; Experimental plots; Tillage;
 Zea mays; Regression analysis
 
 
 323                                NAL Call. No.: 292.8 W295
 Vapor transport in unsaturated soil columns: implications for
 vapor extraction.
 Gierke, J.S.; Hutzler, N.J.; McKenzie, D.B.
 Washington, D.C. : American Geophysical Union; 1992 Feb.
 Water resources research v. 28 (2): p. 323-335; 1992 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil pollution; Contaminants; Toluene; Methane;
 Vapor; Extraction; Transport processes; Sand; Aggregates;
 Mathematical models
 
 Abstract:  A mathematical model was derived to examine the
 impact of gas advection, gas diffusion, gas-water mass
 transfer, gas-water partitioning, sorption, and intraaggregate
 diffusion on subsurface movement of organic vapors. Laboratory
 experiments were performed to determine the validity of the
 model and to investigate the impact of the various mechanisms
 on vapor transport, Columns were packed with a uniform Ottawa
 sand and an aggregated porous soil material (APSM) to compare
 transport in different soil structures. Toluene vapor
 transport was observed in the sand under dry and wet (27%
 water saturation) conditions. The experiments with the APSM
 were performed dry and at 67% water saturation. in all the
 sand and the dry APSM experiments, gas advection and diffusion
 had the greatest impact. In a wet APSM experiment,
 intraaggregate (liquid) diffusion was also important to
 consider for gas velocities greater than approximately 0.05 cm
 s-1. For both soil materials, sorption of toluene vapors
 occurred for dry conditions, while vapor sorption was
 negligible when liquid water was present. These findings imply
 that vapor extraction performance in moist, aggregated soils
 will be affected by nonequilibrium transport. Therefore models
 that are developed for predicting the complete removal of
 contaminants by vapor extraction must account for
 nonequilibrium.
 
 
 324                               NAL Call. No.: 290.9 AM32T
 Variability of optimized parameter estimates based on observed
 record length. Allred, B.; Haan, C.T.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1991 Nov. Transactions of the ASAE v. 34 (6): p.
 2421-2426. maps; 1991 Nov.  Includes references.
 
 Language:  English
 
 Descriptors: Oklahoma; Arkansas; Hydrology; Rain; Runoff;
 Stream flow; Watersheds; Mathematical models
 
 Abstract:  The variability in parameter estimates for a
 hydrologic model as a function of the number of years of data
 available for estimating the parameters was investigated. A
 25-year record on Spavinaw Creek in Oklahoma and Arkansas was
 divided into 25 one-year, 12 two-year, and 5 five-year
 records. Each period was used for parameter estimation. Two
 objective functions, one based on absolute errors and one
 based on error sum of squares, were used. Mean parameter
 values exhibited greater than expected variability, and
 variances in estimated parameters did not decrease as expected
 as the number of years used for parameter estimation increased
 from one to five years. One year was found to dominate one of
 the estimated model parameters for any record length that
 included that particular year. Significant differences between
 parameter values based on the two objective functions were
 found only for one parameter based on one-year optimizations.
 
 
 325                                 NAL Call. No.: 448.3 AP5
 VIRTUS, a model of virus transport in unsaturated soils.
 Yates, M.V.; Ouyang, Y.
 Washington, D.C. : American Society for Microbiology; 1992
 May. Applied and environmental microbiology v. 58 (5): p.
 1609-1616; 1992 May. Includes references.
 
 Language:  English
 
 Descriptors: Groundwater; Viruses; Transport processes; Soil
 water content; Soil water regimes; Movement in soil;
 Inactivation; Soil temperature; Pollutants; Models
 
 Abstract:  As a result of the recently proposed mandatory
 groundwater disinfection requirements to inactivate viruses in
 potable water supplies, there has been increasing interest in
 virus fate and transport in the subsurface. Several models
 have been developed to predict the fate of viruses in
 groundwater, but few include transport in the unsaturated zone
 and all require a constant virus inactivation rate. These are
 serious limitations in the models, as it has been well
 documented that considerable virus removal occurs in the
 unsaturated zone and that the inactivation rate of viruses is
 dependent on environmental conditions. The purpose of this
 research was to develop a predictive model of virus fate and
 transport in unsaturated soils that allows the virus
 inactivation rate to vary on the basis of changes in soil
 temperature. The model was developed on the basis of the law
 of mass conservation of a contaminant in porous media and
 couples the flows of water, viruses, and heat through the
 soil. Model predictions were compared with measured data of
 virus transport in laboratory column studies and, with the
 exception of one point, were within the 95% confidence limits
 of the measured concentrations. The model should be a useful
 tool for anyone wishing to estimate the number of viruses
 entering groundwater after traveling through the soil from a
 contamination source. In addition, model simulations were
 performed to identify parameters that have a large effect on
 the results. This information can be used to help design
 experiments so that important variables are measured
 accurately.
 
 
 326                                 NAL Call. No.: 292.8 J82
 Water balance and soil moisture dynamics of field plots with
 barley and grass ley.
 Johnsson, H.; Hansson, P.E.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1991 Dec.
 Journal of hydrology v. 129 (1/4): p. 149-173; 1991 Dec. 
 Includes references.
 
 Language:  English
 
 Descriptors: Sweden; Hordeum vulgare; Festuca pratensis; Leys;
 Arable land; Nitrogen fertilizers; Soil water; Soil water
 balance; Evapotranspiration; Evaporation; Transpiration; Soil
 physical properties; Plant development; Meteorological
 factors; Drainage; Runoff; Precipitation; Simulation; Physical
 models
 
 Abstract:  A physically based soilwater and heat model was
 used to estimate the water balance of an arable field in
 central Sweden for each of three different crop covers (barley
 with and without N fertilization and grass ley). Annual water
 balances were calculated for each year from 1981 to 1985. On-
 site measurements of soil physical properties, meteorological
 variables and plant development were used as input to the
 model. Simulated soil frost, snow cover, soilwater contents,
 soilwater tensions and relative differences in simulated
 drainage between treatments were in agreement with the
 corresponding measured values. In the simulation, surface
 runoff (70 mm year-1 in all treatments) mainly occurred during
 snowmelt periods and accounted for much of the variation in
 the total runoff estimate. Annual mean precipitation amounted
 to 610 mm year-1, whereas average evapotranspiration was
 calculated to be 320, 360 and 435 mm year-1 in barley without
 N fertilization, barley with N fertilization and grass ley,
 respectively. Soil evaporation accounted for 60, 43 and 23%
 whereas evaporation of intercepted water accounted for 5, 12
 and 19% of the total evapotranspiration, respectively.
 Drainage estimates amounted to 205, 170 and 110 mm year-1.
 
 
 327                                 NAL Call. No.: 56.8 J822
 Water balance components in the Georgia Coastal Plain: a
 GLEAMS model validation and simulation.
 Knisel, W.G.; Leonard, R.A.; Davis, F.M.; Sheridan, J.M.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1991 Nov. Journal of soil and water conservation v. 46 (6): p.
 450-456; 1991 Nov. Includes references.
 
 Language:  English
 
 Descriptors: Georgia; Watersheds; Rain; Runoff; Subsurface
 drainage; Water balance; Simulation models; Validity
 
 
 328                                NAL Call. No.: 280.8 J822
 Water markets and water quality.
 Weinberg, M.; Kling, C.L.; Wilen, J.E.
 Ames, Iowa : American Agricultural Economics Association; 1993
 May. American journal of agricultural economics v. 75 (2): p.
 278-291; 1993 May. Includes references.
 
 Language:  English
 
 Descriptors: U.S.A.; Water quality; Irrigation water; Markets;
 Water use efficiency; Water allocation; Farm management;
 Decision making; Drainage; Simulation models; Water policy
 
 Abstract:  In addition to improving the allocative efficiency
 of water use, water markets may reduce irrigation-related
 water quality problems. This potential benefit is examined
 with a nonlinear programming model developed to simulate
 agricultural decision-making in a drainage problem area in
 California's San Joaquin Valley. Results indicate that a 30%
 drainage goal is achievable through improvements in irrigation
 practices and changes in cropping patterns induced by a water
 market. Although water markets will not generally achieve a
 least-cost solution, they may be a practical alternative to
 economically efficient, but informationally intensive,
 environmental policies such as Pigouvian taxes.
 
 
 329                         NAL Call. No.: TD419.5.W365 1991
 Water pollution modelling, measuring, and prediction.
 Brebbia, C. A.; Wrobel, L. C.
 International Conference on Water Pollution: Modelling,
 Measuring, and Prediction 1st : 1991 : Southampton, England.
 Southampton ; Boston : Computational Mechanics Pub. ; London ;
 New York : Elsevier Applied Science,; 1991.
 748 p. : ill. ; 24 cm.  "Contains the edited versions of some
 of the papers presented at the First International Conference
 on Water Pollution: Modelling, Measuring and Prediction"--P. 4
 of cover.  Includes bibliographical references and index.
 
 Language:  English
 
 Descriptors: Water; Water quality; Sewage
 
 
 330                                NAL Call. No.: 302.8 T162
 Water quality and biological investigation of the lower Cape
 Fear River Basin. Kreutzberger, W.A.; Wakild, C.R.
 Norcross, Ga. : The Technical Association of the Pulp and
 Paper Industry; 1993 Jul.
 Tappi journal v. 76 (7): p. 169-177; 1993 Jul.  Includes
 references.
 
 Language:  English
 
 Descriptors: North Carolina; Pulp and paper industry; Pulp
 mill effluent; Water quality; Biochemical oxygen demand;
 Models; Rivers
 
 
 331                                  NAL Call. No.: TD172.J6
 Water quality modeling in distribution systems.
 Clark, R.M.
 New York, N.Y. : Marcel Dekker; 1992 Jul.
 Journal of environmental science and health : Part A :
 Environmental science and engineering v. 27 (5): p. 1329-1366;
 1992 Jul.  Includes references.
 
 Language:  English
 
 Descriptors: U.S.A.; Drinking water; Water quality;
 Deterioration; Quality standards; Law enforcement;
 Environmental protection; Public agencies; Water distribution;
 Systems; Health hazards
 
 
 332                            NAL Call. No.: TD482.W38 1991
 Water quality modeling in distribution systems conference
 proceedings, February 4-5, 1991, Cincinnati, Ohio.. 
 Proceedings, water quality modeling in distribution systems
 AWWA Research Foundation, United States, Environmental
 Protection Agency Denver, Colo. : The Foundation,; 1991.
 viii, 469 p. : ill., maps ; 23 cm.  Cover title: Proceedings,
 water quality modeling in distribution systems.  Includes
 bibliographical references and index.
 
