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

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

 November, 1994-September, 1995
 196 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. Adaptive modified method of characteristics to solve the
 one-dimensional solute transport equation.
 Lui, H. H.; Dane, J. H.; Guven, O. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1995. v. 59 (3) p. 677-683. 
 Includes references.
 Descriptors: solutes-; movement-in-soil; transport-processes;
 dispersion-; equations-; mathematical-models; simulation-models;
 Abstract: Simulation of advection-dominated solute transport in a
 porous medium is complicated due to the inherent problems of
 numerical dispersion and oscillation. We propose an adaptive
 modified method of characteristics (AMMOC) to simulate
 one-dimensional, advection-dominated solute transport problems,
 which incorporates the advantage of a self-adaptive spatial grid
 system with the computational power of the modified method of
 characteristics (MMOC) to deal with numerical dispersion and
 oscillation. The numerical simulations, including a pure
 advection problem, show that the AMMOC is free of oscillation,
 approximately global mass conservative, and exhibits
 insignificant numerical dispersion. Related to this method, three
 interpolation schemes to obtain the concentration of the
 fictitious particle at the previous time step were also
 evaluated. Our simulations show that the AMMOC, based on a
 clipped quadratic interpolation schemes provides the most
 accurate results.
 NAL Call No.: 56.9-So3
 2. AGNPS tracks pollutants to their source.
 Comis, D. 
 Agric-res v.43, p.22. (1995).
 Descriptors: watersheds-; water-pollution; sources-;
 computer-software; models-; pollutants-; tracking-
 NAL Call No.: 1.98-Ag84
 3. Alternative river management using a linked GIS-hydrology
 Rosenthal, W. D.; Srinivasan, R.; Arnold, J. G. 
 Trans-ASAE v.38, p.783-796. (1995).
 Includes references.
 Descriptors: rivers-; water-quality; simulation-models;
 information-systems; hydrological-data; stream-flow; soil-;
 land-use; weather-; texas-
 Abstract: A geographic information system (GIS)-hydrologic model
 link was used to aid in forming input files for the hydrologic
 model, SWAT (Soil and Water Assessment Tool). The link and SWAT
 prediction of streamflow volume were then tested for the Lower
 Colorado River basin of Texas. With no calibration, simulated
 monthly streamflow volume along the river was underestimated for
 the extreme events, but the relationship was significant (R2 =
 0.75). Model results also suggest that urbanization further
 upstream can significantly affect streamflow downstream. The
 system is general enough to be applicable to other river systems.
 NAL Call No.: 290.9-Am32T
 4. Analysis of nitrogen saturation potential in Rocky Mountain
 tundra and
 Baron, J. S.; Ojima, D. S.; Holland, E. A.; Parton, W. J. 
 Biogeochemistry v.27, p.61-82. (1994).
 Includes references.
 Descriptors: air-pollution; nitrogen-; deposition-;
 nitrogen-cycle; nitrogen-metabolism; soil-flora;
 biological-activity-in-soil; forest-soils; tundra-soils;
 mountain-soils; subalpine-forests; leaching-; watersheds-;
 lakes-; streams-; water-quality; simulation-models; colorado-
 NAL Call No.: QH345.B564
 5. Analytical modelling of pesticide transport from the soil
 surface to a drinking water well.
 Beltman, W. H. J.; Boesten, J. J. T. I.; Zee, S. E. A. T. M. v.
 J-hydrol v.169, p.209-228. (1995).
 Includes references.
 Descriptors: pesticides-; leaching-; water-flow; drinking-water;
 wells-; water-quality; groundwater-pollution; mathematical-models
 Abstract: Pesticide transport through the unsaturated zone was
 modelled with an analytical solution of the convection-dispersion
 equation assuming steady water flow, a linear sorption isotherm
 and first-order transtormation kinetics. Pesticide behaviour in
 the saturated zone was described with an analytical solution of
 the mass balance equation for a cylindrical flow system assuming
 steady flow, no dispersion, linear sorption and first-order
 transformation. This simplified model for the
 unsaturated-saturated soil system was developed to identify the
 processes and parameters with the greatest impact on the fraction
 of applied pesticide reaching a drinking water well. Leaching
 from the unsaturated zone was highly sensitive to the parameters
 describing travel time and transformation rate. Leaching
 increased when heterogeneity of the soil was taken into account.
 Pesticide arrival in the well was only moderately sensitive to
 the characteristic travel time and transformation rate in the
 aquifer. However, this sensitivity increases if zones without
 pesticide application were introduced around the wells
 (protection zones). For representative sandy soils under average
 Dutch rainfall conditions, processes in the unsaturated zone had
 a much larger impact on pesticide arrival in the wells than
 processes in the saturated zone. Protection zones reduced
 pesticide transport to wells substantially if their half-life was
 much smaller than the characteristic travel time of the pesticide
 in the aquifer.
 NAL Call No.: 292.8-J82
 6. An analytical solution for predicting solute transport during
 ponded infiltration.
 Huang, K.; Van Genuchten, M. T. 
 Soil-sci v.159, p.217-223. (1995).
 Includes references.
 Descriptors: solutes-; transport-processes; unsaturated-flow;
 standing-water; infiltration-; mathematical-models
 NAL Call No.: 56.8-So3
 7. Analytical solutions for one-dimensional colloid transport in
 saturated fractures.
 Abdel Salam, A.; Chrysikopoulos, C. V. 
 Adv-water-resour v.17, p.283-296. (1994).
 Includes references.
 Descriptors: groundwater-flow; pollutants-; colloids-; rocks-;
 fracture-; soil-parent-materials; transport-processes;
 equations-; mathematical-models; simulation-models; rock-matrix
 NAL Call No.: TD201.A4
 8. Answers 2000: continuous simulation version.
 Bouraoui, F.; Dillaha, T. A. I. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2120/94-2155) 28 p. 
 Paper presented at the 1994 International Summer Meeting,
 sponsored by the ASAE, June 19-22, 1994, Kansas City, Missouri.
 Descriptors: watersheds-; water-quality; water-pollution;
 nitrogen-; phosphorus-; sediment-; losses-from-soil; runoff-;
 erosion-; simulation-models
 NAL Call No.: 290.9-Am32P
 9. 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. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932080) 17 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers, and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: poultry-manure; nutrients-; losses-;
 application-to-land; water-quality; models-; computer-software
 NAL Call No.: 290.9-Am32P
 10. Application of the MAGIC model to the Glacier Lakes
 Reuss, J. O. 
 Res-pap-RM. [Fort Collins, Colo.] : Rocky Mountain Forest and
 Range Experiment Station, Forest Service, U.S. Dept. of
 Agriculture, 1978-. June 1994. (315) 19 p. 
 Includes references.
 Descriptors: acid-rain; watersheds-; catchment-hydrology;
 streams-; water-quality; simulation-models; national-forests;
 wyoming-; medicine-bow-national-forest
 NAL Call No.: A99.9-F7632U
 11. Application of the precipitation-runoff modeling system model
 to simulate dry season runoff for three watersheds in
 south-central Guam.  Application of the precipitation runoff
 modeling system model to simulate dry season runoff for three
 watersheds in south-central Guam.
 Nakama, L. Y.; United States. Navy Dept. 
 Honolulu, Hawaii : U.S. Dept. of the Interior, U.S. Geological
 Survey ; Denver, CO : Earth Science Information Center, Open-File
 Reports Section [distributor], 1994. v, 38 p. : ill., maps.
 Shipping list no.: 95-0091-P.
 Descriptors: Precipitation-Meteorology-Guam; Runoff-Guam
 NAL Call No.: GB701.W375--no.93-4116
 12. Application to geostatistics for mapping nitrate contaminated
 Dou, C.; Woldt, W. E.; Dahab, M. F.; Bogardi, I. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2091/94-2119) 15 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 20-23, 1994, Kansas City, Missouri.
 Descriptors: nitrate-nitrogen; groundwater-pollution; kriging-;
 NAL Call No.: 290.9-Am32P
 13. Assessing nonpoint-source pollution risk: a GIS application.
 Lull, K. J.; Tindall, J. A.; Potts, D. F. 
 J-for v.93, p.35-40. (1995).
 Includes references.
 Descriptors: water-pollution; risk-;
 geographical-information-systems; land-use; watersheds-;
 montana-; risk-assessment
 NAL Call No.: 99.8-F768
 14. Assessment of in situ solvent extraction for remediation of
 coal tar
 Ali, M. A.; Dzombak, D. A.; Roy, S. B. 
 Water-environ-res v.67, p.16-24. (1995).
 Includes references.
 Descriptors: tars-; coal-; gasification-; industrial-sites;
 groundwater-pollution; pollutants-; contaminants-; solvents-;
 extraction-; simulation-models; wells-; power-industry;
 manufactured-gas-plants; recovery-wells; injection-wells
 NAL Call No.: TD419.R47
 15. Assessment of in situ solvent extraction for remediation of
 coal tar
 Roy, S. B.; Dzombak, D. A.; Ali, M. A. 
 Water-environ-res v.67, p.4-15. (1995).
 Includes references.
 Descriptors: tars-; coal-; gasification-; industrial-sites;
 groundwater-pollution; pollutants-; contaminants-; solvents-;
 extraction-; equations-; mathematical-models; power-industry;
 manufactured-gas-plants; nonqueous-phase-liquids
 NAL Call No.: TD419.R47
 16. Assessment of the fate of two herbicides in a Wyoming
 rangeland soil: column studies.
 Krzyszowska, A. J.; Allen, R. D.; Vance, G. F. 
 J-environ-qual v.23, p.1051-1058. (1994).
 Includes references.
 Descriptors: dicamba-; picloram-; leaching-; persistence-;
 sorption-; soil-organic-matter; degradation-; rangeland-soils;
 groundwater-pollution; simulation-models; LEACHP-model
 Abstract: Extensive use of dicamba (2-methoxy-3,6-dichlorobenzoic
 acid) and picloram (4-amino-3,5,6-trichloropicolinic acid) in
 arid Wyoming, along with large volumes of irrigation water used
 in some areas, has created a concern for the potential
 contamination of surface and groundwaters by these herbicides.
 Persistence and mobility of dicamba and picloram were
 investigated in a Wyoming rangeland soil using batch adsorption
 and soil column studies. The objectives of this study were to
 characterize soil chemical and physical properties that affect
 herbicide transport, examine herbicide sorption, model herbicide
 movement, and estimate degradation rate constants. Essentially no
 sorption of dicamba was detected; however, picloram sorption was
 greatest in the highest organic C content horizon. Both saturated
 (5.90, 2.96, and 0.82 kg ha-1 dicamba and 1.85, 0.97, and 0.47 kg
 ha-1 picloram) and unsaturated (2.76 and 1.00 kg ha-1 for dicamba
 and picloram, respectively) column experiments were conducted.
 The herbicides and Br tracer (34, 38, 69, and 137 micrograms L-1)
 were displaced through the soil columns using distilled water
 that was added in daily increments (60 mL d-1). Degradation rate
 constants were calculated using both simple recovery fraction
 technique and by matching LEACHP-generated breakthrough curves to
 experimental data. For the two columns receiving intermediate
 application rates, anaerobic picloram dissipation was more rapid
 (t1/2 = 19 d) than for aerobic conditions (t1/2 = 87 d). The rate
 of dissipation of dicamba was approximately the same under
 aerobic and anaerobic conditions (t1/2 = 15 and 17 d in the
 saturated and unsaturated columns, respectively). Picloram and
 dicamba dissipation was more rapid at.  application rates, t1/2
 of 23 and 17 d were measured for picloram and dicamba,
 respectively. Both herbicides were found to be highly mobile,
 with the mobility of picloram increasing at higher pore-water
 NAL Call No.: QH540.J6
 17. Changes in acidification of lochs in Galloway, southwestern
 Wright, R. F.; Cosby, B. J.; Ferrier, R. C.; Jenkins, A.; Bulger,
 A. J.; Harriman, R. 
 J-hydrol v.161, p.257-285. (1994).
 Includes references.
 Descriptors: watersheds-; acid-deposition; ions-; acidification-;
 soil-chemistry; water-quality; afforestation-; deforestation-;
 fishes-; population-density; simulation-models; prediction-;
 scotland-; water-chemistry; critical-load
 Abstract: Decades of acid deposition in the Galloway area,
 southwestern Scotland, have resulted in acidification of surface
 waters and damage to fish. In the period since 1980, however,
 acidic deposition has decreased substantially. A survey of 50
 lochs conducted in 1979 and repeated in 1988 reveals major
 changes in water chemistry over this 9 year period. Together
 these two data sets separated in time by 9 years and covering a
 period of relatively large and rapid change in acid deposition
 offer a valuable basis for the evaluation of acidification
 models. Concentrations of SO4 in the lochs were on the average
 42% lower in 1988 relative to 1979. The decline is readily
 explained by the large and rapid decline in sulphate
 concentrations in precipitation in the area. Concentrations of
 non-marine base cations decreased from 155 to 90 microequiv l-1
 and acid neutralising capacity (ANC) increased. The change in ANC
 was due mostly to decreased concentrations of Al. pH levels
 showed no systematic change from 1979 to 1988. The regional
 changes in water chemistry over the period 1979-1988 are
 corroborated by regular measurements at several of these lochs
 over this 9 year period. MAGIC (Model for Acidification of
 Groundwater In Catchments) successfully reproduces the major
 changes in water chemistry observed over the period 1979-1988.
 Both calibration to the 1979 data with prediction of 1988, and
 calibration to the 1988 with reconstruction of 1979 give close
 fits to the observations. The model provides a means by which the
 future impact of acidic deposition and afforestation can be
 evaluated. A fish response function coupled to MAGIC provides the
 basis for evaluation of past and future fish status in the
 region. MAGIC.  indicate that if acidic deposition is held
 constant at 1988 levels, afforestation causes further
 acidification of the lochs. Acidic deposition emerges as the
 major cause of soil and water acidification in the Galloway
 region, although forestry practices can exacerbate the effects.
 NAL Call No.: 292.8-J82
 18. CHEMFRANCE: a regional level III fugacity model applied to
 Devillers, J.; Bintein, S.; Karcher, W. 
 Chemosphere v.30, p.457-476. (1995).
 Includes references.
 Descriptors: air-pollution; soil-pollution; water-pollution;
 groundwater-pollution; pollutants-; organic-compounds; movement-;
 simulation-models; computer-simulation; france-;
 NAL Call No.: TD172.C54
 19. Chemical leaching near the Waiawa Shaft, Oahu, Hawaii. 2.
 Modeling results.
 Loague, K.; Miyahira, R. N.; Green, R. E.; Oki, D. S.;
 Giambelluca, T. W.; Schneider, R. C. 
 Ground-water. Dublin, Ohio : Ground Water Pub. Co. Jan/Feb 1995.
 v. 33 (1) p. 124-138. 
 Includes references.
 Descriptors: groundwater-pollution; chlorpyrifos-; diazinon-;
 metribuzin-; nitrate-; leaching-; simulation-models;
 mathematical-models; groundwater-recharge; hydrology-;
 water-table; hawaii-; pesticide-root-zone-model
 NAL Call No.: TD403.G7
 20. Chemical processes controlling the mobility of waste material
 contaminants in soils.
 Wesselink, L. G.; Dekker, P. M.; Aalbers, T. G. 
 Stud-environ-sci. Amsterdam ; New York, Elsevier Scientific
 Publishing Co. 1994. (60) p. 31-38. 
 In the series analytic: Environmental aspects of construction
 with waste material / edited by J.J.J.M. Goumans, H.A. van der
 Sloot and T.G. Aalbers.  Implications of Construction Materials
 and Technology Developments," held June 1-3, 1994, Maastricht,
 The Netherlands.
 Descriptors: slags-; building-materials; leaching-; percolation-;
 leachates-; sandy-soils; soil-chemistry; chemical-speciation;
 simulation-models; steel-slag; phosphorus-slag
 NAL Call No.: QH540.S8
 21. Climate, interseasonal storage of soil water, and the annual
 water balance.
 Milly, P. C. D. 
 Adv-water-resour v.17, p.19-24. (1994).
 In the special issue: MIT Colloquium on Hydroclimatology and
 Global Hydrology / edited by I. Rodriguez-Iturbe, D. Entekhabi
 and R.L. Bras.
 Descriptors: soil-water-balance; soil-water; seasonal-variation;
 rain-; evaporation-; water-holding-capacity; climate-; runoff-;
 simulation-; simulation-models; mathematical-models; equations-;
 southern-states-of-usa; north-central-states-of-usa;
 NAL Call No.: TD201.A4
 22. Climatic variability of soil water in the American Midwest.
 1. Hydrologic modeling.
 Bae, D. H.; Georgakakos, K. P. 
 J-hydrol v.162, p.355-377. (1994).
 Includes references.
 Descriptors: soil-water; catchment-hydrology; stream-flow; rain-;
 temperature-; evapotranspiration-; temporal-variation;
 spatial-variation; hydrological-data; simulation-models; rivers-;
 minnesota-; iowa-; rainfall-runoff-models;
 des-moines-river-basin; mississippi-river-system
 Abstract: A conceptual hydrologic rainfall-runoff model that is
 an adaptation of the operational US National Weather Service
 hydrologic model is used to simulate the hydrologic processes in
 large basins of the US upper Mississippi region. In particular,
 the conceptual rainfall-runoff model is used to produce daily
 streamflow from daily rainfall, temperature and potential
 evapotranspiration input over three neighboring headwater basins
 that span 2 degrees longitude by 2 degrees latitude. When used
 for simulation of historical flows, the model provides a means of
 inference of the 40 year time series of unrecorded mesoscale soil
 water and actual evapotranspiration for climate studies. In this
 paper we discuss issues associated with parameter estimation, the
 reliability and stability of parameter estimates, and the
 interpretation of soil water estimates. It is concluded that the
 conceptual hydrologic model may be used to estimate the
 variability of aggregate soil water over large areas of the
 Midwestern US provided that: (a) all significant basin inflows
 and outflows are accounted for; (b) model verification yields
 good agreement between observed and simulated flows on a daily
 basis. Parameter sensitivity studies showed that estimating the
 soil's capacity to hold water is most important for flood event
 prediction and flow simulation, and, for such parameters,
 underestimation is more critical than overestimation. Also,
 uncertainty associated with the parametrization of
 evapotranspiration may introduce local errors in the time series
 of soil water estimates produced by the model. In a companion
 paper we present a spatio-temporal analysis of the estimated time
 series of soil water.
 NAL Call No.: 292.8-J82
 23. Combined use of watershed, aquifer and crop simulation models
 to evaluate groundwater recharge through percolation ponds.
 Selvarajan, M.; Bhattacharya, A. K.; Penning de Vries, F. W. T. 
 Agric-syst v.47, p.1-24. (1995).
 Includes references.
 Descriptors: groundwater-recharge; ponds-; aquifers-;
 watersheds-; simulation-models; percolation-; irrigation-;
 runoff-; evapotranspiration-; india-;
 NAL Call No.: HD1.A3
 24. Commodity information and willingness-to-pay for groundwater
 quality protection.
 Bergstrom, J. C.; Dorfman, J. H. 
 Rev-agric-econ v.16, p.413-425. (1994).
 Includes references.
 Descriptors: groundwater-; water-quality; valuation-;
 regional-surveys; consumer-attitudes; information-;
 mathematical-models; georgia-; dougherty-county,-georgia
 Abstract: The potential sensitivity of environmental resource
 valuations to information concerning the resource is of interest
 to researchers and decision-makers involved in estimating and
 applying these numbers. An analysis of the impact of
 characteristic and service information on the economic value of
 groundwater quality is described. Characteristic information
 details the objectively measurable traits of a resource, while
 service information describes the consumption services provided
 by the resource. The analysis provides insight into the impact of
 information on environmental resource valuation decisions.
 Hypothesis tests suggest that changes in the joint levels of
 information may cause significant changes in groundwater quality
 valuation behavior. More theoretical and empirical research is
 required before firm conclusions can be drawn concerning the
 effects of information on groundwater value estimates (e.g.,
 estimated willingness-to-pay for groundwater protection).
 NAL Call No.: HD1773.A3N6
 25. A comparative study of policy measures for groundwater
 pollution control.
 Oh, S. I. 
 J-rural-dev v.16, p.257-275. (1993).
 Includes references.
 Descriptors: nitrates-; groundwater-pollution; pollution-control;
 taxes-; externalities-; environmental-policy; farm-inputs;
 mathematical-models; comparisons-; water-use; social-costs;
 pigouvian-taxes; input-taxes
 NAL Call No.: HD2095.5-.J8
 26. Comparison of erosion predictions with GLEAMS, GLEAMS-WT, and
 GLEAMS-SWAT models for alluvial soils.
 Reyes, M. R.; Bengtson, R. L.; Fouss, J. L.; Carter, C. E. 
 Trans-ASAE v.38, p.791-796. (1995).
 Includes references.
