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

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

 January, 1994 - October, 1994
 176 citations from AGRICOLA
 Diane Doyle
 Water Quality Information Center
 This electronic bibliography is intended primarily to provide
 awareness of recent investigations and discussions of a topic and
 is not intended to be in-depth and exhaustive. The inclusion or
 omission of a particular publication or citation should not be
 construed as endorsement or disapproval. 
 Send suggestions for electronic bibliographies related to water
 resources and agriculture to wqic@ars.usda.gov
 To locate a publication cited in this bibliography, please
 contact your local, state, or university library.  If you are
 unable to locate a particular publication, your library can
 contact the National Agricultural Library (please see "Document
 Delivery Services" at 
 1. An agricultural chemical evaluation and management system.
 Haan, C. T.; Nofziger, D. L.; Gregory, M. 
 J-agric-eng-res v.56, p.301-312. (1993).
 Includes references.
 Descriptors: agricultural-chemicals; movement-in-soil;
 groundwater-pollution; simulation-models;
 geographical-information-systems; evaluation-; management-;
 systems-; oklahoma-
 Abstract: An Agricultural Chemical Evaluation and Management
 System (AGCHEMS), has been developed to investigate the impact of
 various agricultural chemical management scenarios on the
 movement of these chemicals toward groundwater. AGCHEMS was
 developed by integrating a chemical transport model (CMLS), a
 weather simulation model (WGEN), and a geographical information
 system (GIS).  AGCHEMS can evaluate the effect of chemical
 application rate and timing, the particular chemical used, and
 other management practices such as the amount and timing of
 irrigation water.  These factors affect the time and amount of
 the chemical that will reach selected depths in the soil profile. 
 The GIS allows site specific soil information to be used in the
 model.  The GIS can also be used to prepare maps showing the
 vulnerability of areas to exceed selected standards of chemical
 movement.  Uncertainty in the exact values of soil and chemical
 properties and variability in weather sequences can also be
 evaluated and maps generated showing the probability of exceeding
 various amounts of chemical passing preselected depths in the
 soil profile. The results obtained using possible and equally
 likely weather sequences show considerable variability in
 chemical movement due to weather alone.  The implications of this
 variability upon monitoring programmes, the interpretation of
 model studies, and possible regulations on use of agricultural
 chemicals are discussed.
 NAL Call No.: 58.8-J82
 2. Alternating extraction/injection well interactions for in situ
 Shouche, M. S.; Petersen, J. N.; Skeen, R. S.; Hooker, B. S. 
 Appl-biochem-biotechnol. Totowa, N.J. : Humana Press. Spring
 1994. v. 45/46 p. 775-785. 
 Paper presented at the "Fifteenth Symposium on Biotechnology for
 Fuels and Chemicals," May 10-14, 1993, Colorado Springs,
 Descriptors: bioremediation-; bacteria-; microbial-degradation;
 carbon-tetrachloride; biomass-; spatial-distribution;
 groundwater-flow; groundwater-pollution; wells-;
 NAL Call No.: QD415.A1J62
 3. Analyses of slope and runoff factors based on the WEPP erosion
 Huang, C.; Bradford, J. M. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Sept/Oct 1993. v. 57 (5) p. 1176-1183. 
 Includes references.
 Descriptors: water-erosion; geological-sedimentation;
 mathematical-models; equations-; mathematics-; slope-; runoff-;
 sediment-; losses-from-soil; areas-;
 water-erosion-prediction-process; rill-and-interrill-areas
 Abstract: Under process-based erosion model development, the
 source of sediment transported off a field isseparated into
 that from interrill and rill areas, and separate detachment
 equations are  developed. Limitation of this spatial separation
 is that, in many conditions, rill and interillareas are not
 clearly defined a priori. We interpreted the erosion and
 deposition equations usedin the current Water Erosion
 Prediction Project (WEPP) in an alternative fashion such that  
 spatial separation of rill and interrill areas is no longer
 required. Analytic solutions werederived for the WEPP erosion
 and deposition equations under general conditions. Simplified  
 solutions for a specific case, uniform rain on uniform slope,
 were examined closely for slope and  runoff effects on sediment
 delivery. Under both erosion and deposition conditions, analytic  
 solutions show a linear relationship between sediment yield, qs
 and slope, S. The dependency of qson runoff, qw, is either
 linear or quadratic depending on whether the system is dominated
 by anerosion or deposition regime. These analytic findings
 explain results obtained from laboratorystudies in which
 sediment yield was collected under variable slope and rain
 NAL Call No.: 56.9-So3
 4. Analytical models of steady state organic species transport in
 the vadose zone with kinetically controlled volatilization and
 Zaidel, J.; Russo, D. 
 Water-resour-res v.29, p.3343-3356. (1993).
 Includes references.
 Descriptors: soil-pollution; volatile-compounds;
 transport-processes; volatilization-; dissolving-; kinetics-;
 mathematical-models; unsaturated-zone; steady-state-flow
 Abstract: Kinetically controlled volatilization and dissolution
 of nonaqueous phase liquids (NAPLs) may play  an important role
 in the transport of volatile compounds in the unsaturated
 (vadose) zone. In this  study, some one- and two-dimensional
 steady state transport problems are solved analytically. The 
 one-dimensional case is pertinent to pollution by a relatively
 long, mainly horizontally spreadleak of NAPL. The
 two-dimensional case corresponds to situations in which the
 pollution spreadsprimarily vertically, originating at the
 ground surface and migrating to the top of the capillary  
 fringe, and in which the solution domain may be represented by a
 cross-sectional model. Solutionsof the steady state transport
 problems are used to investigate effects of several parameters,  
 characterizing the advective-dispersive and purely diffusive
 transport regimes, on the NAPLconcentration distribution for
 the one- and two-dimensional cases, respectively. Results of this 
 analysis indicate that the mass exchange between NAPL and other
 phases may not reach equilibrium,even for relatively large
 mass transfer rate coefficients and small water infiltration
 rates, ifthis zone has relatively small vertical or horizontal
 extent and is located close to the fullyopen ground surface.
 Analysis of local volatilization and dissolution fluxes shows
 that, underequilibrium conditions, the main losses of the
 organic phase take place at the upper part of theNAPL zone.
 NAL Call No.: 292.8-W295
 5. Analytical solutions for non-equilibrium solute transport in
 three-dimensional porous media.
 Leij, F. J.; Toride, N.; Van Genuchten, M. T. v. 
 J-hydrol v.151, p.193-228. (1993).
 Includes references.
 Descriptors: soil-water-movement; solutes-; transport-processes;
 porous-media; flow-; mathematical-models; unidirectional-flow
 Abstract: The movement of water and chemicals in soils is
 generally better described with multidimensionalnonequilibrium
 models than with more commonly used one-dimension and/or
 equilibrium models. This  paper presents analytical solutions for
 non-equilibrium solute transport in semi-infinite porousmedia
 during steady unidirectional flow. The solutions can be used to
 model transport in porousmedia where the liquid phase consists
 of a mobile and an immobile region (physicalnon-equilibrium)
 or where solute sorption is governed by either an equilibrium or
 a first-orderrate process (chemical non-equilibrium). The
 transport equation incorporates terms accounting for  advection,
 dispersion, zero-order production, and first-order decay. General
 solutions were derivedfor the boundary, initial, and
 production value problems with the help of Laplace and Fourier  
 transforms. A comprehensive set of specific solutions is
 presented using Dirac functions for theinput and initial
 distribution, and/or Heaviside or exponential functions for the
 input, initial,and production profiles. A rectangular or
 circular inflow area was specified for the boundaryvalue
 problem while for the initial and production value problems the
 respective initial and  production profiles were located in
 parallelepipedal, cylindrical, or spherical regions of the  
 soil. Solutions are given for both the volume-averaged or
 resident concentration as well as theflux-averaged or flowing
 concentration. Examples of concentration profiles versus time
 and.  effects of non-equilibrium onthree-dimensional transport
 are very similar to those for one-dimensional transport.
 NAL Call No.: 292.8-J82
 6. Answer-2000: a model for agricultural pollution control
 planning in the USA and the Ukraine.
 Dillaha, T. A. I.; Bouraoui, F.; Kolpak, V. Z.; Beasley, D. B.;
 Platonova, G. Y. 
 Proceedings of Industrial and Agricultural Impacts on the
 Hydrologic Environment  the Second USA/CIS Joint Conference on
 Environmental Hydrology and Hydrogeology / USA/CIS Joint
 Conference on Environmental Hydrology and Hydrogeology.
 Alexandria, VA : Water Environment Federation, c1993.. v. 2 p.
 Title on cover : Environmental impact of agricultural practices
 and agrichemicals / edited by Y. Eckstein and A. Zaporozec.
 Descriptors: agricultural-production; pollution-; control-;
 water-quality; planning-; models-; usa-; ukraine-
 NAL Call No.: GB652.U82-1993
 7. Application of a GIS-based nonpoint source nutrient loading
 model for assessment of land development scenarios and water
 quality in Owasco Lake, New York.
 Heidtke, T. M. 
 Water-sci-technol v.28, p.595-604. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: lakes-; water-quality; phosphorus-; loads-;
 water-pollution; models-; geographical-information-systems;
 land-use; new-york
 NAL Call No.: TD420.A1P7
 8. The application of CREAMS model to forecasting the nitrate and
 chloride leaching from grassland.
 Sapek, B.; Sapek, A. 
 Water-sci-technol v.28, p.649-658. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: permanent-grasslands; groundwater-pollution;
 nitrates-; chlorides-; leaching-; simulation-models;
 forecasting-; poland-
 NAL Call No.: TD420.A1P7
 9. Application of geographic information systems in hydrology and
 water resources management : proceedings of an international
 conference held in Vienna, Austria, from 19 to 22 April 1993 :
 this conference was jointly organized by the International
 Commission on Groundwater of the International Association of
 Hydrological Sciences (IAHS), the United Nations Educational,
 Scientific and Cultural Organization (UNESCO) - as a contribution
 to subprogramme M-2-3 of UNESCO's IHP-IV, Universitat fur
 Bodenkultur, Vienna.
 Kovar, K.;  Nachtnebel, H. P.; International Association of
 Hydrological Sciences. 
 Wallingford : International Association of Hydrological Sciences,
 1993. xi, 693 p. : ill., maps.
 Includes bibliographical references.
 Descriptors: Geographic-information-systems-Congresses;
 NAL Call No.: G70.2.A77--1993
 10. Application of GLEAMS to predict nutrient losses from land
 application of poultry litter.
 Yoon, K. S.; Yoo, K. H.; Wood, C. W.; Hall, B. M. 
 Trans-ASAE v.37, p.453-459. (1994).
 Includes references.
 Descriptors: poultry-manure; runoff-; nitrogen-; phosphorus-;
 water-quality; simulation-models; alabama-;
 groundwater-loading-effects-of-agricul; -manage; -systems
 Abstract: The GLEAMS (Groundwater Loading Effects of Agricultural
 Management System) (version 2.1) water quality model was used to
 predict nutrient (N and P) losses in surface and subsurface
 runoff, and their concentrations in soil layers, following
 application of two rates (9 and 18 t ha-1) of poultry litter and
 a recommended rate of a commercial fertilizer on conventionally
 tilled corn plots at the Tennessee Valley Substation of the
 Alabama Agricultural Experiment Station. Model simulation results
 were compared with field data. The experiment included four
 replications for each of the three soil-amendment treatments. The
 GLEAMS simulation of soluble and sediment P losses in surface
 runoff and NO3-N concentrations in leachate and soil layers were
 not consistent with field data. Simulation of N-transformation
 effects on N losses in surface runoff did not agree with field
 data. The model simulated higher NH4-N than NO3-N losses in
 surface runoff, while field data showed the opposite. The model
 simulated low concentrations of P in leachate at a 1.0 m depth,
 while the observed data showed large variations.
 NAL Call No.: 290.9-Am32T
 11. Assessing the movement of agricultural chemicals through the
 soil profile at the Ohio management systems evaluation area.
 Workman, S. R.; Ward, A. D.; Knisel, W. G. 
 Proceedings of Industrial and Agricultural Impacts on the
 Hydrologic Environment  the Second USA/CIS Joint Conference on
 Environmental Hydrology and Hydrogeology / USA/CIS Joint
 Conference on Environmental Hydrology and Hydrogeology.
 Alexandria, VA : Water Environment Federation, c1993.. v. 2 p.
 Title on cover : Environmental impact of agricultural practices
 and agrichemicals / edited by Y. Eckstein and A. Zaporozec.
 Descriptors: zea-mays; glycine-max; triticum-aestivum;
 vicia-villosa; atrazine-; alachlor-; metribuzin-;
 movement-in-soil; prediction-; simulation-models; leaching-;
 contamination-; ohio-
 NAL Call No.: GB652.U82-1993
 12. Assessment of pollution of groundwater by atrazine.
 Kuhnt, G.; Franzle, O. 
 Land-degrad-rehabil v.4, p.245-251. (1993).
 Special Issue on the June 1992 Conference of the Society for
 Environmental Toxicology and Chemistry (SETAC) / edited by G.P.
 Hekstra, E. Ivanova and J.H. Weverling.
 Descriptors: atrazine-; groundwater-pollution; risk-;
 monitoring-; soil-types; simulation-; models-; germany-
 NAL Call No.: S622.L26
 13. Automated extraction of drainage network and watershed data
 from digital elevation models.
 Martz, L. W.; Garbrecht, J. 
 Water-resour-bull v.29, p.901-908. (1993).
 Includes references.
 Descriptors: drainage-; overland-flow; runoff-; watersheds-;
 hydrological-data; algorithms-; computer-software;
 geomorphology-; oklahoma-;
 Abstract: This paper discusses a computer program which extracts
 a number of watershed and drainage network properties directly
 from digital elevation models (DEM) to assist in the rapid
 parameterization of hydrologic runoff models. The program
 integrates new and established algorithms to address problems
 inherent in the analysis low-relief terrain from raster DEMs
 similar to those distributed by the U.S. Geological Survey for
 7.5-minute quadrangles. The program delineates the drainage
 network from a DEM, and determines the Strahler order, total and
 direct drainage area, length, slope, and upstream and downstream
 coordinates of each channel link. It also identifies the
 subwatershed of each channel source and of the left and right
 bank of each channel link, and assigns a unique number to each
 network node. The node numbers are used to associate each
 subwatershed with the channel link to which it drains, and can be
 used to control flow routing in cascade hydrologic models.
 Program output includes tabular data and raster maps of the
 drainage network and subwatersheds. The raster maps are intended
 for import to a Geographical Information System where they can be
 registered to other data layers and used as templates to extract
 additional network and subwatershed information.
 NAL Call No.: 292.9-Am34
 14. Axisymmetric transport of water and solute underneath a disk
 Quadri, M. B.; Clothier, B. E.; Angulo Jaramillo, R.; Vauclin,
 M.; Green, S. R. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1994. v. 58 (3) p. 696-703. 
 Includes references.
 Descriptors: water-flow; solutes-; movement-in-soil;
 transport-processes; unsaturated-flow; permeability-
 Abstract: No analytical solution exists for two-dimensional,
 axisymmetric flow of both water and solute underneath a disk
 permeameter. We developed a finite-difference numerical scheme
 for such flows. Laboratory experiments were also conducted using
 a box containing repacked sand.  A 1/4-sector disk permeameter
 was located on the surface in one corner. The disk, first
 containing pure water, was placed on the soil for 200 s. It was
 then removed, refilled with a KBr solution, and replaced at 225
 s. Finally after 12.5 min the disk was removed and soil samples
 extracted along three radial transects under the disk. In two
 other experiments, the disk, containing only pure water, was left
 on the soil surface and soil samples removed at the end i.e., 6
 and 14 min. A tensiometer inserted through one face of the box
 and located just 20 mm under the disk recorded the changing soil
 water pressure head with time, h(t).  Good predictions of both
 the water content and Br(-) profiles were achieved with the
 numerical model, and good renditions of h(t) and the transient
 flow rate from the disk, q(t). Our results reinforce the need for
 caution when determining the soil's sorptivity from observations
 of q vs t(1/2).  Care is required in deciding when q has indeed
 become steady.  Numerical models, such as this one might serve as
 parameter-identification tools when using a tracer-filled disk
 permeameter to infer the chemical transport properties of soil.
 NAL Call No.: 56.9-So3
 15. Broiler litter application to land in an agricultural
 watershed: A GIS approach.
 Xu, F.; Prato, T.; Fulcher, C. 
 Water-sci-technol v.28, p.111-118. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: broilers-; poultry-manure; application-to-land;
 agricultural-land; watersheds-; application-rates;
 economic-evaluation; water-pollution; prediction-; optimization-;
 models-; geographical-information-systems; missouri-
 NAL Call No.: TD420.A1P7
 16. Calculating critical loads for acidity with the simple mass
 balance method.
 Sverdrup, H.; Vries, W. de. 
 Water-air-soil-pollut v.72, p.143-162. (1994).
 Includes references.
 Descriptors: acid-deposition; forest-soils; polluted-soils;
 groundwater-pollution; soil-pollution; water-pollution; acidity-;
 soil-acidity; alkalinity-; soil-alkalinity; balance-studies;
 mathematical-models; equations-; sweden-; netherlands-
 NAL Call No.: TD172.W36
 17. CELMOD5--a semi-distributed cell model for conversion of
 rainfall into runoff in semi-arid watersheds.
 Karnieli, A. M.; Diskin, M. H.; Lane, L. J. 
 J-hydrol v.157, p.61-85. (1994).
 Includes references.
 Descriptors: watersheds-; rain-; storms-; runoff-;
 catchment-hydrology; forecasting-; floods-; semiarid-climate;
 Abstract: This paper introduces the general outline of CELMOD5, a
 parametric, semi-distributed, quasi-linear model, for conversion
 of rainfall into surface runoff. The model considers the
 watershed as a series of interconnected cell units, each
 representing a specific portion of the area of the watershed. In
 contrast to grid models using a large number of rectangular
 elements or cells, the number of cells in CELMOD is relatively
 small and their boundaries are chosen according to the watershed
 topography. For each cell, the program computes the surface
 runoff hydrograph at the cell outlet, related to a specified
 record of total rainfall data at a number of rain gages. If
 measured surface runoff data are available for some locations in
 the watersheds, the program can compare these data with computed
 values of surface runoff at the corresponding points of the cell
 model. Detailed descriptions are provided for the main model
 procedures--computation of rainfall excess, conversion of
 rainfall excess into surface outflow, routing the channel inflow
 and subtraction of channel losses. Special attention is given in
 this model to the specific conditions of arid or semi-arid
 watersheds. This paper is also concerned with a technique for
 calibrating and testing a forecasting model of storm hydrographs
 with emphasis on two objective functions--runoff volume and peak
 discharge. A method for evaluation procedure is presented based
 on the following five steps: trial and error calibration:
 sensitivity analysis; bilinear interpolation optimization,
 testing the model on different storm events; testing the model on
 a different watershed. Results are presented for all the larger
 storm events with reliable.  Experimental Watershed in
 southeastern Arizona. The evaluation procedure is demonstrated
 for one particular rainfall-runoff event.
 NAL Call No.: 292.8-J82
 18. Chloride migration in heterogeneous soil. 2. Stochastic
 Destouni, G.; Sassner, M.; Jensen, K. H. 
 Water-resour-res v.30, p.747-758. (1994).
 Includes references.
 Descriptors: transport-processes; chloride-; prediction-;
 Abstract: The observed statistics of chloride breakthrough
 presented by Sassner et al. (this issue) were compared with
 predictions of a stochastic-advective modeling approach. The
 stochastic-advective model based on the observed spatial
 distribution of flow rates and on transport parameters consistent
 with parameter values obtained from local breakthrough curves
 (BTCs) agreed well with the observations. Alternative models that
 agreed well with the local BTCs failed to predict the large-scale
 BTC with realistic parameter values. The results support the
 assumption that compared to advection variability, local
 dispersion within the mobile water will often have a second-order
 effect on field scale solute transport. The stochastic-advective
 model is robust with regard to the rate of mass transfer between
 mobile and immobile water zones. This robustness implies that
 order of magnitude estimates may be sufficient for providing
 useful predictions of both field scale solute transport and the
 associated prediction uncertainty. In contrast, accurate
 estimation of the statistics of solute advection at the scale of
 interest for the transport problem is necessary.
 NAL Call No.: 292.8-W295
 19. Climate change impact on distribution and abundance of
 wildlife species: an analytical approach using GIS.
 Aspinall, R.; Matthews, K. 
 Environ-pollut v.86, p.217-223. (1994).
 Includes references.
 Descriptors: climatic-change; wildlife-; habitats-;
 geographical-distribution; climatic-factors;
 geographical-information-systems; scotland-; species-distribution
 NAL Call No.: QH545.A1E52
 20. Comments on "Boundry Conditions for Displacement Experiments
 through Short Laboratory Soil Columns".
 Shukla, B. S. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1994. v. 58 (3) p. 991-993. 