 Language:  English
 
 Descriptors: Water quality; Water
 
 
 333                          NAL Call. No.: TD370.W3957 1992
 Water quality modelling.
 Falconer, R. A.
 Institution of Water and Environmental Management
 Aldershot, Hants, England ; Brookfield, Vt., USA : Ashgate,;
 1992. xii, 139 p. : ill. ; 24 cm.  Published in association
 with the Institution of Water and Environmental Management. 
 Papers from a one day symposium given by the IWEM and held in
 Harrogate on 11/13/91.  Includes bibliographical references.
 
 Language:  English
 
 Descriptors: Water quality
 
 
 334                               NAL Call. No.: 290.9 AM32T
 Water table management practice effects on water quality.
 Wright, J.A.; Shirmohammadi, A.; Magette, W.L.; Fouss, J.L.;
 Bengtson, R.L.; Parsons, J.E.
 St. Joseph, Mich. : American Society of Agricultural
 Engineers; 1992 May. Transactions of the ASAE v. 35 (3): p.
 823-831; 1992 May.  Includes references.
 
 Language:  English
 
 Descriptors: Water management; Water quality; Water table;
 Drainage; Hydrology; Simulation models; Subsurface irrigation
 
 Abstract:  Impacts of water table management (WTM) practices
 on water quality were modeled using a linked version of CREAMS
 and DRAINMOD (Parsons and Skaggs, 1988). The CREAMS
 denitrification component and the linked DRAINMOD-CREAMS model
 were modified to simulate daily hydrology (runoff,
 infiltration, evaporation, and soil moisture content),
 erosion, and nutrient processes for different WTM conditions.
 Measured data from Baton Rouge, Louisiana, were used to
 validate the linked model, and then controlled drainage-
 subirrigation (CD-SI) was simulated to investigate the effects
 of different WTM systems on runoff, erosion, and nitrogen
 losses. Results of the study indicated that the linked models
 performed better than the original CREAMS model in predicting
 runoff, infiltration, soil moisture content, and erosion, and
 that the modified linked model performed better than both
 CREAMS and the original linked model in predicting nitrogen
 losses from the study site. Results also showed that the CD-SI
 system simulated by the modified DRAINMOD-CREAMS model
 predicted increased denitrification and lowered nitrate
 leaching, unlike the original version. This study concluded
 that the CD-SI system may be used as a BMP to reduce nitrogen
 leaching to shallow groundwater systems for areas with high
 water table conditions.
 
 
 335                                 NAL Call. No.: 292.8 J82
 Water vapor transfer beneath bare soil where evaporation is
 influenced by a turbulent surface wind.
 Ishihara, Y.; Shimojima, E.; Harada, H.
 Amsterdam : Elsevier Scientific Publishers, B.V.; 1992 Feb.
 Journal of hydrology v. 131 (1/4): p. 63-104; 1992 Feb. 
 Includes references.
 
 Language:  English
 
 Descriptors: Soil types; Subsurface layers; Water vapor;
 Evaporation; Transport processes; Diffusion; Diffusivity;
 Wind; Turbulent flow; Air flow; Particle size; Mathematical
 models
 
 Abstract:  A laboratory experiment on evaporation in various
 porous material layers was undertaken by applying a turbulent
 air flow to the exposed surface, to investigate the mechanism
 of the water vapor transport beneath a bare ground surface
 influenced by a turbulent surface wind. Variation of air
 pressure within these layers was also measured. Based on a
 physical model of water vapor transfer, an observed function
 decribing bulk resistance for water vapor transfer with
 evaporating front depth was investigated, using an observed
 power spectrum of the pore-air pressure. The model is based on
 the so-called turbulent mixing theory. The following
 conclusions were reached. When porous material layers are of
 low permeability such as fine sand, water vapor transfer under
 the exposed surface occurs by molecular diffusion as well as
 by turbulent diffusion caused by variation of the pore-air
 pressure due to the turbulent surface wind (P-type). The
 surface turbulence significantly affects the transport just
 beneath the surface. Turbulent diffusivity near the surface is
 determined by horizontal and vertical fluctuating components
 of the pore-air pressure, but with increasing depth is driven
 only by the vertical component. When the porous material layer
 is more permeable, water vapor transfer in this layer is
 analogous to that within a vegetation canopy (F-type), so that
 turbulent diffusivity decays exponentially with depth. The
 turbulent diffusivity is a function of the mixing length. The
 mixing length for F-type was of the order of the particle
 size. For P-type the mixing length ranged from the particle
 size to ten times larger.
 
 
 336                                 NAL Call. No.: 56.8 J822
 WEPP: a new generation of erosion prediction technology.
 Laflen, J.M.; Lane, L.J.; Foster, G.R.
 Ankeny, Iowa : Soil and Water Conservation Society of America;
 1991 Jan. Journal of soil and water conservation v. 46 (1): p.
 34-38; 1991 Jan. Includes references.
 
 Language:  English
 
 Descriptors: Erosion; Universal soil loss equation;
 Prediction; Water erosion
 
 
 337                                 NAL Call. No.: 56.8 J822
 WEPP: soil erodibility experiments for rangeland and cropland
 soils. Laflen, J.M.; Elliot, W.J.; Simanton, J.R.; Holzhey,
 C.S.; Kohl, K.D. Ankeny, Iowa : Soil and Water Conservation
 Society of America; 1991 Jan. Journal of soil and water
 conservation v. 46 (1): p. 39-44; 1991 Jan. Includes
 references.
 
 Language:  English
 
 Descriptors: Water erosion; Prediction; Rangelands; Equations;
 Erodibility; Rill erosion; Crops; Soil
 