 Descriptors: alluvial-soils; erosion-; runoff-; drainage-;
 simulation-models; prediction-; performance-appraisals;
 Abstract: Simulation performances of GLEAMS, GLEAMS-WT, and
 GLEAMS-SWAT were evaluated by comparing their soil loss
 predictions with measured data from two runoff-erosion-drainage
 experimental plots at Baton Rouge, Louisiana. One of the
 experimental plots was surface drained only, and the other was
 both surface and subsurface drained. Although the hydrology
 components of GLEAMS-WT and GLEAMS-SWAT predicted surface runoff
 more accurately than the original GLEAMS, all three models
 seriously underpredicted total soil losses over a seven-year
 period (1981 to 1987). Transport capacity limited soil loss
 prediction values in the models. Hence, we recommend that any
 changes or modifications in the erosion submodel be focused on
 improving transport capacity simulation; changes in the
 detachment simulation routine may not be needed. A calibration
 parameter was added to the erosion subroutine to adjust transport
 capacity. However, even when the models were calibrated for a
 specific site, there were still substantial annual and monthly
 differences between predicted and observed soil losses.
 NAL Call No.: 290.9-Am32T
 27. A conceptual model for ecological risk assessment of
 bottomland hardwood forests.
 Vellidis, G.; Lowrance, R. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-2574) 23 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 14-17, Chicago, Illinois.
 Descriptors: hardwoods-; bottomland-forests; forest-ecology;
 risk-; assessment-; water-quality; models-; georgia-
 NAL Call No.: 290.9-Am32P
 28. A conceptual model of the Galveston Bay ecosystem.
 McFarlane, R. W.; Galveston Bay National Estuary Program. 
 [Webster, Tex.] : Galveston Bay National Estuary Program, [1993]
 xii, 81 p. : ill., maps.
 "October 1993.".
 Descriptors: Estuarine-ecology-Texas-Galveston-Bay;
 Ecosystem-management-Texas-Galveston-Bay; Galveston-Bay-Tex
 NAL Call No.: QH541.5.E8P83--no.42
 29. Conservation tillage a sustainable agricultural practice.
 Lakshminarayan, P. G.; Bouzaher, A.; Johnson, S. R. 
 Environmentally sound agriculture  proceedings of the second
 conference  20-22 April 1994 / p.139-146. (1994).
 Includes references.
 Descriptors: zea-mays; glycine-max; continuous-cropping;
 rotations-; conservation-tillage; tillage-; environmental-impact;
 sustainability-; erosion-; erosion-control; nitrate-nitrogen;
 losses-from-soil; leaching-; runoff-; water-quality;
 simulation-models; statistical-analysis; conventional-tillage;
 NAL Call No.: S589.7.E57-1994
 30. Consideration of spatial variability in nitrate contamination
 to groundwater.
 Goderya, F. S.; Dahab, M. F.; Woldt, W. E. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2091/94-2119) 11 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 20-23, 1994, Kansas City, Missouri.
 Descriptors: nitrate-nitrogen; spatial-variation;
 groundwater-pollution; simulation-models
 NAL Call No.: 290.9-Am32P
 31. Convection, dipersion, and interfacial transport of
 contaminants: homogeneous porous media.
 Quintard, M.; Whitaker, S. 
 Adv-water-resour v.17, p.221-239. (1994).
 Includes references.
 Descriptors: groundwater-pollution; pollutants-; contaminants-;
 dispersion-; convection-; mathematical-models; equations-;
 aquifers-; groundwater-flow
 NAL Call No.: TD201.A4
 32. CREAMS/WEPP sediment deposition equation: a semitheoretical
 Storm, D. E.; Barfield, B. J.; Altendorf, C. T. 
 Trans-ASAE v.37, p.1105-1108. (1994).
 Includes references.
 Descriptors: water-erosion; sediment-; deposition-;
 mathematical-models; equations-; simulation-models;
 sediment-yield; erosion-models
 Abstract: A semitheoretical evaluation of the sediment deposition
 equation used in the CREAMS and WEPP models is presented. The
 original deposition relationship was presented in the CREAMS and
 WEPP models without theoretical or conceptual justification. In
 this article, the relationship is shown to be based conceptually
 on four characteristics: 1) uniform velocity distribution; 2) no
 lateral sediment inflow; 3) discrete particle settling; and 4) a
 uniform sediment concentration--all of which are violated under
 typical field conditions. Why then does the deposition equation
 work? The deposition equation, as applied to a rill, approximates
 the trapping that would occur in a fully-turbulent, rectangular
 reservoir if a rill is discretized into a large number of
 sections. When only one rill section is utilized, the equation
 approximates a quiescent reservoir. Since most shallow rills are
 typically discretized into a number of sections and experience a
 combination of turbulent and quiescent flows, the deposition
 equation should provide a first approximation of field
 NAL Call No.: 290.9-Am32T
 33. Crop nitrogen utilization and soil nitrate loss in a lettuce
 Jackson, L. E.; Stivers, L. J.; Warden, B. T.; Tanji, K. K. 
 Fertil-res v.37, p.93-105. (1994).
 Includes references.
 Descriptors: lactuca-sativa; nutrient-availability; nitrogen-;
 nutrient-uptake; nitrate-; losses-from-soil; denitrification-;
 leaching-; -; transformation-; nitrification-; mineralization-;
 seasonal-variation; rain-; irrigated-conditions; shoots-; roots-;
 nutrient-content; growth-; simulation-models; california-;
 nitrogen-pools; cropped-period; non-cropped-period;
 nitrogen-dynamics; erosion; productivity-impact-calculator-epic
 Abstract: Low N use efficiency and high nitrate (NO3-) pollution
 potentials are problems in intensive vegetable production
 systems. The purpose of this study was to quantify N utilization
 by lettuce (Lactuca sativa L. cv Salinas), and identify periods
 of NO3- loss in an on-farm study in the Salinas Valley in coastal
 California. During autumn and winter, surface moisture remained
 low, and NO3- concentrations increased, reflecting high net
 mineralizable N, as determined by anaerobic incubation, and
 nitrification potential, as determined by the chlorate inhibition
 method. At the onset of a large winter storm, tracer levels of
 15NO3- were injected in the top 5 mm of soil in 30 cm-deep
 cylinders. After two weeks, most of the 15N was present as 15NO3-
 at 10-30 cm depth. By difference, losses to denitrification
 accounted for approximately 25% of the surface-applied 15N.
 Leaching below 30 cm did not occur, since no 15N enrichment of
 NO3-N was measured in anion-exchange resin membranes placed at
 the base of each cylinder. During the crop period, NO3- losses
 were most pronounced after irrigation events. Uptake of N by two
 crops of lettuce (above- and belowground material) was
 approximately equal to fertilizer inputs, yet simulation of N
 fates by the Erosion/Productivity Impact Calculator (EPIC) model
 indicated losses of 14.6 g-N m-2 by leaching and 2.5 g-N m-2 by
 denitrification during the 6-month crop period. The large NO3-
 losses can be attributed to accumulation of soil NO3- during
 winter that was leached or denitrified during the irrigated crop
 NAL Call No.: S631.F422
 34. Darcy-Weisbach roughness coefficients for surfaces with
 residue and gravel cover.
 Gilley, J. E.; Kottwitz, E. R. 
 Trans-ASAE v.38, p.539-544. (1995).
 Includes references.
 Descriptors: crop-residues; gravel-; covers-; upland-areas;
 hydraulic-resistance; runoff-; roughness-; water-flow;
 Abstract: Several types of hydraulic resistance factors may be
 present on upland agricultural areas. It is not known whether
 roughness contributions from individual elements are additive or
 if interactions between resistance factors may occur. In this
 study, Darcy-Weisbach roughness coefficients were measured on
 surfaces containing corn-soybeans, sorghum-cotton, and
 sunflower-wheat residue in addition to gravel cover. Varying
 rates of flow were introduced into a flume in which residue and
 gravel materials were securely attached. Roughness coefficients
 were calculated from measurements of discharge rate and flow
 velocity for Reynolds number values varying from approximately
 1,200 to 13,000. The laboratory data were then used to identify
 the contribution to total hydraulic resistance provided by the
 different types of resistance elements. For most of the
 experimental treatments, the addition of smaller diameter residue
 materials (soybeans, cotton, or wheat) to surfaces containing
 larger resistance elements (corn, sorghum, or sunflower) did not
 significantly affect hydraulic resistance. However, smaller
 diameter residue materials did influence hydraulic resistance
 when they substantially increased the total volume of resistance
 elements. Existing roughness coefficient values were not
 significantly affected by the presence of gravel materials with
 diameters similar to the larger residue materials. The
 experimental results suggest that total hydraulic resistance
 cannot be predicted by simply adding the contributions provided
 by individual resistance elements. When estimating total
 hydraulic resistance on upland agricultural areas, the relative
 size, number, and volume of resistance elements must be
 NAL Call No.: 290.9-Am32T
 35. Description of simazine transport with rate-limited,
 two-stage, linear and nonlinear sorption.
 Streck, T.; Poletika, N. N.; Jury, W. A.; Farmer, W. J. 
 Water-resour-res v.31, p.811-822. (1995).
 Includes references.
 Descriptors: simazine-; transport-processes; sorption-;
 sorption-isotherms; lysimeters-; models-; sorption-models;
 Abstract: This study was conducted to reconcile an apparent
 inconsistency between the simazine laboratory sorption isotherm
 data and the field lysimeter transport experiment reported by
 Poletika et al. (this issue). In this investigation, linear and
 nonlinear one- and two-stage simazine sorption models were fitted
 to the sorption and desorption isotherm laboratory data to obtain
 parameter estimates for use in the transport model. Once
 obtained, the calibrated sorption model was combined with the
 parameterized outflow concentration record from a mobile Br
 tracer to represent rate-limited sorption and transport of the
 simazine added simultaneously with the Br. The calibrated model
 did an excellent job of representing the final simazine profile
 in the soil, particularly with the nonlinear model. This is in
 contrast to a single-stage adsorption model tested by Poletika et
 al. (this issue), which reached poor agreement with the field
 profile when laboratory-measured sorption parameters were used.
 The results demonstrate the compatibility of field and laboratory
 experiments on pesticide movement and also indicate that sorption
 isotherms may require substantially longer to reach equilibrium
 than is customarily allowed in current protocols.
 NAL Call No.: 292.8-W295
 36. Development of an in vitro model for investigating the
 formation of the nuclear Ah receptor complex in mouse Hepa 1c1c7
 Wang, X.; Safe, S. 
 Arch-biochem-biophys v.315, p.285-292. (1994).
 Includes references.
 Descriptors: aromatic-hydrocarbons; receptors-; nuclei-;
 cytosol-; cell-lines; in-vitro; models-; transport-processes;
 vanadium-; atp-; lectins-; dioxins-
 Abstract: An in vitro assay for investigating factors which
 modulate formation of the nuclear aryl hydrocarbon (Ah) receptor
 complex was developed using 9S cytosolic Ah receptor isolated
 from wild-type Hepa 1e1c7 cells treated with
 2,3,7,8-[3H]tetrachlorodibenzo-p-dioxin (TCDD) at 4 degrees C and
 nuclei from Ah-responsive and -nonresponsive wild-type and mutant
 Hepa 1c1c7 cells. Incubation of the radiolabeled ([3H]TCDD) 9S
 cytosolic Ah receptor with nuclei from untreated wild-type
 Ah-responsive mouse Hepa 1e1c7 cells resulted in a time- and
 temperature-dependent formation of the nuclear Ah receptor
 complex as determined by either velocity sedimentation analysis
 or gel mobility shift assays using a consensus 32P-labeled
 dioxin-responsive element. Maximal levels of the nuclear Ah
 receptor formed within 30 min at 37 degrees C and significantly
 lower levels were observed after incubation at 4, 15, or 25
 degrees C. Complementation studies using nuclei from untreated
 wild-type and Ah-nonresponsive class II mutant
 (translocation-deficient) cells and radiolabeled 9S cytosolic
 receptor (bound with [3H]TCDD) from both wild-type and mutant
 cell lines were also carried out. The results indicated that
 nuclear translocation was primarily inhibited using cytosol from
 mutant cells confirming the requirement for the aryl hydrocarbon
 receptor nuclear translocator protein for formation of the
 nuclear Ah receptor complex. The effects of a series of Ah
 receptor antagonists, ATP, vanadate apyrase, phosphatases, and
 lectin WGA, on formation of the nuclear Ah receptor complex were
 also investigated in the in vitro model using radiolabeled
 cytosolic Ah receptor and nuclei from untreated wild-type Hepa
 1c1c7 cells. alpha-Naphthoflavone.  apyrase inhibited and ATP
 enhanced formation of the nuclear Ah receptor complex. The
 results also show that TCDD-induced transformation of the Ah
 receptor was inhibited by alpha-naphthoflavone but not by ATP,
 lectin WGA, or apyrase. These data suggest that the cytosolic Ah
 receptor is phosphorylated prior to ligad binding and ATP is
 required for energy-dependent nuclear import of the Ah receptor.
 NAL Call No.: 381-Ar2
 37. Differences in contingent valuation estimates from referendum
 and checklist questions.
 Jordan, J. L.; Elnagheeb, A. H. 
 J-agric-resour-econ v.19, p.115-128. (1994).
 Includes references.
 Descriptors: groundwater-; water-quality; consumer-attitudes;
 monte-carlo-method; consumer-surveys; probabilistic-models;
 georgia-; willingness-to-pay-
 NAL Call No.: HD1750.W4
 38. Drainage reservoir systems for water quality control.
 Melvin, S. W.; Wilcox, A. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932040) 9 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers, and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: drainage-; reservoirs-; water-quality; models-;
 NAL Call No.: 290.9-Am32P
 39. A dynamic analysis of the impact of water quality policies on
 irrigation investment and crop choice decisions.
 Wu, J. J.; Mapp, H. P.; Bernardo, D. J. 
 J-agric-appl-econ v.26, p.506-525. (1994).
 Includes references.
 Descriptors: maize-; sorghum-; wheat-; irrigation-water;
 irrigated-farming; investment-; water-quality; farm-management;
 decision-making; crop-enterprises; dynamic-models; cost-analysis;
 soil-types; innovation-adoption; economic-impact;
 Abstract: A dynamic model is developed to analyze farmers
 irrigation investment and crop choice decisions under alternative
 water quality protection policies. The model is applied to an
 empirical example in the Oklahoma High Plains. The choices of
 crops and irrigation systems and the resulting levels of
 irrigation, income, and nitrogen runoff and percolation are
 simulated over a ten-year period. An effluent tax on nitrogen
 runoff and percolation is shown to be effective in reducing
 nitrate pollution. The efficacy of cost sharing in adopting
 modern irrigation technologies and restrictions on irrigation
 water use depends on soil type. A tax on nitrogen use is shown to
 be the least effective policy.
 NAL Call No.: HD101.S6
 40. Economic analysis of effluent control from catfish ponds.
 Cerezo, G. A.; Clonts, H. A. 
 Bull-Agric-Exp-Sta,-Auburn-Univ. Auburn, Ala : Agricultural
 Experiment Station, Auburn University, 1960-. May 1994. (621) 40
 Includes references.
 Descriptors: fish-ponds; ictalurus-punctatus; fish-scrap;
 water-quality; water-pollution; effluents-; water-reuse;
 environmental-policy; fishery-management; water-systems;
 watersheds-; costs-; taxes-; cost-benefit-analysis;
 fish-stocking; linear-programming-model
 NAL Call No.: 100-AL1S-1
 41. Economics of screening for pesticides in ground water.
 Natarajan, U.; Rajagopal, R. 
 Water-resour-bull v.30, p.579-588. (1994).
 Includes references.
 Descriptors: pesticides-; groundwater-; water-quality;
 groundwater-pollution; screening-; monitoring-;
 mathematical-models; cost-effectiveness-analysis; usa-;
 sequential-analysis-screening; sample-compositing-screening
 Abstract: In the United States, millions of dollars are currently
 spent to monitor water quality for a whole suite of organic
 compounds. However, results of several surveys conducted in the
 past decade indicate that only a few pesticides occur in a small
 proportion of wells. Screening methods based on historical
 evidence of contamination patterns and knowledge of the locales
 will have significant potential to reduce these costs and
 effectively identify contamination problems. In this paper, the
 economics of utilizing two screening methods, sequential analysis
 and sample compositing, in the design of monitoring strategies is
 captured in the form of mathematical models and illustrated for a
 state-level monitoring program. When the two methods are adopted,
 the total analytical cost to conclusively identify contaminated
 wells in a network of 4,000 wells is shown to range from $12,500
 to $1,575,000 depending on the extent of contamination. In
 contrast, the total analytical cost of a conventional program
 where all the wells in the network are sampled and tested for a
 standard suite of pesticides at a cost of $250/sample is one
 million dollars. Given such wide range in costs, it is prudent to
 incorporate the screening concepts presented in this paper in the
 development of cost-effective monitoring programs.
 NAL Call No.: 292.9-Am34
 42. The effect of farming practices on reducing excess nitrogen
 fertilizer use.
 Huang, W. Y.; Uri, N. D. 
 Water-air-soil-pollut v.77, p.79-95. (1994).
 Includes references.
 Descriptors: nitrogen-fertilizers; rotations-;
 continuous-cropping; sole-cropping; zea-mays; glycine-max;
 application-rates; low-input-agriculture; simulation-models;
 farmland-; mathematical-models; leaching-; meadows-; farm-income
 NAL Call No.: TD172.W36
 43. Empirical analysis of slope and runoff for sediment delivery
 from interril areas.
 Huang, C. H. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. July/Aug 1995. v. 59 (4) p. 982-990. 
 Includes references.
 Descriptors: interrill-erosion; simulation-models; slope-;
 gradients-; runoff-; sediment-; losses-from-soil; relationships-;
 Abstract: Slope steepness (S) and runoff discharge (qw) are two
 major factors in determining sediment delivery rates (qs) from
 interrill areas. Under the current interrill erosion model
 concept, these two factors are assumed to have independent
 effects on qs; thus, each factor can be quantified individually
 if the other factor is kept constant. This study was conducted to
 show the effects of S and qw on qs and their interdependency.
 Sediment discharge rates, measured under different rainfall
 intensities and slope gradients, for eight soils from two
 laboratory studies were analyzed empirically with curve-fitting
 procedures. Results showed that there was a pair of empirical
 equations for each soil: qs = A1 q2w + A2 qw + A3 and qs = B1 S2
 + B2 S + B3, where A1, A2, and A3 are functions of S and B1, B2,
 and B3 are functions of qw. In other words, effects of slope
 steepness and runoff on sediment delivery are dependent on each
 other. When S and qw were combined together as stream power,
 omega, and plotted against sediment concentration, qs/qw, a
 unique nonlinear relationship existed for each soil: qs/qq = D1
 omega 2 + D2 omega + D3, where D1, D2, and D3 are soil-dependent
 coefficients. The stream power, which encompasses both slope and
 runoff effects, may provide improved estimates for interrill
 erosion. Although not based on theory, this result may be useful
 in process-based erosion models.
 NAL Call No.: 56.9-So3
 44. EPIC simulation of water quality impact by land application
 of poutry litter.
 Yoon, K. S.; Yoo, K. H.; Wood, C. W.; Hall, B. M. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-2531/93-2550) 16 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 12-17, 1993, Chicago, Illinois.
 Descriptors: poultry-manure; application-to-land;
 environmental-impact; water-quality; simulation-models;
 NAL Call No.: 290.9-Am32P
 45. Estimating snowmelt runoff erosion indices for Canada.
 Hayhoe, H. N.; Pelletier, R. G.; Coote, D. R. 
 J-soil-water-conserv v.50, p.174-179. (1995).
 Includes references.
 Descriptors: meltwater-; water-erosion; runoff-; runoff-water;
 rain-; simulation-models; computer-simulation; winter-;
 erosivity-; canada-
 NAL Call No.: 56.8-J822
 46. Estimation of in situ unsaturated soil hydraulic functions
 from scaled cumulative drainage data.
 Eching, S. O.; Hopmans, J. W.; Wallender, W. W. 
 Water-resour-res v.30, p.2387-2394. (1994).
 Includes references.
 Descriptors: unsaturated-hydraulic-conductivity;
 soil-water-retention; drainage-; water-flow; transport-processes;
 simulation-; spatial-variation; mathematical-models; california-;
 linear-variability-scaling-technique; inverse-solution-technique
 Abstract: Simulation of water flow and transport processes in
 soils rely on field representative soil hydraulic functions. The
 linear variability concept in combination with the inverse
 technique was used to estimate in situ soil hydraulic properties
 in a 32-ha field. Measured cumulative drainage curves were scaled
 yielding scaling factors. Subsequently, the drainage and moisture
 content distribution of the scaled reference profile were input
 to a numerical model to optimize the soil water retention and
 hydraulic conductivity curves for the reference soil profile by
 inverse solution of the scaled Richards equation. Field hydraulic
 functions for each location were computed from the reference
 curves and scaling factors. In addition, undisturbed soil cores
 taken from 0.3-m and 0.6-m depths at 44 locations were used to
 determine soil texture, and soil water retention and hydraulic
 conductivity curves in the laboratory using the multistep outflow
 technique. These hydraulic functions were scaled using the
 simultaneous scaling technique. The reference field hydraulic
 functions compared well with those determined from the soil cores
 taken from the 0.6-m depth. In situ saturated hydraulic
 conductivity variability was one order of magnitude less than
 that of the soil cores.