 Original article by M.T. van Genuchten and J.C. Parker published
 in Soil Science Society of America Journal, 48(4), p. 703-708.
 Reply by M.T. van Genuchten and J.C. Parker, p. 991-993.
 Descriptors: solutes-; transport-processes; movement-in-soil;
 mathematical-models; diffusion-
 NAL Call No.: 56.9-So3
 21. Comparison of PRZM computer model predictions with field
 lysimeter data for dichlorprop and bentazon leaching.
 Mueller, T. C. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1183-1195.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: dichlorprop-; bentazone-; leaching-;
 simulation-models; prediction-; sandy-soils;
 NAL Call No.: TD172.J6
 22. A comprehensive set of analytical solutions for
 nonequilibrium solute transport with first-order and zero-order
 Toride, N.; Leij, F. J.; Van Genuchten, M. T. 
 Water-resour-res v.29, p.2167-2182. (1993).
 Includes references.
 Descriptors: transport-processes; solutes-; flow-; sorption-;
 kinetics-; mathematical-models; subsurface-layers;
 nonequilibrium-transport-models; semi-infinite-soil-systems
 Abstract: Solute transport in the subsurface is often considered
 to be a nonequilibrium process. Predictive models for
 nonequilibrium transport may be based either on chemical
 considerations by assuming the presence of a kinetic sorption
 process, or on physical considerations by assuming two-region
 (dual-porosity) type formulations which partition the liquid
 phase into mobile and immobile regions. For certain simplifying
 conditions, including steady state flow and linear sorption, the
 chemical and physical nonequilibrium transport models can be cast
 in the same dimensionless form. This paper presents a
 comprehensive set of analytical solutions for one-dimensional
 nonequilibrium solute transport through semi-infinite soil
 systems. The models involve the one-site, two-site, and
 two-region transport models, and include provisions for
 first-order decay and zero-order production. General solutions
 are derived for the volume-averaged (or resident) solute
 concentration using Laplace transforms assuming both first- and
 third-type inlet conditions, and arbitrary initial conditions,
 input solute concentrations, and solute production profiles. The
 solutions extend and generalize existing solutions for
 equilibrium and nonequilibrium solute transport. The general
 solutions are evaluated for some commonly used input and initial
 conditions, and zero-order production profiles. Expressions for
 the flux-averaged concentration are derived from the general and
 specific solutions assuming a third-type inlet condition. Typical
 examples of calculated concentration distributions resulting from
 several sets of initial and input conditions and zero-order
 production functions are also presented and briefly discussed.
 NAL Call No.: 292.8-W295
 23. The conceptual framework for the National Pilot Project on
 Livestock and the Environment. Livestock series report 2.
 Bouzaher, A.; Johnson, S. R.; Neibergs, S.; Jones, R.; Beran, L.;
 Frarey, L.; Hauck, L. 
 Staff-rep-Iowa-State-Univ,-Cent-Agric-Rural-Dev. Ames, Iowa :
 Center for Agricultural and Rural Development, 1986-. Dec 1993.
 (93-SR67) 34 p. 
 Includes references.
 Descriptors: animal-feeding; livestock-;
 environmental-assessment; pilot-projects; water-quality;
 waste-disposal; models-; usa-; texas-; erath-county,-texas
 NAL Call No.: HD1401.S75
 24. A daily runoff simulation in semi-arid watersheds based on
 soil water deficit calculations.
 Karnieli, A.; Ben Asher, J. 
 J-hydrol v.149, p.9-25. (1993).
 Includes references.
 Descriptors: watersheds-; soil-water-content; water-deficit;
 runoff-; storms-; semiarid-zones; simulation-models; arizona-
 Abstract: Initial soil water content just before a rainfall event
 is an input required for the calculation of a basin's water
 balance including infiltration and runoff. However, for most
 watersheds such information is not available because its
 evaluation involves a large amount of labor. The objective of
 this study is to describe a practical model with which to
 estimate time-dependent changes of a basins soil water content.
 It is further used for predicting runoff water yield when
 rainfall depth is the only known component of the water balance
 equation (WBE). Two distinct cases of the WBE are discussed: (1)
 a runoff-producing storm; (2) a storm without runoff. Runoff
 events from four watersheds in southern Arizona were measured
 throughout 8 to 17 years and analyzed in this study.
 Rainfall-runoff relationships are described in this model by an
 empirical quadratic regression equation which includes four
 parameters. They were estimated by an optimization subroutine
 which was used to determine the minimum difference between
 measured and modeled results. The optimized parameters enable
 simulations of the continuous dynamic change of an index of the
 soil water content as well as predictions of runoff depths. It
 was found that the predicted runoff agrees reasonably well with
 the observed runoff. The minimum coefficient of determination
 (r2) between the computed and actual runoff for the multi-annual
 data sets was 0.62 and the maximum 0.86. Runoff threshold value
 was found to be a function of the basin average soil texture. The
 lowest threshold was 4.6 mm for clay soil and the largest was 9.0
 mm for sandy soil. Since direct soil water measurements were not
 taken, we interpreted the acceptable agreement between measured
 and predicted runoff as an indirect validation of the soil water
 model. It is.  simulated runoff on nearby ungaged watersheds in
 semi-arid regions.
 NAL Call No.: 292.8-J82
 25. Darcy-Weisbach roughness coefficients for selected crops.
 Gilley, J. E.; Kottwitz, E. R. 
 Trans-ASAE v.37, p.467-471. (1994).
 Includes references.
 Descriptors: zea-mays; gossypium-hirsutum; hordeum-vulgare;
 glycine-max; helianthus-annuus; triticum-aestivum; runoff-;
 hydraulic-resistance; hydrology-; models-
 Abstract: Total hydraulic resistance on an upland agricultural
 site may be influenced by several factors including standing
 vegetation. In this laboratory study, Darcy-Weisbach roughness
 coefficients were measured for corn, cotton, sorghum, soybeans,
 sunflower, and wheat vegetation. Experimental variables used in
 this investigation in addition to crop type included plant
 population, row spacing, row orientation, and flow rate. For some
 of the experimental tests, a single row of vegetation was
 oriented within a flume parallel to the principal flow direction.
 For the remainder of the tests, rows of vegetation were placed
 perpendicular to the flow using row spacings and plant
 populations recommended by crop management specialists.
 Measurements of discharge rate and flow velocity were used to
 calculate roughness coefficients for Reynolds number values
 ranging from approximately 550 to 22,000. Regression equations
 which relate roughness coefficients to plant population, row
 spacing, and Reynolds number were developed from the laboratory
 data. With the exception of wheat placed perpendicular to flow,
 roughness coefficients produced by standing vegetation were
 negligible. On upland agricultural areas, total hydraulic
 roughness will be influenced primarily by frictional drag over
 the soil surface, and residue and ground cover.
 NAL Call No.: 290.9-Am32T
 26. A decision support system for evaluating the effects of
 alternative farm management systems on water quality and
 Yakowitz, D. S.; Stone, J. J.; Lane, L. J.; Heilman, P.;
 Masterson, J.; Abolt, J.; Imam, B. 
 Water-sci-technol v.28, p.47-54. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: water-quality; farm-management; systems-;
 decision-making; support-systems; farm-income; simulation-models;
 NAL Call No.: TD420.A1P7
 27. Determination of traveltime in the Delaware River, Hancock,
 New York, to the Delaware Water Gap by use of a conservative dye
 White, K. E.;  Kratzer, T. W.; Delaware River Basin Commission. 
 Lemoyne, Pa. : U.S. Dept. of the Interior, U.S. Geological Survey
 ; Denver, Colo. : U.S. Geological Survey, Earth Science
 Information Center, Open-File Reports Section [distributor],
 1994. vi, 54 p. : ill., maps.
 Shipping list no.: 94-0223-P.
 Descriptors: Streamflow-Delaware-River-N; Y; -Del; -and-N; J;
 -Mathematical-models; Water-quality-Delaware-River-N; Y; -Del;
 -and-N; J; -Measurement
 NAL Call No.: GB701.W375--no.93-4203
 28. Determining off-site concentrations of volatile pesticides
 using the trajectory-simulation model.
 Yates, S. R. 
 J-environ-qual v.22, p.481-486. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: pesticides-; volatilization-; atmosphere-;
 losses-from-soil; transport-processes; simulation-models;
 Abstract: An environmental transport model is described and
 illustrated that will enable the prediction of the mass and/or
 concentration of volatile pesticides at any depth in the soil
 profile and at any height in the atmosphere relatively far
 distanced downwind from agricultural fields. The theoretical
 profile shape model is used to determine transport in the
 atmosphere and is coupled to the behavior assessment model (BAM)
 to describe transport in soils. The model outputs include the
 soil-water concentrations, the surface volatilization rate, the
 concentration of pesticides in the atmosphere above the field,
 and the atmospheric concentration at specified distances downwind
 from the field. The results from this approach can be used in
 exposure assessment studies to determine the risk for individuals
 living near agricultural fields.
 NAL Call No.: QH540.J6
 29. Determining parameter precision for modeling nitrate
 leaching: inorganic fertilization in Nordic climates.
 Larocque, M.; Banton, O. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Mar/Apr 1994. v. 58 (2) p. 396-400. 
 Includes references.
 Descriptors: nitrate-; leaching-; deterministic-models;
 fertilizers-; inorganic-compounds; movement-in-soil;
 edaphic-factors; biological-activity-in-soil; cold-zones;
 Abstract: Most NO3- leaching models require the quantification of
 many parameters. Because the majority of these parameters are
 difficult to estimate, it is important to know the impact of
 parameter imprecision to make proper use of a model. A study was
 performed to identify the relative influence of the parameters in
 a deterministic NO3- leaching model (SOILN) used with inorganic
 fertilization in nordic climates. A sensitivity analysis of the
 model was performed using parameters related to the N cycle with
 two reference systems for the parameters corresponding to field
 sites located in Quebec and in southern Sweden. Results from both
 sites showed that atmospheric deposits had little influence on
 NO; leaching in agricultural areas in Quebec and Sweden; the
 variation of parameters related to nitrification also had little
 impact on NO3- leaching at the sites studied; parameters used for
 mineralization, plant uptake, and denitrification had a
 significant impact on NO3- leaching in the simulated conditions;
 parameters related to abiotic factors had a variable influence,
 depending mostly on soil water contents.
 NAL Call No.: 56.9-So3
 30. Determining the green-Ampt effective hydraulic conductivity
 from rainfall-runoff data for the WEPP model.
 Risse, L. M.; Nearing, M. A.; Savabi, M. R. 
 Trans-ASAE v.37, p.411-418. (1994).
 Includes references.
 Descriptors: rain-; runoff-; erosion-; hydraulic-conductivity;
 hydrology-; models-; water-erosion-prediction-project
 Abstract: The Green-Ampt infiltration equation is used in many
 different hydrologic models. The effective hydraulic conductivity
 parameter (Ke) within this equation is needed to obtain reliable
 estimates of infiltration and runoff. In this study, a method was
 developed for calibrating Ke for the Green-Ampt equation as
 integrated with the WEPP continuous simulation model using a
 series of rainfall-runoff events on natural runoff plots. Optimum
 values of Ke were obtained at seven locations, and the average
 Nash-Sutcliffe model efficiency for the Green-Ampt/Wepp
 predictions of runoff on an event basis was 0.46 using these Ke
 values. Green-Ampt/WEPP tended to overpredict runoff on the small
 events and underpredict runoff on the larger events. This bias
 could not be corrected through calibration and indicates a
 structural flaw in the Green-Ampt equation, the WEPP model, or
 the available data. Other estimates of effective hydraulic
 conductivity were obtained from five different parameter
 estimation methods based on relationships involving common soil
 properties and were used in the Green-Ampt/Wepp model to predict
 runoff at each of the locations. None of these methods of
 estimating the effective hydraulic conductivity consistently
 outperformed the others for all the data sets. The average
 Nash-Sutcliffe model efficiency obtained using the best estimated
 parameters was -0.16, indicating that considerable improvement
 was obtained with calibration.
 NAL Call No.: 290.9-Am32T
 31. Development, description, and application of a geographic
 information system data base for water resources in karst terrane
 in Greene County, Missouri.
 Waite, L. A.;  Thomson, K. C.; Geological Survey (U.S.). 
 Rolla, Mo. : U.S. Geological Survey ; Denver, Colo. : Earth
 Science Information Center, Open-File Reports Section
 [distributor], 1993. vi, 31 p. : ill., maps (some col.).
 Shipping list no.: 93-0640-P.
 Descriptors: Geographic-information-systems;
 Karst-Missouri-Greene-County; Hydrogeology-Missouri-Greene-County
 NAL Call No.: GB701.W375-no.93-4154
 32. Development of a non-isothermal method for determination of
 diffusional parameters.
 Moreira, L. A.; Oliveira, F. A. R.; Silva, T. R.; Oliveira, J. C. 
 Int-j-food-sci-technol v.28, p.575-586. (1993).
 Includes references.
 Descriptors: turnips-; food-processing; acidification-;
 blanching-; leaching-; diffusivity-; temperature-;
 diffusion-models; mathematical-models; fick's-second-law
 NAL Call No.: TP368.J6
 33. Development of steady-state diffusion gradients for the
 cultivation of degradative microbial consortia.
 Wolfaardt, G. M.; Lawrence, J. R.; Hendry, M. J.; Robarts, R. D.;
 Caldwell, D. E. 
 Appl-environ-microbiol v.59, p.2388-2391. (1993).
 Includes references.
 Descriptors: microorganisms-; groundwater-;
 microbial-degradation; diclofop-; isolation-techniques;
 cell-culture; gels-; bioreactors-; diffusion-; gradients-;
 groundwater-pollution; simulation-models
 Abstract: A diffusion gradient plate was constructed and
 evaluated for its potential use in the isolation of degradative
 microbial consortia from natural habitats. In this model, a
 steady-state concentration gradient of diclofop methyl,
 established by diffusion through an agarose gel, provided the
 carbon for microbial growth. Colonization of the gel surface was
 observed with epifluorescence and scanning confocal laser
 microscopy to determine microbial responses to the diclofop
 gradient. A detectable gradient developed over a narrow band (<10
 mm). Consequently, quantitative analyses of the microbial
 response to the gradient were difficult to obtain. A
 two-dimensional, finite-element numerical transport model for
 advective-diffusive transport was used to simulate concentration
 and flux profiles in the physical model. The simulated profiles
 were correlated with the measured concentration gradient (R2 =
 0.89) and the cell numbers on the gel surface (R2 = 0.85). The
 numerical model was subsequently used to redesign the physical
 model. The detectable concentration gradient in the modified
 physical model extended over the length of the gel (38 mm). The
 simulated profile again showed a good correlation with the
 measured profile (R2 = 0.96) and the microbial responses to the
 concentration gradient (R2 = 0.99). It was concluded that these
 gradients provide the steady-state environments needed to sustain
 steady-state consortia. They also provide a physical pathway for
 the development of degradative biofilms from low to high
 concentrations of toxicants and simulate conditions under which
 low concentrations of toxicant are supplied at a constant flux
 over long periods of time, such as the conditions that could
 occur in natural environments.
 NAL Call No.: 448.3-Ap5
 34. Digital data acquisition and development of geographic
 information system coverages for use with the public water-supply
 wells and springs in Tennessee.
 Connell, J. F.;  Barron, W. R.; Tennessee. Division of Water
 Nashville, Tenn. : U.S. Dept. of the Interior, U.S. Geological
 Survey ; Denver, Colo. : U.S. Geological Survey Books and
 Open-File Reports Section, distributor, 1993. iii, 28 p. : maps.
 Shipping list no.: 93-0483-P.
 Descriptors: Groundwater-Tennessee-Data-bases;
 NAL Call No.: GB701.W375-no.92-4178
 35. A distributed hydrology-vegetation model for complex terrain.
 Wigmosta, M. S.; Vail, L. W.; Lettenmaier, D. P. 
 Water-resour-res v.30, p.1665-1679. (1994).
 Includes references.
 Descriptors: runoff-; catchment-hydrology; vegetation-;
 simulation-models; canopy-penetration; evapotranspiration-;
 snow-cover; meltwater-; topography-; mountain-areas;
 spatial-distribution; montana-
 Abstract: A distributed hydrology-vegetation model is described
 that includes canopy interception, evaporation, transpiration,
 and snow accumulation and melt, as well as runoff generation via
 the saturation excess mechanisms. Digital elevation data are used
 to model topographic controls on incoming solar radiation, air
 temperature, precipitation, and downslope water movement.  Canopy
 evapotranspiration is represented via a two-layer Penman-Monteith
 formulation that incorporates local net solar radiation, surface
 meteorology, soil characteristics and moisture status, and
 species-dependent leaf area index and stomatal resistance.  Snow
 accumulation and ablation are modeled using an energy balance
 approach that includes the effects of local topography and
 vegetation cover.  Saturated subsurface flow is modeled using a
 quasi three-dimensional routing scheme.  The model was applied at
 a 180-m scale to the Middle Fork Flathead River basin in
 northwestern Montana.  This 2900-km(2), snowmelt dominated
 watershed ranges in elevation from 900 to over 3000 m. The model
 was calibrated using 2 years of recorded precipitation and
 streamflow.  The model was verified against 2 additional years of
 runoff and against advanced very high resolution radiometer based
 spatial snow cover data at the 1-km(2) scale.  Simulated
 discharge showed acceptable agreement with observations.  The
 simulated areal patterns of snow cover were in general agreement
 with the remote sensing observations, but were lagged slightly in
 NAL Call No.: 292.8-W295
 36. The distributed modelling of agricultural nonpoint pollution
 at basin
 Preti, F.; Lubello, C. 
 Water-sci-technol v.28, p.669-674. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: agricultural-chemicals; application-; rivers-;
 watersheds-; water-pollution; models-; italy-
 NAL Call No.: TD420.A1P7
 37. Dynamic simulation modelling for evaluating water quality
 response to agricultural BMP implementation.
 Cassell, E. A.; Clausen, J. C. 
 Water-sci-technol v.28, p.635-648. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: agricultural-land; phosphorus-;
 input-output-analysis; movement-in-soil; groundwater-pollution;
 surface-water; pollution-; sources-; dynamic-models;
 simulation-models; vermont-; best-management-practices
 NAL Call No.: TD420.A1P7
 38. Economic and environmental impacts of water quality
 protection policies. 2. Application to the Central High Plains.
 Bernardo, D. J.; Mapp, H. P.; Sabbagh, G. J.; Geleta, S.;
 Watkins, K. B.; Elliott, R. L.; Stone, J. F. 
 Water-resour-res v.29, p.3081-3091. (1993).
 Includes references.
 Descriptors: groundwater-pollution; groundwater-; water-quality;
 water-policy; agricultural-chemicals; agricultural-production;
 economic-impact; environmental-impact; mathematical-models;
 programming-; simulation-models; models-; oklahoma-; kansas-;
 texas-; new-mexico; colorado-; mathematical-programming-models;
 Abstract: A three-stage modeling framework is applied to evaluate
 the potential economic and environmental impacts of agricultural
 groundwater protection policies in the Central High Plains
 Region. Three alternative policies (limitations on total nitrogen
 applications, limitations on unit-area nitrogen applications, and
 restrictions on the use of selected herbicides) are compared to a
 baseline scenario that reflects the absence of any form of
 groundwater quality protection measures. In general, nitrogen
 restrictions are more effective in reducing nitrate loadings in
 percolation water if implemented on a unit-area basis rather than
 as a total (farm level) restriction. In contrast, the total
 restriction is more effective in controlling runoff losses of
 nitrogen. Both nitrogen restrictions have significant impacts on
 crop production levels and regional agricultural income, while
 the economic consequences of the pesticide restriction are much
 less pronounced. The proposed regional modeling framework
 provides critical information necessary to assess the economic
 and environmental tradeoffs of policy alternatives aimed at
 controlling agricultural nonpoint source pollution.
 NAL Call No.: 292.8-W295
 39. Economic and environmental impacts of water quality
 protection policies. 1. Framework for regional analysis.
 Bernardo, D. J.; Mapp, H. P.; Sabbagh, G. J.; Geleta, S.;
 Watkins, K. B.; Elliott, R. L.; Stone, J. F. 
 Water-resour-res v.29, p.3069-3079. (1993).
 Includes references.
 Descriptors: groundwater-pollution; groundwater-; water-quality;
 water-policy; agricultural-chemicals; agricultural-production;
 economic-impact; environmental-impact; simulation-models;
 mathematical-models; programming-; models-;
 mathematical-programming-models; transport-models
 Abstract: Agricultural production systems provide some unique
 challenges for assessing the regional impacts of water quality
 protection policies. A modeling framework is proposed for
 assessing the environmental and economic consequences of
 groundwater quality protection policies at the regional level.
 The model consists of three components: (1) a crop
 simulation/chemical transport model, (2) a regional economic
 optimization model, and (3) an aquifer groundwater flow model.