                                    # # #
 
                          Author Index
 
 Abriola, L.M.  291
 Adams, R.M.  206
 Addiscott, T.M.  233
 Adelman, D.  191
 Adrian, D.D.  210
 Aharoni, C.  127
 Ahern, Jack  129
 Ahlfeld, D.P.  88
 Ahuja, L.R.  22
 Alberts, E.E.  322
 Alemi, M.H.  168
 Allen, G.  114
 Allen, H.E.  295
 Allen, P.M.  28
 Allen, Roderick L.  227
 Allred, B.  324
 Altafin, I.  137
 Amacher, G.  231
 Ammentorp, H.C.  157
 Antle, J.M.  215
 Arnold, J.A.  196, 197
 Arnold, J.G.  19, 28
 Ashraf, M.S.  167
 Asmussen, L.E.  277
 Aubry, B.F.  62
 Avila, A.  246
 AWWA Research Foundation, United States, Environmental
 Protection Agency  332
 Aylmore, L.A.G.  152
 Bach, L.B.  266
 Bahr, J.M.  296
 Baker, D.E.  258
 Banks, P.A.  27
 Bar-Yosef, B.  91
 Barnes, B.B.  22
 Barnes, N.L.  106
 Barrington, S.F.  78
 Barry, D.A.  84
 Batie, S.S.  116, 135
 Baumer, G.M.  272
 Beck, R.M.  111
 Behl, E.  30
 Behrendt, H.  214
 Ben-Asher, J.  209
 Bengtson, R.L.  179, 334
 Benson, V.W.  194
 Berg, W.A.  248
 Bergstrom, L.  178
 Berisford, Y.C.  175
 Bernado, D.J.  68
 Bernhard, C.  192
 Bernhardt, G.  28
 Beven, K.J.  71
 Bhargava, D.S.  65
 Billett, M.F.  224
 Bingner, R.L.  226, 310
 Black, A.S.  222
 Blackburn, W.H.  34, 242
 Blau, G.E.  237
 Bloom, S.A.  85
 Bode, L.E.  211
 Boekhold, A.E.  134, 244
 Boesen, C.  193
 Boesten, J.J.T.I.  63, 171, 252
 Bogardi, I.  142
 Bogusch, H.C.  194
 Borah, A.  113
 Borah, D.K.  167
 Bottcher, A.B.  95, 223
 Bouldin, D.R.  306
 Bouma, J.  148
 Bouton, M.  273
 Bowen, W.T.  81
 Bradbury, N.J.  216
 Braden, J.B.  115
 Bradford, J.M.  13
 Bras, R.L.  42, 125
 Brebbia, C. A.  329
 Brichford, S.L.  197
 Britt, J.K.  143
 Brooke, D.  47
 Brooke, D.N.  146
 Brusseau, M.L.  170
 Brusven, M.A.  23
 Buchter, B.  173
 Buckley, D.J.A.  307
 Burgoa, B.  85
 Bush, P.B.  27, 89, 175, 309
 Cabe, R.  232
 Cabral, M.C.  125
 Caldwell, D.E.  43
 Campbell, K.L.  95
 Capalbo, S.M.  215
 Carbiener, R.  192
 Carlson, C.G.  212
 Carsel, R.F.  40, 48
 Carsky, R.J.  81
 Cary, Lawrence E.  286
 Centner, T.J.  230
 Chambers, L.W.  296
 Chang, A.C.  74
 Chasves, H.M.L.  304
 Chen, B.  295
 Chen, C.  261, 262
 Chen, J.S.  85
 Chen, W.  283
 Chen, Y.  305
 Christensen, T.H.  157
 Chung, G.Y.  39
 Chung, S.O.  80
 Clark, R.M.  331
 Cloots, A.R.  192
 Coffey, S.W.  196, 197
 Cohen, S.Z.  106
 Coleman, G.A.  248
 Comfort, S.D.  41, 288
 Cooke, L.  29
 Cooley, K.R.  238
 Cooper, A.B.  223
 Corapcioglu, M.Y.  188
 Corradini, C.  162
 Corwin, D.L.  98
 Cresser, M.S.  224
 Cubillo, F.  236
 Curtis, B.  191
 Dane, J.H.  58, 140, 182, 267
 Daniel, T.C.  46, 153, 219
 Darby, R.J.  233
 Darrah, P.R.  149, 150
 Davis, F.M.  213, 327
 Day, R.L.  272
 DeCoursey, D.G.  22
 Deer, H.M.  20
 Deizman, M.M.  156
 Delong, M.D.  23
 Destouni, G.  8, 59, 225, 276
 Deverel, S.J.  249
 Dhawan, S.  155
 Dickinson, W.T.  77, 117
 Diebel, P.L.  116, 135
 Dik, P.E.  177, 178
 Dillard, A.L.  32
 Dillworth, M.E.  24
 Dkstein, L.  142
 Donigian, Anthony S.  166
 Dowd, J.F.  175
 Duckstein, L.  185, 234
 Dudley, L.M.  158, 243
 Dunne, T.  62
 Dunnivant, F.M.  26
 Durborow, T.E.  106
 Dwinell, S.E.  143
 Edwards, D.R.  46, 219
 Ehteshami, M.  20
 Eigel, J.D.  321
 Ekholm, P.  79
 El-Attar, H.A.  288
 Elliot, W.J.  82, 337
 Elliott, R.L.  68, 180
 Ellsworth, T.R.  293, 294
 Eltahir, E.A.B.  42
 Engel, B.A.  321
 Engel, Bernard A.  9
 Engesgaard, P.  100
 Entekhabi, D.  125
 Environmental Research Laboratory (Athens, Ga.)  166
 Erickson, L.E.  155
 Ernst, F.F.  294
 Espeby, B.  37
 Euw, E.L. von  117
 Fabos, Julius Gy  129
 Falconer, R. A.  109, 333
 Fan, L.T.  155
 Farquhar, G.J.  203
 Feng, J.S.  96, 283
 Fermanich, K.J.  153
 Ferrandino, F.J.  67
 Finke, P.A.  148
 Finkner, S.C.  110
 Fio, J.L.  249
 Fisher, A.C.  120
 Flanagan, D.C.  12
 Flanagan, M.  190
 Florida Marine Research Institute, Florida Office of Coastal
 Management  139
 Fluhler, H.  300
 Focazio, Michael J.  50
 Foltz, J.C.  87
 Fong, F.K.  289
 Fontaine, D.D.  237
 Fontaine, T.D.  86
 Foster, G.R.  336
 Fouss, J.L.  179, 334
 Franke, K.J.  315
 Froehlicher, R.  192
 Fujii, R.  249
 Gaber, H.M.  288
 Gale, J.A.  196, 197
 Gambolati, G.  198
 Ganoulis, J.  235
 Garbrecht, J.  64
 Garrote, L.  125
 Gaston, L.A.  221
 Gel'fan, A.N.  53
 Geleta, S.  68, 180
 Geological Survey (U.S.)  31
 Geological Survey (U.S.),California Regional Water Quality
 Control Board--Colorado River Basin Region  75
 Geological Survey (U.S.),Hampton Roads Planning District
 Commission (Va.),Virginia Water Control Board  50
 Gerke, H.H.  51
 Gerritse, R.G.  152
 Ghidey, F.  322
 Gierke, J.S.  323
 Gilley, J.E.  110
 Glaser, P.H.  111
 Glendinning, P.J.  146
 Goh, K.M.  200, 201
 Goldhamer, D.A.  168
 Goodrich, D.C.  126
 Goolsby, D.A.  60
 Goss, D.  194
 Goss, D.W.  245
 Graham, D.N.  203
 Graney, R.L.  25
 Gray, W.G.  44
 Green, R.E.  76, 274
 Griggs, R.H.  180
 Grismer, M.E.  52
 Grunblatt, J.  103
 Gutema, Y.  147
 Guy, B.T.  77
 Haan, C.T.  14, 113, 187, 324
 Habaieb, H.  36
 Haddad, Kenneth D.  139
 Halliday, S.L.  16
 Halstead, J.M.  116
 Hamlett, J.M.  272
 Hammers, W.E.  229
 Hanemann, W.M.  120
 Hanks, R.J.  158
 Hansen, J.A.  1, 254
 Hanson, C.L.  238, 312
 Hansson, P.E.  326
 Harada, H.  335
 Harbor, J.  285
 Harmsen, K.  133
 Harper, J.K.  4
 Harwell, J.H.  90
 Hauser, V.L.  241
 Havens, P.L.  237
 Havis, R.N.  210
 Hayashi, Y.  49
 Hayot, C.  204, 205
 Head, K.L.  142
 Heatwole, C.D.  116, 135, 284
 Hendrix, W.G.  307
 Hendry, M.J.  43
 Heng, L.K.  302
 Herricks, E.E.  115
 Herriges, J.A.  232
 Hill, R.W.  20
 Hills, R.G.  130, 247
 Hino, M.  199
 Hinz, C.  173
 Hipp, B.W.  92
 Hoag, D.L.  38
 Holloway, D.  256
 Holzhey, C.S.  337
 Hongprayoon, C.  306
 Hornsby, A.G.  38, 263
 Host-Madsen, J.  128
 Hostetler, J.  231
 Huang, C.H.  13
 Huang, C.P.  295
 Huang, L.Q.  67, 270
 Huber, Wayne C.  166
 Hudson, D.B.  130, 247
 Humborg, G.  209
 Hummel, J.W.  82
 Hummel, P.R.  40, 48
 Hutzler, N.J.  323
 Imhoff, J.C.  40, 48
 Inskeep, W.P.  41, 288
 Institution of Water and Environmental Management  333
 Ishiguro, M.  268, 269
 Ishihara, Y.  335
 Islam, M.N.  124
 Jabro, J.D.  258
 Jacobsen, O.H.  136
 Jakeman, A.J.  18
 Jakubauskas, M.E.  24
 James, A.  122
 Jansson, P.E.  177
 Jardine, P.M.  26
 Jarvis, N.J.  177, 178
 Jaynes, D.B.  94
 Jennings, G.D.  196, 197
 Jensen, K.H.  128
 Jessup, R.E.  170
 Jian, L.R.  108
 Johnson, P.A.  216
 Johnson, R.C.  11
 Johnson, S.L.  206
 Johnsson, H.  279, 326
 Jones, J.W.  81
 Jones, O.R.  241
 Jones, Philip Edward James,  83
 Jones, R.E.  27
 Jones, R.L.  311
 Jurinak, J.J.  243
 Jury, W.A.  132, 293, 294, 300
 Kamari, J.  79
 Kamra, S.K.  250, 251
 Kanda, M.  199
 Kandil, H.  163
 Katz, J.  299
 Kawanishi, T.  49
 Keefer, T.O.  126
 Keeler, A.G.  120
 Kelly, W.E.  191
 Kenimer, A.L.  211
 Kihou, N.  49
 Kim, C.S.  231
 Kinouchi, T.  199
 Kipp, K.L.  100
 Kirk, G.J.D.  169
 Kirkland, M.R.  247
 Kittle, J.L. Jr  40, 48
 Kladivko, E.J.  321
 Klein, M.  10
 Kleveno, J.J.  76
 Kling, C.L.  328
 Knisel, W.G.  213, 327
 Knisel, W.G. Jr  309
 Knuth, B.A.  313
 Knutson, R.D.  54
 Kobylyanskii, G.V.  181
 Kohl, K.D.  337
 Kondrat'ev, S.A.  72
 Kookana, R.S.  152
 Kotovich, I.N.  181
 Kozloff, K.  154
 Kramer, L.A.  287, 322
 Kramer, R.A.  116
 Kreutzberger, W.A.  330
 Kristiansen, H.  193
 Kroes, J.G.  195
 Kuchment, L.S.  53
 Kuhn, Gerhard  21
 Kunishi, H.M.  259
 Kuo, C.H.  44
 la Cour, Niels  129
 Lacewell, R.D.  114