 NAL Call No.: 292.8-W295
 47. Evaluation of LEACHM. I. Simulation drainage, bromide
 leaching, and corn bromide uptake.
 Jemison, J. M. Jr.; Jabro, J. D.; Fox, R. H. 
 Agron-j v.86, p.843-851. (1994).
 Includes references.
 Descriptors: zea-mays; bromide-; solutes-; ion-transport;
 movement-in-soil; drainage-; leaching-; uptake-; prediction-;
 mathematical-models; computer-simulation; simulation-models;
 Abstract: Use of mathematical models to predict solute transport
 in soils, for research purposes, is increasing, but simpler
 management-oriented models are needed that require less
 field-specific data. Evaluation is needed to know which type of
 model is appropriate. The input-intensive research and simpler
 management options of the pesticide and tracer version of LEACHM
 (LEACHMP) were evaluated to predict drainage in zero-tension pan
 lysimeters, bromide (Br-) leaching, and corn (Zea mays L.) Br-
 uptake from a 3-yr leaching experiment. Eighteen pan lysimeters
 (0.465 m2) were installed 1.2 m below the soil surface to collect
 gravitational water samples. In May 1988, a one-time application
 of KBr was broadcast to all plots at 100 kg Br- ha-1. Corn Br-
 uptake was evaluated by taking whole-plant samples at 2-wk
 intervals in 1988 and 1989. The research model adequately
 predicted drainage. Significant differences between predicted and
 observed drainage were not found, and the correlations were
 significant (0.73 to 0.83). The management model, however,
 significantly underestimated cumulative drainage. The research
 model overestimated Br- leaching, because the
 convection-dispersion equation used in LEACHMP cannot model
 dual-pore water flow and solute diffusion found in this soil. The
 model generally underpredicted corn Br- uptake, which probably
 contributed to the overpredicted Br- leaching. The research
 version of LEACHMP adequately modeled drainage, but a more
 sophisticated approach to solute transport and corn Br- uptake is
 needed to adequately model Br- movement in this soil-plant-water
 system. Management model results were generally less accurate
 than the research model.
 NAL Call No.: 4-AM34P
 48. Evaluation of LEACHM. II. Simulation of nitrate leaching from
 nitrogen-fertilized and manured corn.
 Jemison, J. M. Jr.; Jabro, J. D.; Fox, R. H. 
 Agron-j v.86, p.852-859. (1994).
 Includes references.
 Descriptors: zea-mays; nitrate-nitrogen; leaching-; prediction-;
 nitrogen-fertilizers; liquid-manures; cattle-manure;
 mathematical-models; simulation-models; computer-simulation;
 uptake-; calibration-; volatilization-; denitrification-;
 Abstract: High NO3-N concentrations in groundwater resulting from
 agricultural production have increased the need for mathematical
 models to predict the concentration and mass of NO3-N leached
 from agricultural soils. Study objectives included evaluating the
 N version of LEACHM (LEACHMN) to predict mass of NO3-N leached
 from nonmanured and manured corn (Zea mays L.), and to test two
 methods of model validation. Four treatments (no manure with 0
 and 200 kg N ha-1 and a manure treatment with 0 and 100 kg N
 ha-1) from a NO3 leaching experiment were modeled for 1988, 1989,
 and 1990. Model calibration involved adjusting nitrification,
 denitrification, and volatilization rate constants to minimize
 differences between predicted and observed data. When calibrated
 for each year, LEACHMN produced reasonably accurate predictions
 of NO3-N mass leached; however, LEACHMN tended to overestimate
 summer and underestimate spring leaching losses. The lack of a
 provision in LEACHM to allow solute diffusion out of water flow
 channels, and underpredicted corn N uptake early in the season
 probably created conditions conducive for high leaching losses
 early; following harvest, insufficient NO3-N in the soil profile
 resulted in the model underestimating leaching in the spring.
 Validating LEACHMN using 1988 rate constants for the 1989 and
 1990 years was unsuccessful. When 3-yr average rate constants
 were used, simulation accuracy improved somewhat; most accurate
 simulations were found if 3-yr average values were close to the
 calibrated rate constant for that year. The model's predictive
 capability would probably improve if it contained a more complex
 corn N uptake routine and a dual-pore water flow component.
 NAL Call No.: 4-AM34P
 49. Evaluation of phosphorus loading models for south Florida.
 Zhang, J.; Haan, C. T.; Tremwel, T. K.; Kiker, G. A. 
 Trans-ASAE v.38, p.767-773. (1995).
 Includes references.
 Descriptors: lakes-; phosphorus-; runoff-; water-pollution;
 water-management; simulation-models; algorithms-; prediction-;
 Abstract: Phosphorus enrichment poses a threat to the ecology of
 Florida's Lake Okeechobee. As a part of a phosphorus management
 program, the South Florida Water Management District evaluated
 two nutrient loading models CREAMS-WT and FHANTM. Model
 documentation and algorithms were reviewed Model simulations for
 phosphorus loading were compared to measured data for three sites
 for the period April 1989, through December 1991. Statistical
 correlation of monthly and annual values was analyzed Based on
 these analyses, recommendations concerning the models for
 predicting phosphorus loading from Lake Okeechobee watersheds are
 NAL Call No.: 290.9-Am32T
 50. A farm scale water quality planning system for evaluating
 best management practices.
 Batchelor, W. D.; Dillaha, T. A. I.; Wolfe, M. L.; Heatwole, C.
 D.; Mostaghimi, S. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2156/94-2185) 17 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 19-22, 1994, Kansas City, Missouri.
 Descriptors: water-pollution; water-quality; land-management;
 simulation-models; pollution-control; non-point-source-pollution
 NAL Call No.: 290.9-Am32P
 51. Field and undisturbed-column measurements for predicting
 transport in unsaturated layered soil.
 Ward, A. L.; Kachanoski, R. G.; Bertoldi, A. P. v.; Elrick, D. E. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Jan/Feb 1995. v. 59 (1) p. 52-59. 
 Includes references.
 Descriptors: layered-soils; solutes-; transport-processes;
 soil-analysis; analytical-methods; soil-variability;
 laboratory-methods; field-experimentation; models-;
 Abstract: Transport properties vary considerably over small
 distances in most soils. The stochastic streamtube model offers
 one approach to incorporating heterogeneity into transport
 predictions. This study tested the ability of the streamtube
 concept to predict transport in heterogeneous fields using
 measurements from undisturbed columns. Fifty undisturbed columns
 (0.15-m diam. by 1.5 m deep) were taken every 0.4 m from a
 20-m-long transect in 8 loamy sand soil with variable horizon
 thickness. Each core was instrumented at 0.1-m intervals with
 time domain reflectometry probes to measure resident fluid
 concentrations of a conservative (Cl-) tracer under steady flow
 conditions. Large-scale concentration curves of Cl- from solution
 samplers and coring were obtained from field experiments
 conducted on the same soil under similar boundary conditions.
 Differences were observed in the solute spread and mass recovery,
 but not in the centers of mass. Horizontal scale dependence of
 transport was observed in the field but not in the columns. This
 suggests that a higher dimensionality of transport, probably
 along the horizon interfaces, may be responsible for the observed
 scale dependence in the field. Although the stochastic streamtube
 model gave good predictions of the center of mass, it does not
 appear to be a realistic physical analogue for describing solute
 dispersion in soils with spatially variable layer thickness.
 NAL Call No.: 56.9-So3
 52. Field validation and comparison of LEACHM and NCSWAP.
 Jabro, J. D.; Jemison, J. M. Jr.; Lengnick, L. L.; Fox, R. H.;
 Fritton, D. D. 
 Trans-ASAE v.36, p.1651-1657. (1993).
 Includes references.
 Descriptors: nitrate-; leaching-; simulation-models; prediction-;
 silt-loam-soils; nitrogen-fertilizers; animal-manures;
 Abstract: The abilities of the LEACHM and NCSWAP models to
 simulate nitrate leaching were compared using field data
 collected from a three-year nitrate leaching experiment conducted
 in central Pennsylvania on Hagerstown silt loam soil (fine,
 mixed, mesic, Typic Hapludalf). Nitrate leaching losses below the
 1.2-m depth from N-fertilized and manured corn were measured with
 zero-tension pan lysimeters. Four nitrogen and manure treatments
 were modeled for the growing seasons of 1988, 1989, and 1990
 using the LEACHM and NCSWAP models. The cumulative simulations
 were then compared with the cumulative pan efficiency corrected
 measured data for these three years. Both models were calibrated
 to the site conditions using the growing season data of 1989.
 After the models were calibrated for the 1989 year, they were
 evaluated using 1988 and 1990 nitrate leaching data. Simulated
 results for the calibration year for both models were reasonably
 accurate. Statistical criteria were established from the
 calibration data set (1989) to evaluate the simulations from both
 models for the two validation years (1988 and 1990). Based on
 this statistical criteria, both models generally did not
 successfully predict nitrate leaching below the 1.2-m depth for
 most of the treatments for the validation years. Much of the
 simulation error seemed to be related to the inability of both
 models to simulate the macropore influenced waterflow in the
 well-structured soil and/or the sub-model controlling soil
 nitrogen rate constants. The overall performance of both models
 was compared and it was concluded that the LEACHM model (Md =
 0.38 kg ha-1) statistically performed better than the NCSWAP
 model (Md = -3.44 kg ha-1) in simulating.
 NAL Call No.: 290.9-Am32T
 53. A forest site nitrogen dynamics model for land application of
 Crohn, D. M.; Haith, D. A. 
 Trans-ASAE v.37, p.1135-1144. (1994).
 Includes references.
 Descriptors: sewage-sludge; application-to-land; nitrogen-;
 nitrate-; broadleaved-deciduous-forests; groundwater-; leaching-;
 mathematical-models; computer-simulation; simulation-models;
 nitrate-nitrogen; application-rates; forsento-
 Abstract: The application of municipal sewage sludge to forests
 may raise nitrate-nitrogen concentrations in percolating
 groundwater. In agricultural systems, it is usually assumed that
 the processes governing nitrogen concentrations in leachate are
 relatively short-term, and that other contaminants, such as heavy
 metals, limit long-term application rates. These assumptions may
 not be appropriate for forests because the nitrogen levels in
 these systems change over time and harvests in most forests are
 relatively infrequent. We have modified a computer model from the
 ecology literature to investigate the long-term impact of
 nitrogen additions on groundwater quality in sludge amended
 forests. The model is descended from previous models of forest
 dynamics. It was tested with data from natural and sludge amended
 northeastern forests, and was used to design long-term loading
 rates for a northern hardwood forest in New Hampshire. Higher
 loading rates are possible if applications are made at
 multiple-year intervals as added nitrogen is immobilized in the
 soil and in accumulated litter. If 4.5 Mg/ha (dry weight) of
 anaerobically digested sludge (225 kg/ha total nitrogen) is
 applied at three-year intervals to a 31-year-old site, the model
 predicts that leaching nitrate-nitrogen concentrations will
 respect the 10 mg/l drinking water standard for nitrogen-N in 99%
 of all years.
 NAL Call No.: 290.9-Am32T
 54. A fugacity model of pesticide runoff to surface water:
 development and validation.
 Di Guardo, A.; Calamari, D.; Zanin, G.; Consalter, A.; Mackay, D. 
 Chemosphere v.28, p.511-531. (1994).
 Includes references.
 Descriptors: linuron-; metolachlor-; alachlor-; terbuthylazine-;
 herbicide-residues; water-pollution; runoff-; runoff-water;
 surface-water; simulation-models; fields-; computer-software;
 NAL Call No.: TD172.C54
 55. GIS-based groundwater pollution hazard assessment: a critical
 review of the DRASTIC model.
 Merchant, J. W. 
 Photogramm-eng-remote-sensing v.60, p.1117-1127. (1994).
 In the special issue: GIS / edited by G.A. Maclean and A.L.
 Descriptors: groundwater-pollution;
 geographical-information-systems; land-use; models-; aquifers-;
 NAL Call No.: 325.28-P56
 56. A GIS data interface for water quality modeling.
 Drungil, C. E. C.; Geter, W. F.; Wickey, K. J. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (932565) 12 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 14-17, Chicago, Illinois.
 Descriptors: water-quality; geographical-information-systems;
 watersheds-; catchment-hydrology; simulation-models
 NAL Call No.: 290.9-Am32P
 57. GIS interfaced with field & riparian zone models.
 Tucker, M. A.; Thomas, D. L.; Altier, L. S.; Bosch, D. D. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2120/94-2155) 13 p. 
 Paper presented at the 1994 International Summer Meeting,
 sponsored by the ASAE, June 19-22, 1994, Kansas City, Missouri.
 Descriptors: water-quality; fields-; watersheds-;
 riparian-forests; riparian-vegetation; information-systems;
 pollutants-; computer-simulation; simulation-models
 NAL Call No.: 290.9-Am32P
 58. GLEAMS hydrology submodel modified for shallow water table
 Reyes, M. R.; Bengston, R. L.; Fouss, J. L.; Rogers, J. S. 
 Trans-ASAE v.36, p.1771-1778. (1993).
 Includes references.
 Descriptors: hydrology-; high-water-tables; simulation-models;
 runoff-; percolation-; soil-water; evapotranspiration-;
 Abstract: GLEAMS-Water Table (GLEAMS-WT) is a modified version of
 GLEAMS that accounts for shallow water table fluctuations. The
 modification was accomplished by replacing the evapotranspiration
 and percolation algorithms in GLEAMS with evapotranspiration and
 percolation routines that are affected by shallow water table.
 Furthermore, routines to account for depression storage, steady
 state upward flux from the water table, and water table depth
 predictions were added. The simulation performances of GLEAMS and
 GLEAMS-WT were evaluated by comparing their predictions with
 seven years (1981 through 1987) of measured data from a
 runoff-erosion-drainage experimental plot at Baton Rouge,
 Louisiana. The GLEAMS-WT predictions of surface runoff volume
 were very satisfactory. Total predicted surface runoff volume for
 seven years was only 0.6 cm (0%) greater than the observed runoff
 volume, a significant improvement from GLEAMS underprediction of
 surface runoff volume by 54%. GLEAMS-WT predictions of water
 table depth were satisfactory.
 NAL Call No.: 290.9-Am32T
 59. GLEAMS modeling of BMPs to reduce nitrate leaching in Middle
 Suwannee River Area.
 Reck, W. R. 
 Environmentally sound agriculture  proceedings of the second
 conference  20-22 April 1994 /. St. Joseph, Mich. : American
 Society of Agricultural Engineers, c1994. 1994. 361-367. 
 Includes references.
 Descriptors: groundwater-; water-quality; nitrate-nitrogen;
 leaching-; farming-systems; farm-management; dairy-farming;
 poultry-farming; monitoring-; models-; computer-techniques;
 NAL Call No.: S589.7.E57-1994
 60. GLEAMS-WT hydrology submodel modified to include subsurface
 Reyes, M. R.; Bengston, R. L.; Fouss, J. L. 
 Trans-ASAE v.37, p.1115-1120. (1994).
 Includes references.
 Descriptors: water-table; subsurface-drainage; hydrology-;
 simulation-models; computer-simulation; runoff-;
 surface-drainage; louisiana-
 Abstract: The model GLEAMS-SWAT (GLEAMS with Subsurface drainage
 and WAter Table) is a modified version of GLEAMS that accounts
 for shallow water table fluctuations and subsurface drainage. The
 modification was accomplished by incorporating a subsurface
 drainage routine in GLEAMS-WT. Simulation performances of GLEAMS
 and GLEAMS-SWAT were evaluated by comparing their predictions
 with seven years (1981-1987) of measured data from a
 runoff-erosion-drainage experimental plot at Baton Rouge,
 Louisiana. Validations to test the accuracy of GLEAMS-SWAT
 predictions of surface runoff volume, subsurface drainage volume,
 total volume (surface runoff + subsurface drainage), and water
 table depth were satisfactory. Total predicted surface runoff
 volume for the seven-year period was 94% of the observed runoff
 volume, an improvement from GLEAMS under prediction of surface
 runoff volume which was 71% of the observed runoff Subsurface
 drainage volume and total drainage (runoff + subsurface drainage)
 volume predictions were, respectively, 99% and 96% of the
 observed volumes. Water table depth prediction was deeper than
 the observed depth, especially during the regrowing and growing
 NAL Call No.: 290.9-Am32T
 61. GLEAMS-WT hydrology submodel modified to include subsurface
 Reyes, M. R.; Bengtson, R. L.; Fouss, J. L. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932122) 13 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: water-table; subsurface-drainage; subsurface-runoff;
 hydrology-; simulation-models;
 NAL Call No.: 290.9-Am32P
 62. Gleams-WT with pesticides.
 Reyes, M. R.; Fouss, J. L.; Bengston, R. L.; Gayle, G. A. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (932554) 10 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 14-17, Chicago, Illinois.
 Descriptors: water-table; pesticides-; runoff-;
 simulation-models; ID:
 NAL Call No.: 290.9-Am32P
 63. Gully erosion minimization on reclaimed surface mines using
 SSAST computer model.
 McKenney, R. A.; Gardner, T. W. 
 J-irrig-drain-eng v.120, p.910-924. (1994).
 Includes references.
 Descriptors: coal-mine-spoil; reclaimed-soils; gully-erosion;
 runoff-; infiltration-; geological-sedimentation; hydrology-;
 models-; pennsylvania-;
 stable-slope-and-sediment-transport-model; postmine-hydrology
 NAL Call No.: 290.9-AM3Ps-IR
 64. Herbicide discovery and development: emphasis on groundwater
 Lamoreaux, R. J. 
 Crop-prot v.13, p.483-487. (1994).
 Includes references.
 Descriptors: herbicides-; research-; groundwater-pollution;
 screening-; simulation-models; lysimeters-
 NAL Call No.: SB599.C8
 65. Hierarchical approaches to the study of water quality in
 Hunsaker, C. T.; Levine, D. A. 
 Bioscience v.45, p.193-203. (1995).
 Includes references.
 Descriptors: rivers-; water-quality; land-use; watersheds-;
 geographical-information-systems; simulation-models
 NAL Call No.: 500-Am322A
 66. Hydrologic modeling for riparian management.
 Sheridan, J. M.; Williams, R. G.; Altier, L. S.; Lowrance, R. R.;
 Mills, W. C.; Thomas, D. L. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (932598) 18 p. 
 Paper presented at the "1993 International Winter Meeting of the
 American Society of Agricultural Engineers," December 14-17,
 1993, Chicago, Illinois.
 Descriptors: water-quality; water-pollution; groundwater-
 NAL Call No.: 290.9-Am32P
 67. The impact of GIS-derived topographic attributes on the
 simulation of erosion using AGNPS.
 Srinivasan, R.; Engel, B. A.; Wright, J. R.; Lee, J. G.; Jones,
 D. D. 
 Appl-eng-agric v.10, p.561-566. (1994).
 Includes references.
 Descriptors: erosion-; simulation-models; hydrology-;
 geographical-information-systems; slope-; prediction-;
 pollution-; point-sources;
 Abstract: Topographic attributes such as slope steepness and
 slope length are important factors in predicting soil loss and
 chemical movement using hydrologic simulation models. The
 objective of this study was to examine the effects of various
 slope prediction methods in providing input to the nonpoint
 source (NPS) simulation model AGNPS. Four algorithms/techniques
 (neighborhood, quadratic, best fit plane, and maximum slope
 method) were used to estimate slope from elevation data sets. The
 effect of each of these methods on slope percentages, slope
 lengths, and erosion estimates using the grid-based GRASS
 (Geographical Resources Analysis Support System) GIS and a
 distributed parameter NPS pollution model AGNPS were
 demonstrated. The four slope prediction methods were applied to a
 124-ha (310-acre) watershed located in Waco County, Texas, using
 the AGNPS model. Among the four slope prediction methods, notable
 differences were found in their prediction of topographic
 attributes and the use of these attributes to predict erosion at
 the outlet of the watershed and within the watershed (spatial
 distribution). Observed watershed data best matched simulated
 watershed response using topographic inputs obtained from the
 neighborhood method.
 NAL Call No.: S671.A66
 68. Implementation of a kinematic wave in the runoff block of
 Ferguson, D.; Ball, J. E. 
 Manly Vale, N.S.W. : Water Research Laboratory, The University of
 New South Wales, [1994] 1 v. (in various pagings) : ill..
 At head of title: The University of New South Wales, Water
 Research Laboratory.
 Descriptors: Runoff-Mathematical-models;
 NAL Call No.: GB651.R47--no.183
 69. Integration of a basin-scale water quality model with GIS.
 Srinivasan, R.; Arnold, J. G. 
 Water-resour-bull v.30, p.453-462. (1994).
 Includes references.