 The three submodels are linked and run recursively to simulate
 producer response to alternative water quality policies over a
 multiple-year time horizon. Model solutions provide projections
 of production practices employed on various resource situations
 across the region. Economic evaluation of alternative policies
 may be based upon regional agricultural income, crop production
 levels, input use, and changes in aquifer water levels over time.
 Measures of agricultural nonpoint source pollution provided by
 the model include nitrate, phosphorus and pesticide loadings in
 deep percolation and runoff water, as well as sediment losses.
 NAL Call No.: 292.8-W295
 40. Economics of water resources : from regulation to
 Spulber, N.; Sabbaghi, A. 1. 
 Boston : Kluwer Academic Publishers, c1994. xxvi, 329 p. : ill..
 Includes bibliographical references (p. 289-308) and index.
 Descriptors: Water-resources-development;
 NAL Call No.: HD1691.S72--1994
 41. Effect of depth of impervious layer and adsorption on solute
 transport in tile-drained irrigated lands.
 Kamra, S. K.; Singh, S. R.; Rao, K. V. G. K. 
 J-hydrol v.155, p.251-264. (1994).
 Includes references.
 Descriptors: solutes-; salinity-; transport-processes;
 tile-drainage; irrigated-conditions; adsorption-; saturated-flow;
 unsaturated-flow; groundwater-; effluents-; soil-depth;
 desalinization-; soil-depth; simulation-models; impervious-layer
 Abstract: A two-dimensional finite element model of solute
 transport in a tile-drained soil-aquifer system was applied to
 study the effect of the depth of impervious layer and adsorption
 on salt distribution in the soil and groundwater, and the
 salinity of drainage effluent. The model considers steady state
 water flow in the unsaturated and saturated zones, and includes
 the effect of convective transport, dispersion and linear
 adsorption. The results indicate that though the depth of the
 impervious layer has little effect on salt distribution in the
 unsaturated zone, it significantly influences the quality of the
 drainage effluent. Further, it was found that during the initial
 years of reclamation of a highly saline soil with subsurface
 drainage, the effect of adsorption is more pronounced in the
 unsaturated zone than in the saturated zone and the movement of
 adsorbing solute species is retarded for a longer time in the
 groundwater than in the soil.
 NAL Call No.: 292.8-J82
 42. Effect of land surface representation on forest water and
 carbon budgets.
 Band, L. E. 
 J-hydrol v.150, p.749-772. (1993).
 In the special issue: Water Issues in Forests Today / edited by
 E.M. O'Loughlin and F.X. Dunin.  November 22-26, 1992, Canberra,
 Descriptors: forests-; watersheds-; simulation-models;
 evapotranspiration-; canopy-; photosynthesis-;
 soil-water-content; runoff-; landforms-; topography-;
 Abstract: Forested landscapes often show very well-pronounced
 heterogeneity in the factors that control evapotranspiration,
 runoff production and carbon assimilation at a variety of length
 scales. In hilly or mountainous environments, strong contrasts in
 net radiation, available soil water, soil structure and stand
 characteristics can produce a large variance in both the
 meteorological drivers and surface resistance to carbon and water
 exchange with the atmosphere over distances measured in tens of
 metres. Because of the strong nonlinearities characterizing the
 influence of the environmental variables on surface resistance
 (particularly available soil water), the parametrization of
 surface process models with mean values of the environmental
 variables and no distribution often leads to significant bias in
 areal average carbon and water flux. However, it is often not
 feasible to incorporate directly the full distribution and
 patterns of the landscape for regional-scale models. Continental-
 and subcontinental-scale vegetation data sets currently being
 collected by synoptic-level satellites (e.g. the Advanced Very
 High Resolution Radiometer, AVHRR) do not capture the large
 proportion of landscape variability that exists below the
 resolution of the sensors. This paper explores the impacts of
 various landscape representation schemes that retain a range of
 detail in the description of land surface form and processes on
 simulated areal average evapotranspiration, runoff production and
 net carbon exchange with the atmosphere. Specific comparison is
 made of schemes that attempt to incorporate the topographic
 structure, soil and vegetation distributions of a region with
 schemes that sample the surface at levels similar to current
 coarse-resolution satellites. For strongly.  variations in
 available soil water can have significant effects on areal
 averaged carbon and water flux rates, particularly under drying
 conditions, whereas the spatial variations in radiation,
 temperature and humidity over the terrain appear to have a lesser
 NAL Call No.: 292.8-J82
 43. Effect of simulated climate change on snowmelt runoff
 modeling in selected basins.
 Katwijk, V. F. v.; Rango, A.; Childress, A. E. 
 Water-resour-bull v.29, p.755-766. (1993).
 Includes references.
 Descriptors: meltwater-; runoff-; climatic-change;
 air-temperature; transpiration-; california-; colorado-
 Abstract: The projected increase in the concentration of C02 and
 other greenhouse gases in the atmosphere islikely to result in
 a global temperature increase. This paper reports on the probable
 effects of atemperature increase and changes in transpiration
 on basin discharge in two different mountainsnowmelt regions
 of the western United States. The hydrological effects of the
 climate changes aremodeled with a relatively simple
 conceptual, semi-distributed snowmelt runoff model. Based on the  
 model results, it may be concluded that increased air
 temperatures will result in a shift ofsnowmelt runoff to
 earlier in the snowmelt season. Furthermore, it is shown that it
 is veryimportant to include the expected change in
 climate-related basin conditions resulting from the  modeled
 temperature increase in the runoff simulation. The effect of
 adapting the model parameters  streamflow to April and an  even
 more significant decrease of snowmelt runoff in June and July. If
 the air temperaturesincrease by approximately 5 degrees C and
 precipitation and accumulated snow amounts remain aboutthe
 same, runoff in April and May, averaged for the two basins, is
 expected to increase by 185percent and 25 percent,
 respectively. The runoff in June and July will decrease by about
 60percent each month. Overall, the total seasonal runoff
 decreases by about 6 percent. If increasedC02 concentrations
 further change basin condition by reducing transpiration by the
 maximum amounts.  temperature increase, the April,May, June,
 and July changes would average +230 percent, +40 percent, -55
 percent, and -45 percent,respectively. The total seasonal
 runoff change would be +11 percent.
 NAL Call No.: 292.9-Am34
 44. Effects of motility and adsorption rate coefficient on
 transport of bacteria through saturated porous media.
 Camper, A. K.; Hayes, J. T.; Sturman, P. J.; Jones, W. L.;
 Cunningham, A. B. 
 Appl-environ-microbiol v.59, p.3455-3462. (1993).
 Includes references.
 Descriptors: pseudomonas-aeruginosa; adsorption-; motility-;
 glass-; bioreactors-; transport-processes; pores-; porosity-;
 models-; soil-pore-system; strain-differences; glass-beads
 Abstract: Three strains of Pseudomonas fluorescens with different
 motility rates and adsorption ratecoefficients were injected
 into porous-medium reactors packed with 1-mm-diameter glass
 spheres.Cell breakthrough, time to peak concentration,
 tailing, and cell recovery were measured at threeinterstitial
 pore velocities (higher than, lower than, and much lower than the
 maximal bacterial  motility rate). All experiments were done with
 distilled water to reduce the effects of growth andchemotaxis.
 Contrary to expectations, motility did not result in either early
 breakthrough orearly time to peak concentration at flow
 velocities below the motility rate. Bacterial size  exclusion
 effects were shown to affect breakthrough curve shape at the very
 low flow velocity, butno such effect was seen at the higher
 flow velocity. The tendency of bacteria to adsorb to  
 porous-medium surfaces, as measured by adsorption rate
 coefficients, profoundly influencedtransport characteristics.
 Cell recoveries were shown to be correlated with the ratio of
 advectiveto adsorptive transport in the reactors. Adsorption
 rate coefficients were found to be betterpredictors of
 microbial transport phenomena than individual characteristics,
 such as size,motility, or porous-medium hydrodynamics.
 NAL Call No.: 448.3-Ap5
 45. Environmental : hypermedia programs and water quality models. 
 Environmental hypermedia programs.
 Center for Technology Transfer & Pollution Prevention. 
 West Lafayette, IN : Farm Building Plan Service, Purdue
 University, [1994?] 1 computer laser optical disc  1 booklet. 
 Title from disc label.
 Descriptors: Water-quality-Databases; Water-Pollution-Databases
 NAL Call No.: TD370.E58--1994
 46. Estimation of preferential movement of bromide tracer under
 field conditions.
 Jabro, J. D.; Lotse, E. G.; Fritton, D. D.; Baker, D. E. 
 J-hydrol v.156, p.61-71. (1994).
 Includes references.
 Descriptors: agricultural-chemicals; leaching-;
 saturated-conditions; bromide-; tracers-; saturated-flow;
 macropore-flow; infiltration-; soil-physical-properties;
 saturated-hydraulic-conductivity; spatial-variation;
 simulation-models; preferential-flow; leachm-simulation-model
 Abstract: Leaching of agricultural chemicals from the root and
 vadose zones into groundwater is an important environmental
 concern. To procure a better understanding of the movement and
 transport of agricultural chemicals through the soil profile, a
 field research study was conducted to estimate bromide leaching
 losses under saturated conditions where preferential flow is
 occurring. The field data were then used to evaluate the LEACHM
 model. Eighteen double-ring infiltrometers were used to apply a
 pulse (100 mm depth) of bromide tracer on two previously
 saturated soils located in a karst region of southeastern
 Pennsylvania. Internal drainage over the next seven days resulted
 in nearly 51% of the applied Br(-) being leached to a depth below
 0.80 m. The LEACHM model was used to simulate the amount of
 bromide leached in each infiltrometer. The model predicted,
 accurately, an average of 46% of the applied Br(-) leached below
 the 0.80 m depth. Mean values of bromide concentration in the
 soil profile were predicted within two standard deviations of the
 measured mean for all depths except for the 0.20-0.40 m depth
 increment where the model overpredicted the bromide
 concentration. The model predictions of Br(-) leached were tested
 against field measurements using several statistical tests. The
 LEACHM model performed adequately under preferential flow
 conditions, perhaps because the infiltration rate at each site
 was used as a model input. This, actually, is some measure of the
 macropore flow process and suggests that simple models such as
 LEACHM can be used in the field, as long as a distribution of
 infiltration rates is used as an input.
 NAL Call No.: 292.8-J82
 47. Estimation of snowmelt runoff in the Peace River region using
 a soil moisture budget.
 Hayhoe, H. N.; Pelletier, R. G.; Van Vliet, L. J. P. 
 Can-j-soil-sci v.73, p.489-501. (1993).
 Includes references.
 Descriptors: meltwater-; runoff-; estimation-; prediction-;
 equations-; algorithms-; mathematical-models; water-erosion;
 losses-from-soil; water-budget; winter-; spring-; snow-; depth-;
 frozen-conditions; freeze-thaw-cycles; british-columbia;
 alberta-; frozen-soils
 NAL Call No.: 56.8-C162
 48. Evaluating agricultural nonpoint-source pollution using
 integrated geographic information systems and hydrologic/water
 quality model.
 Tim, U. S.; Jolly, R. 
 J-environ-qual v.23, p.25-35. (1994).
 Technical Reports from the Symposium, "Minimizing Agricultural
 Nonpoint-Source Impacts", November 2, 1992, Minneapolis,
 Descriptors: water-pollution; agriculture-;
 geographical-information-systems; simulation-models
 Abstract: Considerable progress has been made in developing
 physically based, distributed parameter, hydrologic/water quality
 (H/WQ) models for planning and control of nonpoint-source
 pollution.  The widespread use of these models is often
 constrained by the excessive and time-consuming input data
 demands and the lack of computing efficiencies necessary for
 iterative simulation of alternative management strategies. Recent
 developments in geographic information systems (GIS) provide
 techniques for handling large amounts of spatial data for
 modeling nonpoint-source pollution problems. Because a GIS can be
 used to combine information from several sources to form an array
 of model input data and to examine any combinations of spatial
 input/output data, it represents a highly effective tool for H/WQ
 modeling. This paper describes the integration of a
 distributed-parameter model (AGNPS) with a GIS (ARC/INFO) to
 examine nonpoint sources of pollution in an agricultural
 watershed.  The ARC/INFO GIS provided the tools to generate and
 spatially organize the disparate data to support modeling, while
 the AGNPS model was used to predict several water quality
 variables including soil erosion and sedimentation within a
 watershed.  The integrated system was used to evaluate the
 effectiveness of several alternative management strategies in
 reducing sediment pollution in a 417-ha watershed located in
 southern Iowa.  The implementation of vegetative filter strips
 and contour buffer (grass) strips resulted in a 41 and 47%
 reduction in sediment yield at the watershed outlet,
 respectively.  In addition, when the integrated system was used,
 the combination of the above management strategies.  demonstrated
 the utility of integrating a simulation model with GIS for
 nonpoint-source pollution control and planning.  Such techniques
 can help characterize the diffuse sources of pollution at the
 landscape level.
 NAL Call No.: QH540.J6
 49. Evaluating and predicting the spatial and temporal
 variability of storm runoff generation in watersheds of arid and
 semi-arid regions.
 Morin, J.; United States Israel Binational Agricultural Research
 and Development Fund. 
 Bet Dagan, Israel : BARD, 1993. 306 p. : ill. (some col.), maps.
 Final report.
 Descriptors: Rain-and-rainfall-Mathematical-models;
 NAL Call No.: QC925.E93--1993
 50. Evaluating the chemical movement in layered soil model as a
 tool for assessing risk of pesticide leaching to groundwater.
 Nofziger, D. L.; Chen, J. S.; Haan, C. T. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1133-1155.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: pesticides-; leaching-; simulation-models;
 soil-properties; groundwater-pollution; risk-; cmls-model
 NAL Call No.: TD172.J6
 51. Evaluation and comparison of pesticide leaching models for
 registration purposes. Results of simulations performed with the
 pesticide leaching model.
 Klein, M. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1197-1209.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: bentazone-; dichlorprop-; leaching-;
 simulation-models; registration-; macropores-; prediction-;
 NAL Call No.: TD172.J6
 52. Evaluation and comparison of pesticide leaching models for
 registration purposes.
 Bergstrom, L. F.; Jarvis, N. J. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1061-1072.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: pesticides-; leaching-; simulation-models;
 NAL Call No.: TD172.J6
 53. Evaluation of GLEAMS and PRZM for predicting pesticide
 leaching under field conditions.
 Zacharias, S.; Heatwole, C. D. 
 Trans-ASAE v.37, p.439-451. (1994).
 Includes references.
 Descriptors: zea-mays; no-tillage-; pesticides-; leaching-;
 simulation-models; virginia-; groundwater-loading;
 pesticide-rootzone-model; nonpoint-source-pollution
 Abstract: Pesticide simulation models, GLEAMS and PRZM, were
 evaluated for their ability to predict pesticide behavior using
 field data from a plot under no-till corn in the Coastal Plain
 region of Virginia. The models were evaluated in an uncalibrated
 mode as well as with adjustment of important hydrology
 parameters. The evaluation of model performance was based on
 graphical displays and statistical measures. Difference in
 evapotranspiration (ET) predictions by the two models caused the
 simulated results from their hydrology components to vary. Runoff
 and soil moisture measured in the field were predicted reasonably
 well after adjusting important hydrology parameters. Except for
 differences in magnitude, both models predicted the chemical
 concentration profiles similarly. Overall, GLEAMS represented
 pesticide behavior in soil better than PRZM. The models, GLEAMS
 and PRZM, performed well in predicting pesticide mass in the root
 zone, but were less reliable in predicting pesticide
 concentration distributions in soil. Model predictions of
 pesticide fate and transport were not greatly affected by changes
 in curve number and the water holding capacity of the soil.
 NAL Call No.: 290.9-Am32T
 54. Evaluation of methods for determining soil-water retentivity
 and unsaturated hydraulic conductivity.
 Marion, J. M.; Or, D.; Rolston, D. E.; Kavvas, M. I.; Biggar, J.
 Soil-sci v.158, p.1-13. (1994).
 Includes references.
 Descriptors: soil-water-retention;
 unsaturated-hydraulic-conductivity; determination-;
 soil-analysis; analytical-methods; evaluation-;
 soil-water-content; matric-potential; transport-processes;
 NAL Call No.: 56.8-So3
 55. Evaluation of runoff and erosion models.
 Wu, T. H.; Hall, J. A.; Bonta, J. V. 
 J-irrig-drain-eng v.119, p.364-382. (1993).
 Includes references.
 Descriptors: erosion-; runoff-; sediment-yield; measurement-;
 NAL Call No.: 290.9-AM3Ps-IR
 56. Evaluation of the GLEAMS model for pesticide leaching in
 Shirmohammadi, A.; Knisel, W. G. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1167-1182.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: dichlorprop-; bentazone-; leaching-; drainage-;
 NAL Call No.: TD172.J6
 57. Experimental approach and simulation of the retention
 processes limiting orthophosphate transport in groundwater.
 Isenbeck Schroter, M.; Doring, U.; Moller, A.; Schroter, J.;
 Matthess, G. 
 J-contam-hydrol v.14, p.143-161. (1993).
 Includes references.
 Descriptors: groundwater-pollution; orthophosphates-;
 simulation-models; sorption-; retention-
 NAL Call No.: TD426.J68
 58. An expert systems approach for assessing the potential for
 pesticide contamination of ground water.
 Crowe, A. S.; Mutch, J. P. 
 Ground-water. Dublin, Ohio : Ground Water Pub. Co. May/June 1994.
 v. 32 (3) p. 487-498. 
 Includes references.
 Descriptors: pesticides-; groundwater-pollution; expert-systems;
 assessment-; models-
 NAL Call No.: TD403.G7
 59. An exploration of the economics of farm management
 alternatives to improve water quality.
 Heilman, P.; Yakowitz, D. S.; Stone, J. J.; Kramer, L. A.; Lane,
 L. J.; Imam, B. 
 Application of advanced information technologies  effective
 management of natural resources  proceedings of the 18-19 June
 1993 Conference, Spokane, Washington /. St. Joseph, Mich. :
 American Society of Agricultural Engineers, c1993.. p. 194-205. 
 Includes references.
 Descriptors: water-quality; pollutants-; farm-management;
 farm-income; decision-making; simulation-models; usda-; iowa-;
 prototype-decision-support-system; agricultural-research-service
 NAL Call No.: GE5.A66-1993
 60. Farm-level evaluation of alternative policy approaches to
 reduce nitrate leaching from midwest agriculture.
 Swinton, S. M.; Clark, D. S. 
 Agric-resour-econ-rev v.23, p.66-74. (1994).
 Includes references.
 Descriptors: farming-; nitrate-nitrogen; leaching-;
 pollution-control; economic-policy; economic-analysis;
 federal-programs; models-
 NAL Call No.: HD1773.A2N6
 61. Fate of aldicarb in the vadose zone beneath a cotton field.
 Cai, D.; Xiang, F.; Jiang, X.; Zhu, Z.; Hua, X.; Dai, Z. 
 J-contam-hydrol v.14, p.129-142. (1993).
 Includes references.
 Descriptors: soil-pollution; aldicarb-; pesticide-residues;
 movement-in-soil; groundwater-pollution; cotton-; fields-;
 simulation-models; jiangsu-
 NAL Call No.: TD426.J68
 62. A finite element model for simulating runoff and soil erosion
 from mechanically treated agricultural lands. 2. Field validation
 and applications.
 Sharda, V. N.; Singh, S. R.; Sastry, G.; Dhruvanarayana, V. V. 
 Water-resour-res v.30, p.2299-2310. (1994).
 Includes references.
 Descriptors: agricultural-land; erosion-; runoff-;
 soil-conservation; precipitation-; simulation-models
 Abstract: The finite element model for simulation of runoff and
 erosion as developed by Sharda and Singh (this issue) is
 evaluated using data collected from agricultural land treated
 with major mechanical soil and water conservation measures,
 namely, contour bunding, graded bunding, bench terracing, and
 conservation bench terracing. The simulated and experimentally
 realized hydrographs and soil loss values are in reasonably good
 agreement for various measures. Probable reasons for
 discrepancies between the predicted and observed values are
 discussed. The model has the potential of being used on a single
 storm or a continuous basis provided the soil, crop, and climatic
 parameters are precisely known or estimated for a given location
 and for the period under consideration. The model logically
 simulates the effects of flow, topographic, soil, and crop
 parameters such as antecedent moisture level, roughness
 coefficient, saturated hydraulic conductivity, slope, depth of
 impoundment, size of outlet, longitudinal slope of the channel,
 vertical interval, and cropping management factor. The model is
 found to be quite sensitive to changes in roughness coefficient,
 rainfall excess rate, and cover management factor, and hence
 these parameters need to be assessed carefully in the field. The
 general applicability of the model as a planning tool for soil
 conservation measures and the scope for future development are
 also discussed.
 NAL Call No.: 292.8-W295
 63. A finite element model for simulating runoff and soil erosion
 from mechanically treated agricultural lands. 1. Governing
 equations and solutions.
 Sharda, V. N.; Singh, S. R. 
 Water-resour-res v.30, p.2287-2298. (1994).