 Laenen, Antonius  227
 Laflen, J.M.  336, 337
 Lafolie, F.  204, 205
 Lam, D.C.L.  119
 Landers, J.C.  313
 Lane, L.J.  118, 336
 Larsen, F.  193
 Larsen, H.D.  228
 Larson, R.S.  115
 Lawrence, J.R.  43
 Leatham, D.J.  114
 Lee, D.J.  97
 Lee, D.Y.  74
 Lee, J.  295
 Lee, J.G.  87
 Leij, F.J.  7, 58, 136, 140, 172, 182, 267
 Leonard, R.A.  61, 213, 327
 Lerner, D.N.  253
 Letson, D.  257
 Leu, J.M.  303
 Lin, J.C.  25
 Lindau, C.W.  306
 Linden, A.M.A. van der  171
 Line, D.E.  196
 Littlewood, I.G.  18
 Liu, C.C.K.  96, 283
 Liu, C.L.  303
 Loague, K.  76, 96, 265, 274, 319
 Loehr, R.C.  66
 Lotse, E.G.  258
 Loureiro, C.O.  291
 Lovell, A.C.  114
 Lowery, B.  153
 Lucey, K.J.  60
 Lundin, L.C.  279
 Ma, L.  173
 Macur, R.E.  41
 Maddock, T. III  185
 Madramootoo, C.A.  320
 Magette, W.L.  159, 334
 Makuch, J.  256
 Malchow, H.  271
 Mansell, R.S.  85
 Mapp, H.P.  68
 Marbun, O.  46
 Mariam, D.W.  65
 Martin, M.A.  87
 Martinko, E.A.  24
 Massachusetts Agricultural Experiment Station  129
 Massachusetts, Division of Water Pollution Control, Geological
 Survey (U.S.)  308
 Matthew, R. G. S.  109
 Matthies, M.  214
 Matthiessen, P.  47, 146
 May, L.  147
 McCarthy, J.F.  26
 McCoy, B.J.  35, 39
 McDonnell, J.J.  160
 McDowell, T.C.  143
 McIntosh, C.S.  189
 McIsaac, G.F.  82
 McKenzie, D.B.  323
 McMahon, T.A.  70
 McNamara, J.P.  111
 Meadows, J. Kevin  75
 Melone, F.  162
 Messing, I.  177
 Meyer, C.R.  12
 Michael, J.L.  89
 Michel, A.N.  44
 Miller, C.T.  163
 Miller, D.A.  272
 Milligan, J.H.  242
 Mills, M.J.  146
 Mills, W.C.  32
 Ming, L.S.  108
 Miranda, M.J.  112
 Mitchell, J.K.  82, 211
 Mohamoud, Y.M.  73
 Moldrup, P.  1, 254
 Monke, E.J.  321
 Montas, H.J.  320
 Moore, I.D.  287
 Moore, J.A.  282
 Mostaghimi, S.  156
 Mueller, T.C.  27
 Murphree, C.E.  226
 Mutchler, C.K.  226
 Myhre, B.E.• 317
 Napoleon, E.J.  314
 Nash, T.  285
 Nathan, R.J.  70
 National Council of the Paper Industry for Air and Stream
 Improvement (U.S.)  278
 Nearing, M.A.  304
 Neary, D.G.  89, 175
 Newman, J.B. •34
 Nguyen, M.L.  200, 201
 Nielsen, D.R.  168
 Nkedi-Kizza, P.  85
 Noegrohati, S.  229
 Nofziger, D.L.  14
 Nordstedt, R.A.  99
 Norris, P.E.  68
 Nutter, W.L.  309
 Okwach, G.E.  17
 Olimpio, Julio C.  308
 Olson, R.L.  290
 Opaluch, J.J.  3
 Osmond, D.L.  196
 Ottichilo, W.K.  103
 Ouyang, Y.  325
 Overton, Donald E.,  264
 Ozaki, Y.  49
 Panday, S.  188
 Pandey, S.  55
 Paniconi, C.  198
 Panuska, J.C.  287
 Papatolios, K.T.  253
 Parker, J.C.  84
 Parlange, J.Y.  84, 141
 Parlange, M.B.  141
 Parrish, R.S.  289
 Parsons, J.E.  334
 Patrick, W.H. Jr  306
 Penson, J.B. Jr  54
 Peralta, R.C.  20
 Perry, G.M.  206
 Peterson, G.W.  272
 Phillips, I.R.  222, 255
 Pignatello, J.J.  67, 270
 Pikes Peak Area Council of Governments, Geological Survey
 (U.S.)  21
 Pinder, G.  207
 Pinder, G.F.  88
 Pinol, J.  246
 Piper, S.  105
 Piper, S.L.  69
 Plate, E.J.  234
 Porro, I.  297
 Porter, P.S.  57
 Posch, M.  79
 Postma, D.  193
 Potter, K.N.  194
 Powers, S.E.  291
 Prasher, S.O.  78
 Price, Richard E.  144
 Priesack, E.  6
 Prinz, D.  218
 Punthakey, J.F.  93
 Putti, M.  198
 Quintana, J.O. ‹81
 Rachhpal-Singh  169
 Ranjha, A.Y.  20
 Rao, K.V.G.K.  250, 251
 Rao, P.S.C.  170, 202
 Rashmawi, E.A.  52
 Ravina, I.  56
 Refsgaard, J.C.  157
 Reichard, Eric George  75
 Rekolainen, S.  79
 Requena, A.M.  20
 Rhoades, J.D.  98
 Ribaudo, M.O.  69
 Rijtema, P.E.  195
 Ritzi, R.W. Jr  45
 Robarts, R.D.  43
 Robson, A.J.  11
 Roda, F.  246
 Rodriguez, B.  236
 Rogowski, A.S.  33
 Rojas, K.W.  22
 Rolston, D.E.  1, 35, 254
 Rose, C.W.  141
 Rosenthal, W.D.  92
 Ross, D.  285
 Roth, K.  132
 Roy, W.R.  2
 Rudra, R.P.  77, 117
 Russell, Clifford S.  292
 Russo, D.  273, 275
 Russo, J.  272
 Sabatini, D.A.  90
 Sabbagh, G.J.  68, 179, 180
 Sadeghi, A.M.  259, 298
 Salvich, P.G.  123
 Samsel, Theodore B.  50
 Sanchez, C.A.  57
 Sanders, P.  295
 Sardin, M.  172
 Sariev, A.L.  181
 Sarin, S.C.  186
 Sbaa, M.  242
 Schalk, C.W.  80
 Schenck, C.  192
 Schmucker, J.F.  114
 Schnitkey, G.D.  112
 Schwart, R.B.  114
 Schweich, D.  172, 301
 Scott, J. C.  31
 Scotter, D.R.  184, 302
 Scow, K.M.  39
 Segerson, K.  3
 Selassie, T.G.  243
 Selim, H.M.  26, 173, 174, 221
 Sequeira, R.A.  290
 Setia, P.  105
 Seyfried, M.S.  202, 238
 Shabtai, R.  176, 280, 281
 Shafike, N.G.  185
 Shanholtz, V.O.  284
 Shani, U.  158
 Sharpley, A.N.  248
 Shaviv, A.  56
 Shaw, R.R.  138
 Sheridan, J.M.  327
 Shih, S.F.  101, 317, 318
 Shimojima, E.  335
 Shiono, K.  109
 Shirley, E.D.  118
 Shirmohammadi, A.  159, 334
 Shirmohammadi, Adel,1952-  9
 Shnek, M.  56
 Shoemaker, L.L.• 159
 Shogren, Jason F.  292
 Shouse, P.J.  294
 Shukurov, M.S.  181
 Sichani, S.A.  321
 Siegel, D.I.  111
 Silva, F.F. da  305
 Simanton, J.R.  228, 337
 Simmons, D.E.  33
 Simmons, K.E.  258
 Simunek, J.  164, 165
 Sinange, R.K.  103
 Singh, S.R.  250, 251
 Singh, U.  316
 Skaggs, R.W.  163
 Skaggs, T.H.  7
 Smith, A.E.  217
 Smith, C.M.  223
 Smith, C.N.  277, 289
 Smith, E.G.  54
 Smith, M.C.  95
 Smith, R.E.  162, 208, 210
 Smith, R.T.  45
 Smith, S.J.  248
 Smith, W.N.  78
 Smolen, M.D.  197
 Snyder, W.M.  32
 Soderstrom, M.  102
 Soerens, T.S.  90
 Soileau, J.M.  240, 260
 Somlyody, L.  137
 Sparks, D.L.  127, 295
 Spooner, J.  196, 197
 Squillace, P.J.  107
 Stagnitti, F.  141
 Starr, J.L.  84, 298
 Steenhuis, T.S. O141
 Stein, A.  148
 Stewart, D.J.  86
 Stewart, M.K.  160
 Still, D.A.  318
 Stone, J.F.  68
 Stone, J.J.  118
 Storm, Daniel E.  161
 Suarez, D.L.  164, 165
 Taff, S.J.  154
 Tan, Y.R.  101
 Tauer, W.  218
 Taylor, C.R.  54
 Taylor, D.B.  116, 135, 186
 Taylor, J.W.  175, 309
 Tedaldi, D.J.  66
 Thomas, A.W.  32
 Thomas, D.L.  95
 Thomas, Daniel L.  9
 Thomas, M.V.  99
 Thomson, N.R.  203
 Thornton, P.K.  316
 Thurman, E.M.  107
 Tillman, Dottie  144
 Tillotson, P.M.  237
 Tillotson, W.R.  217
 Tilman, R.W.  184
 Touchton, J.T.  260
 Tracy, J.C.  183
 Troch, F.P. de  36
 Troch, P.A.  36
 Truman, C.C.  61, 213
 Tucciarelli, T.  207
 Turnbull, A.  146
 Uchrin, C.G.  299
 United States, Army, Corps of Engineers, Chicago District,
 U.S. Army Engineer Waterways Experiment Station  144
 United States, Bureau of Land Management, Geological Survey
 (U.S.)  227, 286
 Van Genuchten, M.T.  7, 51, 136, 140, 172, 250, 251
 Van Genuchten, M.Th  84
 Van Mullem, J.A.  220
 Vinther, F.P.  145
 Vogtle, T.  218
 Wagenet, R.J.  261, 262
 Waggoner, B.L.  98
 Wakild, C.R.  330
 Walker, W.R.  20
 Wallace, R.  305
 Wallach, R.  15, 131, 176, 239, 280, 281
 Wallis, J.R.  121
 Wambua, J.  17
 Wang, Y.  154
 Ward, A.D.  80
 Weaver, R.D.  4
 Weber, W.J. Jr  291
 Weinberg, M.  328
 Wells, W.G. II  314
 Weltz, M.A.  228
 Wetzstein, M.E.  230
 Whistler, J.L.  24
 White, R.E.  302
 Whitehead, P.G.  11, 18
 Whitmore, A.P.  151, 216
 Wierenga, P.J.  130, 247, 297
 Wight, J.R.  312
 Wilcox, B.P.  238, 242
 Wilen, J.E.  328
 Williams, A.A.  189
 Williams, J.  17
 Williams, J.R.  180, 194, 248
 Williams, R.J.  146
 Willis, D.  147
 Wohlgemuth, P.M.  314
 Wolf, J.K.  33
 Wolfaardt, G.M.  43
 Wolfe, M.L.  16, 104
 Wood, J.C.  34
 Woolhiser, D.A.  126
 Wright, J.A.  334
 Wrobel, L. C.  329
 Yamaguchi, T.  1, 254
 Yan, J.  187
 Yates, M.V.  325
 Yates, S.R.  5
 Yomota, A.  124
 Yoneyama, T.  49
 Yoo, K.H.  240, 260
 Yoon, K.S.  240, 260
 Zanyk, B.N.  43
 Zee, S.E.A.T.M. van der  63, 134, 244
 Zhang, H.  14
 Zhang, W.  62
 Zhu, M.  186
 Zilliox, L.  192
 