 Descriptors: water-quality; watersheds-;
 geographical-information-systems; simulation-models;
 integrated-systems; texas-
 Abstract: Geographic Information Systems (GIS) have been
 successfully integrated with distributed parameter, single-event,
 water quality models such as AGNPS (Agricultural Nonpoint Source)
 and ANSWERS (Areal Nonpoint Source Watershed Environmental
 Response Simulation). These linkages proved to be an effective
 way to collect, manipulate, visualize, and analyze the input and
 output date of water quality models. However, for
 continuous-time, basin large-scale water quality models,
 collecting and manipulating the input data are more
 time-consuming and cumbersome due to the method of disaggregation
 (subdivisions are based on topographic boundaries). SWAT (Soil
 and Water Assessment Tool), a basin-scale water quality model,
 was integrated with a GIS to extract input data for modeling a
 basin. This paper discusses the detailed development of the
 integration of the SWAT water quality model with GRASS
 (Geographic Resources Analysis Support System) GIS, along with an
 application and advantages. The integrated system was applied to
 a simulated 114 sq. km upper portion of the Seco Creek Basin by
 subdividing it into 37 subbasins. The average monthly predicted
 streamflow is in agreement with measured monthly streamflow
 NAL Call No.: 292.9-Am34
 70. Interceptor drains for lagoon seepage capture.
 Huffman, R. L.; Feng, J. S. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (934018) 8 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers," and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: lagoons-; waste-disposal-sites; drainage-equipment;
 simulation-models; groundwater-; seepage-; water-quality
 NAL Call No.: 290.9-Am32P
 71. Interpreting non-steady state tracer breakthrough experiments
 in sand and clay soils using a dual-porosity model.
 Saxena, R. K.; Jarvis, N. J.; Bergstrom, L. 
 J-hydrol v.162, p.279-298. (1994).
 Includes references.
 Descriptors: sandy-soils; clay-soils; macropore-flow; tracers-;
 chlorine-; triticum-; leaching-; porosity-; solutes-;
 transport-processes; simulation-models
 Abstract: The effects of preferential flow on 36Cl transport in
 undisturbed sand and clay soil monolith lysimeters were
 quantified using a dual-porosity model (MACRO). A double tracer
 test with 3H and 36Cl was performed simultaneously to check the
 possible occurrence of sidewall flow in the lysimeters. In the
 dual-porosity model MACRO, simulations can be performed in both
 one and two flow domains. Run in one flow domain, the model
 reduces to numerical solutions of Richards' equation and the
 convection-dispersion equation. In the sandy soil, the occurrence
 of preferential flow was tested by simulating in one domain,
 assuming that a certain pore fraction takes no part in water flow
 and solute transport. For the clay soil, the one domain case was
 compared with two domain simulations accounting for macropore
 flow. The double-tracer tests showed that sidewall flow did not
 occur in either soil type. Simulations of water flow showed good
 agreement with observed seepage until late autumn, but were less
 good during winter because the model does not account for soil
 freezing and snowpack/ snowmelt. Simulated water flows were
 similar in one and two domain simulations, presumably because
 water contents in the lysimeters were maintained close to field
 capacity during the experiment. The simulations indicated that
 preferential flow occurred in the sandy soil, with the observed
 36Cl breakthrough curves, assuming an unwetted volumetric pore
 fraction of 20%, reproduced reasonably well. The rate of 36Cl
 leaching was consequently increased by c. 25% compared with the
 simulation assuming no preferential flow. Macropore flow was
 clearly demonstrated in the clay soil. The two domain simulation
 matched the.  soil water pressure head defining the boundary
 between pore domains was set to -50cm. This implies that
 preferential 36Cl transport was taking place in a wide range of
 pore sizes, including smaller mesopores. The one domain
 simulation failed to predict the pattern of breakthrough of 36Cl
 in the clay soil, in that it seriously underestimate leaching at
 early times and overestimated leaching towards the end of the
 experiment. Accounting for preferential flow with the dual
 porosity model resulted in significantly improved estimates of
 solute transport, compared to the classical convective-dispersive
 treatment, for both nonstructured sands and structured clay
 NAL Call No.: 292.8-J82
 72. Irrigation storage reservoirs as a water supply solution for
 Upper Telogia Creek.
 Reck, W. R. 
 Environmentally sound agriculture  proceedings of the second
 conference  20-22 April 1994 / p.176-183. (1994).
 Includes references.
 Descriptors: irrigation-water; water-supply; water-harvesting;
 storage-; reservoirs-; runoff-irrigation; water-reuse;
 environmental-impact; water-resources; computer-simulation;
 simulation-models; florida-
 NAL Call No.: S589.7.E57-1994
 73. A knowledge-based system linked to AGNPS/GRASS interface.
 Mohite, M.; Whittaker, A. D.; Srinivasan, R. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (933041) 20 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers,"
 June 20-23, 1993, Spokane, Washington.
 Descriptors: erosion-; watersheds-; expert-systems
 NAL Call No.: 290.9-Am32P
 74. Leaching characteristics of banded and broadcast inorganic
 Dixon, K. L.; Smith, M. C.; Thomas, D. L.; Knisel, W. G. 
 Trans-ASAE v.36, p.1779-1788. (1993).
 Includes references.
 Descriptors: leaching-; bromide-; chloride-; tracers-;
 broadcasting-; band-placement; downward-movement; diffusion-;
 models-; groundwater-pollution; sandy-loam-soils
 Abstract: A field study was conducted on an Ocilla loamy coarse
 sand to determine the leaching characteristics of banded and
 broadcast applications of bromide and chloride. Bromide and
 chloride were applied in two treatments to eight plots absent of
 any crop. One treatment consisted of banding one tracer while
 broadcasting the other. For the second treatment, the banded and
 broadcast chemicals were reversed. Lateral and vertical movement
 was observed and comparisons were made between banded and
 broadcast tracer applications. Results indicate soil variability,
 dispersion, and diffusion negated potential banding effects on
 the solute plume below the root zone.
 NAL Call No.: 290.9-Am32T
 75. Leaching potential of turf care pesticides: a case study of
 Long Island golf courses.
 Primi, P.; Surgan, M. H.; Urban, T. 
 Ground-water-monit-remediat. Dublin, OH : Ground Water Pub. Co.,
 c1993-. Summer 1994. v. 14 (3) p. 129-138. 
 Includes references.
 Descriptors: lawns-and-turf; golf-courses; pesticides-;
 metabolites-; leaching-; sandy-soils; groundwater-;
 groundwater-pollution; monitoring-; simulation-models;
 analytical-methods; case-studies; new-york
 Abstract: Pesticides used to maintain golf course turf can
 threaten ground water.  This concern is particularly important in
 most of New York's Long Island, where generally sandy soils
 overlie a sole source aquifer.  This study uses two methods to
 evaluate the potential for pesticides that are commonly used on
 Long Island's golf courses to leach to ground water. Adapting the
 Pesticide Root Zone Model (PRZM), Release 1, for dense turf and
 applying site-specific soil data, certain pesticides, including
 metalaxyl and trichlorfon, are identified as potential problem
 leachers.  PRZM simulations also identify the Long Island soils,
 including the sandy Plymouth and Carver soils, which are most
 vulnerable to leaching. When adequate input data for PRZM is
 unavailable, the ground water ubiquity score (GUS) method may be
 useful.  GUS leachability classifications of pesticides commonly
 applied on Long Island golf courses, and of pesticides actually
 detected in ground water samples taken on Long Island, agree with
 PRZM predictions and the field data.  The GUS method is applied
 to the evaluation of the leaching potential of pesticide
 degradation products (DCPA, maneb, and mancozeb metabolites), and
 the degradation products are shown to be a greater threat to
 ground water than their parent compounds. These methods are
 potentially useful in designing ground water monitoring programs
 and for guiding the pesticide use and selection decisions of golf
 course managers.
 NAL Call No.: GB1001.G76
 76. Long-term sulfate dynamics at Lange Bramke (Harz) used for
 testing two acidification models.
 Lange, H.; Hauhs, M.; Schmidt, S. 
 Water-air-soil-pollut v.79, p.339-351. (1995).
 In the special issue: Biogeochemical monitoring in small
 catchments / edited by J. Cerny, M. Novak, T. Paces and R.K.
 Weider.  Evaluation of Integrated Monitoring in Small
 Catchments," held September 18-20, 1993, Prague, Czech Republic.
 Descriptors: sulfate-; nitrate-; hydrogen-ions; soil-solution;
 runoff-; acidification-; elements-; anions-; cations-;
 mountains-; watersheds-; forest-soils; coniferous-forests;
 picea-abies; lower-saxony; magic-model; bem-model
 NAL Call No.: TD172.W36
 77. A lumped parameter water balance of a semi-arid watershed.
 Flerchinger, G. N.; Cooley, K. R.; Hanson, C. L.; Seyfried, M.
 S.; Wight, J. R. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2120/94-2155) 17 p. 
 Paper presented at the 1994 International Summer Meeting,
 sponsored by the ASAE, June 19-22, 1994, Kansas City, Missouri.
 Descriptors: watersheds-; semiarid-zones; water-balance;
 precipitation-; profiles-; soil-water; groundwater-; runoff-;
 vegetation-; evapotranspiration-; simulation-models; idaho-
 NAL Call No.: 290.9-Am32P
 78. Managing agricultural pollution using a linked geographical
 information system and non-point source pollution model.
 Morse, G.; Eatherall, A.; Jenkins, A. 
 J-Inst-Water-Environ-Manag v.8, p.277-286. (1994).
 Includes references.
 Descriptors: pollution-; agriculture-; simulation-models;
 geographical-information-systems; computer-software; prediction-
 Abstract: This study documents the development of a link between
 a geographical information system (GIS) and a non-point source
 pollution model. The GIS ARC/INFO was linked to the agricultural
 non-point source pollution model and ORACLE data sources.
 Application of the system is demonstrated using the Bedford-Ouse
 catchment as a suitable case study. Water quality impacts are
 predicted from source data describing topography, soils, land use
 and river network. The model results were in agreement with
 observed nitrate concentrations at the catchment outlet, and more
 appropriate data sources are considered to be the main priority
 for improving model predictive ability. Management scenarios were
 established to assess the impact of changing agricultural
 management practices on predicted water quality. The approach has
 significant potential for the management of agricultural
 pollution in the UK.
 NAL Call No.: TD420.W374
 79. Managing underground storage tanks in urban environments: a
 geographic information systems approach.
 Hudak, P. F.; Speas, R. K.; Schoolmaster, F. A. 
 Water-resour-bull v.31, p.439-445. (1995).
 Includes references.
 Descriptors: soil-pollution; groundwater-pollution; fuel-tanks;
 underground-storage; management-; urban-areas;
 geographical-information-systems; databases-; texas-;
 Abstract: Fuels contained in underground storage tanks (USTs) are
 a major source of soil and ground water contamination. Effective
 management of the problem at the urban level is difficult due to
 a large number of tanks and a vast array of factors (e.g., tank
 characteristics, geology) that determine environmental hazards.
 The problem is compounded by frequent abandonment and reuse of
 service stations, which makes it difficult to track the status Of
 underground tanks. Geographic information systems (GIS) are
 ideally suited to organizing location and attribute data for
 variables that are pertinent to the UST management problem. A
 GIS-based UST management system was developed and applied to 136
 current and former gasoline service stations in Denton, Texas.
 The system is effective for tank inventory and can be applied in
 a proactive fashion to identify potentially problematic
 facilities. In the event of a leak or spill, the management
 system can support the implementation of reactive measures to
 mitigate subsurface contamination. Potential beneficiaries of
 such a system include planning departments, environmental
 regulatory agencies, emergency management officials, lending
 institutions, gasoline distributors, and oil companies.
 NAL Call No.: 292.9-Am34
 80. Mass transfer in soils with local stratification of hydraulic
 Li, L.; Barry, D. A.; Culligan Hensley, P. J.; Bajracharya, K. 
 Water-resour-res v.30, p.2891-2900. (1994).
 Includes references.
 Descriptors: soil-; transport-processes; hydraulic-conductivity;
 solutes-; layered-soils; mass-transfer; mathematical-models;
 Abstract: The two-region model was developed originally to
 describe nonsorbing chemical transport in soils with dead-end
 pores based on the concept of mobile and immobile regions in the
 soil. It has been shown that the model can simulate solute
 transport in soils with local stratification, or inhomogeneity,
 of hydraulic conductivity. However, the physical basis of the
 model becomes questionable, since the mobile-immobile region
 concept does not apply in stratified soils. In both soil types
 the nonequilibrium effect is caused by an apparent mass transfer
 process within the soil, as distinct from advection and
 diffusion. Where there are immobile regions, the mass transfer is
 due to solute interregion diffusion alone. In stratified soils
 the nonequilibrium mass transfer process is affected also by
 local flow variations. A conceptual model, numerical simulations,
 and laboratory experiments are presented to analyze these
 effects. For a given soil with fixed local stratification of
 hydraulic conductivity, it is shown that in the low-velocity
 range, the apparent mass transfer rate parameter, alpha, scales
 as V2/D (V is pore water velocity in the two-region model and D
 is the longitudinal dispersion coefficient), which implies that
 the mass transfer process is predominantly affected by local flow
 variations. When the velocity is relatively high, alpha varies
 with DT/h2 (DT is the interregion diffusion coefficient and h is
 the characteristic thickness of the stratified layers) and the
 mass transfer process is dominated by interregion diffusion.
 These scaling relations for alpha reflect the two mechanisms
 controlling the mass transfer process in locally stratified
 soils. They have implications.  prototype soils. In particular,
 the relationship alpha varies with V2/D leads to the conclusion
 that exact physical modeling of nonsorbing chemical transport
 coupled with apparent mass transfer in locally stratified soils
 may be viable.
 NAL Call No.: 292.8-W295
 81. Measured and RZWQM predicted atrazine dissipation and
 movement in a field soil.
 Ma, Q. L.; Ahuja, L. R.; Rojas, K. W.; Ferreira, V. F.;
 DeCoursey, D. G. 
 Trans-ASAE v.38, p.471-479. (1995).
 Includes references.
 Descriptors: agricultural-chemicals; environmental-impact;
 surface-water; groundwater-; atrazine-; transformation-; runoff-;
 simulation-models; distribution-; profiles-; sorption-;
 Abstract: The ARS Root Zone Water Quality Model (RZWQM) was
 developed recently to study the fate and behavior of
 agrochemicals in the environment and the effects of agricultural
 management on surface and groundwater quality. In this article,
 model performance was tested by comparing three years of field
 data for water and atrazine movement (runoff and concentration
 profiles) and atrazine transformation obtained under different
 management conditions with those simulated by RZWQM. Accuracy of
 model simulation was quantified by standard linear regression
 techniques. The regression correlation coefficients (R2) between
 average measured and simulated data for water runoff, atrazine
 runoff, atrazine persistence, and atrazine distribution in the
 soil profile were 0.87, 0.92, 0.97, and 0.73, respectively.
 Evaluation of the model, using best estimates for properties of
 atrazine and hydrologic characteristics of the field soil and
 limited calibration for water runoff, suggests that the model
 effectively simulates the important processes operating on water
 and chemicals.
 NAL Call No.: 290.9-Am32T
 82. A method for developing probability distributions for rill
 flow and density.
 Lewis, S. M.; Barfield, B. J.; Storm, D. E. 
 Trans-ASAE v.37, p.1879-1887. (1994).
 Includes references.
 Descriptors: rill-erosion; water-flow; overland-flow;
 probability-; probability-analysis; imagery-; photographs-;
 eroded-soils; runoff-; sediment-yield; digital-terrain-model;
 Abstract: Procedures are presented and evaluated for developing
 probability distribution functions for rill numbers (density) and
 rill flow rates that can be used to represent the stochasticity
 of rill networks in recent erosion models such as PRORIL. Subsoil
 and topsoil data sets, including photographs, collected at the
 University of Kentucky were used in the evaluation. Photographic
 images were corrected for optical distortion and visually
 analyzed to develop the rill networks. A digital terrain model
 (DTM) that allowed combining of channels, but not flow splitting,
 was also utilized to develop a flow network and compared to the
 photographically determined network. The DTM generated network
 did not provide a good fit to the photographically determined
 network, likely because of problems with interpolation and with
 the inability to predict rill splitting. The DTM generated
 networks were utilized to develop probability density functions
 (PDFs) for rill numbers and conditional PDFs for rill flow rates
 given a number of rills. The binomial distribution provided a
 good fit to rill number distributions as defined by the
 Kolmogorov-Smirnov test. The Weibull distribution provided the
 best fit to the conditional PDF for flow rates, but the goodness
 of fit was poor. This lack of fit, likely due to inadequacies of
 the DTM, should improve with improved DTMs.
 NAL Call No.: 290.9-Am32T
 83. A method for simulating cadmium transport in soil: model
 development and experimental evaluation.
 Al Soufi, R. W. 
 J-hydrol v.163, p.233-247. (1994).
 Includes references.
 Descriptors: cadmium-; contaminants-; transport-processes;
 polluted-soils; acid-soils; adsorption-; desorption-; soil-ph;
 mathematical-models; simulation-; models-
 Abstract: A model for simulating cadmium transport in soil is
 presented. The calculation scheme is based on a three-dimensional
 advection-dispersion model. The adsorption process is defined by
 a lumped parameter mathematical model in which the amount of ions
 that remains in solution is correlated with the amount that
 originally exists in the input solution. Desorption is defined in
 the same way by correlating the amount of ions desorbed with the
 amount of ions held by the soil solid surface. Both relationships
 incorporate the effect of soil solution pH which is defined by a
 power equation that predicts the pH value at any time and at any
 depth, from the pH of the input solution and elapsed time. Soil
 column experiments were conducted to validate the performance of
 the model. Also, batch tests were employed to determine the
 essential adsorption-desorption parameters that are required to
 operate the model. In light of the results, it was concluded that
 the model satisfactorily forecasts cadmium concentration and the
 pH of soil solution under varied acidic conditions. However,
 values of model parameters are strictly empirical and need to be
 determined for each soil type.
 NAL Call No.: 292.8-J82
 84. A methodology for the evaluation of global warming impact on
 soil moisture and runoff.
 Valdes, J. B.; Seoane, R. S.; North, G. R. 
 J-hydrol v.161, p.389-413. (1994).
 Includes references.
 Descriptors: global-warming; soil-water; variation-; runoff-;
 precipitation-; temperature-; evapotranspiration-;
 Abstract: This paper presents a numerical evaluation of the
 viability of soil moisture and direct surface runoff due to
 global warming. An analytical model of the soil moisture balance
 based on our previous work is used to evaluate the probability
 distribution of the soil moisture concentration and resulting
 surface runoff. The input of hydroclimatic values is based on the
 approach suggested by C.W. Richardson in 1981. Our results show
 that not only the mean of the distribution of both soil moisture
 and runoff change, as expected, but that the variability of the
 values around the means also changes. The results of our research
 have immediate applications on the planning of reservoir
 operation for irrigation demands and evaluation of the change in
 surface runoff expected due to global warming.
 NAL Call No.: 292.8-J82
 85. Minimum leaching scheduling of nitrogen fertilization and
 Falkovitz, M. S.; Feinerman, E. 
 Bull-math-biol v.56, p.665-686. (1994).
 Includes references.
 Descriptors: nitrogen-fertilizers; irrigation-;
 mathematical-models; leaching-; optimization-
 Abstract: This paper develops and applies dynamic mathematical
 model for optimal scheduling of nitrogen fertilization and
 irrigation that minimizes nitrogen leaching subject to a target
 level of yield.  The analysis assumes a single crop grown during
 a single growing season of a given length. It is shown that
 substitution of water for nitrogen along a given plant growth
 path decreases nitrogen leaching and, therefore, groundwater
 contamination.  It is proved that a minimum leaching solution to
 the optimization problem is obtained with a single nitrogen
 application at the beginning of the season and irrigation
 scheduling that maintains a wet soil throughout the growing
 period.  A numerical example utilizing experimental data for an
 irrigated summer corn in Israel confirms and quantifies the
 analytical findings.
 NAL Call No.: 442.8-B872
 86. Mn2+ as a contrast reagent for NMR studies of 35Cl- and 81Br-
 transport through model biological membranes.
 Riddell, F. G.; Zhou, Z. 
 J-inorg-biochem v.55, p.279-293. (1994).
 Includes references.
 Descriptors: membranes-; models-; transport-processes;
 ion-transport; chloride-; bromide-; manganese-; spectral-data;
 Abstract: One major problem in using NMR to study halide ions in
 biological and model biological systems has been to find a
 contrast reagent to differentiate between halide ions in
 different compartments. Mn2+ is shown to be a very efficient NMR
 relaxation agent for the halide ions chloride and bromide and
 preferable to Co2+ at high magnetic fields. Its use is
 demonstrated in experiments in which halide ions are exchanged
 across the membranes of egg yolk phosphatidylcholine vesicles by
 the phase transfer catalysts tetrabutylammonium ion and
 benzyltributylammonium ion. Benzyl-tributylammonium ion is shown
 to be the more rapid anion transporter through the membrane.
 Valinomycin is found to cotransport ammonium ions with chloride
 as an ion pair at a faster rate than the phase transfer
 NAL Call No.: QD415.B5
 87. Model accuracy in snowmelt-runoff forecasts extending from 1
 to 20 days.
 Rango, A.; Martinec, J. 
 Water-resour-bull v.30, p.463-470. (1994).
 Includes references.
 Descriptors: meltwater-; runoff-; forecasts-; simulation-;
 forecasting-; surface-water; hydrology-; models-; canada-;
 hydrological-forecasting; surface-water-hydrology;
 Abstract: This paper examines the performance of snowmelt-runoff
 models in conditions approximating real-time forecast situations.