 Includes references.
 Descriptors: agricultural-land; erosion-; runoff-; infiltration-;
 soil-water-balance; geological-sedimentation; precipitation-;
 soil-conservation; simulation-models; equations-
 Abstract: A finite element model simulating runoff and soil
 erosion from agricultural lands is developed. The computational
 efficiency and stability of various numerical schemes used for
 time integration are critically examined employing L2 and
 Chebycheff (Chebyshev) norms. Predictor-corrector and fully
 implicit schemes are found to give the least values of norms,
 thereby permitting larger time steps. A finite element solution
 of the one-dimensional Richards equation with a sink term
 simulates rain infiltration and soil moisture balance in cropped
 fields. A criterion to ensure stability and convergence of the
 solution is suggested. A finite element solution of the sediment
 continuity equation in conjunction with a fully implicit scheme
 for time integration and Yalin's equation for sediment transport
 capacity is developed to simulate soil erosion. The potential of
 the model to reasonably simulate runoff and soil erosion is
 demonstrated by comparing the finite element solutions with the
 analytical solutions under simplified configurations and with
 experimental data.
 NAL Call No.: 292.8-W295
 64. Flux-averaged concentrations for transport in soils having
 nonuniform initial solute distributions.
 Toride, N.; Leij, F. J.; Van Genuchen, M. T. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Nov/Dec 1993. v. 57 (6) p. 1406-1409. 
 Includes references.
 Descriptors: soil-physics; solutes-; transport-processes;
 movement-in-soil; mathematical-models
 Abstract: The need to distinguish between volume-averaged or
 resident concentrations [c(r)] and flux-averagedor flowing
 concentrations [c(r)] is now widely accepted. Flux-averaged
 concentrations associated  with the convection-dispersion
 equation (CDE) have been mostly used for solute transport
 problemsinvolving uniform initial distributions. We present
 flux-averaged concentrations for nonuniform  initial
 distributions using analytical solution methods for a
 semi-infinite soil system andnumerical methods for a finite
 system. Mathematically, c(r) is equivalent to c(r) associated
 witha first-type inlet condition (rather than a third-type
 condition) only for semi-infinite soil  profiles having uniform
 initial conditions. We show that, for a stepwise initial
 distribution, c,can be both negative or much greater than the
 initial concentration of c(r), especially during theearly
 stages of solute displacement. This physically odd situation
 results from the fact that  c(r) represents a solute flux rather
 than a directly measurable volumetric concentration.  
 Flux-averaged concentrations at the exit of a finite soil column
 with a uniform initialdistribution are nearly identical to
 c(r) for a semi-infinite system when the column Pecletnumber
 is greater than approximately 5. However, if the initial
 distribution involves a highgradient in c(r) near the exit,
 c(r) values for finite and semi-infinite systems at the exit can  
 be very different, similarly as those for c(r) because of the
 adoption of different outlet.
 NAL Call No.: 56.9-So3
 65. Gaining forests but losing ground: a GIS evaluation in a
 Himalayan watershed.
 Schreier, H.; Brown, S.; Schmidt, M.; Shah, P.; Shrestha, B.;
 Nakarmi, G.; Subba, K.; Wymann, S. 
 Environ-manage. New York, Springer-Verlag. Jan/Feb 1994. v. 18
 (1) p. 139-150. 
 includes references.
 Descriptors: watersheds-; deforestation-;
 geographical-information-systems; evaluation-; mountain-areas;
 NAL Call No.: HC79.E5E5
 66. General stochastic unit hydrograph.
 Hjelmfelt, A.; Wang, M. 
 J-irrig-drain-eng v.120, p.138-148. (1994).
 Includes references.
 Descriptors: watersheds-; runoff-water; rain-; stochastic-models;
 NAL Call No.: 290.9-AM3Ps-IR
 67. GIS application to water quality management in the upper
 Volga River
 Belyaeva, T.; Higgins, J. M.; Kirpichnikova, N.; Lanzova, I.;
 Hagerman, J. R. 
 Water-sci-technol v.28, p.119-127. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: water-resources; water-management;
 geographical-information-systems; russia-; usa-;
 NAL Call No.: TD420.A1P7
 68. GOSSYM/COMAX: a cotton crop management emphasizing irrigation
 scheduling and water quality.
 McKinion, J. M.; Boone, M. Y. L.; Porter, D. O.; Whisler, F. D. 
 Proceedings of Industrial and Agricultural Impacts on the
 Hydrologic Environment  the Second USA/CIS Joint Conference on
 Environmental Hydrology and Hydrogeology / USA/CIS Joint
 Conference on Environmental Hydrology and Hydrogeology.
 Alexandria, VA : Water Environment Federation, c1993.. v. 2 p.
 Title on cover : Environmental impact of agricultural practices
 and agrichemicals / edited by Y. Eckstein and A. Zaporozec.
 Descriptors: gossypium-; irrigated-farming;
 irrigation-scheduling; simulation-models; water-quality;
 NAL Call No.: GB652.U82-1993
 69. Groundwater contamination from agricultural sources in
 Northern Italy: long-term monitoring and mathematical modelling.
 Fortina, L.; Capodaglio, A. G.; Baldi, M. 
 Water-sci-technol v.28, p.369-377. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: groundwater-pollution; herbicides-;
 mathematical-models; italy-
 NAL Call No.: TD420.A1P7
 70. Groundwater quality.
 Mayer, A. S.; Imhoff, P. T.; Mitchell, R. J.; Rabideau, A. J.;
 McBride, J. F.; Miller, C. T. 
 Water-environ-res v.66, p.532-585. (1994).
 Includes references.
 Descriptors: groundwater-pollution; pollutants-;
 transport-processes; water-quality; monitoring-; biodegradation-;
 movement-in-soil; groundwater-flow; sorption-; desorption-;
 pesticides-; leaching-; models-; literature-reviews
 NAL Call No.: TD419.R47
 71. Groundwater quality management of a low inertia basin:
 application to the San Mateo Basin, California.
 Bagtzoglou, A. C.; Khan, M. N.; Guymon, G. L. 
 Water-resour-manag v.7, p.189-205. (1993).
 Includes references.
 Descriptors: groundwater-; water-quality; water-management;
 watersheds-; groundwater-recharge; water-yield;
 finite-element-analysis; models-; water-storage; california-;
 Abstract: A two-dimensional finite element model is applied to
 the San Mateo Basin, California in order toinvestigate
 feasible and efficient management alternatives to enhance the
 basin yield andpreserve the basin water quality. The model
 utilizes lumped approximation methods for thedetermination of
 its subsurface boundary conditions, and incorporates a variety of
 hydrologicalprocesses. The model solves uncoupled flow and
 transport equations using a nodal domainintegration technique
 for the flow model and an integrated finite difference method for
 thetransport model. The model incorporates the basin inputs
 and outputs as ocean flux, well and  phreatophyte extractions,
 subsurface inflow, precipitation and streambed percolation.
 Modelingresults indicate that the sustained yield may be
 maximized by interception of ocean outflow fromthe basin. An
 improvement of about four times of the historical sustained yield
 was achieved.This strategy required relocation of existing
 wastewater recharge ponds and increasing basinextractions. In
 order to intercept most of the ocean outflow by increasing basin
 extractions,simulated subsurface seawater intrusion was
 observed. The water quality study indicated that thebasin
 yield could be increased significantly by moderately relaxing the
 water quality criterianear the ocean.
 NAL Call No.: TC401.W27
 72. Growing corn root effects on interrill soil erosion.
 Bui, E. N.; Box, J. E. Jr. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. July/Aug 1993. v. 57 (4) p. 1066-1070. 
 Includes references.
 Descriptors: zea-mays; roots-; length-; density-;
 soil-stabilization; interrill-erosion; erosion-control;
 crop-growth-stage; runoff-; sediment-; losses-from-soil;
 erodibility-; mathematical-models; georgia-;
 Abstract: The relationship between plant roots and interrill soil
 erosion is important in dynamic soil erosion predictions.
 Rainstorm simulations of similar intensity (63.5 mm h-1) were
 conducted in the summer of 1989 on 1 by 1 m field plots of Cecil
 sandy loam (clayey, kaolinitic, thermic Typic Kanhapludult) to
 study the effect of different root length densities, L(v) (cm
 cm-3), of corn (Zea mays L.), during vegetative, preanthesis, and
 anthesis plant developmental stages on interrill soil erosion.
 Sediment loss and runoff data were assigned to treatments, L(va),
 on the basis of L(v) range to reduce rooting variability
 associated with plant developmental stage. To avoid confounding
 by canopy cover, corn plants were cut at the stem base and
 removed for the first four sets of simulations. A reference set
 of simulations was performed on a fallow plot containing no
 roots, L(va). Runoff and detached sediment were collected in
 buckets from each plot during successive 5-min intervals over a
 1-h period. Thirty cores, 5 cm in diam. and 5 cm deep, were taken
 from each 1-m2 plot and roots were washed from the cores and
 measured. Means for runoff and detached sediment were generally
 not significantly different for the high L(v) or L(va), and
 L(va0). When L(va) was < 1.5 cm cm-3, runoff and detached
 sediment were significantly lower during the first 30 min of
 simulated rainfall. High densities of live corn roots did not
 reduce interrill soil erosion from a moldboard-plowed Cecil sandy
 NAL Call No.: 56.9-So3
 73. A hedonic analysis of herbicides: do user safety and water
 quality matter.
 Beach, E. D.; Carlson, G. A. 
 Am-j-agric-econ. Ames, Iowa : American Agricultural Economics
 Association. Aug 1993. v. 75(3) p. 612-623. 
 Includes references.
 Descriptors: herbicides-; weed-control; water-quality; safety-;
 farmers'-attitudes; econometric-models; zea-mays; glycine-max;
 decision-analysis; usa-; arkansas-; iowa-; north-carolina; ohio-;
 Abstract: Farmers may value water quality and user safety
 characteristics of herbicides as they select among products to
 obtain weed control. Expenditures per application in the U.S.
 corn and soybean herbicide markets are explained by several
 safety characteristics in addition to market and weed control
 characteristics. The explicit inclusion of safety characteristics
 in the farm decision model indicates that not all safety aspects
 of pesticide use are external to farmers. Leaching potential and
 user toxicity are statistically significant, but their
 elasticities are small relative to broadleaf and grass weed
 control efficacy.
 NAL Call No.: 280.8-J822
 74. Human intestinal cell line Caco-2: a useful model for
 studying cellular and molecular regulation of biotin uptake.
 Ma, T. Y.; Dyer, D. L.; Said, H. M. 
 Biochim-biophys-acta v.1189, p.81-88. (1994).
 Includes references.
 Descriptors: biotin-; nutrient-uptake; regulation-;
 transport-processes; intestines-; cell-lines
 Abstract: The mechanisms of enterocyte and molecular regulation
 of biotin uptake are poorly understood. An intestinal cell line
 possessing the transport characteristics of native intestinal
 cells is highly desirable to investigate the finer details of the
 cellular processing and molecular regulation of biotin transport.
 In the present study, we investigated the uptake of the
 water-soluble vitamin biotin by a human intestinal cell line
 Caco-2. Uptake of both low (4 nM) and high (20 micromolar)
 concentrations of biotin by confluent monolayers of Caco-2 cells
 was appreciable and linear for up to 10 min of incubation.
 Replacement of Na+ in the incubation medium with other monovalent
 cations -- K+, choline, Li+ and NH4+ -- caused a significant
 inhibition of biotin uptake; a relatively lesser inhibition was
 seen with Li+. Initial rate of uptake of biotin was
 temperature-dependent and saturable as a function of
 concentration at 37 degrees C but not at 4 degrees C. The Vmax
 and apparent Km of the temperature-dependent saturable process
 were 520 pmol/mg protein per min and 9.5 micromolars,
 respectively. The addition of unlabeled biotin and the structural
 analogue desthiobiotin to the incubation media caused a
 significant inhibition of the uptake of [3H]biotin. The
 inhibitory effect of desthiobiotin was competitive in nature with
 an inhibition constant (Ki) of 41 micromolar. Biocytin, on the
 other hand, was a weak inhibitor and biotin methyl ester and
 diaminobiotin did not have any effect. Pretreatment of Caco-2
 cells with the monovalent cation ionophore gramicidin and the
 Na+, K+-ATPase inhibitor ouabain caused significant inhibition of
 biotin uptake. Pretreatment with the K+ ionophore valinomycin did
 not affect biotin.  biotin- to Na+ coupling was found to be 1:1.
 Growing confluent Caco-2 cells in a biotin-deficient environment
 resulted in rapid up-regulation of biotin transport with a marked
 increase (258%) in the Vmax of biotin uptake. These findings
 demonstrate that biotin uptake by Caco-2 cells is via a
 carrier-mediated systm. This system is temperature-dependent,
 driven by Na+-gradient and is regulated by the substrate level.
 These in-vitro findings are very similar to and further confirm
 previous findings in human and animal studies and dispute other
 findings previously reported for Caco-2 cells; the present study
 also demonstrates the suitability of this system for further
 characterization of the cellular and molecular regulation of
 biotin uptake.
 NAL Call No.: 381-B522
 75. Hystem-EXTRAN: improvements to EPA-EXTRAN.
 Fuchs, L.; Scheffer, C. 
 Water-sci-technol v.29, p.63-71. (1994).
 Selected Proceedings of the 6th International Conference on Urban
 Storm Drainage, September 12-17, 1993, Niagara Falls, Canada /
 edited by J.C. Marsalek and H.C. Torno.
 Descriptors: rain-; runoff-; hydrology-; water-management;
 NAL Call No.: TD420.A1P7
 76. Identification of road salt contamination using multiple
 regression and GIS.
 Mattson, M. D.; Godfrey, P. J. 
 Environ-manage. New York, Springer-Verlag. Sept/Oct 1994. v. 18
 (5) p. 767-773. 
 Includes references.
 Descriptors: streams-; salt-; sodium-chloride; water-pollution;
 regression-analysis; geographical-information-systems;
 NAL Call No.: HC79.E5E5
 77. The impact of changes in the runoff formulation of a general
 circulation model on surface and near-surface parameters.
 Viterbo, P.; Illari, L. 
 J-hydrol v.155, p.325-336. (1994).
 Special Issue: Mesoscale Hydrology and General Circulation
 Descriptors: soil-water; runoff-; simulation-models;
 precipitation-; infiltration-; evapotranspiration-;
 air-temperature; geographical-distribution; forecasting-
 Abstract: The surface and near-surface properties of the European
 Centre for Medium Range Weather Forecasting (ECMWF) general
 circulation model are shown to be sensitive to the
 parametrization of runoff.  If a border subgrid-scale
 distribution of precipitation is assumed when computing runoff,
 the infiltration increases, more water becomes available for
 evaporation and the model surface cools.  The averaged Bowen
 ratio over land is shown to decrease from 1.5 to 0.9 in a
 Northern Hemisphere summer experiment.  Possible implications for
 the estimation of soil moisture and evapotranspiration using a
 global data assimilation-forecasting system are discussed.
 NAL Call No.: 292.8-J82
 78. Impact of coal combustion waste on the microbiology of a
 model aquifer.
 Brunning, J. S.; Caldwell, D. E.; Lawrence, J. R.; Robarts, R. D. 
 Water-air-soil-pollut v.74, p.103-120. (1994).
 Includes references.
 Descriptors: aquifers-; groundwater-; pollution-;
 fluidized-bed-wastes; coal-; combustion-; infiltration-;
 leaching-; landfills-; landfill-leachates; groundwater-;
 water-quality; alkalinity-; heterotrophic-microorganisms;
 bacteria-; bacterial-count
 NAL Call No.: TD172.W36
 79. The impact of recession infiltration on runoff volume
 computed by the kinematic wave model.
 Stone, J. J.; Shirley, E. D.; Lane, L. J. 
 Trans-ASAE v.36, p.1353-1361. (1993).
 Includes references.
 Descriptors: runoff-water; infiltration-; rain-; kinematics-;
 Abstract: The effect of recession infiltration on runoff volume
 is quantified using the kinematic wave modelfor the case of
 lateral inflow made up of constant rainfall excess during the
 period of rainfalland constant infiltration after rainfall
 ends.  A general solution is obtained using thefollowing
 non-dimensional quantities; Q*=Q/R(e) (runoff volume divided by
 rainfall excess volume),t* = t(e)/D (time to kinematic
 equilibrium divided by the duration of rainfall excess), and f* = 
 f/r(e) (infiltration rate divided by rainfall excess rate). 
 Using these quantities, therelationship for the reduction of
 runoff volume is Q* =1-m/(m+1) t* [f*/(f*+1)](l/m) when t* < 
 [(f*+])/f*]/(l/m) and Q* = 1/(m+1) t*1(-m) (f*+1)/f* when t* >
 [(f*+1)/f*](l/m) where m is thekinematic wave depth-discharge
 exponent.  The first equation corresponds to the case when flow  
 ceases after the characteristic from distance and time zero,
 C(0,0), reaches the end of the plane.The second equation
 corresponds to the case when the flow ceases and C(0,0) does not
 reach theend of the plane.  These equations approximate the
 reduction of runoff volume for the more generalcase of time
 varying rainfall excess under constant and variable rainfall as
 would be the casewhen the rainfall excess is generated using
 the Green-Ampt infiltration equation.
 NAL Call No.: 290.9-Am32T
 80. Importance of soil and cropping systems in the development of
 regional water quality policies.
 Geleta, S.; Sabbagh, G. J.; Stone, J. F.; Elliott, R. L.; Mapp,
 H. P.; Bernardo, D. J.; Watkins, K. B. 
 J-environ-qual v.23, p.36-42. (1994).
 Technical Reports from the Symposium, "Minimizing Agricultural
 Nonpoint-Source Impacts", November 2, 1992, Minneapolis,
 Descriptors: triticum-aestivum; sorghum-bicolor; zea-mays;
 cropping-systems; soil-types; crop-yield; nitrate-nitrogen;
 leaching-; water-quality; irrigation-; simulation-models;
 geographical-information-systems; oklahoma-
 Abstract: Targeting certain soils and cropping systems may be
 necessary in consideration of regional water quality protection
 policies.  However, little information is available relating
 soils and cropping practices to regional water quality problems.
 This study evaluates crop yield and NO3-N movement to surface and
 groundwater on four soils and nine principal cropping systems in
 the High Plains region of Oklahoma. The cropping systems involve
 wheat (Triticum aestivum L.), grain sorghum [Sorghum bicolor (L.)
 Moench], and corn (Zea mays L.), and are part of a regional data
 base also containing soils and chemical management information. 
 For each combination of crop, soil, cropping system, and chemical
 alternative, a 20-yr simulation was made. The simulation was
 based on a modeling system that includes EPIC-PST (crop
 growth/chemical movement model) interfaced with a Geographic
 Information System (GIS), Earthone.  Results of each simulation
 included crop yield and NO3-N movement in runoff and percolation. 
 Results show wide variations in NO3-N losses for different soils,
 irrigation systems, and cropping systems. When compared with
 continuous irrigated wheat and grain sorghum cropping systems,
 double-cropped wheat-grain sorghum resulted in greater NO3-N loss
 in percolation.  Compared with sprinkler and LEPA (low energy
 precision application) irrigation systems, furrow irrigation
 resulted in high NO3-N loss on both fine-textured and
 coarse-textured soils, with significantly greater loss on the
 coarser-textured soils.  The modeling framework can be used to
 compare alternative water quality policies. Broad policies such
 as a restriction on the amount of N that can be applied per
 hectare can be compared with targeted.  coarser soils or under
 furrow irrigation.
 NAL Call No.: QH540.J6
 81. Infiltration and redistribution of organic liquids in layered
 porous media.
 Cary, J. W.; Simmons, C. S.; McBride, J. F. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1994. v. 58 (3) p. 704-711. 
 Includes references.
 Descriptors: porous-media; oils-; transport-processes;
 infiltration-; redistribution-; mathematical-models; vaclose-zone
 Abstract: The remediation of many toxic waste sites throughout
 the world requires a better understanding of the flow of organic
 liquids in the vadose zone.  The infiltration and redistribution
 of three water-immiscible oils into columns filled with porous
 material containing different textural layers are reported.  In
 some experiments, oil followed water into the columns and in
 others, water followed oil.  An explicit, one-dimensional,
 multiphase flow code was used to model the results. The numerical
 model contains elements of code that: (i) mimic the Haines jump
 phenomenon in dry sand, (ii) account for oil entrapment when
 water infiltrates, (iii) include forces on the oil phase caused
 by surface-spreading pressures at the oil front in water-wetted
 pores, (iv) include forces on the oil phase caused by water
 intrusion into hydrophilic oil-saturated pores, and (v) generate
 a factor that matches the water potentials of textural layers for
 the initial boundary conditions. In general, the model did a
 reasonable job of predicting the distribution of both water and
 oil 8 h after infiltration was started, though some unresolved
 problems persist.  The liquid potential matching factor and the
 hydrophobicity of the mineral particles induced by a transmission
 oil have practical applications.  The matching factor may be
 easily adapted to all codes that model flow through layers. The
 in situ creation of hydrophobic mineral particles may prove
 useful for containing immiscible organic liquids that leak into
 the vadose zone.