                          Subject Index
 
 2,4,5-t  214
 2,4-d  92, 217
 Absorption  211
 Accuracy  1
 Acid soils  85
 Acidity  224
 Activity  197
 Adsorption  2, 6, 26, 132, 168, 221, 243, 249, 268, 288, 295
 Afforestation  18
 Aggregate data  3
 Aggregates  6, 82, 155, 172, 204, 205, 323
 Agricultural byproducts  108
 Agricultural chemicals  15, 19, 25, 43, 54, 131, 167, 176,
 196, 215, 230, 232, 256, 277, 280, 281, 283, 296, 311
 Agricultural development  192
 Agricultural economics  105
 Agricultural land  79, 112, 154, 156, 197, 307
 Agricultural policy  3, 54, 116, 231
 Agricultural pollution  292
 Agricultural production  72, 189, 196, 215
 Agricultural regions  55
 Agricultural sector  3
 Agricultural soils  8, 40, 47, 49, 57, 73, 94, 133
 Agricultural wastes  99, 117
 Air flow  335
 Air quality  89
 Air temperature  312
 Alabama  240, 260
 Alachlor  27, 95, 211, 321
 Aldicarb  171, 289
 Algae  137, 271
 Algorithms  44, 100, 163, 231
 Alkaline soils  249
 Alluvial soils  108, 249
 Alternative farming  87
 Aluminum oxide  85
 Ammonia  306
 Ammonium nitrogen  306
 Anaerobic digestion  99
 Analytical methods  296
 Andosols  269
 Angling  69
 Animal wastes  99, 284
 Anion exchange  255
 Application date  46, 171
 Application methods  112, 159
 Application rates  97
 Application to land  46, 156
 Aquatic communities  271
 Aquatic environment  25
 Aquifers  26, 45, 66, 96, 193, 235, 250, 251, 253, 291, 299
 Arable land  193, 326
 Arable soils  244, 258, 279
 Arkansas  46, 219, 324
 Artemisia tridentata  242
 Artificial precipitation  13
 Assessment  76, 151, 318
 Atrazine  67, 78, 92, 95, 180, 270, 321
 Attenuation  76
 Autocorrelation  273
 Automation  104
 Autumn  171
 Availability  211
 Azinphos-methyl  309
 B horizons  85
 Bayesian theory  232
 Behavior  134
 Belgium  36
 Beliefs  232
 Bentazone  10
 Benzene  299
 Bibliographies  256
 Biochemical oxygen demand  330
 Biodegradation  155
 Biomass  6
 Biomass production  137
 Bioremediation  39
 Bogs  111
 Boron  158
 Boundaries  15
 Brazil  137
 Broadleaved evergreen forests  246
 Bromacil  94
 Bromide  151, 247, 255, 268, 289, 296
 Bromides  95
 Bromine  269, 288
 Brown earths  149, 150
 Buchloe dactyloides  92
 Buffering capacity  56
 Cabt  87
 Cadmium  134, 173, 244
 Calcareous soils  56, 158
 Calcium  221, 255
 Calcium ions  224, 268
 Calculation  269
 Calibration  25
 California  52, 120, 165, 249, 294, 314
 Canopy  42, 228
 Capacity  218, 296
 Capillary fringe  199
 Capillary rise  73
 Carbaryl  92
 Carbofuran  309, 321
 Carbon  26, 259
 Carbon dioxide  164, 165
 Carbonates  45
 Carcinoma  142
 Case studies  36, 115, 283
 Cash flow  114
 Catchment hydrology  11, 18, 19, 28, 141, 209, 246, 260
 Cation exchange  182, 221, 224, 255, 268
 Cation exchange capacity  221, 268
 Characteristics  70
 Chemical degradation  43
 Chemical properties  246
 Chemicals  14, 239, 255
 China  108
 Chloride  255, 302
 Chlorides  178
 Chlorine  136
 Chlorpyrifos  92, 321
 Citrus reticulata  108
 Clay  33, 140
 Clay loam soils  259
 Clay soils  41, 178, 280
 Clearcutting  18
 Climate  28
 Climatic factors  10, 19, 42, 70, 97, 175
 Climatic zones  194
 Cloethocarb  10
 Coarse textured soils  136
 Coastal plains  159
 Coasts  227
 Colorado  190
 Commercial soil additives  112
 Compact soils  268
 Comparisons  1, 15, 26, 79, 85, 183, 194, 266
 Composts  305
 Computer assisted instruction  285
 Computer graphics  119, 121
 Computer hardware  121
 Computer simulation  2, 27, 29, 61, 78, 87, 119, 121, 151,
 169, 195, 208, 236, 238, 285, 287, 315, 320
 Computer software  40, 48, 118, 119, 121, 138, 211, 236, 310
 Computer techniques  12, 29, 68, 104, 272, 307
 Computers  223
 Concentration  47, 65, 107, 253
 Condensation  181
 Coniferous forests  37, 193
 Connecticut  67, 141
 Conservation tillage  240, 260
 Constraints  44
 Contaminants  26, 43, 88, 140, 170, 282, 323
 Contamination  3, 54, 142, 176, 239, 280, 281
 Continuous cropping  87, 171
 Control methods  232
 Convection  1, 84, 269
 Cooperative extension service  263
 Corn belt of U.S.A.  105
 Corn belt states of U.S.A.  87
 Cost benefit analysis  215
 Cost effectiveness analysis  154
 Costa Rica  202
 Costs  38, 116, 185, 206, 207, 231, 232
 Cotton  290
 Crop growth stage  194
 Crop management  68, 194, 305
 Crop production  46, 91, 108, 112, 179, 316
 Crop residues  73, 108
 Crop yield  38, 46, 97, 102, 206, 312
 Cropping systems  55, 159, 202
 Crops  102, 218, 337
 Crumbs  157
 Crusts  73
 Cultivation  159
 Culture media  305
 Cyanazine  167, 321
 Cycling  108, 200, 201
 Cynodon dactylon  92, 217
 Dairy farms  114
 Dairy wastes  114
 Data analysis  190
 Data banks  12
 Data collection  24
 Databases  40, 48, 119, 190, 272
 Decision making  55, 185, 263, 328
 Decomposition  108
 Degradation  41, 170, 225
 Delta soils  108
 Deltas  108, 120
 Denitrification  49, 100, 145, 157, 254, 259
 Denmark  100, 145
 Depth  251, 306
 Desertification  103
 Design  20
 Desorption  2, 39, 56, 249, 281
 Deterioration  331
 Determination  84, 85, 148, 305
 Deterministic models  51, 130, 134, 183, 247
 Deuterium  160
 Diazinon  92
 Dicamba  41, 92
 Diffusion  6, 39, 151, 157, 184, 205, 243, 269, 306, 335
 Diffusion models  56, 177, 178, 184
 Diffusivity  6, 149, 150, 157, 268, 306, 335
 Discharge  111, 199, 246
 Dispersion  1, 49, 84, 249, 259, 289, 293
 Dissolving  249
 Distribution  222
 Disturbed soils  148, 268
 Ditches  108, 296
 Diuron  171
 Drainage  42, 64, 79, 161, 179, 195, 220, 234, 249, 279, 296,
 326, 328, 334
 Drainage water  108, 249, 250, 251
 Drained conditions  163, 243
 Drinking water  60, 142, 216, 311, 331
 Dry matter accumulation  108
 Dry season  108
 Dynamic models  53, 120, 206, 230, 231
 Dynamic programming  186
 Dynamics  172
 Eastern scotland  224
 Ecology  111
 Econometric models  189
 Economic analysis  135
 Economic evaluation  55
 Economic impact  38, 54, 68, 87, 147, 186, 189, 206
 Economics  197
 Ecosystems  89
 Edaphic factors  228
 Effects  72
 Effluents  251
 Electrical conductivity  243
 England  47, 146, 216, 253
 Environment  143
 Environmental factors  4, 10, 165
 Environmental impact  38, 68, 87, 89, 143, 147, 186, 215, 257,
 263, 284, 315, 316
 Environmental legislation  230, 307
 Environmental policy  112, 115
 Environmental protection  143, 313, 331
 Epidemiology  142
 Equations  5, 15, 51, 56, 65, 70, 74, 88, 90, 127, 134, 177,
 181, 184, 188, 198, 301, 337
 Equilibrium  56, 66, 222, 268, 288
 Erodibility  337
 Erosion  17, 23, 87, 108, 118, 154, 179, 190, 226, 260, 287,
 310, 314, 320, 336
 Erosion control  34, 159, 242, 285
 Errors  52, 76, 140, 151
 Estimated costs  114
 Estimatesª 79
 Estimation  52, 69, 71, 194, 265
 Eutrophication  137
 Evaluation  151
 Evaporation  42, 141, 326, 335
 Evapotranspiration  34, 80, 171, 179, 194, 326
 Exchangeable cations  221, 222, 268
 Exchangeable sodium  221, 243, 255
 Experimental design  151
 Experimental plots  322
 Expert systems  16, 119
 Extraction  323
 Farm income  206
 Farm indebtedness  114
 Farm inputs  135, 206, 231
 Farm management  186, 206, 328
 Farmers' attitudes  232
 Farming systems  135, 186
 Farmland  23, 191, 195, 234
 Farmyard manure  112
 Feasibility  55
 Federal programs  34, 105, 313
 Fenamiphos  283
 Fens  111
 Fenvalerate  309
 Fertigation  91
 Fertilizer requirement determination  91, 201, 233
 Fertilizer technology  91
 Fertilizers  22, 92, 106, 108, 159, 202, 305
 Festuca pratensis  326
 Field experimentation  210
 Field tests  25, 95
 Finite element analysis  45, 96
 Finland  79
 Fish  115
 Fishery management  86, 120, 139
 Fishing  147
 Fixation  85
 Flood dams and reservoirs  144
 Flood irrigation  94
 Flooded rice  306
 Flooding  124
 Floods  36, 53
 Florida  57, 85, 99, 101, 143, 263, 317, 318
 Flow  7, 11, 28, 59, 70, 71, 79, 108, 128, 131, 220, 299
 Fluids  91
 Food chains  86
 Food safety  54
 Forecasting  36
 Forest management  175
 Forest soils  37, 197
 Forest steppe  53
 Forestry  89
 Forests  72, 175, 307
 Formation  72
 France  192
 Frequency  79
 Fresh water  120
 Frost  279
 Frozen conditions  279
 Fuel tanks  74
 Fungicides  106
 Furrow irrigation  20
 Game theory  230
 Geochemistry  66, 100, 193
 Geographic information systems  31, 50, 129, 139, 308
 Geographical distribution  101, 194, 317
 Geographical information systems  263
 Geography  103, 272, 284, 307
 Geological sedimentation  19, 77, 248, 285
 Geology  111
 Geomorphology  192
 Georgia  61, 95, 175, 180, 189, 230, 277, 327
 German federal republic  10, 234
 Glacial till soils  37
 Gley soils  269
 Glycine max  38, 45, 87, 165
 Golf courses  106, 217, 315
 Golf green soils  106, 217
 Gossypium  240
 Gossypium hirsutum  260
 Grain crops  192
 Grape marc  305
 Graphic arts  310
 Grasses  46
 Grassland management  223, 242
 Grassland soils  216
 Grasslands  192
 Grazing effects  200, 201, 223
 Green and ampt equation  73, 220
 Green manures  81
 Greenhouses  181
 Ground vegetation  42, 228
 Groundwater  3, 28, 30, 54, 61, 63, 66, 95, 98, 101, 102, 105,
 111, 123, 143, 180, 183, 185, 197, 199, 207, 215, 231, 237,
 246, 249, 252, 277, 299, 309, 311, 317, 321, 325
 Groundwater flow  28, 52, 75, 88, 90, 100, 111, 188, 198, 235,
 298, 301
 Groundwater level  28
 Groundwater pollution  2, 14, 16, 20, 29, 33, 35, 38, 43, 44,
 45, 49, 68, 74, 88, 89, 90, 106, 107, 116, 128, 135, 142, 143,
 155, 159, 183, 185, 188, 189, 191, 192, 193, 195, 198, 203,
 206, 212, 214, 230, 231, 235, 245, 253, 256, 274, 283, 291,
 295, 296, 297
 Groundwater recharge  33, 191, 195, 253
 Growth  108
 Growth models  208
 Growth rate  6
 Gully erosion  285
 Gypsum  249
 Habitats  23, 115
 Half life  41
 Hapludults  13, 221
 Hatcheries  120
 Hawaii  76, 106, 283
 Health hazards  331
 Heat flow  164, 165, 266
 Heathland  193
 Heavy metals  133, 173
 Height  13
 Herbage  312
 Herbicide residues  27, 67, 92, 94, 106, 107, 217, 270
 Heterogeneity  134
 High water tables  108
 Hill grasslands  62
 Histosols  57
 Hordeum vulgare  134, 145, 326
 Horizons  224
 Horizontal flow  58, 259, 275, 298
 Humid tropics  202
 Hyacinths  99
 Hydraulic conductivity  45, 62, 66, 73, 88, 148, 178, 223,
 225, 261, 262, 273, 275
 Hydraulic resistance  110
 Hydraulics  44, 109, 128
 Hydrodynamic dispersion  5, 63, 71, 182, 184, 298