 These tests are one part of an intercomparison of models recently
 conducted by the World Meteorological Organization (WMO). Daily
 runoff from the Canadian snowmelt basin Illecille-waet (1155 km2,
 509-3150 m a.s.l.) was forecast for 1 to 20 days ahead. The
 performance of models was better than in a previous WMO project,
 which dealt with runoff simulations from historical data, for the
 following reasons: (1) conditions for models were more favorable
 than a real-time forecast situation because measured input data
 and not meteorological forecast inputs were distributed to the
 modelers; (2) the selected test basin was relatively easy to
 handle and familiar from the previous WMO project; and (3) all
 kinds of updating were allowed so that some models even improved
 their accuracy towards longer forecast times. Based on this
 experience, a more realistic follow-up project can be imagined
 which would include temperature forecasts and quantitative
 precipitation forecasts instead of measured data.
 NAL Call No.: 292.9-Am34
 88. A model for evaluating irrigation-induced water quality
 problems in irrigation and drainage systems.
 Manguerra, H. B.; Garcia, L. A.; Quinn, N. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2091/94-2119) 15 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 20-23, 1994, Kansas City, Missouri.
 Descriptors: irrigation-systems; drainage-systems; water-quality;
 temporal-variation; models-
 NAL Call No.: 290.9-Am32P
 89. A model for sorption, flux and plant uptake of cadmium in a
 Palm, V. 
 Water-air-soil-pollut v.77, p.169-190. (1994).
 Includes references.
 Descriptors: cadmium-; metal-ions; sorption-; profiles-;
 transport-processes; ion-uptake; plants-; mathematical-models;
 simulation-models; algorithms-; hydrology-
 NAL Call No.: TD172.W36
 90. Model study on environmentally relevant information based on
 agricultural statistics.  Modellstudie zu umweltrelevanten
 Informationen aus der Agrarstatistik.
 Corell, G. 1. 
 Munster : Lit, [1994] xix, 198 p. : ill..
 "August 1994.".
 Descriptors: Agricultural-pollution; Agriculture-Statistics
 NAL Call No.: TD195.A34M62--1994
 91. Modeling and error analysis of kinematic-wave equations of
 furrow irrigation.
 Reddy, J. M.; Singh, V. P. 
 Irrig-sci v.15, p.113-121. (1994).
 Includes references.
 Descriptors: furrow-irrigation; mathematical-models;
 infiltration-; runoff-; design-; errors-; analysis-; equations-
 Abstract: A moving control volume approach was used to model the
 advance phase of a furrow irrigation system whereas a fixed
 control volume was used to model the nearly stationary phase and
 the runoff rate. The resulting finite-difference equations of the
 kinematic-wave model were linearized and explicit algebraic
 expressions were obtained for computation of advance and runoff
 rate. The solutions for the advance increment and the runoff rate
 were compared with the nonlinear scheme, the zero-inertia model,
 and a set of field data. A close agreement was found between the
 models and the field data. Assuming a constant infiltration rate,
 a differential equation was derived to estimate the error between
 the kinematic-wave model and the zero-inertia model in predicting
 the flow cross-sectional area along the field length. The
 differential equation and two dimensionless terms were used to
 define the limits for use of the kinematic-wave model in furrow
 NAL Call No.: S612.I756
 92. Modeling for optimal management of agricultural and domestic
 wastewater loading to streams.
 Ejaz, M. S.; Peralta, R. C. 
 Water-resour-res v.31, p.1087-1096. (1995).
 Includes references.
 Descriptors: streams-; water-pollution; water-quality;
 waste-water; dairy-wastes; sewage-; waste-water-treatment;
 overland-flow; simulation-models; optimization-; simulation;
 Abstract: A simulation/optimization (S/O) model to aid managing
 multiobjective wastewater loading to streams while maintaining
 adequate downstream water quality is presented. The conflicting
 objectives are to maximize the human and dairy cattle populations
 from which treated wastewater can be discharged to the river
 system. Nonindustrial municipal (domestic) wastewater undergoes
 primary and secondary treatment by a sewage treatment plant (STP)
 before entering as a steady point source. Dairy wastewater is
 treated by overland flow (OLF) land treatment before entering the
 stream as a controlled steady diffuse source. Maximum dual-source
 loading strategies which do not degrade downstream water quality
 beyond specified limits are developed. For each computed loading
 strategy, an optimal OLF system design is also determined. The E
 constraint method is used to obtain sets of noninferior
 solutions. Sets of noninferior solutions are represented
 graphically to show the trade-off between human and bovine
 populations that can be maintained. Each set is computed for a
 different upstream flow rate to illustrate sensitivity to
 nondeterministic upstream flow rates. The nonlinear constraints
 utilized restrict downstream concentrations of 5-day biochemical
 oxygen demand, dissolved oxygen, nitrogen (organic, ammonia,
 nitrite, and nitrate), organic and dissolved phosphorus, and
 chlorophyll a. Concentrations are described via regression
 equations. The new regression expressions, surrogates for the
 complex advective-dispersive equation, permit rapid and feasible
 solutions by this unique S/O model.
 NAL Call No.: 292.8-W295
 93. Modeling infiltration during complex rainfall sequences.
 Corradini, C.; Melone, F.; Smith, R. E. 
 Water-resour-res v.30, p.2777-2784. (1994).
 Includes references.
 Descriptors: infiltration-; redistribution-; rain-; storms-;
 soil-water-movement; ponding-; soil-water-content; runoff-;
 simulation-models; surface-saturation
 Abstract: An extension of the conceptual model earlier developed
 by Smith et al. (1993) is presented. Their basic model considered
 the problem of point infiltration during a storm consisting of
 two parts separated by a rainfall hiatus, with surface saturation
 and runoff occurring in each part. The model is here extended
 toward further generality, including the representation of a
 sequence of infiltration-redistribution cycles with situations
 not leading to soil surface saturation, and rainfall periods of
 intensity less than the soil infiltration capacity. The model
 employs at most a two-part profile for simulating the actual one.
 When the surface flux is not at capacity, it uses a slightly
 modified version of the Parlange et al. (1985) model for
 description of increases in the surface water content and the
 Smith et al. (1993) redistribution equation for decreases.
 Criteria for the development of compound profiles and for their
 reduction to single profiles are also incorporated. The extended
 model is tested by comparison with numerical solutions of
 Richards's equation, carried out for a variety of experiments
 upon two contrasting soils. The model applications yield very
 accurate results and support its use as part of a watershed
 hydrologic model.
 NAL Call No.: 292.8-W295
 94. Modeling multiple reactive solute transport with adsorption
 under equilibrium and nonequilibrium conditions.
 Marzal, P.; Seco, A.; Ferrer, J.; Gabaldon, C. 
 Adv-water-resour v.17, p.363-374. (1994).
 Includes references.
 Descriptors: groundwater-pollution; groundwater-flow;
 pollutants-; solutes-; adsorption-; physicochemical-properties;
 equations-; mathematical-models; equations-; transport-processes;
 soil-physical-properties; soil-chemistry; soil-water-movement;
 simulation-models; solute-transport-equations;
 NAL Call No.: TD201.A4
 95. Modeling nutrient transport in vegetative filter strips.
 Chaubey, I.; Edwards, D. R.; Daniel, T. C.; Moore, P. A. Jr. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2120/94-2155) 28 p. 
 Paper presented at the 1994 International Summer Meeting,
 sponsored by the ASAE, June 19-22, 1994, Kansas City, Missouri.
 Descriptors: water-; water-quality; grass-strips;
 water-pollution; poultry-manure; runoff-; pollutants-;
 infiltration-; mathematical-models; prediction-
 NAL Call No.: 290.9-Am32P
 96. Modeling of biologically mediated redox processes in the
 Lensing, H. J.; Vogt, M.; Herrling, B. 
 J-hydrol v.159, p.125-143. (1994).
 Special Issue: Field laboratory and modelling studies of flow and
 transport processing / edited by H.S. Wheater, P.A.C. Raats, and
 A.C. Armstrong.  Sciences Programme Session HS1 of the XVII
 General Assembly of the European Geophysical Society, April 6-10,
 1992, Edinburgh.
 Descriptors: groundwater-pollution; bacteria-; growth-rate;
 metabolism-; redox-reactions; transport-processes; ions-;
 monitoring-; simulation-models; bioremediation-
 Abstract: To model bacterially catalyzed redox processes a
 multicomponent transport reaction model is presented. The
 transport part of the model solves the transient convection
 dispersion differential equations. The pure chemical submodel is
 conceptually similar to conventional thermodynamic equilibrium
 models. The kinetic submodel describes the heterotrophic
 metabolisms of several groups of microorganisms. To model a
 complete redox sequence (aerobic carbonaceous oxidation,
 denitrification, Fe(III)-reduction, Mn(IV)-reduction, and sulfate
 reduction) four functional bacterial groups are defined. Their
 growth and metabolisms are formulated in terms of Monod
 equations. As in other biofilm models, diffusion-limited exchange
 between the different phases (mobile pore water, biophase, and
 aquifer material) is also considered in this approach. The
 submodels are coupled by the equations of the microbially
 mediated redox reactions. This numerical technique permits direct
 mechanistic modeling of the influence of microbially catalyzed
 redox reactions on the chemical milieu of an aquifer. A two-step
 method is applied to solve the coupled transport and biochemical
 reaction equations. The numerical model was applied to field data
 of a natural subsurface flow path.
 NAL Call No.: 292.8-J82
 97. Modeling of intial discharges from hydraulic barriers
 underlying solid and hazardous waste landfills.
 Al Jobeh, Z. Y. 
 Proc-Ind-Waste-Conf. Chelsea, Mich. : Lewis Publishers. 1994. v.
 48 p. 309-315. 
 Meeting held on May 10-12, 1993, West Lafayette, Indiana.
 Descriptors: landfills-; landfill-leachates; soil-pollution;
 polluted-soils; groundwater-pollution; mathematical-models
 NAL Call No.: TP995.A1I5
 98. Modeling perspective of the deforestation impact in stream
 water quality of small preserved forested areas in the Amazonian
 Forti, M. C.; Neal, C.; Jenkins, A. 
 Water-air-soil-pollut v.79, p.325-337. (1995).
 In the special issue: Biogeochemical monitoring in small
 catchments / edited by J. Cerny, M. Novak, T. Paces and R.K.
 Weider.  Evaluation of Integrated Monitoring in Small
 Catchments," held September 18-20, 1993, Prague, Czech Republic.
 Descriptors: tropical-rain-forests; logging-effects;
 deforestation-; simulation-models; water-quality; streams-;
 sulfate-; anions-; cations-; acidification-; soil-organic-matter;
 organic-matter; reserved-forests; amazonas-; magic-model;
 NAL Call No.: TD172.W36
 99. Modeling pesticide transport in subsurface drained soils.
 Thooko, L. W.; Rudra, R. P.; Dickinson, W. T.; Patni, N. K.;
 Wall, G. J. 
 Trans-ASAE v.37, p.1175-1181. (1994).
 Includes references.
 Descriptors: pesticides-; pesticide-residues; atrazine-;
 herbicide-residues; leaching-; subsurface-drainage;
 simulation-models; computer-simulation; zea-mays;
 movement-in-soil; ontario-; drainmod-
 Abstract: Transport of chemicals through the soil profile and
 crop root zone, and the discharge from subsurface drainage lines
 into surface water can be a significant source of water
 pollution. This study measured and simulated subsurface drain
 outflows and atrazine loads in the subsurface drains from a field
 site in Ottawa, eastern Ontario, Canada, during 1988 and 1989.
 Corn was grown for silage at the site, and an H-flume with an
 automated water sampler was used to monitor temporal changes in
 quantity and quality of subsurface drain outflows from a 14-ha
 field site. A drainage simulation model, DRAINMOD, was combined
 with a chemical transport model, GLEAMS, to simulate the chemical
 transport of atrazine through the soil into the subsurface drain
 outflow. The model was calibrated with 1989 field data and
 compared to measured 1988 data. The calibrated DRAINMOD model
 predicted subsurface drain outflows for 1988 with a coefficient
 of determination of 0.40 and a standard error of the estimate,
 S(y/x), of 0.09 mm. Measured Atrazine concentrations exceeded 6
 micrograms/kg on one occasion, but simulated Atrazine
 concentrations did not exceed 2.5 micrograms/kg. The model
 underpredicted atrazine mass in the subsurface drain outflows.
 Spring underpredictions of atrazine mass discharge was due to
 underprediction of subsurface drain flows while fall
 underpredictions were due to underpredictions of atrazine
 concentrations. Effects of temperature on atrazine half life and
 adsorption constant may be partially responsible for these
 results. This integrated model of chemical transport with the
 drainage simulation model provides a useful tool for studying
 chemical transport through.
 NAL Call No.: 290.9-Am32T
 100. Modeling the effects of agricultural practices on nitrate
 concentration of shallow ground water in the Coastal Plain.
 Xie, M.; Huffman, R. L.; Jennings, G. D. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2091/94-2119) 16 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 20-23, 1994, Kansas City, Missouri.
 Descriptors: nitrate-nitrogen; wells-; monitoring-;
 water-quality; groundwater-pollution; simulation-models;
 NAL Call No.: 290.9-Am32P
 101. Modeling the water balance in cold regions.
 McConkey, B. G.; Mulla, D. J.; McCool, D. K. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932141) 21 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: snow-; soil-; frost-; infiltration-; runoff-
 NAL Call No.: 290.9-Am32P
 102. Modeling tile drainage in an irregular network.
 Waller, P. M.; Jaynes, D. B. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932125) 13 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: tile-drainage; water-quality;
 finite-element-analysis; simulation-models
 NAL Call No.: 290.9-Am32P
 103. Modeling transport kinetics in clinoptilolite-phosphate rock
 Allen, E. R.; Ming, D. W.; Hossner, L. R.; Henninger, D. L. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Jan/Feb 1995. v. 59 (1) p. 248-255. 
 Includes references.
 Descriptors: clinoptilolite-; rock-phosphate; systems-;
 nutrients-; ammonium-; phosphorus-; potassium-; release-;
 transport-processes; kinetics-; mathematical-models
 Abstract: Nutrient release in clinoptilolite-phosphate rock
 (Cp-PR) systems occurs through dissolution and cation-exchange
 reactions. Investigating the kinetics of these reactions expands
 our understanding of nutrient release processes. Research was
 conducted to model transport kinetics of nutrient release in
 Cp-PR systems. The objectives were to identify empirical models
 that best describe NH4, K, and P release and define
 diffusion-controlling processes. Materials included a Texas
 clinoptilolite (Cp) and North Carolina phosphate rock (PR). A
 continuous-fiow thin-disk technique was used. Models evaluated
 included zero order, first order, second order, parabolic
 diffusion, simplified Elovich, Elovich, and power function. The
 power-function, Elovich, and parabolic-diffusion models
 adequately described NH4, K, and P release. The power-function
 model was preferred because of its simplicity. Models indicated
 nutrient release was diffusion controlled. Primary transport
 processes controlling nutrient release for the time span observed
 were probably the result of a combination of several interacting
 transport mechanisms.
 NAL Call No.: 56.9-So3
 104. Modelling Ca-solubility in MSWI bottom ash leachates.
 Comans, R. N. J.; Meima, J. A. 
 Stud-environ-sci. Amsterdam ; New York, Elsevier Scientific
 Publishing Co. 1994. (60) p. 103-110. 
 In the series analytic: Environmental aspects of construction
 with waste material / edited by J.J.J.M. Goumans, H.A. van der
 Sloot and T.G. Aalbers.  Implications of Construction Materials
 and Technology Developments," held June 1-3, 1994, Maastricht,
 The Netherlands.
 Descriptors: solid-wastes; refuse-; ash-; building-materials;
 calcium-; leaching-; solubility-; minerals-; ph-; leachates-;
 chemical-speciation; simulation-models; equipment-;
 municipal-solid-waste-incinerators; calcium-minerals;
 NAL Call No.: QH540.S8
 105. Modelling leaching and recharge in a bare transitional
 red-brown earth ponded with low salinity water in summer.
 Cai, L.; Prathapar, S. A.; Beecher, H. G. 
 Aust-j-exp-agric v.34, p.1085-1092. (1994).
 Special Issue: Temperate Rice: Achievements and Potential.
 Descriptors: red-soils; soil-water-content; ponding-;
 saturated-hydraulic-conductivity; infiltration-; salts-;
 leaching-; water-table; depth-; soil-depth; simulation-models;
 summer-; winter-
 NAL Call No.: 23-Au792
 106. Modelling wash-off and leaching of pollutants by spring-time
 Vasilyev, A. 
 J-hydrol v.159, p.215-222. (1994).
 Special Issue: Field laboratory and modelling studies of flow and
 transport processing / edited by H.S. Wheater, P.A.C. Raats, and
 A.C. Armstrong.  Sciences Programme Session HS1 of the XVII
 General Assembly of the European Geophysical Society, April 6-10,
 1992, Edinburgh.
 Descriptors: pollutants-; agricultural-chemicals; phosphates-;
 leaching-; runoff-; subsurface-runoff; water-quality;
 water-pollution; watersheds-; models-; estonia-;
 Abstract: The quality of water in Estonian rivers in the spring
 is influenced strongly by the conditions in the catchments, and
 in particular by the amount of ice within the soil. After cold
 winters, the soil is extensively frozen and surface runoff
 predominates. After warmer winters, water flows through the soil
 and leaches pollutants from the soil. Increased pollutant load to
 Matsalu Bay has been identified by calibrating a water quality
 model for the period 1959-1966 and then running the same model
 for a test period (1977-1991). The observed concentrations during
 the test period were higher than those predicted by the
 calibrated model, indicating a real increase in pollutant load.
 NAL Call No.: 292.8-J82
 107. Models and modeling of hydrogeologic processes.
 Narasimhan, T. N. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Mar/Apr 1995. v. 59 (2) p. 300-306. 
 Paper presented at the John Philip Symposium held at the 56th
 annual meeting of the Soil Science Society of America, November
 3, 1992, Minneapolis, MN.
 Descriptors: soil-physics; hydrology-; soil-water-movement;
 water-flow; subsurface-layers; transport-processes;
 mathematical-models; computer-techniques
 Abstract: J.R. Philip recently articulated a concern of many
 earth scientists that computer-based mathematical models are
 impacting soil science practice and soil science education in an
 undesirable way. Unrealistic faith in the ability of these models
 to predict the future has encouraged overzealous use of models at
 the expense of the observational enterprise. These real concerns
 draw attention to the fact that much needs to be learned about
 the proper use of models in general and computer-based models in
 particular in the earth sciences. I was impressed by Philip's
 thoughts, and here reflect on the current status and the role of
 models of hydrogeologic processes. While agreeing with Philip's
 concerns about the improper use of models, I advance a
 perspective that models (analytical or numerical) are tools with
 inherent limitations. Despite their overenthusiastic use,
 computer-based models are potentially capable of helping us
 advance our knowledge of earth processes in unprecedented ways.
 As we seek to exploit this tool to its full potential, we may be
 challenged to reexamine and refine our conceptual foundations so
 that hydrologic processes are described more precisely than has
 hitherto been possible.
 NAL Call No.: 56.9-So3
 108. Modification of DRAINAGE model by using the nitrogen
 component from the GLEAMS model.
 Verma, A.; Kanwar, R. S.; Tim, U. S. 
 Trans-ASAE v.38, p.717-724. (1995).
 Includes references.
 Descriptors: groundwater-; drainage-; agricultural-chemicals;
 leaching-; nitrogen-; nitrate-nitrogen; groundwater-; pollution-;
 Abstract: The NITRO subroutine of the DRAINAGE model (Kanwar et
 al., 1983) was modified using the nitrogen transformation
 components of the GLEAMS (Leonard et al., 1987) model to predict
 more accurately the leaching of NO3-N to subsurface drainage
 water. Predicted values of tile flows and nitrate concentrations
 in tile effluent have shown a good agreement with observed data
 for the period from 1984 to 1992. There were some discrepancies
 between the predicted and observed values in the beginning of the
 simulation period resulting from lack of field data for
 soil-profile initialization. Despite the assumed steady-state
 condition within each time increment (one day) and the complexity
 of the drainage system, the modified DRAINAGE model has shown the
 capability to reasonably estimate long-term N loss with tile
 effluent. Average deviation and standard error between the
 predicted and observed NO3-N concentrations in the tile water
 indicated that the modified DRAINAGE model developed in this
 study resulted in better predictions of NO3-N concentrations in
 the drainage water than the original DRAINAGE model.
 NAL Call No.: 290.9-Am32T
 109. Modification of RZWQM for simulating subsurface drainage by
 adding a tile flow component.
 Singh, P.; Kanwar, R. S. 
 Trans-ASAE v.38, p.489-498. (1995).
 Includes references.
 Descriptors: subsurface-drainage; water-quality; water-flow;
 rain-; soil-properties; tillage-; simulation-models;
 computer-simulation; performance-appraisals
 Abstract: Fluctuating water table and subsurface drain flow
 components were incorporated in the Root Zone Water Quality Model
 (RZWQM) to enable the model to simulate subsurface drain flows.