 NAL Call No.: 56.9-So3
 82. Influence of amount and method of irrigation water
 application on leaching of atrazine.
 Troiano, J.; Garretson, C.; Krauter, C.; Brownell, J.; Huston, J. 
 J-environ-qual v.22, p.290-298. (1993).
 Includes references.
 Descriptors: atrazine-; leaching-; percolation-; irrigation-;
 soil-water-content; spatial-distribution; sandy-soils;
 simulation-models; california-; leachm-model
 Abstract: A study was conducted to relate leaching of an
 herbicide, atrazine
 amine], and inorganic water tracers, Br- and Cl-, to the amount
 of deep-percolating water produced from irrigation. Soil at the
 site was classified as a Dehli Loamy Sand (Mixed, Thermic, Tepic
 Xeropsamment) which was an unstructured sandy soil that was low
 in organic C content, conditions conducive to solute leaching.
 The relationship between depth of solute movement and amount of
 deep-percolating water was measured in sprinkler, basin, and
 furrow irrigation methods. Soil distribution of inorganic tracers
 indicated that graded levels of added water treatments, which
 were based on reference evapotranspiration, produced
 corresponding increases in the depth of percolated water.
 Atrazine's soil distribution indicated greater downward movement
 in response to increases in amount of deep-percolating water.
 Magnitude of leaching differed between irrigation methods and
 increased in the order: sprinkler < basin < furrow. Simulations
 using the LEACHM model provided a physically based explanation
 for the differences in water movement between sprinkler and basin
 methods. The total amount of applied water was similar at each
 level of percolation but sprinkler irrigations were more
 frequent, resulting in more evaporation and, consequently, less
 water available for deep percolation. Both amount and method of
 water application are important factors that determine pesticide
 movement and that, in irrigated agriculture, must be considered
 as integral components of pesticide management.
 NAL Call No.: QH540.J6
 83. The influence of variable precipitation patterns on
 simulations of pesticide mobility.
 Roth, G.; Stahl, G.; Iwan, J. 
 Pestic-sci v.38, p.341-346. (1993).
 Includes references.
 Descriptors: pesticides-; leaching-; precipitation-; variation-;
 temperature-; frequency-distribution; weather-data;
 monte-carlo-method; simulation-models
 Abstract: The behaviour of pesticides in the soil is governed by
 a variety of complex processes including theclimatic
 conditions. To investigate the influence of these specific
 factors, a Monte-Carlo Methodwas used to generate sequences of
 daily precipitation and temperature data representing natural  
 weather behaviour. Simulations of the leaching process were
 performed for different compounds withthese sequences while
 all other environmental parameters were held constant. The
 results indicatedthat the use of stochastic variables yields
 new insight into the leaching process. It is shownthat the
 naturally occurring variability of the weather pattern has a
 crucial influence on theleaching of pesticides.
 NAL Call No.: SB951.P47
 84. Integrated flux model for unsteady transport of trace organic
 chemicals in soils.
 Moldrup, P.; Poulsen, T. G.; Rolston, D. E.; Yamaguchi, T.;
 Hansen, J. A. 
 Soil-sci v.157, p.137-152. (1994).
 Includes references.
 Descriptors: organic-compounds; transport-processes;
 movement-in-soil; drained-conditions; deterministic-models;
 unsaturated-soils; vadose-zone;
 NAL Call No.: 56.8-So3
 85. Integrating water quality modeling with ecological risk
 assessment for nonpoint source pollution control: a conceptual
 Chen, Y. D.; McCutcheon, S. C.; Rasmussen, T. C.; Nutter, W. L.;
 Carsel, R. F. 
 Water-sci-technol v.28, p.431-440. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: water-quality; protection-; pollution-control;
 ecology-; risk-; assessment-; models-; usa-;
 NAL Call No.: TD420.A1P7
 86. Integration of geographic information systems and a computer
 model to evaluate impacts of agricultural runoff on water
 He, C.; Riggs, J. F.; Kang, Y. T. 
 Water-resour-bull v.29, p.891-900. (1993).
 Includes references.
 Descriptors: runoff-; river-water; water-pollution;
 water-quality; nitrogen-; phosphorus-; simulation-models;
 geographical-information-systems; michigan-;
 agricultural-nonpoint-source-pollution-model-agnps; cass-river;
 saginaw-bay; best-management-practices
 Abstract: This study integrates an Agricultural Non-Point Source
 Pollution Model (AGNPS), the Geographic Resource Analysis Support
 System (GRASS) (U.S. Army Corps of Engineers, 1987), and GRASS
 WATERWORKS (a hydrologic modeling tool box being developed at the
 Michigan State University Center for Remote Sensing) to evaluate
 the impact of agricultural runoff on water quality in the Cass
 River, a subwatershed of Saginaw Bay. AGNPS is used to estimate
 the amounts, origin, and distribution of sediment, nitrogen (N),
 and phosphorus (P) in the watershed. GRASS and GRASS WATERWORKS
 are used to generate parameters needed for AGNPS from digital
 maps, which include soil association, land use, watershed
 boundaries, water features, and digital elevation. Outputs of the
 model include spatially distributed estimates of volume and peak
 runoff, overland and channel erosion, sediment yields, and
 concentrations of nitrogen and phosphorus. Management scenarios
 are explored in the AGNPS model to minimize sedimentation and
 nutrient loading. Scenarios evaluated include variations in crop
 cover, tillage methods, and other agricultural management
 practices. In addition, areas vulnerable to erosion are
 identified for best management practices.
 NAL Call No.: 292.9-Am34
 87. Interfacial tension-induced transport of nonaqueous phase
 liquids in model aquifer systems.
 Anderson, M. A. 
 Water-air-soil-pollut v.75, p.51-60. (1994).
 Includes references.
 Descriptors: soil-pollution; groundwater-; pollution-; solvents-;
 fuels-; transport-processes; immiscible-displacement;
 surface-tension; toluene-; sand-
 NAL Call No.: TD172.W36
 88. Investigating prediction capability of HEC-1 and KINEROS
 kinematic wave runoff models.
 Obiukwu Duru, J.; Hjelmfelt, A. T. Jr. 
 J-hydrol v.157, p.87-103. (1994).
 Includes references.
 Descriptors: watersheds-; rain-; storms-; runoff-;
 catchment-hydrology; prediction-; simulation-models
 Abstract: In this study, two distributed parameter, physically
 based, kinematic wave hydrologic models, HEC-1 and KINEROS, were
 tested on a 30.4 ha watershed located near Treynor, Iowa. The
 study had two objectives: (1) to determine the ability of the
 models to predict runoff with very limited calibration: (2) to
 determine how accurately the models can simulate runoff given
 accurate model parameters. The results show that HEC-1 can
 achieve good prediction of runoff with very limited calibration.
 It was not, however, possible to achieve the same level of
 prediction with the KINEROS model. Given good calibration, both
 models can simulate the rainfall runoff process with great
 NAL Call No.: 292.8-J82
 89. Lake water quality modeling for projected future climate
 Stefan, H. G.; Hondzo, M.; Fang, X. 
 J-environ-qual v.22, p.417-431. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: lakes-; water-reservoirs; global-warming;
 carbon-dioxide; temperature-; dissolved-oxygen; size-; depth-;
 turbidity-; phytoplankton-; seasonal-variation; water-quality;
 simulation-models; water-temperature; trophic-status
 Abstract: A deterministic, one-dimensional numerical simulation
 model for water temperature and dissolved oxygen (DO) in lakes of
 different size, depth, and trophic status has been formulated,
 validated, and applied to lakes in the north central USA. The
 standard error of predictions is on the order of 1 degree C for
 temperature and 1.5 mg L(-1) for DO. The model is driven by
 weather measurements at off-lake weather stations. Simulations
 can be made for the open water season at daily timesteps and for
 as many years as weather data are available without any parameter
 adjustments. The model has been used to simulate the effect of
 climate change due to a doubling of atmospheric CO2 on water
 temperatures and DO in 27 lake classes in Minnesota. The lakes
 have been differentiated by surface area, maximum depth, and
 trophic status. Maximum water temperature near the surface is
 projected to increase by no more than 2 degrees C in midsummer,
 and DO will drop by less than 2 mg L(-1) in the surface waters
 but will remain above 7 mg L(-1). In contrast, hypolimnetic water
 temperature in midsummer may rise by as much as 4 degrees C or
 may become colder by as much as 4 degrees C. Hypolimnetic DO will
 be lower by as much as 8 mg L(-1) in midsummer and DO depletion
 is projected to occur for a longer period of time in midsummer in
 lakes with seasonal summer stratification. Changes will be
 largest in spring and fall because the summer stratification
 season will lengthen by 20 to 90 d for different lake types.
 NAL Call No.: QH540.J6
 90. Leachate geochemistry at a municipal landfill, Memphis,
 Mirecki, J. E.; Parks, W. S. 
 Ground-water. Dublin, Ohio : Ground Water Pub. Co. May/June 1994.
 v. 32 (3) p. 390-398. 
 Includes references.
 Descriptors: landfill-leachates; municipal-refuse-disposal;
 wells-; groundwater-; samples-; chemical-composition;
 concentration-; alluvium-; aquifers-; geochemistry-; models-;
 groundwater-pollution; tennessee-
 NAL Call No.: TD403.G7
 91. Long-term (15 years) results of NPS controls in an
 agricultural watershed upon a receiving lake's water quality.
 Garrison, P. J.; Asplund, T. R. 
 Water-sci-technol v.28, p.441-449. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: watersheds-; agricultural-land; runoff-water;
 sediment-; nutrients-; prediction-; models-; pollution-control;
 phosphorus-; loads-; lakes-; water-quality; wisconsin-
 NAL Call No.: TD420.A1P7
 92. Measuring and modeling root water uptake based on 36chloride
 discrimination in a silt loam soil affected by groundwater.
 Schmidhalter, U.; Selim, H. M.; Oertli, J. J. 
 Soil-sci v.158, p.97-105. (1994).
 Includes references.
 Descriptors: daucus-carota; roots-; water-uptake; measurement-;
 salinization-; groundwater-; saline-water; capillary-rise;
 water-table; soil-depth; models-; solutes-; transport-processes;
 chloride-; soil-water-content
 NAL Call No.: 56.8-So3
 93. Miscible displacement and theoretical techniques for
 simultaneous study of pesticide sorption and degradation during
 Gamerdinger, A. P.; Dowling, K. C.; Lemley, A. T. 
 SSSA-spec-publ p.115-123. (1993).
 In the series analytic: Sorption and degradation of pesticides
 and organic chemicals in soil / edited by D.M. Linn, T.H. Carski,
 M.L. Brusseau and F.H. Chang.  chemicals in soils," held on
 October 30, 1991, Denver, Colorado.
 Descriptors: pesticides-; transport-processes; models-;
 transformation-; sorption-; estimation-; techniques-
 NAL Call No.: S590.S62
 94. Model farms results reviewed as project nears an end.
 Carver, N. 
 Inside-edge v.3, p.1-2. (1993).
 Descriptors: water-quality; farms-; models-; residues-;
 project-appraisal; iowa-
 NAL Call No.: S561.6.I8I572
 95. Model of integrated effects of boron, inert salt, and water
 flow on crop yield.
 Shani, U.; Hanks, R. J. 
 Agron-j v.85, p.713-717. (1993).
 Includes references.
 Descriptors: hordeum-vulgare; zea-mays; growth-models;
 mathematical-models; equations-; phytotoxicity-; boron-;
 salts-in-soil; soil-salinity; soil-water; water-flow;
 transport-processes; leaching-; available-water; crop-yield;
 yield-losses; simulation-models; utah-
 Abstract: High boron concentration in the soil causes yield
 reduction. Recently, a piecewise linear response curve was
 applied to describe yield response to B in near steady-state
 conditions. However, application of similar curves to field
 situations where water, B, and other ion contents are transient
 and nonhomogeneous is limited. The objective of this study was to
 develop a model for simulation of the integrated effects of B,
 inert salt, and water on crop yield under field conditions. The
 model computes water flow in response to irrigation, rain, or
 evapotranspiration processes and subsequently computes inert salt
 and B transport. Crop yield is related to soil matric and osmotic
 potentials and B toxicity. Effects of B toxicity are considered
 by adapting the steady-state approach to the transient situation.
 Field experiments with barley (Hordeum vulgare L.) and corn (Zea
 mays L.) were conducted on the Utah Power & Light Co. research
 farm (Huntington, UT). Soil was Penoyer loam [coarse-silty, mixed
 (calcareous), mesic Typic Torriorthent]. Line source irrigation
 was used to obtain different irrigation levels. The effects of B,
 Salt mixture of Na, Ca, Cl, and SO4), and B + Salt on yield were
 studied in barley. The effect of B + Salt was studied also in
 corn. Measurements and simulations were in close agreement for
 both crops. Barley yield ranked B + Salt < B < Salt < control.
 Corn yield ranked B + Salt < control. The B adsorption properties
 result in less leaching than do those of an inert ion like Cl.
 The effects of initial and boundary conditions together with the
 B adsorption characteristics on B concentration in the soil
 solution and the subsequent yield reduction are presented. This
 model can serve for an analysis of the long-term effects of high
 B and help in understanding the relative.
 NAL Call No.: 4-AM34P
 96. A model of nitrate leaching from agricultural systems in
 Virginia's Northern Neck.
 Johnson, T. G.; Parker, J. C. 
 Blacksburg : Virginia Water Resources Research Center, Virginia
 Polytechnic Institute and State University, 1993. xviii, 308 p..
 Includes bibliographical references (p. 125-137).
 97. Model simulations of dissolved oxygen characteristics of
 Stefan, H. G.; Fang, X. 
 Environ-manage. New York, Springer-Verlag. Jan/Feb 1994. v. 18
 (1) p. 73-92. 
 Includes references.
 Descriptors: lakes-; water-quality; dissolved-oxygen;
 simulation-models; climatic-change; minnesota-
 NAL Call No.: HC79.E5E5
 98. A modeling approach to evaluate best management practices.
 Williams, R. D.; Nicks, A. D. 
 Water-sci-technol v.28, p.675-678. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: agricultural-land; crops-; river-water;
 water-pollution; protection-; soil-management; water-quality;
 improvement-; models-; usa-; vegetative-filter-strips
 NAL Call No.: TD420.A1P7
 99. Modeling mined land reclamation strategies in a GIS
 Younos, T. M.; Yagow, E. R.; Zipper, C. E.; Diplas, P. 
 Appl-eng-agric v.9, p.61-68. (1993).
 Includes references.
 Descriptors: mined-land; reclamation-; computer-software;
 models-; erosion-control; environmental-impact; virginia-
 Abstract: The erosion potential from mined lands is considered a
 major environmental threat. Mathematical models can be used to
 predict and demonstrate the effectiveness of various reclamation
 strategies for reducing erosion potential. The objective of this
 project was to use the Universal Soil Loss Equation (USLE) with a
 sediment yield component to evaluate the comparative effects of
 alternative reclamation strategies in a Geographic Information
 System (GIS) environment. The study site was an abandoned mined
 land (AML) site located in southwest Virginia. Topographic and
 landuse information for the site were obtained from topographic
 maps, aerial photographs, and field observation. The GIS tools
 were used to create digital data layers, store, analyze, and
 display information. The USLE factors were spatially derived from
 elevation, landuse, surface-water system, and watershed boundary
 data layers. The basic and derived data layers were then used to
 estimate the magnitude of soil loss and sediment yield. The
 methodology was used to predict the soil loss and sediment yield
 at the existing AML site, and to compare the effectiveness of
 three reclamation options for reducing soil loss and sediment
 yields. Results demonstrate the usefulness of the GIS tools for
 planning land reclamation strategies.
 NAL Call No.: S671.A66
 100. Modeling mobility and effects of contaminants in wetlands.
 Dixon, K. R.; Florian, J. D. Jr. 
 Environ-toxicol-chem v.12, p.2281-2292. (1993).
 Annual Review Issue: Wetland Ecotoxicology and Chemistry.
 Descriptors: wetlands-; simulation-models; contaminants-;
 pollutants-; transport-processes; literature-reviews
 NAL Call No.: QH545.A1E58
 101. Modeling subsurface drainage and surface runoff with WEPP.
 Savabi, M. R. 
 J-irrig-drain-eng v.119, p.801-813. (1993).
 Includes references.
 Descriptors: subsurface-drainage; surface-drainage; erosion-;
 erosion-control; models-; water-erosion-prediction-project
 NAL Call No.: 290.9-AM3Ps-IR
 102. Modeling the effects of salt-water intrusion dynamics for a
 coastal karstified block connected to a detrital aquifer.
 Calvache, M. L.; Pulido Bosch, A. 
 Ground-water. Dublin, Ohio : Ground Water Pub. Co. Sept/Oct 1994.
 v. 32 (5) p. 767-777. 
 Includes references.
 Descriptors: aquifers-; coastal-areas; saline-water;
 contamination-; groundwater-flow; landforms-; simulation-models;
 mathematical-models; water-quality; salinization-;
 groundwater-pollution; spain-
 NAL Call No.: TD403.G7
 103. Modeling the transport of solutes to groundwater using
 transfer functions.
 Roth, K.; Jury, W. A. 
 J-environ-qual v.22, p.487-493. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: solutes-; transport-processes; chemicals-;
 unsaturated-flow; groundwater-; mathematical-models
 Abstract: Transport of chemicals through the unsaturated zone
 into groundwater is in general a highly nonlinear process with a
 pronounced spatial structure of which only a very limited number
 of measurements is economically and technically feasible. In most
 applications, it is thus not practicable to model these processes
 with high spatial and temporal resolutions. However, in an
 agricultural environment chemicals are usually applied to large
 areas, and we are generally interested in their long-term effects
 on groundwater quality. With these restrictions, the transport
 processes may be averaged in space and time over sufficiently
 large regions such that it may be permissible to use a
 stationary, linear approximation. An efficient way to study such
 systems exploits that a stationary, linear system is completely
 determined by its transfer function, that is, by its response to
 a narrow pulse input. We use a general formalism to represent the
 transport processes implicitly by the relation between the flux
 and the resident concentration of a conservative chemical. To
 model the transport of nonconservative chemicals, this
 description is coupled, as it was done by (Villermaux, 1981),
 with a model of the local interactions. We obtain an expression
 for the transfer function of a linearly adsorbing chemical with
 linear adsorption kinetics and first-order decay in the water and
 in the adsorbed phase which is based on the measured transfer
 function of a conservative tracer. This procedure has the major
 advantage that parameter estimation and model validation tests
 can be applied to the chemical reaction processes alone. KEEP.
 NAL Call No.: QH540.J6
 104. Movement of nitrogen through and agricultural riparian zone.
 2. Distributed modeling.
 Nikolaidis, N. P.; Shen, H.; Heng, H.; Hu, H. L.; Clausen, J. C. 
 Water-sci-technol v.28, p.613-623. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: riparian-forests; pollutants-; sources-; nitrogen-;
 groundwater-pollution; surface-water; water-pollution;
 movement-in-soil; mathematical-models; connecticut-
 NAL Call No.: TD420.A1P7
 105. New models for unsaturated soil hydraulic properties.
 Zhang, R.; Genuchten, M. T. v. 
 Soil-sci v.158, p.77-85. (1994).
 Includes references.
 Descriptors: soil-water-retention;
 unsaturated-hydraulic-conductivity; mathematical-models;
 solutes-; transport-processes; water-flow
 NAL Call No.: 56.8-So3
 106. NLEAP simulation of residual soil nitrate for irrigated and
 nonirrigated corn.
 Follett, R. F.; Shaffer, M. J.; Brodahl, M. K.; Reichman, G. A. 
 J-soil-water-conserv v.49, p.375-382. (1994).
 Descriptors: zea-mays; sandy-soils; irrigated-conditions;
 soil-water-regimes; nitrogen-fertilizers; application-rates;
 nitrate-; residues-; leaching-; nitrogen-; nutrient-uptake;
 precipitation-; seasonal-variation; simulation-models;
 crop-yield; nitrate-leaching-and-economic-analysis-package;
 NAL Call No.: 56.8-J822
 107. Nondestructive determination of hydrogeometrical
 characteristics of soil macropores.
 Wang, D.; Norman, J. M.; Lowery, B.; McSweeney, K. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Mar/Apr 1994. v. 58 (2) p. 294-303. 
 Includes references.
 Descriptors: macropores-; characterization-;
 nondestructive-testing; dimensions-; water-flow; macropore-flow;
 transport-processes; mathematical-models
 Abstract: Hydrological and geometrical parameters of macropores
 are essential for modeling water and solute transport through
 soils containing macropores. This study was conducted to develop
 a fast and nondestructive technique for determining the
 hydrological and geometrical characteristics of soil macropores.