 Hydrodynamics  235
 Hydrogen ions  224
 Hydrogeology  50
 Hydrologic cycle  286
 Hydrologic models  227
 Hydrological data  70, 190, 312
 Hydrology  9, 64, 72, 80, 104, 111, 113, 121, 187, 208, 259,
 324, 334
 Hydrolysis  306
 Hydromorphic soils  192
 Hysteresis  249, 305
 Idaho  23, 230
 Identification  36
 Illinois  73, 82
 Immiscible displacement  203
 Improvement  12
 Inactivation  325
 Inceptisols  13
 Income  54
 Incorporation  280, 306
 Indexes  57, 143, 284
 India  251
 Indiana  313, 321
 Indicator plants  271
 Indicator species  111, 271
 Infiltration  33, 62, 66, 73, 118, 125, 130, 162, 176, 210,
 220, 228, 247, 279, 281, 319
 Information  232
 Information retrieval  12
 Information storage  12
 Information storage and retrieval systems  139, 278
 Information systems  3, 23, 138, 256, 307
 Insecticide residues  92, 106
 Integrated pest management  315
 Intensive cropping  192
 Interactions  210
 Interception  42, 228
 Interface  140, 267
 Interrill erosion  13
 Iodide  296
 Ion exchange  173, 243
 Ion transport  259
 Ions  246
 Iowa  60, 107, 230
 Iron oxides  85
 Irrigated conditions  201
 Irrigated soils  102, 249
 Irrigation  55, 66, 68, 97, 123, 147, 249, 305
 Irrigation scheduling  41, 102
 Irrigation water  91, 102, 108, 235, 249, 328
 Japan  124
 Kansas  24, 190
 Kaolinite  221
 Kenya  17, 103
 Kinematics  124, 126
 Kinetics  26, 56, 84, 85, 118, 125, 127, 152, 172, 173, 243,
 281, 288
 Labeling  311
 Laboratory methods  85, 259, 266, 268, 298, 306
 Laboratory tests  128
 Lakes  86, 115, 313
 Land diversion  313
 Land management  28, 138, 154, 285, 313
 Land types  285, 307
 Land use  154, 192, 193, 197, 285, 307
 Landsat  24, 318
 Lasers  13
 Law  114
 Law enforcement  331
 Lawns and turf  315
 Layered soils  125, 136, 140, 267
 Leachates  33, 106, 231
 Leaching  10, 20, 27, 29, 38, 41, 47, 51, 57, 61, 63, 67, 76,
 78, 81, 94, 95, 102, 105, 106, 123, 133, 134, 140, 143, 145,
 148, 151, 153, 168, 171, 174, 175, 178, 180, 184, 194, 200,
 201, 202, 216, 217, 222, 229, 233, 237, 243, 245, 249, 252,
 254, 255, 258, 259, 263, 270, 273, 274, 289, 299, 302, 309,
 316, 321
 Leakage  74
 Legal liability  230
 Legumes  186
 Length  84
 Leys  326
 Linear models  132, 261, 262
 Linuron  152
 Liquid fertilizers  91
 Literature reviews  89, 99, 174, 200, 201, 300
 Livestock enterprises  112
 Livestock numbers  112
 Loam soils  1, 145
 Lolium multiflorum  145
 Long term experiments  66, 145
 Losses  115, 156, 159
 Losses from soil  81, 117, 213, 245, 260, 302
 Losses from soil systems  20, 46, 57, 61, 108, 145, 169, 202,
 211, 216, 223, 228, 259, 304, 306, 320, 322
 Louisiana  179, 180, 221
 Lowland areas  269
 Lysimeters  10
 Lysimetry  153
 Macropore flow  37, 80, 177, 178, 261, 262
 Macropores  22, 37, 177, 204, 261, 262, 269
 Madhya pradesh  55
 Magnesium  221, 222, 255
 Maize  112, 192
 Mali  209
 Management  12, 40, 91, 137
 Manures  99
 Mapping  23
 Maps  102
 Marine resources  139
 Markets  328
 Maryland  159, 259
 Mass transfer  291
 Massachusetts  106
 Mathematical models  1, 3, 4, 5, 6, 7, 13, 15, 26, 32, 35, 39,
 49, 51, 52, 53, 56, 58, 60, 62, 72, 73, 79, 84, 85, 91, 92,
 94, 96, 97, 98, 99, 100, 106, 112, 114, 115, 124, 126, 128,
 131, 135, 136, 140, 141, 142, 147, 149, 150, 157, 158, 160,
 162, 163, 164, 165, 170, 171, 172, 173, 174, 176, 177, 178,
 180, 181, 182, 185, 188, 198, 199, 205, 210, 216, 217, 221,
 225, 232, 235, 239, 240, 241, 242, 244, 246, 248, 249, 250,
 251, 252, 254, 255, 257, 259, 266, 267, 268, 269, 270, 271,
 274, 276, 277, 280, 281, 288, 289, 291, 293, 294, 295, 299,
 300, 301, 302, 305, 306, 319, 323, 324, 335
 Mathematics  13, 74, 90, 151
 Matric potential  266
 McCook Reservoir (Ill.)  144
 Measurement  13, 47, 145, 149, 150, 151, 153, 160, 207, 209,
 215, 247, 266, 269, 270, 285
 Mecoprop  47
 Medicago sativa  87
 Mediterranean climate  246
 Meltwater  37, 53
 Metals  295
 Meteorological factors  194, 208, 252, 326
 Methane  323
 Methane production  99
 Methodology  38, 168, 194, 237, 263
 Metolachlor  67, 180, 270, 289
 Metribuzin  27
 Michigan  29, 115
 Microbial activities  168
 Microbial contamination  282
 Microbial degradation  2, 6, 39, 43
 Microcomputers  119, 285
 Microeconomic analysis  3, 87
 Microeconomics  4
 Mineralization  81, 233, 258
 Minnesota  107, 154, 230, 313
 Mississippi  226
 Missouri  165
 Mixtures  305
 Models  36, 40, 42, 43, 47, 54, 57, 65, 66, 67, 69, 70, 102,
 103, 107, 108, 117, 125, 137, 143, 146, 190, 192, 193, 196,
 197, 203, 212, 215, 218, 220, 222, 253, 267, 272, 282, 284,
 296, 297, 303, 307, 310, 313, 325, 330
 Mole drainage  302
 Monitoring  47, 79, 91
 Montana  220
 Monte carlo method  63
 Mounds  111
 Mountain areas  159
 Movement  282
 Movement in soil  6, 14, 22, 26, 33, 43, 45, 57, 68, 74, 76,
 84, 85, 91, 94, 96, 125, 132, 140, 151, 152, 153, 158, 174,
 182, 183, 184, 194, 208, 214, 221, 222, 243, 249, 250, 251,
 254, 255, 259, 267, 268, 269, 283, 288, 291, 296, 297, 300,
 325
 Movement to roots  76
 Mulches  17
 Multivariate analysis  70
 Musa paradisiaca  108
 Nebraska  110, 190, 191
 Netherlands  148, 195, 244, 252
 New Jersey  295, 299
 New Mexico  130, 247
 New South Wales  70, 123
 New York  111
 New Zealand  160, 200, 201, 223
 Nitrate  49, 81, 100, 136, 142, 148, 191, 195, 234, 259
 Nitrate fertilizers  142, 191, 195, 234
 Nitrate nitrogen  60, 151, 216, 258, 259
 Nitrates  29, 45, 116, 167, 192, 193, 206, 231, 233, 253
 Nitrification  254, 258
 Nitrogen  46, 72, 81, 91, 106, 108, 145, 156, 159, 169, 194,
 216, 254, 258, 260
 Nitrogen balance  81, 258
 Nitrogen fertilizers  16, 60, 186, 231, 233, 316, 326
 Nontarget effects  89
 Norflurazon  27
 North Carolina  13, 38, 330
 Northern scotland  224
 Nutrient availability  56, 81
 Nutrient content  108
 Nutrient intake  200, 201
 Nutrient requirements  91
 Nutrient sources  259
 Nutrient uptake  56, 81, 91
 Nutrients  72, 108, 202, 212
 Objectives  86
 Ohio  45
 Oklahoma  68, 113, 187, 248, 324
 On line  36
 Ontario  117
 Optimization  115
 Optimization methods  44
 Oregon  206
 Organic compounds  2, 6, 74, 90, 155, 188
 Organic fertilizers  156
 Organic matter  26, 108
 Organic wastes  156
 Organochlorine insecticides  229
 Oryza sativa  108, 269, 306
 Overland flow  15, 77, 107, 124, 126, 176, 199, 210, 239, 280,
 281
 Oxidation  100, 249
 Oxygen consumption  157
 Oxygen transport  157
 Paddy soils  268, 269, 306
 Pans  268
 Participation  69
 Particle size  65, 335
 Particle size distribution  204, 205
 Particle velocity  205
 Pastures  200, 201
 Peatlands  111
 Pennsylvania  258
 Percolation  34, 61, 194
 Permeability  58, 73
 Permethrin  309
 Persistence  41, 171, 274
 Pest control  68
 Pesticide residues  10, 54, 106, 146, 214, 289
 Pesticides  20, 22, 25, 30, 38, 61, 63, 68, 76, 87, 89, 95,
 105, 115, 143, 153, 175, 189, 211, 212, 213, 237, 245, 252,
 263, 274, 311, 315
 Petroleum  74, 128, 299
 Petroleum hydrocarbons  74
 Ph  91, 306
 Phosphates  167
 Phosphorus  46, 56, 57, 72, 79, 85, 112, 200, 260
 Phosphorus pentoxide  108
 Phthalates  259
 Physical models  37, 53, 283, 326
 Physicochemical properties  51, 63, 134, 221, 249, 294
 Phytoplankton  271
 Picea abies  37
 Picloram  288
 Pig farming  112
 Pinus sylvestris  37
 Pinus taeda  175
 Placement  44
 Plains  159
 Planning  197
 Plant communities  111, 190
 Plant density  62
 Plant development  326
 Plant nutrition  91
 Plant water relations  8
 Plants  252
 Plastic cladding  181
 Plowing  216
 Podzolic soils  255
 Pollutants  2, 14, 16, 39, 90, 96, 117, 147, 167, 183, 188,
 198, 208, 210, 235, 253, 257, 274, 291, 295, 297, 301, 325
 Polluted soils  39, 74, 244
 Pollution  23, 79, 115, 208, 232, 272, 287, 316
 Pollution control  112, 231
 Populations  120
 Pore size distribution  276
 Pore volume  268, 269
 Pores  6, 221, 268
 Porosity  148, 172, 178, 204, 205
 Porous media  51
 Pot culture  305
 Potassium  108, 221, 222, 255
 Potassium bromide  184
 Potassium chloride  302
 Potassium nitrate  259
 Poultry manure  46, 219
 Practice  12, 159
 Prairies  228
 Precipitation  37, 41, 60, 95, 171, 187, 220, 238, 312, 326 
 Precipitation (Meteorology)  286
 Prediction  7, 12, 14, 25, 56, 65, 66, 71, 81, 96, 130, 141,
 163, 164, 165, 169, 170, 175, 176, 178, 203, 209, 220, 221,
 222, 223, 224, 228, 238, 242, 247, 248, 250, 251, 253, 260,
 273, 274, 280, 281, 289, 293, 294, 296, 297, 304, 309, 312,
 322, 336, 337
 Prevention  29, 296
 Probabilistic models  53, 71, 183
 Probabilities  161
 Probability  32
 Problem solving  44, 187, 192
 Production  164, 165
 Profiles  67, 76, 134, 140, 148, 175, 239, 258, 289
 Profit functions  189
 Profitability  38, 114, 135
 Program development  12
 Program evaluation  313
 Programming  187
 Public agencies  331
 Public health  143
 Pulp and paper industry  330
 Pulp mill effluent  330
 Pumps  44
 Pyrites  100
 Qualitative techniques  140
 Quality standards  331
 Quantitative analysis  49, 120, 128
 Quantitative techniques  13
 Quebec  320
 Rain  11, 14, 18, 32, 36, 42, 53, 55, 62, 64, 70, 73, 76, 77,
 108, 113, 117, 125, 126, 160, 162, 167, 176, 199, 209, 210,
 213, 226, 228, 241, 265, 281, 303, 319, 324, 327
 Rainy season  108
 Random sampling  88
 Rangeland soils  319
 Rangelands  190, 228, 238, 242, 312, 319, 337
 Ranking  143, 272, 284
 Ratios  243
 Recharge  66, 123
 Reclamation  124, 243
 Redistribution  162, 247
 Redox reactions  100
 Reduction  100, 193
 Reflectance  65
 Regional planning  129
 Registration  30, 143
 Regression analysis  229, 322
 Regulations  120, 189, 230, 231, 232, 311
 Relationships  176
 Reliability  232
 Remote sensing  24, 65, 103, 138, 209
 Removal  72
 Replication  151
 Reserved areas  34
 Reservoirs ư137, 144
 Respiration  164
 Responses  65
 Retention  173
 Returns  38, 112
 Reviews  197
 Rhizosphere  149, 150, 169
 Rill erosion  337
 Riparian vegetation  23
 Risk  25, 55, 106, 114, 142, 234, 235, 263
 River water  52, 107, 257
 Rivers  147, 234, 236, 330
 Root exudates  149, 150
 Root systems  91
 Root zone flux  22, 212
 Roots  108, 268, 269
 Rotations  45, 87
 Rsfsr  72
 Runoff  11, 17, 18, 19, 25, 28, 32, 34, 36, 37, 62, 64, 68,
 70, 73, 77, 79, 80, 82, 87, 95, 105, 106, 110, 112, 113, 118,
 124, 126, 141, 162, 167, 176, 179, 180, 181, 187, 190, 195,