 Parameters in a modified model were calibrated using observed
 subsurface drain flows for 1990. Model performance was evaluated
 by predicting subsurface drain flows for 1991 and 1992 by using
 the calibrated parameters and comparing the predicted drain flows
 with observed subsurface drain flows for the same years. The
 modified RZWQM model, in general, showed a good response to
 rainfall in terms of time of peak flows. However, the modified
 RZWQM model overpredicted total tile flows by an average of 13%,
 and the magnitudes of peak tile flows were generally
 underpredicted Selected soil properties (bulk density,
 macroporosity, and residue content) in the surface horizon were
 changed to investigate tillage effects on tile flows using the
 modified RZWQM. Four different tillage systems, chisel plow (CP),
 moldboard plow (MB), no-tillage (NT), and ridge-tillage (RT),
 were considered. Predicted tillage effects on subsurface drain
 flows were consistent with the observed effects (i.e., maximum
 tile flow for NT and minimum tile flow for MB).
 NAL Call No.: 290.9-Am32T
 110. Modification of the DRAINMOD-CREAMS model to incorporate a
 nutrient submodel.
 Saleh, A. R.; Bengtson, R. L.; Fouss, J. L. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932127) 23 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: subsurface-drainage; runoff-; nitrogen-; models-
 NAL Call No.: 290.9-Am32P
 111. Multidimensional infiltration: points, furrows, basins,
 wells, and disk.
 Clothier, B. E.; Green, S. R.; Katou, H. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Mar/Apr 1995. v. 59 (2) p. 286-292. 
 Paper presented at the John Philip Symposium held at the 56th
 annual meeting of the Soil Science Society of America, November
 3, 1992, Minneapolis, MN.
 Descriptors: infiltration-; soil-water-movement; water-flow;
 solutes-; transport-processes; theory-; mathematical-models;
 sorption-; sorption-isotherms
 Abstract: Multidimensional infiltration theory continues to be an
 area of soil physics research dominated by the works of J.R.
 Philip. The point source of these endeavors was his landmark
 paper in 1966. Here in our contribution honoring John Philip, we
 first discuss the multidimensional, similarity-solution
 antecedents that were queried by him nearly 30 yr ago. We then
 list the new theoretical developments contained in this
 comprehensive treatise on multidimensional flow into unsaturated
 soil. Next we comment on the three steady-state sequels derived
 by J.R. Philip, P.A.C. Raats, and R.A. Wooding, especially in
 relation to the experimental studies they spawned. Experiments
 initially began with attempts to verify directly the various
 multidimensional flow theories. But experimental procedures soon
 came to use, in an inverse sense, these theories to permit
 measurements of the hydraulic properties of field soil. The disk
 permeameter, currently a widely used device, employs
 multidimensional theory. In a variety of ways, disks are used to
 infer the hydraulic properties of field soil in the pressure
 potential range close to saturation. However, here we propose a
 method by which the disk permeameter can be used to deduce in
 situ the nonlinear adsorption isotherm that holds for the
 transport of reactive chemicals through soil. We demonstrate this
 proposal by using in the inverse sense of parameter
 identification, not an analytical description, but rather a
 two-dimensional numerical simulation of the flow of water and
 transport of solute away from a surface disk maintained at a
 given pressure potential, and some fixed concentration of
 reactive solute.
 NAL Call No.: 56.9-So3
 112. Multigrid simulation of the transport of multicomponent
 solute in groundwater.
 Shen, H.; Yang, X.; Nikolaidis, N. P. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2091/94-2119) 13 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 20-23, 1994, Kansas City, Missouri.
 Descriptors: solutes-; transport-processes; groundwater-;
 simulation-models; mathematical-models
 NAL Call No.: 290.9-Am32P
 113. A multiple-pore-region concept to modeling mass transfer in
 subsurface media.
 Gwo, J. P.; Jardine, P. M.; Wilson, G. V.; Yeh, G. T. 
 J-hydrol v.164, p.217-237. (1995).
 Includes references.
 Descriptors: soil-pore-system; transport-processes;
 saturated-conditions; mathematical-models
 Abstract: Recent studies in soil science literature have strongly
 indicated the need to incorporate pore structures in near-surface
 mass transport modeling. There is increasing evidence suggesting
 that pore structures. such as fractures and macropores,
 facilitate the transport of water and solutes along a
 preferential flow path while water and solutes are moved into
 micropores and rock matrices concurrently. This study presents a
 conceptual model a multiple-pore-region (or multi-region) concept
 to account for pore structures as well as the resultant widely
 distributed pore water velocities in macroporous media. Pore
 regions can either be physically identified as discrete features.
 such as fractures and rock matrices, or be experimentally
 deterrnined by separation of water retention curves according to
 pore classification schemes. A multi-region mechanism is proposed
 to account for the effect of local-scale and field-scale
 heterogeneities on mass transport under variably saturated
 conditions. Two numerical codes for subsurface fluid flow and
 solute transport have been developed with the multi-region
 concept, in which a first-order mass exchange model is adopted to
 simulate the redistribution of pressure heads and solute
 concentrations among pore regions. The computer codes are used to
 demonstrate the applicability of the concept to fractured porous
 media, and to test a three-pore-region hypothesis using
 laboratory soil column tracer injection data. Based upon the
 parameters obtained from fitting multi-region and mobile-immobile
 models to these data. we successfully demonstrated that the
 former model has the advantage of maintaining consistent
 conceptual models over the latter.
 NAL Call No.: 292.8-J82
 114. A multiregion model describing water flow and solute
 transport in heterogeneous soils.
 Hutson, J. L.; Wagenet, R. J. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1995. v. 59 (3) p. 743-751. 
 Includes references.
 Descriptors: solutes-; transport-processes; computer-simulation;
 simulation-models; mathematical-models; soil-variability;
 Abstract: Many different processes influence chemical
 breakthrough patterns from soil columns, including chemical
 kinetics, diffusion, matrix geometry, and flow heterogeneity.
 TRANSMIT, a multiregion model that reflects many of these
 features, was used to simulate a suite of solute breakthrough
 curves from soil columns subjected to both transient and
 steady-state flow. When utilized as a two-region model, TRANSMIT
 matched analytical solutions for steady-state flow through
 two-region soils. The TRANSMIT model is easily expanded to
 describe a wide range of multiregion and two-dimensional
 geometries and is applicable to transient and steady-state flow
 typical of both laboratory experiments and field situations.
 Sorption and degradation parameters can be varied, and nonuniform
 surface boundary condition, resulting from irrigation method and
 banded chemical placement, can be described.
 NAL Call No.: 56.9-So3
 115. New definitions for moisture recycling and the relationship
 with land-use changes in the Sahel.
 Savenije, H. H. G. 
 J-hydrol v.167, p.57-78. (1995).
 Includes references.
 Descriptors: moisture-; recycling-; evapotranspiration-;
 land-use; vegetation-; rain-; runoff-; mathematical-models;
 sahel-; west-africa
 Abstract: In the Sahel, recycling of moisture through
 evapotranspiration appears to be responsible for more than 90% of
 the rainfall. As a result, there exists an important feedback
 mechanism between land-use and climate, which has immediate
 implications for the management of natural resources. The
 challenge is to find sustainable combinations of land-use and
 vegetation that maximize recycling of moisture, while at the same
 time allowing adequate agncultural production. In this paper, a
 theory of moisture recycling is presented including the
 derivation of moisture recycling indicators, one of which is
 based on the salinity of the rainfall. Subsequently, the theory
 is verified with observations of rainfall and runoff in the Sahel
 over the period 1950-1990.
 NAL Call No.: 292.8-J82
 116. Nitrate monitoring and modeling for poultry litter
 application to pine seedlings.
 Minkara, M. Y.; Wilholt, J. H.; Wood, C. W.; Yoo, Y. H. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-2601/93-3510) 18 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 14-17, 1993, Chicago, Illinois.
 Descriptors: pinus-; seedlings-; poultry-manure;
 organic-fertilizers; leaching-; nitrate-nitrogen;
 NAL Call No.: 290.9-Am32P
 117. Nitrogen loading model for wellhead protection areas.
 Horsley, S. W. 
 Ground-water-monit-remediat. Dublin, OH : Ground Water Pub. Co.,
 c1993-. Winter 1995. v. 15 (1) p. 66-67. 
 Descriptors: nitrogen-; nitrate-nitrogen; wells-; water-quality;
 models-; massachusetts-
 NAL Call No.: GB1001.G76
 118. Nitrogen management, irrigation method, and nitrate leaching
 in the arid
 Miller, G. D.; Anderson, J. C. 
 Environmentally sound agriculture  proceedings of the second
 conference  20-22 April 1994 / p.113-119. (1994).
 Includes references.
 Descriptors: irrigated-farming; irrigation-water;
 water-management; irrigation-scheduling; nitrogen-; management-;
 nitrogen-fertilizers; nutrient-sources; application-methods;
 split-dressings; fertigation-; meteorological-factors; nitrate-;
 leaching-; soil-types-textural; simulation-models;
 economic-analysis; groundwater-; environmental-protection;
 western-states-of-usa; nutrient-management; single-application
 NAL Call No.: S589.7.E57-1994
 119. Non-point-source pollution from interrill flow areas.
 Parr, A.; Limback, S.; McEnroe, B.; Zou, S. 
 J-irrig-drain-eng v.120, p.1056-1066. (1994).
 Includes references.
 Descriptors: agricultural-land; runoff-; overland-flow;
 pollutants-; pollution-; models-; agricultural-runoff;
 mass-transport-models; flow-models
 NAL Call No.: 290.9-AM3Ps-IR
 120. A numerical study of variable density flow and mixing in
 porous media.
 Fan, Y.; Kahawita, R. 
 Water-resour-res v.30, p.2707-2716. (1994).
 Includes references.
 Descriptors: groundwater-pollution; soil-pollution;
 contaminants-; flow-; density-; gravity-; hydraulic-conductivity;
 hydrodynamics-; porous-media; simulation-; mathematical-models
 Abstract: A numerical study of a negatively buoyant plume
 intruding into a neutrally stratified porous medium has been
 undertaken using finite different methods. Of particular interest
 has been to ascertain whether the experimentally observed
 gravitational instabilities that form along the lower edge of the
 plume are reproduced in the numerical model. The model has been
 found to faithfully reproduce the mean flow as well as the
 gravitational instabilities in the intruding plume. A linear
 stability analysis has confirmed the fact that the negatively
 buoyant plume is in fact gravitationally unstable and that the
 stability depends on two parameters: a concentration Rayleigh
 number and a characteristic length scale which is dependent on
 the transverse dispersivity.
 NAL Call No.: 292.8-W295
 121. On the velocity covariance and transport modeling in
 heterogeneous anisotropic porous formations. 2. Unsaturated flow.
 Russo, D. 
 Water-resour-res v.31, p.139-145. (1995).
 Includes references.
 Descriptors: unsaturated-flow; transport-processes; velocity-;
 covariance-; stochastic-processes; mathematical-models; theory-;
 Abstract: Velocity covariances, and the resultant macrodispersion
 coefficient tensor, derived by Russo (this issue) for saturated
 flow conditions, are applied for unsaturated flow conditions,
 employing the assumption that for a given mean capillary pressure
 head, water saturation is a deterministic constant and log
 conductivity is a multivariate normal, stationary random space
 function. The applicability of the approach for modeling flow and
 transport in the vadose zone was evaluated by the use of the
 stochastic theory of Yeh et al. (1985a, b) for steady,
 unsaturated flow. Results of the analyses suggest that the
 approach may be applicable to vadose zone flow and transport, as
 long as the scale of heterogeneity in the direction of the mean
 flow is smaller than approximately one tenth of the
 characteristic length of unsaturated flow. For porous formation
 of given statistics, the magnitude of macrodispersion in
 unsaturated flow is larger than that in saturated flow, and
 increases as water saturation decreases. For a given water
 saturation, transport in unsaturated flow may approach asymptotic
 Fickian behavior more slowly than in saturated flow, when the two
 formation properties log kappas and alpha are positively
 cross-correlated and when the correlation scale of alpha is
 relatively large as compared with the correlation scale of log
 NAL Call No.: 292.8-W295
 122. On the velocity covariance and transport modeling in
 heterogeneous anisotropic porous formations. 1. Saturated flow.
 Russo, D. 
 Water-resour-res v.31, p.129-137. (1995).
 Includes references.
 Descriptors: saturated-flow; transport-processes; velocity-;
 covariance-; mathematical-models; theory-
 Abstract: Velocity covariances for saturated heterogeneous
 formations with anisotropic structures were derived for mean flow
 parallel and perpendicular to the formation bedding and were
 employed for modeling transport in these formations by the use of
 a Lagrangian formulation. Relatively simple analytical
 expressions, each requiring only a single numerical integration,
 were obtained for the longitudinal and transverse components of
 the velocity covariance, the displacement covariance, and the
 macrodispersion coefficient tensors, all as functions of the
 anisotropy of the formation. Closed-form analytical expressions
 were derived for the longitudinal and transverse components of
 the velocity variance and for the asymptotic values of the
 transverse components of the displacement covariance. The
 applicability of this approach for modeling flow and transport in
 the vadose zone is tested in the companion to this paper by the
 use of the stochastic theory of Yeh et al. (1985a, b) for
 unsaturated flow.
 NAL Call No.: 292.8-W295
 123. Optimal ground-water remediation methods applied to a
 Superfund site: from formulation to implementation.
 Ahlfeld, D. P.; Page, R. H.; Pinder, G. F. 
 Ground-water. Dublin, Ohio : Ground Water Pub. Co. Jan/Feb 1995.
 v. 33 (1) p. 58-70. 
 Includes references.
 Descriptors: groundwater-pollution; aquifers-;
 groundwater-extraction; pumps-; water-purification;
 groundwater-recharge; simulation-models; optimization-;
 NAL Call No.: TD403.G7
 124. Optimization of saturated hydraulic conductivity for WEPP.
 Risse, L. M.; Nearing, M. A.; Savabi, M. R.; Laflen, J. M. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932028) 19 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers, and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: water-erosion; hydraulic-conductivity; models-;
 calibration-; runoff-water
 NAL Call No.: 290.9-Am32P
 125. Optimizing irrigation management for pollution control and
 sustainable crop yield.
 Musharrafieh, G. R.; Peralta, R. C.; Dudley, L. M.; Hanks, R. J. 
 Water-resour-res v.31, p.1077-1086. (1995).
 Includes references.
 Descriptors: irrigation-water; saline-water; salts-in-soil;
 water-management; groundwater-pollution; pollution-control;
 crop-yield; sustainability-; simulation-models; optimization-;
 utah-; simulation; optimization-models
 Abstract: Irrigation strategies which maximize crop yield while
 preventing salt from leaching to the groundwater or undesirable
 salt increases in the root zone are computed by using a
 one-dimensional simulation/optimization management model. The
 included constraint equations maintain a water volume balance and
 salt transport in the unsaturated zone. Implicit finite
 difference forms of the unsaturated water flow equation
 (Richards7 equation), the diffusion-convection solute transport
 equation, functions describing the hydraulic properties of the
 medium, a root extraction function, and other constraints are
 used. The model uses a large discretization in time. A cyclic
 prediction and correction type of approach is adopted to
 eliminate the inaccuracy that would otherwise result from the
 coarse discretization. As a result of the procedure presented,
 intercell water and mass flux rates in the optimization model
 have the same accuracy as those in a more finely discretized
 simulation model. The model is applied to a research farm in
 Huntington, Utah, where salty water is used for irrigation. In
 that process detailed soil water and salt profiles are computed
 and spatially distributed moisture content and concentration
 constraints are satisfied.
 NAL Call No.: 292.8-W295
 126. Partitioning small scale spatial variability of runoff and
 erosion on sagebrush rangeland.
 Pierson, F. B.; Blackburn, W. H.; Van Vactor, S. S.; Wood, J. C. 
 Water-resour-bull v.30, p.1081-1089. (1994).
 Includes references.
 Descriptors: artemisia-tridentata; rangelands-; erosion-;
 interrill-erosion; runoff-; spatial-variation;
 soil-classification; hydrology-; models-; idaho-;
 Abstract: Most hydrologic models require input parameters which
 represent the variability found across an entire landscape. The
 estimation of such parameters is very difficult, particularly on
 rangeland. Improved model parameter estimation procedures are
 needed which incorporate the small-scale and temporal variability
 found on rangeland. This study investigates the use of a surface
 soil classification scheme to partition the spatial variability
 in hydrologic and interrill erosion processes in a sagebrush
 plant community. Four distinct microsites were found to exist
 within the sagebrush coppice-dune dune-interspace complex. The
 microsites explained the majority of variation in hydrologic and
 interrill erosion response found on the site and were discernable
 based on readily available soil and vegetation information. The
 variability within each microsite was quite low and was not well
 correlated with soil and vegetation properties. The surface soil
 classification scheme defined in this study can be quite useful
 for defining sampling pmcedures, for understanding hydrologic and
 erosion processes, and for parameterizing hydmlogic models for
 use on sagebrush  rangeland.
 NAL Call No.: 292.9-Am34
 127. Performance of AGNPS in the Pacific Northwest.
 Arakere, S.; Molnau, M. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2156/94-2185) 16 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 19-22, 1994, Kansas City, Missouri.
 Descriptors: water-pollution; watersheds-; catchment-hydrology;
 water-quality; simulation-models; prediction-;
 NAL Call No.: 290.9-Am32P
 128. Performance of the DRAINMOD-CREAMS model with an
 incorporated nutrient submodel.
 Saleh, A. R.; Bengston, R. L.; Fouss, J. L. 
 Trans-ASAE v.37, p.1109-1114. (1994).
 Includes references.
 Descriptors: nitrogen-; leaching-; losses-from-soil;
 subsurface-drainage; simulation-models; fields-; water-table;
 Abstract: The CREAMS nutrient submodel and the modified
 DRAINMOD-CREAMS model were applied to subsurface drained and
 nonsubsurface drained fields. The CREAMS nutrient submodel
 overestimated the total nitrogen losses from the subsurface
 drained and the nonsubsurface drained fields by 61 and 91%,
 respectively. The modified DRAINMOD-CREAMS model overestimated
 the total nitrogen losses from the subsurface drained and the
 nonsubsurfaced drained fields by 36 and 40%, respectively. The
 modified DRAINMOD-CREAMS model significantly improved the
 simulation of the nitrogen losses from the subsurface drained and
 the nonsubsurface drained fields by reducing the error by 25 and
 51%, respectively.
 NAL Call No.: 290.9-Am32T
 129. Performance of transport models in predicting nitrate in
 runoff from high water table areas.
 Ramanarayanan, T. S.; Sabbagh, G. J.; Reyes, M. R.; Bengston, R.
 L.; Storm, D. E.; Fouss, J. L. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2120/94-2155) 13 p. 
 Paper presented at the 1994 International Summer Meeting,
 sponsored by the ASAE, June 19-22, 1994, Kansas City, Missouri.
 Descriptors: zea-mays; water-quality; sediment-; nitrate-;
 runoff-; losses-from-soil; crop-yield; water-pollution; erosion-
 NAL Call No.: 290.9-Am32P
 130. Phloem mobility of xenobiotics. V. Structural requirements
 for phloem-systemic pesticides.
 Kleier, D. A. 
 Pestic-sci v.42, p.1-11. (1994).
 Includes references.
 Descriptors: pesticides-; transport-processes;
 structure-activity-relationships; translocation-; phloem-;
 pharmacokinetics-; mathematical-models; chemical-structures
 Abstract: Remote and relatively inaccessible parts of plants such
 as roots and meristematic tissue can readily be reached by
 foliar-applied xenobiotics if the latter are capable of entering
 into and moving in the phloem. Development of a passive transport
 model provides a description of the time course of this movement
 and its dependence upon the physical properties of the chemical
 and the condition of the plant vascular system. The model so
 developed is used to formulate principles for rendering otherwise
 non-systemic xenobiotics phloem-mobile. These principles can be
 categorized according to the nature of the chemical modifications
 that facilitate phloem translocation. These modifications include
 (a) sugar conjugation, (b) acid functionalization, and (c)
 formation of quaternary salts from basic parents. The potential
 of these modifications to facilitate the phloem translocation of
 a wide range of pesticides is discussed.
 NAL Call No.: SB951.P47
 131. Plant residue impact on rainfall interception.
 Savabi, M. R.; Stott, D. E. 
 Trans-ASAE v.37, p.1093-1098. (1994).
 Includes references.
 Descriptors: zea-mays; glycine-max; triticum-aestivum;
 crop-residues; rain-; interception-; soil-water-balance; runoff-;
 computer-simulation; simulation-models
 Abstract: Rainfall interception by different amounts of corn (Zea
 Mays), soybean (Glycine Max L.), and winter wheat (Triticum
 aestivum L.) residue was studied under simulated rainfall. Given
 the same amount of residue mass, winter wheat residue intercepts
 significantly more rainfall than corn and soybean residue.
 Statistically, corn and soybean residues intercept the same
 amount of rainfall. Age of the residues had no impact on the
 amount of rainfall intercepted by the residues. Mathematical
 relationships were derived for estimating rainfall interception
 rates for different types and amounts of residue. The findings
 were incorporated into the Water Erosion Prediction Project
 (WEPP) computer model to improve soil water balance predictions.