 We measured the rate of water flowing into ant and earthworm
 burrows with a macropore infiltrometer and estimated burrow
 diameter, volume, and depth from the measured flow rate and a
 water flow model. To evaluate the estimated burrow parameters, we
 made castings of the ant and earthworm burrows with a dental
 plaster. The burrows had similar diameters (2.1 mm for laminar
 flow; 2.9 mm for turbulent flow) but different volumes and depths
 [281-cm(3) volume and 0.60-m depth for ant burrows; 210-cm(3)
 volume and 0.82-m depth for earthworm burrows]. This technique is
 reasonable for ant burrows because the root mean square
 difference (RMSD) between casting and infiltrometer-calculated
 volumes is 17%; however, errors are larger for earthworm burrows
 (RMSD is 73%). Saturated soil matrix hydraulic conductivity
 [K(s)] estimated from the infiltrometer measurement of earthworm
 burrows were comparable to matrix K(s) of the bulk silt loam. The
 matrix K(s) values estimated for ant burrows were about eight
 times smaller than matrix K(s) of the bulk sandy soil. Such large
 decrease in K(s) is probably caused by infilling of burrow walls
 by ants with fine materials. Combining the macropore
 infiltrometer measurements with the model is a useful means of
 estimating the hydrological and geometrical parameters of ant and
 possibly earthworm burrows.
 NAL Call No.: 56.9-So3
 108. Nonpoint source (NPS) pollution modeling using models
 integrated with geographic information systems (GIS).
 Engel, B. A.; Srinivasan, R.; Arnold, J.; Rewerts, C.; Brown, S.
 Water-sci-technol v.28, p.685-690. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: pollution-; sources-; watersheds-; rain-;
 agricultural-chemicals; runoff-water; water-pollution;
 water-erosion; geographical-information-systems; models-; usa-;
 NAL Call No.: TD420.A1P7
 109. Nonpoint sources.
 Line, D. E.; Osmond, D. L.; Coffey, S. W.; Arnold, J. A.; Gale,
 J. A.; Spooner, J.; Jennings, G. D. 
 Water-environ-res v.66, p.585-601. (1994).
 Includes references.
 Descriptors: water-pollution; soil-pollution; water-quality;
 water-resources; pollutants-; pesticides-; biodegradation-;
 pollution-control; models-; monitoring-; literature-reviews
 NAL Call No.: TD419.R47
 110. Numerical approach to the overland flow process in
 vegetative filter strips.
 Munoz Carpena, R.; Parsons, J. E.; Gilliam, J. W. 
 Trans-ASAE v.36, p.761-770. (1993).
 Includes references.
 Descriptors: erosion-control; overland-flow; pollution-control;
 runoff-; sediment-; shelterbelts-; simulation-models;
 water-pollution; mathematical-models; north-carolina
 Abstract: Agricultural and other disturbed lands contribute to
 non-point source pollution of water bodies (streams and lakes).
 Vegetative filter strips (VFS) are often recommended to reduce
 off-site impacts. Design guidelines to optimize performance of
 VFS are not readily available. A process-based model is presented
 to simulate the hydrology of a Vegetative Filter Strip for a
 given event. The model consists of a quadratic finite element
 overland flow submodel, based on the kinematic wave
 approximation, coupled with an infiltration submodel based on a
 modification of the Green-Ampt equation for unsteady rainfall.
 The model is used to study the effect of soil type, stope,
 surface roughness, buffer length, storm pattern and field inflow
 on the VFS performance. Filter performance, i.e., reduction of
 the runoff volume, velocity and peak, is higher for denser grass
 cover, smaller slopes and soils with higher infiltration
 capacity. Time to peak(s) depended mainly on the roughness-slope
 NAL Call No.: 290.9-Am32T
 111. Observed and simulated transport of a conservative tracer
 under line-source irrigation.
 Comfort, S. D.; Inskeep, W. P.; Lockerman, R. H. 
 J-environ-qual v.22, p.554-561. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: solutes-; transport-processes; soil-water-regimes;
 irrigation-; soil-depth; simulation-models;
 agricultural-chemicals; silt-loam-soils; montana-; vadose-zone;
 Abstract: Although a number of solute transport models are
 currently available to predict the transport of agrichemicals in
 the vadose zone, validation of these models under field
 conditions has been limited. This study monitored the transport
 of a conservative tracer (Br-) under three water regimes (high,
 medium, and low) imposed by a line-source irrigation system and
 tested the validity of the simulation model, LEACHM, to predict
 Br- transport. In July 1990, RbBr was surface applied to 12
 uncropped columns at 56 kg Br- ha(-1). Four columns (0.203-m
 diam., 1.2-m length) were positioned in each water regime and
 equipped with soil solution samplers at .36-, 0.66-, and 0.96-m
 depths. Soil solution samples were taken 20 times over 80 d to
 monitor Br- transport. Cumulative water applied to each water
 regime, by irrigation and precipitation, ranged between 251 and
 458 mm. Results indicated dramatic differences in Br- transport
 among water regimes. Complete Br- breakthrough curves (with apex
 concentrations of approximately 60 mg Br- L(-1) were observed
 under high water regime at all depths whereas the majority of Br-
 applied to the low water regime remained at or near the 0.36-m
 depth. Inputs used to predict Br- transport in LEACHM simulations
 were either measured directly or estimated from experimental
 conditions. To simulate Br- transport for each water regime, we
 used three LEACHM input files, which reflected the variability of
 the soil profile water release retention coefficients. Results
 indicated that LEACHM's predictions of Br- concentration (at all
 depths and under all water regimes) differed from observed means
 by an average (n = 180) of 9.0 to 9.4 mg Br- L(-1) (approximately
 15-16% of the average apex concentrations). These results
 indicate that under the experimental system studied, LEACHM. 
 vadose zone.
 NAL Call No.: QH540.J6
 112. One-dimensional infiltration with moving finite elements and
 improved soil water diffusivity.
 Cox, C. L.; Jones, W. F.; Quisenberry, V. L.; Yo, F. 
 Water-resour-res v.30, p.1431-1438. (1994).
 Includes references.
 Descriptors: soil-water; solutes-; diffusivity-; infiltration-;
 transport-processes; mathematical-models; transport-models
 Abstract: A problem of significant interest to environmental
 scientists is the flow of water and solutes through the vadose
 zone. The partial differential equations which govern this flow
 are typically time-dependent and nonlinear. Valid solutions to
 these equations require (1) accurate relationships between
 various coefficients and variables on which they depend (e.g.,
 coefficient of diffusivity and water content) and (2)
 sophisticated numerical methods which can handle complexities
 such as sharp moving fronts. In cases where coefficients are not
 known explicitly, curve-fitting techniques are needed to smooth
 out scattered experimental data. Nonlinear coefficients can then
 be calculated. A constrained least squares spline fit is compared
 to empirical function fits which have appeared recently. Then, a
 state-of-the-art numerical technique is used to accurately model
 transient flow through unsaturated homogeneous soils. The moving
 finite element method of Miller and colleagues is an adaptive
 approach in the sense that the grid moves so that nodes are
 concentrated where they are most needed. As a result, better
 accuracy is achieved with fewer nodes than are required for
 standard fixed-grid methods. Petzold's robust Gear-type solver
 DASSL is used for time-integration. Numerical results are
 compared to experimental data. Mass balance errors are
 negligible, and accurate solutions are obtained at all time
 steps. Though only one-dimensional problems are considered here,
 the numerical approach generalizes to heterogeneous media and
 problems in higher dimensions.
 NAL Call No.: 292.8-W295
 113. Outdoor testing of the condensation characteristics of
 plastic film covering materials using a model greenhouse.
 Geoola, F.; Peiper, U. M.; Geoola, F. 
 J-agric-eng-res v.57, p.167-172. (1994).
 Includes references.
 Descriptors: greenhouses-; plastic-film; cladding-; field-tests;
 solar-radiation; light-transmission; condensation-; runoff-water;
 round-arch-greenhouses; transparency-loss; film-ageing
 NAL Call No.: 58.8-J82
 114. Parameter identification for a runoff model for forest
 Luce, C. H.; Cundy, T. W. 
 Water-resour-res v.30, p.1057-1069. (1994).
 Includes references.
 Descriptors: forests-; roads-; runoff-; erosion-; infiltration-;
 overland-flow; rain-; simulation-; algorithms-; idaho-;
 colorado-; montana-
 Abstract: Rainfall simulation is a commonly used approach for
 studying runoff and erosion from forest roads, and a method is
 needed to estimate infiltration parameters from these
 experiments.  We used two algorithms, the Simplex and Shuffled
 Complex Evolution, to estimate parameters for a physically based
 infiltration and overland flow model.  Each algorithm was tested
 by estimating parameters for 92 field-measured hydrographs from
 forest roads.  Nine of the field-measured hydrographs allowed us
 to further test whether estimated parameters could be extended to
 other antecedent conditions and plot sizes.  The results
 demonstrate (1) the physically based model is able to estimate
 hydrographs from forest roads, (2) the two algorithms find unique
 parameter sets in spite of an error surface that suggests
 identifiability problems between the hydraulic conductivity and
 pressure parameters, (3) the two algorithms converged to the same
 parameter values, and (4) that parameters estimated for one
 antecedent condition and plot size can be extended to others with
 reasonably mall error.
 NAL Call No.: 292.8-W295
 115. Pesticide leaching data to validate simulation models for
 registration purposes.
 Bergstrom, L.; Jarvis, N.; Stenstrom, J. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1073-1104.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: dichlorprop-; leaching-; sandy-soils; loam-soils;
 clay-soils; simulation-models; bentazone-
 NAL Call No.: TD172.J6
 116. Point/nonpoint source trading of pollution abatement:
 choosing the right trading ratio.
 Malik, A. S.; Letson, D.; Crutchfield, S. R. 
 Am-j-agric-econ v.75, p.959-967. (1993).
 Includes references.
 Descriptors: pollution-control; law-enforcement; costs-;
 water-quality; trading-; uncertainty-; mathematical-models;
 ratios-; usa-; abatement-costs
 Abstract: In programs for trading pollution abatement between
 point and nonpoint sources, the trading ratiospecifies the
 rate at which nonpoint source abatement can be substituted for
 point sourceabatement.  The appropriate value of this ratio is
 unclear because of qualitative differencesbetween the two
 classes of sources.  To identify the optimal trading ratio, we
 develop and analyzea model of point/nonpoint trading.  We find
 the optimal trading ratio depends on the relativecosts of
 enforcing point versus nonpoint reductions and on the uncertainty
 associated with  nonpoint loadings.  The uncertainty does not
 imply a lower bound for the optimal trading ratio.
 NAL Call No.: 280.8-J822
 117. Potassium and phosphorus uptake by competing pine and grass:
 observations and model verification.
 Smethurst, P. J.; Comerford, N. B. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Nov/Dec 1993. v. 57 (6) p. 1602-1610. 
 Includes references.
 Descriptors: pinus-elliottii; seedlings-; panicum-;
 plant-competition; interspecific-competition; potassium-;
 phosphorus-; nutrient-uptake; computer-simulation;
 simulation-models; root-systems; surface-area;
 transport-processes; soil-fertility; pinus-elliotii-var;
 -elliotii; panicum-aciculare
 Abstract: A computer model (COMP8) was recently presented that
 simulates nutrient uptake by competing andsingle root systems.
 However, the model needed independent verification. Our
 objectives here wereto: (i) determine if uptake by each
 species was a simple function of each species' root surface  
 area, and (ii) verify COMP8 for K and P uptake by slash pine
 (Pinus elliottii Engelm. var.elliottii) seedlings in
 competition with Panicum aciculare Desv. ex Poir. in Lam. grass
 plants.Pine and grass plants were grown together at low and
 high initial soil-solution concentrations.  Observed and
 predicted uptake values were compared by linear regression and by
 t tests using  variances predicted by Monte Carlo analysis. For
 high initial solution conditions, wequantitatively predicted
 pine uptake for all cases of P and for three of four cases for K.
 Grass Kuptake was accurately predicted in all three cases;
 however, none of the three cases of grassuptake of P were
 correct. For the low initial solution concentrations, only one
 case of pine andno cases of grass uptake were predicted
 accurately. For neither K nor P was uptake by pine(expressed
 as a percentage of that taken up by pine and grass combined) in a
 1:1 relationship withthe percentage of surface area in pine
 roots. We conclude that uptake by the competing rootsystems is
 not a simple function of their relative root surface areas and
 that COMP8 provides anadequate description of nutrient uptake
 by competing and contrasting root systems under certain.
 NAL Call No.: 56.9-So3
 118. A pragmatic field-scale approach for modeling pesticides.
 Hutson, J. L.; Wagenet, R. J. 
 J-environ-qual v.22, p.494-499. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: pesticides-; leaching-; soil-water-movement;
 Abstract: Environmental assessments of the fate of pesticides and
 other agricultural chemicals usually require estimation of
 chemical concentrations, with some indication of their accuracy.
 These estimations are usually based on a few measurements
 combined with existing data bases and predictive tools that
 include regression equations, empirical relationships, and
 simulation models. Comprehensive simulation models are attractive
 from a scientific standpoint, since they consider leaching of the
 chemical by water as well as the various chemical, biological,
 and physical processes that affect the chemical's fate during its
 transport. A number of simulation modeling approaches have been
 developed to describe soil-water-chemical systems, but a
 fundamental question remains regarding the degree of model
 complexity required to simulate agrochemical movement to
 groundwater. Most model complexity in soil-water-chemical
 simulation models arises from the manner in which water flow and
 chemical transport are considered. It is therefore logical,
 especially for management purposes, to consider alternative,
 pragmatic, and yet sufficiently accurate approaches to the
 description of water flow and chemical transport. Such approaches
 would require less characterization of soil hydraulic and
 physical/chemical properties and would reduce computation time. A
 method for such simplification and use is described, starting
 with LEACHP, a model based on the Richards and
 convection-dispersion equations. The resulting model is shown to
 be sufficiently accurate for many management decisions.
 NAL Call No.: QH540.J6
 119. Predicting attainable water quality using the ecoregional
 Schonter, R.; Novotny, V. 
 Water-sci-technol v.28, p.149-158. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: water-quality; body-water; protection-;
 integrated-systems; water-resources; water-management;
 ecosystems-; prediction-; models-; wisconsin-;
 NAL Call No.: TD420.A1P7
 120. Predicting bromide leaching under field conditions using
 slim and macro.
 Jabro, J. D.; Jemison, J. M. Jr.; Fox, R. H.; Fritton, D. D. 
 Soil-sci v.157, p.215-223. (1994).
 Includes references.
 Descriptors: agricultural-chemicals; leaching-; movement-in-soil;
 macropore-flow; simulation-models; computer-simulation;
 groundwater-pollution; risk-; prediction-; preferential-flow
 NAL Call No.: 56.8-So3
 121. Predicting spatial distributions of nitrate leaching in
 northeastern Colorado.
 Wylie, B. K.; Shaffer, M. J.; Brodahl, M. K.; Dubois, D.; Wagner,
 D. G. 
 J-soil-water-conserv v.49, p.288-293. (1994).
 Includes references.
 Descriptors: agricultural-land; nitrate-nitrogen; leaching-;
 spatial-distribution; groundwater-pollution; nitrate-;
 contamination-; prediction-; simulation-models;
 geographical-information-systems; point-sources; colorado-;
 NAL Call No.: 56.8-J822
 122. Predicting water yield from a mountain ash forest catchment
 using a terrain analysis based catchment model.
 Vertessy, R. A.; Hatton, T. J.; O'Shaughnessy, P. J.; Jayasuriya,
 M. D. A. 
 J-hydrol v.150, p.665-700. (1993).
 In the special issue: Water Issues in Forests Today / edited by
 E.M. O'Loughlin and F.X. Dunin.  November 22-26, 1992, Canberra,
 Descriptors: mountain-forests; eucalyptus-regnans; water-yield;
 simulation-models; catchment-hydrology; evapotranspiration-;
 water-balance; soil-water; interception-; runoff-; stream-flow;
 Abstract: The structure, capabilities and performance of a
 distributed parameter hydrologic model are described. The model,
 called Topog-Yield, permits a transient analysis of
 unsaturated-saturated flow and evapotranspiration to be performed
 across complex terrain using a one-dimensional framework. It is
 applied to a 0.32 km2 mountain ash (Eucalyptus regnans) forest
 catchment in the central Victorian highlands, Australia. We
 compare observed and predicted daily runoff values for the site
 over a continuous 12 year period (1972-1983) when the catchment
 vegetation was in an undisturbed climax condition. All input
 parameter values were based on published or measured data,
 although some variables were adjusted within the range of known
 variability to yield a best fit between predicted and observed
 streamflow in the first year of simulation, 1972. Although the
 model was 'calibrated' for the first year, all variables other
 than climatic inputs remained fixed for the following 11 years.
 Modelled and observed daily runoff values compare well throughout
 the period of simulation, despite a wide range of climatic
 conditions. When modelled daily runoff values were lumped on a
 monthly basis, the model was able to explain 87% of the variation
 in observed monthly streamflows over the 12 year period. Modelled
 annual runoff was within +/- 5% of observed values for 6 of the
 12 years of record. Annual runoff prediction errors exceeded +/-
 10% of observed values in only 2 of the 12 years. By the end of
 the 12 year simulation, the model had over-predicted runoff by
 less than 5%. Input data requirements and model results are
 discussed in the light of a preliminary sensitivity analysis.
 NAL Call No.: 292.8-J82
 123. Preferential transport of nitrate through soil columns
 containing root channels.
 Li, Y.; Ghodrati, M. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1994. v. 58 (3) p. 653-659. 
 Includes references.
 Descriptors: nitrate-; transport-processes; movement-in-soil;
 macropore-flow; root-channels; mathematical-models; comparisons-;
 Abstract: Preferential flow has been increasingly recognized as
 an important mechanism for water and solute transport.  The
 objectives of this study were to characterize transport of
 through root channels in uniformly packed soil columns and to
 compare three commonly used solute transport models in describing
 NO3 transport through the soil-root channel columns.  Root
 channels were created by growing corn (Zea mays L.) or alfalfa
 (Medicago sativa L.) in 0.6-m-long soil columns.  Transport of
 Was then systematically studied with each of these macropore
 systems at a range of fluxes (from 0.042K(sm) to 0.47K(sm), where
 K(sm) is the saturated hydraulic conductivity of the macroporous
 system).  A nonlinear least-squares program was used to fit the
 convection-dispersion equation (CDE), the physical nonequilibrium
 model (MIM) and a stochastic model (SM) to the experimental data. 
 The results show that significant preferential movement of NO3
 occurred in the decayed root channels at fluxes as low as
 0.042K(sm). The MIM model provided a better description of the
 breakthrough curves than the CDE and the SM, while none of them
 were adequate to predict the preferential movement of the solute.
 NAL Call No.: 56.9-So3
 124. Proceedings of the Symposium on Geographic Information
 Systems and Water Resources.
 Harlin, J. M.;  Lanfear, K. J.; Symposium on Geographic
 Information Systems and Water Resources (1993 : Mobile, A. 
 Bethesda, Md. : American Water Resources Association, c1993. xvi,
 640 p. : ill. (some col.), maps (some col.).
 Includes bibliographies and indexes.
 Descriptors: Geographic-information-systems; Water-supply-
 NAL Call No.: TC401.A5-no.93-1
 125. Progress in the understanding of runoff generation dynamics
 in forests.
 Bonell, M. 
 J-hydrol v.150, p.217-275. (1993).
 In the special issue: Water Issues in Forests Today / edited by
 E.M. O'Loughlin and F.X. Dunin.  November 22-26, 1992, Canberra,
 Descriptors: tropical-forests; runoff-; sloping-land;
 humid-tropics; hydrology-; research-; simulation-models;
 Abstract: This work reviews the runoff generation process in
 forests. A survey of the delivery mechanisms of hillslope runoff
 and the difficulties of incorporating some of them in recent
 physically based models is considered. The research challenge in
 reconciling the results from recent stream hydrogeochemistry
 studies with the results from previous hillslope hydrometric
 experiments is also highlighted. 'Physically based' runoff
 process models for application to forest land management problems
 are then summarised. The work concludes by proposing a new,
 intensive phase in experimental hydrology which should support
 the continued development of new algorithms in runoff process
 modelling. Particular attention should be given to tropical
 forests and the need for additional hillslope hydrology research
 to address the important issues associated with hillslope
 management and conversion.
 NAL Call No.: 292.8-J82
 126. A prototype shell for running field scale natural resource
 simulation models.
 Hernandez, M.; Heilman, P.; Lane, L. J.; Stone, J. J.; Abolt, J.
 A.; Masterson, J. E. II. 
 Application of advanced information technologies  effective
 management of natural resources  proceedings of the 18-19 June
 1993 Conference, Spokane, Washington /. St. Joseph, Mich. :
 American Society of Agricultural Engineers, c1993.. p. 142-149. 
 Includes references.