 199, 211, 213, 219, 220, 223, 226, 227, 228, 234, 238, 239,
 240, 241, 242, 248, 260, 263, 264, 265, 280, 281, 285, 303,
 309, 310, 312, 319, 320, 322, 324, 326, 327
 Runoff farming  218
 Runoff irrigation  218
 Runoff water  15, 42, 46, 53, 55, 72, 92, 108, 125, 131, 156,
 209, 216, 239, 282, 313
 Rural areas  70
 Saccharum officinarum  108
 Saline sodic soils  243
 Saline soils  243
 Saline water  66, 97, 102, 235
 Salinity  52, 91, 123
 Salmon  120
 Salts in soil  243, 249
 Salvage felling and logging  314
 Samples  270
 Sampling  79, 102, 277
 Sand  140, 221, 323
 Sandy loam soils  27, 259, 266, 273
 Sandy soils  85, 134, 145, 171, 252
 Satellite imagery  103, 209
 Saturated conditions  152, 243, 249
 Saturated flow  51
 Saturated hydraulic conductivity  37, 59, 130, 141, 276, 305,
 319
 Scotland  11, 18
 Screening  284
 Seasonal variation  60, 246, 257
 Sediment  26, 65, 72, 108, 167, 285, 314, 320
 Sediment transport  109, 264
 Sediment yield  82, 154, 226
 Seed orchards  309
 Seepage  80, 141, 183
 Selection  102
 Selection methods  307
 Selenium  168, 249
 Semiarid soils  130, 247
 Semiarid zones  17, 55, 209
 Sewage  137, 329
 Sewage effluent  307
 Sewage effluent disposal  307
 Sheep  200, 201
 Silt loam soils  184, 280, 288, 302, 306
 Silviculture O89
 Simazine  47, 152
 Simulation  58, 100, 120, 162, 163, 170, 183, 199, 209, 213,
 224, 251, 259, 261, 262, 269, 275, 326
 Simulation models  1, 8, 10, 11, 12, 14, 17, 18, 19, 20, 22,
 24, 25, 27, 28, 30, 33, 34, 37, 38, 41, 44, 45, 55, 64, 68,
 74, 76, 77, 80, 81, 82, 85, 86, 87, 89, 92, 95, 104, 106, 110,
 111, 113, 118, 119, 121, 123, 127, 128, 142, 148, 150, 151,
 152, 153, 154, 155, 156, 158, 159, 164, 165, 167, 168, 169,
 173, 175, 179, 182, 186, 187, 191, 194, 195, 199, 200, 201,
 202, 204, 206, 207, 208, 211, 213, 217, 219, 223, 224, 226,
 228, 233, 236, 237, 242, 245, 256, 257, 258, 260, 263, 265,
 266, 268, 279, 283, 285, 289, 290, 298, 302, 304, 309, 311,
 312, 316, 319, 321, 322, 327, 328, 334
 Site factors  3, 228, 284, 307
 Site selection  218
 Size  13, 157
 Slope  62
 Slopes  37, 141, 226
 Sloping land  124, 125, 176, 281
 Snow  279
 Social values  307
 Sodium  243, 255
 Soil  102, 134, 155, 218, 229, 283, 295, 337
 Soil air  157, 168
 Soil amendments  219
 Soil analysis  84, 152, 254
 Soil biology  164
 Soil boundaries  13, 140, 267
 Soil chemistry  57, 66, 127, 164, 168, 174, 224, 258, 300
 Soil compaction  269
 Soil conservation  17, 34, 105, 138, 241, 285
 Soil depth  8, 27, 37, 59, 108, 141, 210, 225, 249, 255, 265,
 279, 280, 289
 Soil erosion  161, 264
 Soil fertility  17, 202, 233
 Soil flora  6, 39, 168
 Soil management  306
 Soil morphological features  171
 Soil morphology  148
 Soil movement  115
 Soil organic matter  85, 148, 216, 244
 Soil ph  244, 295
 Soil physical properties  141, 307, 326
 Soil physics  56, 177, 178
 Soil pollution  2, 14, 35, 39, 43, 67, 74, 76, 90, 112, 128,
 134, 155, 156, 159, 188, 193, 203, 270, 291, 295, 297, 301,
 323
 Soil pore system  6, 172, 279, 288, 298
 Soil properties  10, 40, 47, 57, 78, 82, 95, 117, 252, 263,
 273  Soil salinity  97, 102, 251
 Soil solution  1, 6, 15, 56, 84, 91, 221, 222, 239, 244, 255 
 Soil sterilization  168
 Soil structure  148
 Soil surveys  148
 Soil temperature  37, 41, 145, 153, 171, 266, 279, 325
 Soil testing  1, 151
 Soil texture  8, 20, 148, 319
 Soil types  65, 192, 228, 293, 294, 335
 Soil types (genetic)  173
 Soil variability  130, 136, 148, 194, 244, 247, 307
 Soil water  22, 49, 62, 71, 95, 130, 141, 145, 153, 157, 160,
 176, 194, 221, 246, 247, 266, 275, 288, 298, 326
 Soil water balance  55, 141, 163, 194, 202, 326
 Soil water content  1, 13, 73, 91, 148, 157, 162, 183, 222,
 261, 262, 265, 266, 279, 281, 325
 Soil water movement  1, 8, 41, 74, 85, 90, 136, 162, 175, 184,
 188, 198, 199, 214, 243, 254, 255, 266, 267, 288, 289, 301
 Soil water potential  305
 Soil water regimes  325
 Soil water retention  37, 136, 148, 266, 273, 305
 Soil zonation  225
 Solar radiation  312
 Solubility  56, 133
 Solutes  1, 5, 6, 7, 8, 14, 49, 51, 58, 59, 71, 84, 98, 130,
 132, 140, 149, 150, 157, 163, 170, 172, 174, 176, 177, 178,
 182, 184, 199, 210, 225, 243, 246, 247, 249, 250, 251, 267,
 268, 275, 276, 281, 283, 293, 294, 297, 300, 302
 Solvents  229
 Sorghum bicolor  97
 Sorption  39, 56, 57, 63, 85, 149, 150, 152, 170, 173, 229,
 244, 259, 270, 281, 289, 306
 Sorption isotherms  26, 85, 150, 244, 288
 South Dakota  212
 Southern plains states of U.S.A.  241
 Southern states of U.S.A.  54, 89, 309
 Soybeans  55
 Spacing  251
 Spain  236, 246
 Spatial distribution  3, 6, 33, 91, 100, 102, 164, 165, 221,
 249, 266, 271
 Spatial variation  13, 33, 63, 71, 148, 194, 244, 265, 266,
 273, 275, 276, 279
 Species diversity  89
 Splash erosion  77
 Spodosols  85, 244
 Spread  296
 Spreading  267
 Spring  171
 Standards  295
 Statistical analysis  151, 273
 Statistical data  151
 Statistical methods  267
 Steady flow  165, 297
 Steppes  228
 Stochastic models  59, 63, 88, 116, 207, 234, 273, 275, 312
 Stochastic programming  116
 Storage  194, 258
 Storms  162, 220, 226, 248
 Straw  99
 Stream flow  18, 28, 60, 113, 160, 246, 324
 Streams  82, 224, 246
 Strontium  268
 Subsoil  33, 221, 265, 269
 Substrates  6
 Subsurface barriers  140
 Subsurface drainage  251, 327
 Subsurface irrigation  334
 Subsurface layers  5, 85, 199, 291, 335
 Subsurface runoff  40
 Subtropics  108, 143
 Sulfur  201
 Superphosphates  200, 201
 Supply response  189
 Surface layers  13, 73, 131, 225, 283
 Surface roughness  13, 110
 Surface water  15, 28, 46, 106, 111, 197, 210, 215, 241, 309
 Survival  114
 Susceptibility  16
 Suspensions  65
 Sustainability  108, 316
 Swamps  111
 Sweden  37, 326
 Systems  331
 Systems approach  283
 Taiwan  303
 Taxes  189, 206, 232
 Teaching methods  285
 Technology  4
 Technology transfer  138
 Temperature  246, 306
 Temporal variation  91, 108, 151, 271
 Terbufos  211
 Terrain  287
 Tests  296
 Texas  16, 28, 66, 114, 190, 248, 257
 Thematic mapper  24
 Theory  127, 270, 290
 Thermal conductivity  266
 Thermal diffusivity  266
 Thermodynamics  66
 Thickness  148
 Tile drainage  80, 250, 251
 Tillage  13, 17, 73, 82, 110, 159, 240, 260, 322
 Time  172
 Time lag  249
 Timing  46
 Toluene  299, 323
 Topography  13, 126, 307
 Topsoil  178, 265
 Toxicity  143
 Toxicology  263
 Tracers  289, 296
 Traditional farming  240
 Transformation  63, 156, 170, 293
 Transient flow  8, 51, 165, 297
 Transpiration  326
 Transport  88
 Transport processes  1, 2, 5, 6, 7, 8, 13, 15, 26, 39, 49, 51,
 56, 58, 59, 71, 74, 79, 84, 85, 90, 91, 94, 98, 100, 127, 130,
 131, 132, 136, 149, 150, 152, 157, 158, 160, 163, 164, 165,
 168, 169, 170, 172, 173, 174, 176, 177, 182, 183, 188, 193,
 198, 199, 204, 205, 208, 210, 221, 225, 235, 239, 244, 247,
 249, 250, 254, 261, 262, 266, 267, 268, 269, 270, 275, 276,
 281, 283, 288, 293, 294, 298, 300, 301, 306, 323, 325, 335
 Transverse distribution  58
 Trends  120
 Trichloroethylene  2
 Trickle irrigation  91
 Tritiated water  184
 Triticum aestivum  97, 165, 233
 Triticum turgidum  97
 Tritium  247
 Tunisia  102
 Turbidity  65
 Turbulent flow  335
 Two dimensional flow  58
 U.S.A.  4, 12, 34, 183, 194, 328, 331
 U.S.S.R.in europe  53, 72
 Uncertainty  14
 Underground storage  74
 Undisturbed sampling  259
 Unfrozen water  279
 Universal soil loss equation  285, 336
 Unsaturated flow  96, 136, 157, 163, 199, 225, 273, 275, 276,
 297
 Unsaturated hydraulic conductivity  305
 Upland areas  110, 124
 Uptake  63, 133, 134, 252, 258
 Upward movement  111
 Urban areas  197
 Urea  306
 Urea fertilizers  169
 Usage  38, 215, 231
 Usda  12, 105, 138
 Uses  189
 Utah  20
 Validity  244, 290, 327
 Vapor  2, 323
 Variance  267
 Variation  14, 151
 Vegetation  28, 111, 190
 Velocity  199, 259, 269, 288, 289, 298
 Vermont  230, 307
 Vertical movement  275, 289, 293, 309
 Victoria  70, 235
 Virginia  116, 135, 186, 284
 Viruses  325
 Volatile compounds  35
 Volatilization  2, 169, 306
 Volcanic ash  305
 Wales  216
 Washington  147
 Waste disposal  46, 99
 Waste disposal sites  307
 Waste treatment  137
 Waste water  66
 Waste water treatment  236
 Wastes  185
 Water  31, 83, 102, 166, 199, 292, 329, 332
 Water allocation  328
 Water balance  153, 327
 Water conservation  32
 Water content  246
 Water distribution  199, 220, 331
 Water erosion  12, 34, 82, 228, 241, 242, 285, 304, 322, 336,
 337
 Water flow  22, 37, 48, 49, 51, 110, 120, 130, 141, 160, 164,
 165, 171, 208, 247, 250, 261, 262, 275, 279
 Water harvesting  55, 209
 Water holding capacity  141
 Water management  20, 28, 48, 52, 80, 98, 101, 115, 119, 120,
 121, 138, 185, 207, 236, 334
 Water policy  4, 69, 328
 Water pollution  3, 24, 47, 57, 60, 61, 69, 72, 78, 87, 106,
 107, 146, 147, 154, 156, 180, 195, 196, 197, 234, 236, 252,
 257, 258, 260, 263, 277, 284, 321
 Water purification  137, 147
 Water quality  4, 9, 19, 21, 24, 30, 40, 46, 48, 52, 54, 60,
 65, 66, 69, 86, 89, 97, 98, 105, 108, 109, 111, 114, 120, 122,
 135, 137, 144, 147, 154, 163, 190, 194, 197, 207, 215, 219,
 223, 224, 231, 234, 236, 241, 245, 246, 251, 257, 260, 263,
 271, 277, 278, 287, 308, 311, 313, 317, 318, 328, 329, 330,
 331, 332, 333, 334
 Water quality management  83, 122, 292
 Water recreation  147
 Water relations  55
 Water requirements  218
 Water resources  113, 119, 120, 121, 137, 197
 Water storage  218
 Water supply  185
 Water table  52, 80, 111, 163, 179, 203, 251, 334
 Water transport  282
 Water uptake  171
 Water use efficiency  328
 Water vapor  266, 335
 Water yield  70, 141
 Water, Underground  75, 308
 Watershed management  129, 139, 187, 259
 Watersheds  11, 18, 23, 24, 28, 32, 53, 64, 70, 72, 89, 113,
 115, 126, 141, 154, 160, 175, 179, 190, 209, 224, 226, 238,
 241, 246, 265, 272, 286, 303, 310, 320, 324, 327
 Weather  175
 Weather data  53, 312
 Weed competition  38
 Weed control  38
 Wells  101, 102, 253, 317
 West  Africa  218
 Wetlands  313, 318
 Wetting front  73, 130
 Wheat  55
 Wind  335
 Wisconsin  296, 313
 Wyoming  190
 Xylene  299
 Yield forecasting  312
 Yield losses  102
 Yield response functions  55
 Zea mays  45, 61, 87, 97, 165, 171, 179, 252, 322
 Zoning  53
 Zooplankton  271
 