 The model was tested using a 50-year simulation of the impact of
 rainfall interception by plant residues on the soil water balance
 of a no-till farm under corn-soybean rotation near Champaign,
 Illinois. The results of WEPP model simulations indicate that
 rainfall interception by crop residues reduces the average annual
 storm runoff by 13% and average daily root zone soil water
 content by 9% on a Midwest farm under corn-soybean rotation.
 NAL Call No.: 290.9-Am32T
 132. Plot-scale solute transport in a semiarid agricultural soil.
 Yasuda, H.; Berndtsson, R.; Bahri, A.; Jinno, K. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. July/Aug 1994. v. 58 (4) p. 1052-1060. 
 Includes references.
 Descriptors: agricultural-soils; semiarid-soils; solutes-;
 transport-processes; soil-variability; mathematical-models;
 tunisia-; preferential-flow
 Abstract: In semiarid areas, agricultural production is
 determined by limited water and nutrient supply. To develop
 efficient management practices, it is of importance to predict
 solute transport. In line with this, we present observed and
 calculated plot-scale solute transport in an agricultural
 experimental field in northern Tunisia. A pulse of Br(-)-tagged
 water was applied on the surface of two small field plots and
 leached under steady-state soil water conditions. Solute samples
 were withdrawn through ceramic samplers at five different depths
 within each plot. The experimental data indicated a high degree
 of bypass or preferential flow within the small plots and
 nonsigmoid breakthrough curves, suggesting tailing phenomena and
 immobile fractions of soil water. The data were evaluated using
 the classical two-parameter convection-dispersion equation (CDE)
 and the four-parameter nonequilibrium convection-dispersion
 equation (NECDE). Pore water velocities, v, and dispersion
 coefficients, D, were calculated by fitting the analytical
 solution of these two models to the breakthrough curves based on
 individual sample locations as well as using all samples in the
 plot simultaneously. None of the models could be fitted when data
 from all solute sampling depths were used in the optimization
 simultaneously. When using data at individual sample locations,
 the fit was somewhat better for the NECDE than for the CDE. The
 estimated values of D and v could be described by a power law
 NAL Call No.: 56.9-So3
 133. Ponded infiltration as a cause of the instability of
 continuous macropores.
 Berg, J. A. v. d.; Ullersma, P. 
 J-hydrol v.159, p.169-186. (1994).
 Special Issue: Field laboratory and modelling studies of flow and
 transport processing / edited by H.S. Wheater, P.A.C. Raats, and
 A.C. Armstrong.  Sciences Programme Session HS1 of the XVII
 General Assembly of the European Geophysical Society, April 6-10,
 1992, Edinburgh.
 Descriptors: macropores-; macropore-flow; soil-water-movement;
 solutes-; transport-processes; infiltration-;
 saturated-hydraulic-conductivity; temporal-variation;
 Abstract: A model is presented which yields the range of the
 hydraulic parameters that are critical for the collapse of
 continuous macropores in a given soil under certain hydrological
 circumstances. These continuous macropores are important, as they
 control the hydraulic conductivity at saturation and the
 infiltration capacity of most soils. The conceptual model is
 based on data from earlier infiltration experiments on soil
 columns in situ; it consists basically of a soil matrix with
 discontinuous macropores which is traversed by a vertical
 macropore channel. The experiments suggested that under the
 transient flow conditions that occur in the soil when ponded
 infiltration ends, the wall of a macropore channel can become
 unstable. Collapse will occur if the shear stress caused by the
 seepage to the channel exceeds the shear strength of the soil
 particles in the wall of the macropore channel. The model
 ascertains the magnitude of this shear stress from the transient
 gradient of the hydraulic head G over a length L which is the
 distance between the wall of the macropore channel and air
 encapsulated by the water in the soil matrix. For given
 parameters L, k (hydraulic conductivity) and mu (specific
 storativity) the behaviour of G as a function of time is derived
 from the equation for non-stationary, horizontal flow of soil
 water. The solution consists of a series of exponential
 functions; one term is characterized by the emptying time of the
 macropore channel and the others by the relaxation time (...). It
 is shown how, for a certain soil, a domain of k and p values
 conducive to collapse can be found. Each point within this domain
 defines a length scale for L. The moment of collapse is. 
 determined for three different soil textures (silt loam, sandy
 loam and loamy sand). The application of the model shows that
 ponded infiltration can create conditions appropriate for the
 collapse of macropores and, therefore, for the decrease of the
 saturated conductivity.
 NAL Call No.: 292.8-J82
 134. Predicting alachlor mobility using batch sorption kinetic
 Gaston, L. A.; Locke, M. A. 
 Soil-sci v.158, p.345-354. (1994).
 Includes references.
 Descriptors: silt-loam-soils; alachlor-; movement-in-soil;
 sorption-; kinetics-; equilibrium-; transport-processes;
 mathematical-models; nonequilibrium-sorption
 NAL Call No.: 56.8-So3
 135. Predicting field-scale solute transport using in situ
 measurements of soil hydraulic properties.
 Wesenbeeck, I. J. v.; Kachanoski, R. G. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1995. v. 59 (3) p. 734-742. 
 Includes references.
 Descriptors: solutes-; transport-processes; unsaturated-flow;
 prediction-; soil-analysis; soil-water-content; pressure-;
 hydraulic-conductivity; matric-potential; measurement-;
 spatial-distribution; mathematical-models; ontario-
 Abstract: Predicting unsaturated solute transport using measured
 hydraulic parameters has been difficult due to the inherent
 variability of soil properties, and the difficulty in obtaining
 accurate estimates of hydraulk properties in situ. The objective
 of this study was to determine if in situ measurement of soil
 hydraulic conductivity, the alpha soil parameter, and the water
 content vs. pressure head (h) relationship could be used to
 predict field-scale solute transport. A series of steady state
 solute transport experiments were conducted on a Fox sand (fine
 loamy over sandy or sandy-skeletal, mixed, mesic Typic Hapludalf
 soil in Ontario, Canada. The transport of Cl- under steady-state
 water flux was monitored in three separate experiments using
 solution samplers. Steady-state water flux densities applied at
 the soil surface were 9.72 X 10(-6), 1.53 X 10(-5), and 8.68 X
 10(-8) m s-1, respectively, for the three sites. After completion
 of the transport experiments at Site II, measurements of soil
 hydraulic conductivity and the alpha parameter were made using
 the Guelph pressure infiltrometer (GPI) beside each location and
 depth where solute breakthrough curves (BTCs) were measured, as
 well as at the soil surface. Undisturbed soil cores were taken at
 each location where GPI measurements were made for estimating the
 parameters in the water content (pressure head) using van
 Genuchten's equations. The GPI- and core-measured hydraulic
 parameters obtained at Site II were used to predict the
 field-scale solute travel time probability density function (PDF)
 at thee same site, and at Sites I and III using a
 stochastic-convective model. Observed solute travel time PDFs
 were predicted quite well at high surface water fluxes, which
 were close to the field saturated hydraulic conductivity, KFS, by
 both the GPI and core methods. Both methods underpredicted the
 variability of the observed travel time PDF.
 NAL Call No.: 56.9-So3
 136. Predicting the transport of atrazine in soils: second-order
 and multireaction approaches.
 Ma, L.; Selim, H. M. 
 Water-resour-res v.30, p.3489-3498. (1994).
 Includes references.
 Descriptors: atrazine-; soil-; transport-processes; prediction-;
 soil-properties; prediction-; mathematical-models; kinetics-
 Abstract: As a follow-up to a previous paper (Ma and Selim,
 1994a), this study was designed to further validate a modified
 second-order, two-site (SOTS) model for describing atrazine
 transport in column miscible experiments. Moreover, the
 capability of the SOTS model was compared with that of the
 multireaction transport model (MRTM) of Selim (1989). For both
 models the necessary parameters were derived from batch
 experiments and tritium tracer breakthrough results. The models
 were used solely to predict atrazine breakthrough curves (BTCs)
 for different experimental conditions. We also proposed an
 alternative way of analyzing tritium BTCs, where the hydrodynamic
 dispersion coefficient D and an effective solute transport length
 Le were used as fitting parameters. Tritium fitted D and Le were
 used in both models to arrive at atrazine BTC predictions. The
 SOTS model provided superior predictions over MRTM for all (14)
 atrazine BTCs regardless of (1) input concentration C0, (2) soil
 column length L, (3) pore water velocity v, (4) multiple pulse
 applications, and (5) flow interruption (incubation). We conclude
 that the SOTS model was capable of describing chemical
 heterogeneity of atrazine retention and transport. BTC
 predictions lend credence to the transport parameter Le in
 predicting solute transport in soils.
 NAL Call No.: 292.8-W295
 137. Predicting transport of bromide in a furrow irrigated field
 using computer models.
 Izadi, B.; King, B.; Westermann, D.; McCann, I. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2156/94-2185) 22 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 19-22, 1994, Kansas City, Missouri.
 Descriptors: surface-irrigation; furrow-irrigation; solutes-;
 transport-processes; simulation-; models-
 NAL Call No.: 290.9-Am32P
 138. Prediction of solute transport using a transfer function
 model and the convection-dispersion equation.
 Zhang, R. 
 Soil-sci v.160, p.18-27. (1995).
 Includes references.
 Descriptors: solutes-; transport-processes; movement-in-soil;
 prediction-; mathematical-models; comparisons-; accuracy-
 NAL Call No.: 56.8-So3
 139. Pressure sensitivity to microirrigation emitter plugging.
 Hills, D. J.; Povoa, A. F. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932130) 18 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: microirrigation-; hydraulics-; water-quality;
 NAL Call No.: 290.9-Am32P
 140. Prioritizing nonpoint source phosphorus loading using a
 grass-modeling system.
 Chen, Z.; Storm, D. E.; Smolen, M. D.; Haan, C. T.; Gregory, M.
 S.; Sabbagh, G. J. 
 Water-resour-bull v.30, p.589-594. (1994).
 Includes references.
 Descriptors: phosphorus-; water-pollution; water-quality;
 watersheds-; geographical-information-systems; simulation-models;
 oklahoma-; geographic-resources-analysis-support-system;
 nonpoint-source-pollution; battle-creek-watershed
 Abstract: A UNIX-based windows application was developed to
 integrate a phosphorus transport model with the Geographic
 Resources Analysis Support System (GRASS). The system prioritizes
 potential phosphorus loading from fields or cells in a watershed
 and can evaluate the effects of alternate management practices on
 phosphorus yield. The model simulates phosphorus loading by using
 a daily mass balance on a unit-area basis and incorporates the
 effects from rainfall, topography, soil properties, fertilizer
 and animal waste application, and management. Model predictions
 include dissolved and sediment-bound phosphorus yield, runoff
 volume, and sediment yield. Within the integrated GRASS-modeling
 system, the user can obtain model input data, execute the model
 using various options, rank model input and output data, and
 display them as GRASS-based maps or data tables. All functions
 are menu driven, developed using C language and X-window tools to
 run on a SUN workstation platform. The system provides a powerful
 and efficient tool for prioritizing phosphorus loading from
 nonpoint sources.
 NAL Call No.: 292.9-Am34
 141. Quantifying dewatering characteristics of agricultural
 wastes and materials.
 Straub, R. J.; Koegel, R. G.; Kim, J. Y. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (934036) 17 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers," and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: alfalfa-; maize-; residues-; cattle-slurry; models-;
 dewatering-; moisture-content
 NAL Call No.: 290.9-Am32P
 142. Raindrop-induced soil detachment and sediment transport from
 interrill areas.
 Sharma, P. P.; Gupta, S. C.; Foster, G. R. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. May/June 1995. v. 59 (3) p. 727-734. 
 Includes references.
 Descriptors: interrill-erosion; erodibility-;
 soil-physical-properties; mathematical-models; rain-; impact-;
 kinetic-energy; sediment-; transport-processes; soil-texture;
 clay-; soil-detachability; transportability-; rain-intensity
 Abstract: Physically based soil erosion simulation models require
 input parameters of soil detachment and sediment transport due to
 the action and interactions of both raindrops and overland flow.
 In this study, we report on the soil detachability and
 transportability parameters for raindrop-impact-dominated
 interrill erosion processes. The detachability parameter is
 derived by integrating estimated soil detachment due to single
 raindrop impact over all the raindrops occurring in a storm.
 Using artifical rainfall characteristics and soil properties as
 inputs, we simulated raindrop-induced soil detachment rates for
 33 cropland soils used in the USDA-ARS Water Erosion Prediction
 Project (WEPP) experiments in the USA. The magnitude of
 difference between the predicted detachment and the measured
 interrill sediment delivery rates decreased with clay content.
 This suggests that in coarse-textured soils, most of the
 sediments are redistributed within the interrill area. Small
 differences between detachment rates and sediment delivery rates
 in clayey soils indicate that the interrill erosion is detachment
 limited. A raindrop-induced interrill transportability parameter
 is derived by dividing the measured sediment delivery rates with
 the product of rainfall rate and unit effective kinetic energy.
 The derived transportability parameter increases linearly with an
 increase in clay content, thereby suggesting the predominant role
 of raindrop impact in the sediment delivery process, specifically
 on up-slope areas with shallow overland flow. The
 raindrop-induced soil detachment and sediment transport process
 can be represented by incorporating intensity and effective
 kinetic energy of rainfall into the basic interrill erosion
 NAL Call No.: 56.9-So3
 143. Rainfall-induced leaching and leaf losses from drying
 alfalfa forage.
 Smith, D. M.; Brown, D. M. 
 Agron-j v.86, p.503-510. (1994).
 Includes references.
 Descriptors: alfalfa-hay; drying-; yield-losses; quality-;
 forage-; rain-; leaching-; duration-; leaves-; shedding-;
 dry-matter; mathematical-models; equations-; leaf-shatter;
 Abstract: Efforts to construct models of forage yield and quality
 loss during the field drying of hay are hindered by a lack of
 quantitative information concerning several modes of loss. This
 study attempted to quantify leaching and rainfall-induced leaf
 shatter from drying alfalfa (Medicago sativa L. 'Magnum') forage.
 A rainfall simulator was used to treat samples from four forage
 cuttings in 1989 and 1990 at four levels of tissue moisture
 between 760 and 150 g kg-1 (wet basis). Rainfall amounts of 0
 (control), 5, 10, 15, and 20 mm were used at intensity levels of
 20 and 40 mm h-1. Leaves lost due to rainfall were collected,
 samples of forage tissue were analyzed for quality and yield
 changes and samples of leachate water were collected from beneath
 hay samples for analysis. Results showed that leaf shatter is not
 directly induced by rainfall. Analysis of forage tissue showed
 that leaching of soluble dry matter caused dry weight losses and
 increases (P less than or equal to 0.05) in the proportion of
 fiber in tissue. Leachate analysis provided a more precise
 measure of leaching losses. Analysis of leachates for total
 dissolved and suspended dry matter demonstrated that leaching
 increases with rainfall amount and as tissue moisture levels
 decline. At 700 g kg-1 (wet basis) moisture, leaching losses
 reached only 0.3% of initial sample dry matter, while at 170 g
 kg-1 moisture they were as great as 1.7%. Leaching was also
 greater (P less than or equal to 0.05) under rainfall at 20 mm
 h-1 than 40 mm h-1. A regression equation generated from the
 leachate data can be used to model leaching losses within
 prescribed limits.
 NAL Call No.: 4-AM34P
 144. Regional cooperation in the use of irrigation water:
 efficiency and income distribution.
 Yaron, D.; Ratner, A. 
 Agric-econ v.4, p.45-58. (1990).
 Includes references.
 Descriptors: irrigation-water; water-use; salinity-;
 water-allocation; water-quality; income-distribution;
 agricultural-regions; linear-models; efficiency-; israel-
 Abstract: The paper presents an analysis of the economic
 potential of regional cooperation in water use in irrigation
 under conditions characterized by a general trend of increasing
 salinity. Income maximizing solutions for the region are derived
 and the related income distribution schemes are solved for, with
 the aid of cooperative game theory algorithms and shadow cost
 pricing. Distinction is made between distribution policies with
 and without side payments. The reasonableness and the
 acceptability of these schemes is later critically evaluated. The
 Nash-Harsanyi approach seems to be the most appropriate for the
 conditions studied.
 NAL Call No.: HD1401.A47
 145. Regulating groundwater pollution: effects of geophysical
 response assumptions on economic efficiency.
 Fleming, R. A.; Adams, R. M.; Kim, C. S. 
 Water-resour-res v.31, p.1069-1076. (1995).
 Includes references.
 Descriptors: groundwater-; groundwater-pollution; nitrates-;
 nitrogen-fertilizers; application-to-land; leaching-; time-lag;
 pollution-control; regulations-; taxes-; mathematical-models;
 production-functions; geophysics-; leaching-time-lags
 Abstract: Most economic studies of groundwater pollution ignore
 important geophysical complexities of groundwater contamination.
 For example, most studies assume that nitrogen fertilizer
 instantaneously leaches into an underlying water aquifer. In
 reality, there are time lags between fertilizer application and
 nitrate contamination of groundwater which complicate
 establishment of efficient regulations. This paper uses an
 optimal control model to examine empirically the effects of time
 lags on regulatory efficiency. Results indicate that ignoring
 time lags can lead to regulatory actions that set suboptimal user
 fees, which lead to levels of damage greater than anticipated.
 The results confirm that transport time lags are important when
 setting pollution control policies. In the case of very long time
 lags, pollution control policies may have no effect. The impact
 that time lags have on policy is stable with regard to changes in
 key model parameters and changes in the production function.
 NAL Call No.: 292.8-W295
 146. Riparian forest buffer system research at the Coastal Plain
 Experiment Station, Tifton, GA.
 Hubbard, R. K.; Lowrance, R. R. 
 Water-air-soil-pollut v.77, p.407-432. (1994).
 In the special issue: Wetlands of the interior southeastern
 United States / edited by C.C. Trettin, W.M. Aust, and J.
 Wisniewski.  Conference on "Wetland Ecology, Management, and
 Conservation," held September 28-30, 1993, Knoxville, Tennessee.
 Descriptors: riparian-forests; riparian-vegetation; grasses-;
 vegetation-management; clearcutting-; selective-felling;
 wetlands-; biological-treatment; waste-water-treatment;
 dairy-wastes; pig-slurry; aldicarb-; insecticide-residues;
 nutrients-; removal-; nutrient-uptake; simulation-models;
 nitrate-; denitrification-; water-quality; runoff-; groundwater-;
 groundwater-pollution; water-pollution; georgia-
 NAL Call No.: TD172.W36
 147. Role of information in the adoption of best management
 practices for water quality improvement.
 Feather, P. M.; Amacher, G. S. 
 Agric-econ v.11, p.159-170. (1994).
 Includes references.
 Descriptors: water-quality; information-; incentives-;
 farm-management; innovation-adoption; profitability-;
 demonstration-farms; federal-programs; usda-;
 mathematical-models; usa-; demonstration-projects
 Abstract: This study investigates the role of information in
 influencing the adoption of improved farm management practices. A
 lack of producer information regarding both the profitability and
 the environmental benefits of adopting improved practices may be
 a reason why widespread adoption of these practices has not
 occurred. Compared to direct regulation or financial incentives,
 raising producer information levels may be a more cost-effective
 method of increasing adoption. The United States Department of
 Agriculture has recently established and begun implementing a
 program based on this idea. To test the validity of the program,
 a two-stage adoption model is specified and estimated using data
 from a survey of producers in the program area. The results
 indicate that producer perceptions play an important role in the
 decision to adopt. Changing these perceptions by means of an
 educational program may be a reasonable alternative to financial
 incentives in encouraging BMP adoption.
 NAL Call No.: HD1401.A47
 148. Runoff and sediment yield modelling : proceedings of the
 International Symposium, RSY-93 : Warsaw, Poland, September
 14-16, 1993.
 Banasik, K.;  Zbikowski, A.; Poland. Ministerstwo Edukacji
 Narodowej. Lesnictwa. Wydzial Melioracji i Inzynierii Srodowiska.
 Warsaw, P. 
 Warsaw : Warsaw Agricultural University Press, 1993. vii, 315 p.
 : ill., maps.
 "The International Symposium on Runoff and Sediment Yield
 Modelling, September 14-16, 1993 was organized and hosted by the
 Department of Hydraulic Structures, Faculty of Land Reclamation
 and Environmental Engineering at the Warsaw Agricultural
 University"--Added t.p. verso.  Srodowiska, Zasobow Naturalnych i
 Lesnictwa; Wydzial Melioracji i Inzynierii Srodowiska"--Added
 t.p. verso.
 Descriptors: Runoff-Congresses; Sediment-transport-Congresses;
 NAL Call No.: GB980.R86--1993
 149. Scaling, soil moisture and evapotranspiration in runoff
 Wood, E. F. 
 Adv-water-resour v.17, p.25-34. (1994).
 In the special issue: MIT Colloquium on Hydroclimatology and
 Global Hydrology / edited by I. Rodriguez-Iturbe, D. Entekhabi
 and R.L. Bras.
 Descriptors: soil-water; evapotranspiration-; simulation-models;
 algorithms-; runoff-; landscape-; transpiration-; evaporation-;
 NAL Call No.: TD201.A4
 150. Sediment transport by wind: a wind tunnel study.
 Wilson, G. R.; Zobeck, T. M.; Gregory, J. M.; Zartman, R. E. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-2531/93-2550) 16 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 12-17, 1993, Chicago, Illinois.