 Descriptors: water-quality; decision-making; simulation-models;
 interface-; design-; usda-; usa-; agricultural-research-service
 NAL Call No.: GE5.A66-1993
 127. Quantifying soil erosion for the Shihmen Reservoir
 watershed, Taiwan.
 Lo, K. F. A. 
 Agric-syst v.45, p.105-116. (1994).
 Includes references.
 Descriptors: watersheds-; erosion-; sediment-; nutrients-; flow-;
 transport-processes; sediment-yield; simulation-models; taiwan-;
 NAL Call No.: HD1.A3
 128. Real-time flood forecasting in mountainous river basins with
 long- and short-term runoff model.
 Islam, M. N.; Nagai, A.; Yomota, A. 
 J-irrig-eng-rural-plann p.48-66. (1994).
 Includes references.
 Descriptors: flooding-; runoff-; hydrological-data; filters-;
 simulation-; forecasting-; optimization-; models-;
 mountain-areas; comparisons-; japan-
 NAL Call No.: S671.J68
 129. Regional scale ground water quality monitoring : methods and
 case studies.
 Hudak, P. F.;  Loaiciga, H. A.;  Marino, M. A.; California Water
 Resources Center. 
 [Riverside, Calif.] : California Water Resources Center, 1993.
 xi, 74 p. : ill., maps.
 "April, 1993.".
 Descriptors: Water-quality-management-Mathematical-models;
 Water-quality-management-Case-studies; Ground-water-Quality
 NAL Call No.: GB705.C2C676--no.203
 130. Regulation of nitrogen pollution in agriculture.
 Johnson, S. R. 1.; United States Israel Binational Agricultural
 Research and Development Fund. 
 Bet Dagan, Israel : BARD, 1994. 223 leaves : ill..
 Final report.
 Descriptors: Nitrogen-fertilizers-Control-Mathematical-models
 NAL Call No.: S651.R43--1994
 131. Removing numerically induced dispersion from finite
 difference models for solute and water transport in unsaturated
 Moldrup, P.; Yamaguchi, T.; Rolston, D. E.; Vestergaard, K.;
 Hansen, J. A. 
 Soil-sci v.157, p.153-161. (1994).
 Includes references.
 Descriptors: solutes-; soil-water; transport-processes;
 simulation-models; mathematical-models; calculation-; errors-;
 correction-factors; calculation-schemes
 NAL Call No.: 56.8-So3
 132. Risk versus economic return in managing groundwater nitrate
 Adelman, D. H.; Dahab, M. F. 
 Water-sci-technol v.28, p.55-63. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: groundwater-pollution; nitrates-; farm-management;
 farming-; techniques-; prediction-; decision-making; models-;
 returns-; irrigated-farming; irrigation-water; utilization-;
 nitrogen-fertilizers; application-rates; nebraska-
 NAL Call No.: TD420.A1P7
 133. Root zone effects on tracer migration in arid zones.
 Tyler, S. W.; Walker, G. R. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Jan/Feb 1994. v. 58 (1) p. 25-31. 
 Paper presented at the Symposium on "Recharge in arid and
 semiarid regions," October 28-30, 1991, Denver, Colorado.
 Descriptors: groundwater-recharge; estimation-; soil-water;
 root-zone-flux; transport-processes; mathematical-models;
 arid-zones; tracer-techniques; errors-
 Abstract: The study of groundwater recharge and soil water
 movement in arid regions has received increased attention in the
 search for safe disposal sites for hazardous wastes. In passing
 through the upper 1 to 2 m of most soil profiles, tracers
 indicative of recharge such as Cl, 2H, 18O, Br, 3H, and 36Cl are
 subjected to a wide range of processes not encountered deeper in
 the profile. This transition zone, where water enters as
 precipitation and leaves as recharge, is often ignored when
 environmental tracers are used to estimate deep soil water flux
 and recharge, yet its effect may be profound. In this work, we
 reexamine the processes of root extraction and its effect on the
 velocity and distribution of tracers. Examples are presented for
 idealized conditions, which show clearly the relation between the
 root zone processes and the deep drainage or recharge. The
 results indicate that, when recharge is small and root zone
 processes are not accounted for, tracer techniques can
 significantly overestimate recharge until the tracer has moved
 well below the root zone. By incorporating simple models of root
 zone processes, a clearer understanding of tracer distributions
 and a more accurate estimate of recharge can then be made.
 NAL Call No.: 56.9-So3
 134. Runoff changes simulated using a rainfall-runoff model.
 Buchtele, J. 
 Water-resour-manag v.7, p.273-287. (1993).
 Includes references.
 Descriptors: runoff-; change-; rivers-; rain-; watersheds-;
 simulation-models; climatic-change; czechoslovakia-
 Abstract: The Sacramento rainfall-runoff model has been used in
 experiments with 60 year daily series for the Czech part of the
 Labe River basin; simulations with decreased and/or increased
 inputs (precipitations, air temperature, evapotranspiration)
 provide results that could be used to appraise the runoff changes
 due to climatic warming. Simulations with the modified parameters
 are used for evaluation of runoff changes caused by land-use
 changes. For both purposes, the long-term data sets appear to be
 desirable; it is then possible to take into account 'accidental'
 influences. The simulations also provide, as an output, the water
 contents in different zones of soil moisture; the relationships
 among evapotranspiration, soil moisture, and baseflow clearly
 appear in these results.
 NAL Call No.: TC401.W27
 135. Runoff hydrograph estimation using artificial neural
 Hjelmfelt, A. T. Jr.; Wang, M. 
 Application of advanced information technologies  effective
 management of natural resources  proceedings of the 18-19 June
 1993 Conference, Spokane, Washington /. St. Joseph, Mich. :
 American Society of Agricultural Engineers, c1993.. p. 315-320. 
 Includes references.
 Descriptors: runoff-; rain-; hydrology-; models-; prediction-;
 algorithms-; simulation-models; missouri-; rainfall-runoff-models
 NAL Call No.: GE5.A66-1993
 136. RUSLE model description and database sensitivity.
 Renard, K. G.; Ferreira, V. A. 
 J-environ-qual v.22, p.458-466. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: surface-water; water-quality; simulation-models;
 computer-software; revised-universal-soil-loss-equation-model
 Abstract: Water quality modeling generally requires estimates of
 the amount of eroded material entering water courses. This
 information is necessary because sediment often transports
 adsorbed chemicals. Numerous models have been developed to assist
 with assessment of this problem. These models often contain some
 modification of the Universal Soil Loss Equation (USLE). A
 recently initiated effort to improve USLE technology has produced
 a computer-based model, RUSLE (Revised USLE), which employs new
 relationships to estimate values of the six factors in the
 equation. Three input databases are
 NAL Call No.: QH540.J6
 137. Selection of herbicide alternatives based on probable
 leaching to groundwater.
 Franklin, R.; Quisenberry, V. L.; Gossett, B. J.; Murdock, E. C. 
 Weed-technol v.8, p.6-16. (1994).
 Includes references.
 Descriptors: water-quality; groundwater-pollution; herbicides-;
 leaching-; weed-control; chemical-control; coastal-plain-soils;
 movement-in-soil; estimation-; persistence-; prediction-;
 mathematical-models; south-carolina
 NAL Call No.: SB610.W39
 138. A semi-analytical solution for one-dimensional solute
 transport in soils.
 Yamaguchi, T.; Moldrup, P.; Rolston, D. E.; Peterson, L. W. 
 Soil-sci v.158, p.14-21. (1994).
 Includes references.
 Descriptors: solutes-; transport-processes; mathematical-models;
 NAL Call No.: 56.8-So3
 139. Similarity analysis of runoff generation processes in
 real-world catchments.
 Larsen, J. E.; Sivapalan, M.; Coles, N. A.; Linnet, P. E. 
 Water-resour-res v.30, p.1641-1652. (1994).
 Includes references.
 Descriptors: runoff-; watersheds-; agricultural-land;
 quantitative-analysis; prediction-; rain-; simulation-models;
 western-australia; rainfall-runoff-models;
 Abstract: This paper addresses the question of similarity of
 runoff generation processes between catchments in the eastern
 wheat belt of Western Australia, and the use of dimensionless
 parameterizations to quantify this similarity.  A spatially
 distributed rainfall-runoff model, simulating runoff generation
 by both the infiltration excess (Horton type) and saturation
 excess (Dunne type) mechanisms, was developed for catchments in
 the region.  Seven small experimental catchments, with
 field-measured soil hydraulic properties and topography, were
 used in the study.  Following on from the similarity theory
 developed by Sivapalan et al. (1987), a number of dimensionless
 similarity parameters were constructed using the field-measured
 soil and topographic properties, a characteristic length scale,
 and a characteristic flow velocity. The objective was to
 determine whether the dominant runoff generation mechanism on a
 catchment could be reliably predicted by these similarity
 parameters.  This was achieved through sensitivity analyses
 carried out with the rainfall-runoff model.  Two dimensionless
 parameters, K(*/0) and f*, were found to be critical for
 characterizing the similarity or dissimilarity of the runoff
 generation responses between the seven experimental catchments. 
 Within the assumptions of the analysis, two catchments in the
 wheat belt region can be considered to be hydrologically similar,
 in terms of their runoff responses, if K(*/0) and f* are
 identical in both catchments.  The dominant mechanism of runoff
 generation on any catchment can be reliably predicted, provided
 that the values of K(*/0) and f* are known.  A partial
 quantification of the Dunne diagram.  excess and saturation
 excess mechanisms, was achieved by artificially varying K(*/0)
 and f* in the rainfall-runoff model to explore the full range of
 possible runoff generation responses.
 NAL Call No.: 292.8-W295
 140. A simple energy budget algorithm for the snowmelt runoff
 Kustas, W. P.; Rango, A.; Uijlenhoet, R. 
 Water-resour-res v.30, p.1515-1527. (1994).
 Includes references.
 Descriptors: runoff-; meltwater-; energy-balance;
 solar-radiation; algorithms-; prediction-; simulation-models
 Abstract: The snowmelt runoff model (SRM) uses a degree-day
 approach for melting snow in a basin. A simple radiation
 component was combined with the degree-day approach (restricted
 degree-day method) in an effort to improve estimates of snowmelt
 and reduce the need to adjust the melt factor over the ablation
 season. A daily energy balance model was formulated that requires
 not only the input of radiation but also measurements of daily
 wind speed, air temperature, and relative humidity. The three
 approaches for computing snowmelt, namely, the degree-day,
 restricted degree-day, and daily energy balance model were tested
 at the local scale by comparing melt rates with lysimeter outflow
 measurements. Because radiation measurements are not often
 available, a simple model for simulating shortwave and longwave
 components of the radiation balance that requires minimal
 information (i.e., daily cloud cover estimates, air temperature,
 and relative humidity) was developed. It was found that clouds
 and their effects on daily insolation at the surface can produce
 significant differences between measured and model estimates. In
 the comparisons of snowmelt estimates with the lysimeter outflow,
 the restricted degree-day method yielded melt rates that were in
 better agreement with the observed outflow than the degree-day
 method and were practically the same as estimates given by the
 energy balance model. A sensitivity analysis of runoff generated
 with SRM using as input the local snowmelt computations given by
 the three models and measured outflow from the lysimeter was
 performed for a basin. A comparison of the synthetic hydrographs
 for the basin suggests that a radiation-based snowmelt factor may
 improve runoff predictions at the basin scale.
 NAL Call No.: 292.8-W295
 141. Simulating acidification and recovery processes in
 experimental catchments with the ILWAS model.
 Eary, L. E.; Jenne, E. A.; Vail, L. W. 
 Water-air-soil-pollut v.74, p.29-63. (1994).
 Includes references.
 Descriptors: acid-deposition; acidification-; watersheds-;
 soil-chemistry; simulation-models; mathematical-models;
 discharge-; cations-; ion-exchange; surface-water; water-quality;
 cation-exchange-capacity; norway-; base-cations; deacidification-
 NAL Call No.: TD172.W36
 142. Simulating funnel-type preferential flow and overall flow
 property induced by multiple soil layers.
 Ju, S. H.; Kung, K. J. S. 
 J-environ-qual v.22, p.432-442. (1993).
 Paper presented at the USDA-ARS Beltsville Agricultural Research
 Center Symposium XVII, "Agricultural Water Quality Priorities, A
 Team Approach to Conserving Natural Resources," May 4-8, 1992,
 Beltsville, MD.
 Descriptors: sandy-soils; soil-water-movement; unsaturated-flow;
 transport-processes; mathematical-models; simulation-models
 Abstract: Funnel-type preferential flow was observed in
 Plainfield sand (sandy, mixed, mesic Typic Udipsamment) of
 central Wisconsin. The objective of this paper was (i) to develop
 a numerical model based on the Rich. ards equation and finite
 element scheme to simulate this preferential flow in a soil
 profile with inclined layers, and (ii) to determine flow
 properties in a soil with funnel-type preferential paths. The
 model was first validated by testing against two-dimensional
 (2-D) laboratory results and then used to simulate water flow
 patterns in hypothetical 2D soil profiles made of medium sand
 with multiple randomly distribution inclined coarse layers. The
 following results were found from the numerical experiments: (i)
 funnel-type preferential flow paths could be deterministically
 simulated if soil layering structure, hydraulic conductivity of
 the overall profile, and threshold potential of the embedded
 coarse layers were known; (ii) distribution of the vertical
 component of flux was determined by the funneling effect along
 the upper coarse sand leases. The lenses located in deeper parts
 of the profile would only influence macrotortuosity of the
 preferential flow paths; (iii) funnel-type preferential flow
 paths were determined not only by soil structures and textures
 but also by water application rate; and (iv) although funnel-type
 preferential paths were very complex, the vertical component of
 flux could be very simply described by two stochastic
 parameters-the mean and standard deviation of a log-normal
 distribution after the.
 NAL Call No.: QH540.J6
 143. Simulating nutrient uptake by single or competing and
 contrasting root systems.
 Smethurst, P. J.; Comerford, N. B. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Sept/Oct 1993. v. 57 (5) p. 1361-1367. 
 Includes references.
 Descriptors: nutrient-uptake; root-systems;
 interspecific-competition; simulation-models;
 computer-techniques; mathematical-models; solutes-;
 Abstract: Simulation of nutrient uptake by competing root systems
 is necessary to assist in the quantitativeunderstanding of
 these processes, to predict the consequences of competition for
 nutrients, and toprioritize future research on the mechanisms
 of nutrient competition. Our objective was to applypreviously
 published concepts to a computer model based on solute transport
 theory that would havethe ability to simulate nutrient uptake
 by root systems of one or two competing plant species.  
 Analytical solutions were used for calculating the volume of soil
 allocated to each root systemand the concentrations of solute
 at the root surfaces. We included in the model (i) a depletion  
 zone that increased with time until it reached the no-transfer
 boundary, (ii) an adjustment of theaverage concentration in
 the depletion zone to account for newly encountered solute as the
 zoneincreased in radius, (iii) a variable root-absorbing power
 (alpha), and (iv) a routine tocorrectly account for all soil
 in simulations with two contrasting root systems. Predicted
 uptakefor single-species scenarios in soils of contrasting
 nutrient supply characteristics was verifiedagainst that
 predicted by the commonly used Barber-Cushman model, NUTRIENT
 UPTAKE (maximumdiscrepancy was 23%), which utilizes a
 numerical solution. The ratio of uptakes predicted by both  
 models was a function of c4 root radius, effective-diffusion
 coefficient, and buffer power in amore complex way than
 previously suggested in the literature. Sensitivity analysis
 indicated that.  elliottii) relative to  competing grass would be
 most sensitive to variations in root-length density of the grass,
 or insoil water content, if only soil parameters were
 NAL Call No.: 56.9-So3
 144. Simulation by NCSWAP of seasonal nitrogen dynamics in corn.
 I. Soil nitrate.
 Lengnick, L. L.; Fox, R. H. 
 Agron-j v.86, p.167-175. (1994).
 Includes references.
 Descriptors: zea-mays; computer-simulation; calibration-;
 simulation-models; nitrogen-cycle; cycling-; carbon-;
 soil-fertility; nitrates-; seasonal-variation; leaching-;
 soil-water-movement; soil-structure; soil-morphological-features;
 agricultural-soils; edaphic-factors; organic-fertilizers;
 pennsylvania-; inorganic-fertilizers
 Abstract: Computer simulation models of crop-soil systems offer
 the potential to increase understanding of soil N cycle
 processes, thereby improving management of N resources in
 agricultural systems. NCSWAP (Nitrogen, Carbon, Soil, Water, And
 Plant) is a comprehensive, deterministic computer model of the
 plant-soil system that simulates seasonal soil C and N cycles
 under the control of temperature, moisture, microbial activity,
 and crop growth. The objective of this study was to validate
 NCSWAP using data collected during a 3-yr N-rate study in central
 Pennsylvania that investigated seasonal N dynamics in corn (Zea
 mays L.) provided with N as liquid dairy manure or as NH4NO3.
 Seasonal soil NO3 concentration in the upper soil layer, seasonal
 aboveground N accumulation by corn, and water leached past 1.2 m
 during the second year of the study were used to calibrate input
 values controlling soil water flow and NO3 production from
 mineralization of soil organic N sources. The validation of
 NCSWAP identified several limitations in the water flow and C and
 N cycling submodels as well as in the potential of the model to
 simulate seasonal N dynamics in corn. Validation simulations were
 about as accurate as calibration simulations, reflecting the
 ability of the model to simulate C and N dynamics without
 recalibration from year to year. Much of the simulation error was
 related to an overestimation of NO3 leaching caused by the
 inability of the model's microporous flow submodel to simulate
 the macropore-influenced water flow in the well-structured soil
 used in the validation.
 NAL Call No.: 4-AM34P
 145. Simulation models, GIS and nonpoint--source pollution:
 January 1991-December 1993.
 Makuch, J.; Emmert, B. 
 Quick-bibliogr-ser. Beltsville, Md., National Agricultural
 Library. Feb 1994. (94-06)  78 p. 
 Updates QB 92-69.
 Descriptors: simulation-models; agricultural-chemicals;
 water-quality; bibliographies-
 NAL Call No.: aZ5071.N3
 146. Simulation of bentazon leaching in sandy loam soil from
 Mellby (Sweden) with the PESTLA model.
 Boesten, J. J. T. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1231-1253.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: bentazone-; leaching-; sandy-loam-soils; soil-water;
 water-flow; drainage-water; evapotranspiration-; sorption-;
 NAL Call No.: TD172.J6
 147. Simulation of dichlorprop and betazon leaching in soils of
 contrasting texture using the MACRO model.
 Jarvis, N. J.; Stahli, M.; Bergstrom, L.; Johnsson, H. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1255-1277.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: dichlorprop-; bentazone-; leaching-;
 transport-processes; soil-water; water-flow; solutes-;
 soil-texture; macropore-flow; soil-water-balance
 NAL Call No.: TD172.J6
 148. Simulation of dichlorprop leaching in three texturally
 distinct soils using the pesticide leaching model.
 Hall, D. G. M. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1211-1230.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: dichlorprop-; leaching-; simulation-models;
 macropores-; transport-processes; sandy-loam-soils; silty-soils;
 clay-soils; clay-loam-soils
 NAL Call No.: TD172.J6
 149. Simulation of simazine transport through soil columns using
 time-dependent sorption data measured under flow conditions.
 Kookana, R. S.; Schuller, R. D.; Aylmore, L. A. G. 
 J-contam-hydrol v.14, p.93-115. (1993).
 Includes references.
 Descriptors: soil-pollution; simazine-; transport-processes;
 sandy-soils; flow-; sorption-; simulation-models
 NAL Call No.: TD426.J68
 150. Simulation of the movement of bentazon in soils using the
 CALF and PRZM models.
 Nicholls, P. H. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1157-1166.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: bentazone-; leaching-; simulation-models;
 pesticide-residues; flow-; leachates-; estimation-
 NAL Call No.: TD172.J6
 151. Simulation of the water management system of a peach canning
 Mate, J. I.; Singh, R. P. 
 Comput-electron-agric v.9, p.301-317. (1993).
 Includes references.
 Descriptors: water-use-efficiency; recycling-; peaches-;
 canning-; water-management; simulation-models; water-systems;
 structural-design; water-flow; water-conservation;
 mathematical-models; computer-software; water-quality;
 water-reuse; extendtm-computer-software
 NAL Call No.: S494.5.D3C652
 152. Soil conservation in Cuba: a key to the new model for
 Gersper, P. L.; Rodriguez Barbosa, C. S.; Orlando, L. F. 
 Agric-human-values v.10, p.16-23. (1993).
 In the special issue: Low-input sustainable agriculture in Cuba /
 edited by J.A. Carney.
 Descriptors: low-input-agriculture; sustainability-;
 soil-conservation; soil-fertility; tillage-; fertilizers-;
 nitrogen-fixing-bacteria; green-manures; rotations-;
 intercropping-; vermicomposting-; agricultural-wastes;
 recycling-; animal-production; cuba-
 NAL Call No.: HT401.A36
 153. Soil conservation planning at the watershed level using the
 Universal Soil Loss Equation with GIS and microcomputer
 technologies: a case study.