 ***************************************************************
                               SEARCH STRATEGY
 
 Set     Items       Description
 
 S1      40216       (MODEL?)/TI,DE,ID
 
 S2      13239       (POLLUTION(2N)AGRICULTUR? OR
         AGRICULTURAL()WASTE? OR WATER()QUALITY OR
         GROUNDWATER()POLLUTION OR
         TRANSPORT()PROCESSES OR LEACHING OR
         RUNOFF)/TI,DE,ID
 
 S3      1606        S1 AND S2
 
 S4      1333        (ANSWERS OR CNS OR STORM OR ARM OR
         CREAMS)/TI,DE,ID
 
 S5      42707       (MODEL? OR SIMULATION? ?)/TI,DE,ID
 
 S6      124         S4 AND S5
 
 S7      98          (CPM OR GLEAMS OR NTRM OR PRZM OR WEPP OR
         AGNPS OR HSPF OR NPS OR SWAM OR SWMM OR
         SWRRB)/TI
 
 S8      356         (GIS OR GEOGRAPHIC()INFORMATION()SYSTEM?
         ?)/TI,DE,ID
 
 S9      73680       SH=(P200 OR WOOO OR J800)
 
 S10     76          S8 AND S9
 
 S11     1788        S3 OR S6 OR S7 OR S10
 
 S12     394         S11 AND (PY=(1991 OR 1992 OR 1993)
 


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