 Mellerowica, K. T.; Rees, H. W.; Chow, T. L.; Ghanem, I. 
 J-soil-water-conserv v.49, p.194-200. (1994).
 Includes references.
 Descriptors: agricultural-land; watersheds-; water-erosion;
 risk-; universal-soil-loss-equation;
 geographical-information-systems; mapping-; computer-techniques;
 soil-conservation; erosion-control; regional-planning;
 land-resources; new-brunswick
 NAL Call No.: 56.8-J822
 154. Soil moisture and runoff simulations using four catchment
 rainfall-runoff models.
 Hughes, D. A. 
 J-hydrol v.158, p.381-404. (1994).
 Includes references.
 Descriptors: soil-water; runoff-; rain-; soil-depth; watersheds-;
 grasslands-; catchment-hydrology; deterministic-models;
 variation-; accuracy-
 Abstract: Four deterministic rainfall-runoff models are briefly
 described and applied to a small (0.18 km2) grassland catchment
 in the Eastern Cape Province of South Africa. The models vary in
 complexity, from a variable time step model with two soil layers
 and incorporating probability distribution principles for some of
 the parameters, through two daily time step models, to a
 relatively simple, but widely used, monthly time step model. The
 model parameters have largely been determined from measured
 physical characteristics (topography, soils, vegetation, etc.) of
 the catchment and not through calibration. As well as comparing
 the simulated runoff values, the model performances are compared
 using observed values of soil moisture measured over a period of
 some 29 months. Although the four models produce similar results,
 the variable time step model simulates the observed soil moisture
 variation most successfully and the monthly model least
 successfully. Most of the differenes in the simulation results
 can be explained by either the differences in complexity of the
 modelling approach or the resolution of the input data.
 NAL Call No.: 292.8-J82
 155. Soil nitrate leaching potential indices: using a simulation
 model as a screening system.
 Khakural, B. R.; Robert, P. C. 
 J-environ-qual v.22, p.839-845. (1993).
 Includes references.
 Descriptors: nitrate-nitrogen; leaching-; losses-from-soil;
 simulation-models; groundwater-pollution; minnesota-
 Abstract: Simulation models LEACHM-N (Leaching Estimation and
 Chemistry Model) and NLEAP (Nitrate Leachingand Economic
 Analysis Package) were first tested using NO3 leaching data
 obtained from lysimeterand tile drainage studies conducted at
 three University of Minnesota experiment stations. Both  
 simulation models did well in simulating total (seasonally
 accumulated) leaching loss of NO3-Nfrom the soil profile.
 LEACHM-N was selected as a screening took to develop soil NO3
 leachingpotential (NLP) ratings using soil survey information
 and representative county weather stationdata. Simulated
 growing season total NO3-N leached from the soil profile (below
 1.5 m) were usedas NLP index. Crop management practices and
 initial N were kept constant. Soil NO3 leachingpotential
 ratings for three Minnesota counties, Redwood, Stearns, and
 Sherburne were developed  using this method. This soil NLP rating
 information was included in the Soil Survey InformationSystem
 (SSIS) to create leaching potential rating maps, which can be
 used to plan best Nmanagement schemes.
 NAL Call No.: QH540.J6
 156. A solute transport model for the acid leaching of copper in
 soil columns.
 Montero, J. P.; Munoz, J. F.; Abeliuk, R.; Vauclin, M. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1994. v. 58 (3) p. 678-686. 
 Includes references.
 Descriptors: solutes-; transport-processes; movement-in-soil;
 copper-; leaching-; acid-treatment; sulfuric-acid; convection-;
 dispersion-; mass-transfer; mathematical-models; mining-;
 technology-; solution-mining-technology
 Abstract: Modeling solution mining technique has recently
 received much attention in order to estimate metal recovery
 rates.  We studied the acid leaching of Cu minerals found in mine
 tailings using a mathematical transport model and tab-scale
 experiments on both batches and saturated soil columns.  The
 model is a one-dimensional macroscopic solute transport model
 that considers simultaneously (i) the convection, dispersion, and
 consumption of H2SO4, and (ii) the convection, dispersion,
 solubilization, and adsorption-desorption of Cu. Time-dependent
 batch experiments were carried out to understand the relationship
 between H2SO4 Consumption and Cu extraction in tailing Cu
 materials under stagnant conditions.  Additionally,
 miscible-displacement experiments were conducted to obtain
 empirical data on Cu recovery in saturated soil columns that
 receive a constant pulse of H2SO4 and were designed to check the
 model's capability to simulate the transport phenomena.  This was
 done by estimating the model parameters independently from the
 batch experiments.  Since some findings from both experiments
 were consistent with each other, modeling assumptions, such as a
 second-order kinetic relationship for Cu dissolution (by H2SO4)
 and a first-order equilibrium isotherm for Cu, were appropriate
 in order to simulate the Cu recovery concentration at the outlet
 of each column.  Finally, model equations were solved using
 finite differences and analytical solutions for Cu and H2SO4
 transport equations, respectively, and model parameters were
 estimated using least squares techniques.
 NAL Call No.: 56.9-So3
 157. Spatial and qualitative reasoning for modeling physical
 Vieu, L.; Martin Clouaire, R. 
 AI-appl v.8, p.61-74. (1994).
 Includes references.
 Descriptors: erosion-; simulation-; models-; watersheds-; rain-;
 NAL Call No.: QA76.76.E95A5
 158. Statistical water quality modelling for urban runoff control
 Li, J. Y.; Adams, B. J. 
 Water-sci-technol v.29, p.181-190. (1994).
 Selected Proceedings of the 6th International Conference on Urban
 Storm Drainage, September 12-17, 1993, Niagara Falls, Canada /
 edited by J.C. Marsalek and H.C. Torno.
 Descriptors: runoff-water; water-quality; urban-areas;
 probabilistic-models; simulation-models; urban-planning
 NAL Call No.: TD420.A1P7
 159. Streamlines for diffusive flow in vertical and surface
 tillage: a model study.
 Kirkham, M. B. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Jan/Feb 1994. v. 58 (1) p. 85-93. 
 Includes references.
 Descriptors: soil-air; air-flow; flow-to-roots; oxygen-;
 diffusion-; transport-processes; horizontal-flow;
 mathematical-models; chiselling-; vertical-flow;
 vertically-tilled; hortizontally-tilled
 Abstract: Methods of tillage must permit adequate flow of O2 to
 plant roots. The objective of this work is to calculate
 streamlines of O2 flow from chisel holes oriented vertically and
 horizontally (surface tillage) in the soil to plant roots.
 Streamlines are perpendicular to equipotential lines. They also
 have the property that the difference in value between two
 streamlines gives the quantity of fluid (in this case, O2)
 flowing between them. Therefore, streamlines are often more
 important than equipotentials. Streamlines for flow of O2 from
 the chisel holes in the soil to plant roots were calculated by
 use of the relaxation method, in which both a coarse grid (2.54
 cm on a side) and a fine grid (1.27 cm on a side) were used.
 Transit times were calculated from the flownet resulting from the
 streamlines and equipotential lines. Calculations with the coarse
 grid showed that, for the vertical chisel case, 75% of the flow
 goes out of the side of the chisel opening closest to the sheet
 of plant roots and 25% of the flow goes out of the side of the
 chisel opening farthest away from the sheet of plant roots; for
 the fine grid, the values are 63 and 37% for the two sides of the
 chisel hole, respectively. For both the vertically and
 horizontally tilled cases, stagnant areas were identified in the
 soil. Transit times were short for both tillage cases on the
 order of minutes), confirming the general assumption that
 diffusion is the major mechanism of gas transport in soil.
 NAL Call No.: 56.9-So3
 160. Sweet corn response to combined effects of saline water and
 nitrogen fertilization.
 Beltrao, J.; Asher, J. B.; Magnusson, D. 
 Acta-hortic p.53-58. (1993).
 Paper presented at the International Symposium on Irrigation of
 Horticultural Crops, November 23-27, 1992, Almeria, Spain.
 Descriptors: zea-mays; sweetcorn-; irrigation-; saline-water;
 nitrogen-fertilizers; crop-yield; dynamic-models;
 simulation-models; salts-; leaching-; wilting-point; israel-
 NAL Call No.: 80-Ac82
 161. Tennessee's NPS cost-share funds available for ag.
 Water-prot-conserv-manage v.6, p.2. (1993).
 Descriptors: water-quality; water-pollution; pollution-control;
 funds-; tennessee-
 NAL Call No.: TD424.35.T2W37
 162. Toxicity and estimated water quality criteria values in
 mallard ducklings exposed to pentachlorophenol.
 Nebeker, A. V.; Griffis, W. L.; Schuytema, G. S. 
 Arch-environ-contam-toxicol. New York, Springer-Verlag. Jan 1994.
 v. 26 (1) p. 33-36. 
 Includes references.
 Descriptors: pentachlorophenol-; feeding-; anas-platyrhynchos;
 toxicity-; tissues-; concentration-; water-pollution;
 threshold-models; bioaccumulation-
 NAL Call No.: TD172.A7
 163. Translocation of alpha-sarcin across the lipid bilayer of
 asolectin vesicles.
 Onaderra, M.; Mancheno, J. M.; Gasset, M.; Lacadena, J.; Schiavo,
 G.; Martinez del Pozo, A.; Gavilanes, J. G. 
 Biochem-j v.295, p.221-225. (1993).
 Includes references.
 Descriptors: aspergillus-; proteins-; mycotoxins-; liposomes-;
 membranes-; models-; transport-processes; glycine-max
 Abstract: alpha-Sarcin is a cytotoxic protein produced by the
 mould Aspergillus giganteus. Insertion of alpha-sarcin into
 asolectin membranes has been demonstrated by protein labelling
 with photoreactive phospholipids. alpha-Sarcin added externally
 to tRNA-containing asolectin liposomes degrades the entrapped
 tRNA. Trypsin-containing asolectin liposomes were also prepared.
 Encapsulated trypsin degrades alpha-sarcin, even in the presence
 of a large excess of external hen egg-white trypsin inhibitor to
 prevent any alpha-sarcin degradation outside the vesicles. These
 processes occur only with acidic phospholipids and were not
 observed when phosphatidylcholine vesicles were used. These
 results indicate that alpha-sarcin penetrates the lipid bilayer
 and becomes exposed to the lumen of negatively charged liposomes.
 NAL Call No.: QP501.B64
 164. Two-dimensional transport model for variably saturated
 porous media with major ion chemistry.
 Simunek, J.; Suarez, D. L. 
 Water-resour-res v.30, p.1115-1133. (1994).
 Includes references.
 Descriptors: porous-media; transport-processes; models-;
 transient-flow; two-dimensional-flow; solutes-; ions-;
 soil-chemistry; subsurface-irrigation; surface-irrigation
 Abstract: We present the development and demonstrate the use of
 the two-dimensional finite element code UNSATCHEM-2D for modeling
 major ion equilibrium and kinetic nonequilibrium chemistry in
 variably saturated porous media.  The model is intended for
 prediction of major ion chemistry and water and solute fluxes for
 soils under transient conditions.  Since the solution chemistry
 in the unsaturated zone is significantly influenced by variations
 in water content, temperature, and CO2 concentrations in the soil
 gas, all these variables are also calculated by the model.  The
 major variables of the chemical system are Ca, Mg, Na, K, SO4,
 Cl, NO3, alkalinity, and CO2. The model accounts for equilibrium
 chemical reactions between these components such as complexation,
 cation exchange, and precipitation-dissolution.  For the
 precipitation-dissolution of calcite and dissolution of dolomite,
 either equilibrium or multicomponent kinetic expressions are used
 which include both forward and back reactions.  Other
 dissolution-precipitation reactions considered include gypsum,
 hydromagnesite, and nesquehonite.  Since the ionic strength of
 soil solutions can often reach high values, both modified
 Debye-Huckel and Pitzer expressions were incorporated into the
 model to calculate single ion activities.  The need for an
 iterative coupling procedure between the solute transport and
 chemical modules is demonstrated with an example which considers
 root water uptake and irrigation using moderately saline water. 
 The utility of the model is further illustrated with
 two-dimensional simulations with surface and subsurface
 irrigation from a line source.
 NAL Call No.: 292.8-W295
 165. Uncalibrated performance of the finite element storm
 hydrograph model.
 Hession, W. C.; Shanholtz, V. O.; Mostaghimi, S.; Dilaha, T. A. 
 Trans-ASAE v.37, p.777-783. (1994).
 Includes references.
 Descriptors: erosion-; runoff-water; simulation-models;
 Abstract: The capability of the Finite Element Storm Hydrograph
 Model (FESHM) to simulate runoff events in an ungaged context was
 evaluated using data from an experimental watershed. The FESHM
 was used to simulate 30 runoff events over a 17-year period of
 record. The results from these simulations were evaluated using
 various statistical analyses. Regression methodology then was
 used to assess expected error and model bias. Runoff volumes were
 simulated more closely than peak flows. The model simulated
 runoff volume adequately for site-specific and screening
 analysis, but peak flow estimates were adequate only for
 screening purposes. The relationship of predicted to observed
 peak flows was found to be linear with low peaks being
 underpredicted and higher peak flows overpredicted. Although the
 runoff volume regression line was close to the desired equal
 value line, scatter or variance was great and no linear
 relationship was evident. Peak flow and volume simulation errors
 were related to rainfall intensity. These simulation biases are
 likely due to a combination of inadequate representation of the
 infiltration process by the model and inappropriate input
 parameters. A resolution of these biases and corrective action
 was beyond the scope of this study. However, a starting point is
 provided for future model investigations or modifications.
 Finally, it appears that some form of calibration is needed to
 use the FESHM with confidence.
 NAL Call No.: 290.9-Am32T
 166. Urban storm drainage : selected proceedings of the 6th
 International Conference on Urban Storm Drainage, held in Niagara
 Falls, Canada, 12-17 September 1993. 1st ed.
 Marsalek, J. 1.;  Torno, H. C.; International Conference on Urban
 Storm Drainage (6th : 1993 : Niagara Falls, C. 
 Oxford ; New York : Pergamon Press, 1994. x, 465 p. : ill., maps.
 "Organized by International Association on Water Quality (IWAQ)
 [and] International Association on Hydraulics Research
 (IAHR)"--P. facing t.p.
 Descriptors: Urban-runoff-Mathematical-models-Congresses;
 Storm-sewers-Congresses; Drainage-Congresses;
 NAL Call No.: TD420.A1P7--v.29-no.1-2
 167. Use of a rainfall-runoff model for simulating effects of
 forest management on streamflow in the east fork Lobster Creek
 Basin, Oregon.  Use of a rainfall runoff model for simulating
 effects of forest management on streamflow.
 Nakama, L. Y.;  Risley, J. C.; Geological Survey (U.S.). 
 Portland, Or. : U.S. Geological Survey ; Denver, CO : Earth
 Science Information Center, Open-File Reports Section
 [distributor], 1993. iv, 40 p. : ill., maps.
 Shipping list.: 93-653-P.
 Descriptors: Rain-and-rainfall-Oregon-Mathematical-models;
 NAL Call No.: GB701.W375--no.93-4040
 168. Use of GIS to rank counties for potential groundwater
 Smith, P. A.; Scott, H. D. 
 Ark-farm-res v.42, p.4-5. (1993).
 Includes references.
 Descriptors: information-systems; groundwater-;
 groundwater-pollution; monitoring-; probabilistic-models;
 pesticides-; prediction-; arkansas-;
 NAL Call No.: 100-Ar42F
 169. The use of pesticide leaching models in a regulatory
 setting: an industrial perspective.
 Russell, M. H.; Layton, R. J.; Tillotson, P. M. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1105-1116.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: pesticides-; leaching-; simulation-models;
 registration-; regulatory-issues
 NAL Call No.: TD172.J6
 170. Use of simulation models for registration purposes:
 evaluation of pesticide leaching to groundwater in the
 Brouwer, W. W. M. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A29, p.1117-1132.
 Special Issue on the Evaluation and Comparison of Pesticide
 Descriptors: pesticide-residues; leaching-;
 groundwater-pollution; netherlands-
 NAL Call No.: TD172.J6
 171. Use of the EPIC model to predict runoff transport of
 surface-appled inorganic fertilizer and poultry manure
 Edwards, D. R.; Benson, V. W.; Williams, J. R.; Daniel, T. C.;
 Lemunyon, J.; Gilbert, R. G. 
 Trans-ASAE v.37, p.403-409. (1994).
 Includes references.
 Descriptors: pastures-; fertilizers-; poultry-manure; runoff-;
 simulation-models; water-quality; arkansas-;
 Abstract: The Erosion Productivity Impact Calculator (EPIC) model
 was applied to four fields established in "tall" fescue (Festuca
 arundinacea Schreb.) in northwestern Arkansas to predict runoff
 and transport of nitrogen, phosphorus, and sediment. Fertilizer
 form varied among the fields with two receiving inorganic
 fertilizer, one receiving poultry (Gallus domesticus) litter, and
 one receiving poultry manure. Soil and grazing parameters also
 differed among fields. Runoff and nutrient/sediment transport
 observed over 20 months were compared to EPIC predictions
 generated without calibration. Significant correlation between
 event predictions and observations were found in half the cases.
 There was significant correlation between observed and predicted
 calendar year total transport for all outputs except
 nitrate-nitrogen. The findings indicate that EPIC can accurately
 reflect runoff quality trends when executed without calibration
 for pasture fields in northwestern Arkansas.
 NAL Call No.: 290.9-Am32T
 172. Use of the gleams model to estimate pesticide overland and
 subsurface transport in USDA Forest Service nursery applications.
 Craig, J. P.; Weiss, R. C. 
 Water-sci-technol v.28, p.425-429. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: surface-water; water-systems; water-pollution;
 pesticides-; concentration-; usda-; forest-nurseries;
 drainage-water; models-; mississippi-; idaho-; michigan-;
 NAL Call No.: TD420.A1P7
 173. Using GLEAMS to evaluate the agricultural waste application
 rule-based decision support (AWARDS) computer program.
 Ford, D. A.; Kruzic, A. P.; Doneker, R. L. 
 Water-sci-technol v.28, p.625-634. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: agricultural-wastes; application-to-land;
 computer-software; pollutants-; loads-; water-pollution;
 simulation-models; groundwater-pollution; surface-water;
 NAL Call No.: TD420.A1P7
 174. Using the CREAMS pesticides transfer sub-model at a rainfall
 simulation scale.
 Gouy, V.; Belamie, R. 
 Water-sci-technol v.28, p.679-683. (1993).
 Paper presented at the IAWQ First International Conference on
 "Diffuse (Nonpoint) Pollution: Sources, Prevention, Impact,
 Abatement." September 19-24, 1993, Chicago, Illinois.
 Descriptors: runoff-water; water-pollution; pesticides-;
 rainfall-simulators; concentration-; prediction-; models-
 NAL Call No.: TD420.A1P7
 175. Validation of AGNPS for small watersheds using an integrated
 AGNPS/GIS system.
 Mitchell, J. K.; Engel, B. A.; Srinivasan, R.; Wang, S. S. Y. 
 Water-resour-bull v.29, p.833-842. (1993).
 Includes references.
 Descriptors: watersheds-; pollution-; runoff-; sediment-;
 erosion-; catchment-hydrology; simulation-models;
 geographical-information-systems; integrated-systems;
 topography-; illinois-; agricultural-nonpoint-source
 Abstract: The AGNPS (Agricultural NonPoint Source) model was
 evaluated for predicting runoff and sedimentdelivery from
 small watersheds of mild topography. Fifty sediment yield events
 were monitored fromtwo watersheds and five nested
 subwatersheds in East Central Illinois throughout the growing  
 season of four years. Half of these events were used to calibrate
 parameters in the AGNPS model.Average calibrated parameters
 were used as input for the remaining events to obtain runoff and 
 sediment yield data. These data were used to evaluate the
 suitability of the AGNPS model forpredicting runoff and
 sediment yield from small, mild-sloped watersheds. An integrated
 AGNPS/GIS  necessary to thisstudy. This system is one where
 the AGNPS model was integrated with the GRASS (Geographic  
 Resources Analysis Support System) GIS (Geographical Information
 System) to develop a decisionsupport tool to assist with
 management of runoff and erosion from agricultural watersheds.
 The  running the model,and interpretation of the results.
 NAL Call No.: 292.9-Am34
 176. Water pollution II : modelling, measuring, and prediction.
 Brebbia, C. A.;  Wrobel, L. C. L. C. 1.; International Conference
 on Water Pollution: Modelling, M. a. P. 2. 1. M. I. 
 Southampton ; Boston : Computational Mechanics Publications,
 c1993. 739 p. : ill..
 "Contains the proceedings of the Second International Conference
 on Water Pollution held in June 1993, Milan, Italy"--P. [4] of
 Descriptors: Water-Pollution-Congresses;
 Water-Pollution-Measurement-Congresses; Water-quality-Congresses;
 NAL Call No.: TD419.5.W365--1993

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