 Descriptors: wind-erosion; sediment-; transport-processes;
 NAL Call No.: 290.9-Am32P
 151. A sensitivity analysis and parametric study for the
 evaluation of the optimal management of a contaminated aquifer.
 Latinopoulos, P.; Theodosiou, N.; Mylopoulos, Y.; Mylopoulos, N. 
 Water-resour-manag v.8, p.11-31. (1994).
 Includes references.
 Descriptors: aquifers-; groundwater-pollution; groundwater-flow;
 contaminants-; pollutants-; transport-processes; water-quality;
 water-management; optimization-; models-; simulation-models
 Abstract: A typical groundwater remediation problem is studied by
 using a combined simulation-optimization model. The management
 procedure employs groundwater flow and contaminant transport
 simulation models in conjunction with linear and quadratic
 programming techniques. The methodology is applied to the
 hydrodynamic control of a contaminant plume that has to be
 stabilized and removed by a system of pumping wells. The paper
 focuses mainly upon a sensitivity analysis to the aquifer
 transmissivity. The effect of changes in the transmissivities of
 a zoned aquifer upon the optimal solutions of the management
 problem is examined by considering the optimal pumping rates, the
 time to remediation and the pumped groundwater volume as the key
 output variables of the remediation strategies. In addition, the
 influence of the dispersivities and the imposed hydraulic
 gradient upon the same output variables is critically evaluated.
 The results of the study illustrate the need for uncertainty
 reduction in the knowledge of the hydrogeologic parameters.
 NAL Call No.: TC401.W27
 152. Sensitivity analysis in erosion prediction modeling.
 Deer, L. A.; Nearing, M. A. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2120/94-2155) 31 p. 
 Paper presented at the 1994 International Summer Meeting,
 sponsored by the ASAE, June 19-22, 1994, Kansas City, Missouri.
 Descriptors: water-erosion; runoff-; losses-from-soil; sediment-;
 crop-yield; simulation-models; performance-appraisals
 NAL Call No.: 290.9-Am32P
 153. Sensitivity analysis of a simple layer-equilibrium model for
 the one-dimensional leaching of solutes.
 Corwin, D. L. 
 J-environ-sci-health,-Part-A,-Environ-sci-eng v.A30, p.201-238.
 Includes references.
 Descriptors: solutes-; leaching-; soil-; mathematical-models
 NAL Call No.: TD172.J6
 154. Sensitivity of metal-bioleaching operation to process
 Sreekrishan, T. R.; Tyagi, R. D. 
 Process-biochem v.30, p.69-80. (1995).
 Includes references.
 Descriptors: sewage-sludge; heavy-metals; leaching-; removal-;
 sulfur-; oxidation-; microbial-activities; waste-treatment;
 solubility-; mathematical-models
 NAL Call No.: TP1.P7
 155. Simplified model of integrated water and solute uptake by
 salts- and selenium-accumulating plants.
 Ben Asher, J. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. July/Aug 1994. v. 58 (4) p. 1012-1016. 
 Includes references.
 Descriptors: crops-; roots-; ion-uptake; water-uptake;
 transpiration-; salinization-; soil-toxicity;
 mathematical-models; irrigation-water; water-quality; salinity-;
 Abstract: The rate of soil salinization and the accumulation of
 toxic ions in soils are affected by evapotranspiration and the
 uptake of ions by plant roots. These are two counteracting
 processes and the interrelationship between them can be
 quantified by a mathematical model. The objectives of this study
 were to: (i) formulate an analytical model describing soil
 salinization and accumulation of toxic ions and (ii) suggest a
 criterion for irrigation water quality [C*(O)] and demonstrate
 its behavior under varying transpiration rates. The processes by
 which the soil becomes saline were simulated with an analytical
 solution to the convection-diffusion equation. The model was
 based on ion and water uptake by plant roots. The calculations
 indicated that crops classified as salinity tolerant remove more
 salt from the soil than salinity-sensitive crops. The rates of
 ion removal are 5, 15, and 40 X 10(-3) dS m(-1)d(-1) for
 salinity-sensitive, semisensitive, and tolerant crops,
 respectively. Therefore the ratio between the uptake rates of
 ions and water per unit soil volume is presented here as a
 criterion for the upper limit of allowable salinity in irrigation
 water. This ratio is inversely related to transpiration rate
 (evaporation neglected). Theoretically, the maximum allowable
 salinity of salt-tolerant crops, [C*(O)], decreases from 20 to 4
 dS m(-1) when the transpiration rate increases from 2 to 10 X
 10(-3) m d(-1). For the same transpiration rate increase, C*(O)
 of sensitive crops decreases from 3 to 0.5 dS m(-1); thus, a
 lower quality of water can be permitted for irrigation in a
 moderate or cool climate than in an arid climate. The model
 applies also for Se-accumulating crops.  removed from a soil
 solution containing a high concentration [C*(O)=1 mg kg(-1)] when
 the uptake rate of the growing crop is 25.8 X 10(-3) mg kg(-1)
 NAL Call No.: 56.9-So3
 156. Simulated transport of three cations through porous media:
 effect of different approaches to modeling cation exchange
 Grant, S. A.; Mansell, R. S.; Bloom, S. A.; Rhue, R. D. 
 Water-resour-res v.31, p.185-198. (1995).
 Includes references.
 Descriptors: porous-media; cations-; cation-exchange; solutes-;
 transport-processes; simulation-models; thermodynamics-;
 prediction-; loam-soils; thermodynamic-selectivity-coefficient;
 Abstract: Batch cation exchange and column experiments were
 conducted to evaluate selectivity coefficients which have been
 suggested for describing cation exchange reactions in solute
 transport models. Vanselow selectivity coefficients were
 calculated for cation exchange equilibria with a cation resin and
 for equilibria reported in the literature with a Yolo loam soil.
 Experimental column data were compared with data from simulations
 generated by a numerical solute transport model to evaluate
 Vanselow, Gaines-Thomas, and statistical thermodynamic
 selectivity coefficients. With the cation resin, the statistical
 thermodynamic selectivity coefficient gave the most reliable
 estimate of column effluent cation concentrations. In a column
 packed with the Yolo loam soil, the Vanselow selectivity
 coefficient gave the most accurate prediction of column response.
 Use of variable (as opposed to fixed) Vanselow selectivity
 coefficients gave more accurate predictions of column
 experiments. The use of ternary cation exchange data did not
 improve predictions of column response.
 NAL Call No.: 292.8-W295
 157. Simulating aldicarb transport in a drained field.
 Munster, C. L.; Skaggs, R. W.; Parsons, J. E.; Evans, R. O.;
 Gilliam, J. W.; Breve, M. A. 
 Trans-ASAE v.37, p.1817-1824. (1994).
 Includes references.
 Descriptors: aldicarb-; insecticide-residues;
 transport-processes; subsurface-drainage; tile-drainage;
 drainage-; subsurface-irrigation; groundwater-flow;
 groundwater-pollution; simulation-models; computer-simulation;
 north-carolina; conventional-drainage; controlled-drainage;
 subirrigation-; vs2dt-model
 Abstract: The United States Geological Survey computer model
 Variably Saturated Two Dimensional Transport (VS2DT) was modified
 to treat boundary conditions imposed by parallel subsurface drain
 tubes. The modified model was used to simulate groundwater flow
 and aldicarb transport in research plots under conventional
 drainage, controlled drainage, and subirrigation. The reliability
 of the model was tested by comparing model predictions with field
 NAL Call No.: 290.9-Am32T
 158. Simulating NO3-N transport to subsurface drain flows as
 affected by tillage under continuous corn using modified RZWQM.
 Singh, P.; Kanwar, R. S. 
 Trans-ASAE v.38, p.499-506. (1995).
 Includes references.
 Descriptors: subsurface-drainage; water-flow; water-quality;
 nitrate-nitrogen; tillage-; simulation-models;
 computer-simulation; performance-appraisals
 Abstract: The Root Zone Water Quality Model (RZWQM) was
 previously modified to simulate subsurface drain flows and
 evaluate the impact of different tillage systems on subsurface
 drain flows (Singh and Kanwar, 1994). This article discusses
 further modifications made in the RZWQM to simulate
 nitrate-nitrogen (NO3-N) concentrations and N03-N losses with
 subsurface drain flows. Daily NO3-N concentrations were simulated
 in subsurface drain flows under four different tillage systems:
 chisel plow (CP), moldboard plow (MB), no-tillage (NT), and
 ridge-nllage (RT) by using the modified RZWQM. Simulations were
 conducted for the growing seasons of three years (1990 to 1992).
 Simulated N03-N concentrations and losses with subsurface drain
 flows were compared with the measured data obtained from a water
 quality research site at Nashua, Iowa. Predicted NO3-N
 concentrations generally followed the same pattern as the
 observed concentrations. Simulated annual average NO3-N
 concentrations in subsurface drain flows were within 11%
 (averaged over all three years) of observed annual average NO3-N
 concentrations in subsurface drain flows. The model correctly
 predicted maximum concentrations under MB treatment and minimum
 under NT for all three years. Simulated annual NO3-N losses were
 within 14% (averaged over all three years) of observed annual
 NO3-N losses. Various N03-N transformation processes need to be
 calibrated as a function of tillage system to improve model
 NAL Call No.: 290.9-Am32T
 159. Simulating solute transport in an aggregated soil with the
 Brusseau, M. L.; Gerstl, Z.; Augustijn, D.; Rao, P. S. C. 
 J-hydrol v.163, p.187-193. (1994).
 Includes references.
 Descriptors: aggregates-; solutes-; transport-processes;
 Abstract: The capability of the first-order, dual-porosity model,
 which explicitly accounts for non-ideal transport caused by the
 presence of 'immobile' water, to predict the non-ideal transport
 of non-sorbing solute in a constructed aggregated soil has been
 investigated. Miscible-displacement experiments performed with a
 well-characterized aggregated soil and a non-reactive tracer
 (pentafluorobenzoate) served as the source of the data. Values
 for the input parameters associated with physical non-equilibrium
 were determined independently and compared with values obtained
 by curve fitting of the experimental measurements. The calculated
 and optimized values compared well, suggesting that the
 non-equilibrium parameters represent actual physical phenomena.
 NAL Call No.: 292.8-J82
 160. Simulation and evaluation of alternative nutrient management
 practices on a demonstration watershed.
 Stone, K. C.; Hunt, P. G.; Coffey, S. W. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-2572) 13 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 14-17, Chicago, Illinois.
 Descriptors: surface-water; groundwater-; plant-nutrition;
 watersheds-; catchment-hydrology; water-quality;
 simulation-models; evaluation-; crop-management; north-carolina;
 NAL Call No.: 290.9-Am32P
 161. Simulation of ground-water flow in the Albuquerque Basin,
 central New Mexico, 1901-1994, with projections to 2020. 
 Simulation of ground water flow in the Albuquerque Basin, central
 New Mexico, 1901-1994, with projections to 2020.
 Kernodle, J. M.;  McAda, D. P.;  Thorn, C. R.; Albuquerque
 (N.M.). Dept. of Public Works. 
 Albuquerque, N.M. : U.S. Dept. of the Interior, U.S. Geological
 Survey ; Denver, Colo. : Earth Science Information Center,
 Open-File Reports Section [distributor], 1995. ix, 114 p. : ill.,
 maps (some col.).
 One map on 1 folded leaf in pocket.
 Groundwater-flow-New-Mexico-Albuquerque-Region-Mathematical-models; Geographic-information-systems; Albuquerque-Basin-N; M
 NAL Call No.: GB701.W375--no.94-4251
 162. Simulation of nitrogen dynamics in farmland areas of
 Jensen, C.; Stougaard, B.; Ostergaard, H. S. 
 Soil-use-manage v.10, p.111-113. (1994).
 Includes references.
 Descriptors: agricultural-land; nitrogen-content; nitrate-;
 leaching-; losses-from-soil; crop-production;
 dry-matter-accumulation; deterministic-models; validity-;
 crop-management; fertilizers-; cropping-systems; subsoil-;
 soil-texture; precipitation-; denmark-
 Abstract: Each year since 1986 information has been collected 
 about the farming systems at intersections of a nationwide 7 km
 square grid in Denmark. These management data and corresponding
 soil analyses were used in the model DAISY to simulate water and
 nitrogen dynamics. The model was validated with respect to
 harvested dry matter yield and nitrogen content in the soil.
 Simulated nitrate leaching from farmland areas from 1 April 1989
 to 31 March 1993 was related to precipitation zones, soil type,
 fertilizer strategies and cropping systems. The mean simulated
 nitrate leaching for the whole of Denmark was 74 kg N/ha/yr, with
 a large yearly variation in the period considered. The simulated
 nitrate leached from soils with a sandy subsoil corresponded to
 51% of the applied fertilizer, twice that leached from soils with
 a loamy subsoil. The application of pig manure resulted in
 average leaching losses of 105 kg N/ha/yr. The simulated nitrate
 leaching losses at sites where only artificial fertilizer was
 applied were in the following order: cereal with undersown grass
 < crop followed by winter cereal or winter rape < cereal or rape
 without a catch crop < root crops without a catch crop. Where
 only artificial fertilizers were applied, the simulated mean
 annual leaching was 59 kg N/ha from spring barley and 40kg N/ha
 from winter wheat. A map of simulated nitrate leaching in Denmark
 was produced using a Geographical Information System.
 NAL Call No.: S590.S68
 163. Simulation of runoff transport of animal waste constituents.
 Wang, Y.; Edwards, D. R.; Daniel, T. C.; Scott, H. D. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2156/94-2185) 23 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by the American Society of Agricultural Engineers,"
 June 19-22, 1994, Kansas City, Missouri.
 Descriptors: poultry-manure; transport-processes;
 nitrate-nitrogen; phosphorus-; losses-from-soil; water-pollution;
 NAL Call No.: 290.9-Am32P
 164. Simulation of TCE migration and biodegradation in a porous
 medium under conditions of finite degradation capacity.
 Tompson, A. F. B.; Knapp, R. B.; Hanna, M. L.; Taylor, R. T. 
 Adv-water-resour v.17, p.241-249. (1994).
 Includes references.
 Descriptors: bioremediation-; trichloroethylene-;
 microbial-degradation; immobilization-; sand-;
 gram-negative-bacteria; mathematical-models;
 groundwater-pollution; simulation-models;
 NAL Call No.: TD201.A4
 165. Simulation of the impacts of climate change on runoff and
 soil moisture in Australian catchments.
 Chiew, F. H. S.; Whetton, P. H.; McMahon, T. A.; Pittock, A. B. 
 J-hydrol v.167, p.121-147. (1995).
 Includes references.
 Descriptors: watersheds-; climatic-change; runoff-; soil-water;
 temperature-; precipitation-; catchment-hydrology;
 simulation-models; australia-; global-climate-model
 Abstract: The impacts of climate change on runoff and soil
 moisture in 28 Australian catchments are simulated using a
 hydrologic daily rainfall-runoffmodel. Two methods are used to
 provide the climate change scenarios. First, a range of arbitrary
 changes in temperature and precipitation are applied to the
 calibrated rainfall-runoff model to study the sensitivity of
 runoff and soil moisture to potential changes in the climate.
 Second, results from five global climate model (GCM) enhanced
 greenhouse expenments are analysed to provide regional climate
 change scenarios to estimate the range of plausible changes in
 runoff and soil moisture by the years 2030 and 2070. The
 sensitivity analyses indicate that changes in rainfall are always
 amplified in runoff with the amplification factor for runoff
 being higher in drier catchments. The change in rainfall has
 little effect on the soil moisture in wet catchments but in drier
 catchments, the percentage change in soil moisture levels can be
 greater than the percentage change in rainfall. Compared to
 precipitation, temperature increases alone have negligible
 impacts on the runoff and soil moisture. The simulations using
 the GCM scenanos indicate increases in annual runoff of up to 25%
 by the year 2030 in the wet tropical catchments near the
 north-east coast of Australia. The GCMs do not agree in the
 direction of rainfall change in south-east Australia, and the
 simulations show runoff changes of up to +/-20% by 2030. For
 Tasmanian catchments, up to 10% increase in runoff is simulated
 whereas for catchments in the South Australian Gulf, up to 35%
 decrease in annual runoff is simulated for 2030. Near the western
 coast of Australia, the simulations show runoff changes of up to. 
 about runoff modifications that may require a significant
 planning response. They are also indicative of the fact that
 hydrological impacts affecting water supply and flood studies may
 be important in considering the cost and benefits of potential
 climate change.
 NAL Call No.: 292.8-J82
 166. Simulation of water applied nitrogen distribution under
 surge irrigation.
 Boldt, A. L.; Watts, D. G.; Eisenhauer, D. E.; Schepers, J. S. 
 Trans-ASAE v.37, p.1157-1165. (1994).
 Includes references.
 Descriptors: fertigation-; furrow-irrigation; nitrogen-; runoff-;
 leaching-; computer-simulation; simulation-models; sifum-;
 Abstract: Fertigation during surge flow irrigation is a promising
 means of delaying nitrogen (N) fertilizer application on furrow
 irrigated corn and thereby reducing the potential for leaching of
 nitrate-nitrogen into groundwater. A computer model, SIFUM (Surge
 Irrigation Fertigation Uniformity Model), was developed to
 simulate the distribution, uniformity, and runoff losses of
 fertigation-applied N during surge irrigation of furrows. The
 model, SIFUM, was used to help develop fertigation management
 strategies for field application that can provide acceptable N
 distributions across a range of soil conditions and furrow flow
 rates for surge irrigation with free outflow of runoff with no
 runoff recovery. Simulation groups included injecting N during
 (a) all surges, (b) the advance surges only, (a) the post advance
 surges only, and (d) the middle surges (last of advance plus
 first of cutback). For each of these groups, fertigation was
 simulated both for the entire on-time of each surge cycle and for
 only a portion of the on-time. The application efficiency of the
 low quarter (AELQ) was used as an index for evaluating the
 efficiency of fertigation treatments. Simulation results show
 that to obtain the best N efficiency on high-intake soils,
 fertigation can occur during any portion or all of the on-time of
 a surge cycle, but should be applied during all cycles, i.e., for
 the entire irrigation. For medium and low intake soils,
 fertigation should be applied during all of the on-time of a
 surge cycle and may be applied for either all of the irrigation
 or just the advance surges.
 NAL Call No.: 290.9-Am32T
 167. A spatial decision support system for assessing agricultural
 nonpoint source pollution.
 Srinivasan, R.; Engel, B. A. 
 Water-resour-bull v.30, p.441-452. (1994).
 Includes references.
 Descriptors: pollution-; watersheds-; runoff-; erosion-;
 geographical-information-systems; simulation-models;
 integrated-systems; texas-
 Abstract: A spatial decision support system (SDSS) was developed
 to assess agricultural nonpoint source (NPS) pollution using an
 NPS pollution model and geographic information systems (GIS).
 With minimal user interaction, the SDSS assists with extracting
 the input parameters for a distributed parameter NPS pollution
 model from user-supplied GIS base layers. Thus, significant
 amounts of time, labor, and expertise can be saved. Further, the
 SDSS assists with visualizing and analyzing the output of the NPS
 pollution simulations. Capabilities of the visualization
 component include displays of sediment, nutrient, and runoff
 movement from a watershed. The input and output interface
 techniques/algorithms used to develop the SDSS, along with an
 example application of the SDSS, are described.
 NAL Call No.: 292.9-Am34
 168. Spatial variation of daily rainfall and network design.
 Abtew, W.; Obeysekera, J.; Shih, G. 
 Trans-ASAE v.38, p.843-845. (1995).
 Includes references.
 Descriptors: rain-; runoff-; phosphorus-; rain-gauges; design-;
 network-analysis; water-management; spatial-variation;
 mathematical-models; florida-
 Abstract: A high-density pilot network of 10 rain gauges was
 implemented in the Everglades Nutrient Removal (ENR) Project to
 quantify areal rainfall over the site for accurate computation of
 water budget. The ENR Project, located in south Florida, is a
 1500 ha wetland that was constructed to reduce phosphorus loads
 in agricultural runoff from the Everglades Agricultural Area
 (EAA) that enters the Water Conservation Areas (WCAs). The first
 158 days of wet season daily rainfall data were used to evaluate
 the adequacy (or redundancy) of the network. A spatial
 correlation function was developed to characterize the spatial
 variation of wet season rainfall over the site. An exponential
 spatial correlation model was fitted to the data with an R2 value
 of 0.74. A method that compares relative error to rain gauge
 density was applied to determine the required minimum gauge
 density. It was determined that a five rain gauge network with
 uniform distribution was the most efficient design.
 NAL Call No.: 290.9-Am32T
 169. Statewide GIS screening of selected corn pesticides in
 Messier, S. R.; Hamlett, J. M.; Petersen, G. W.; Harrison, S. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-3554) 16 p. 
 Paper presented at the "1993 International Winter Meeting ored by
 the American Society of Agricultural Engineers," December 14-17,
 1993, Chicago, Illinois.
 Descriptors: groundwater-pollution; pesticides-; leaching-;
 geographical-information-systems; screening-; zea-mays; models-;
 NAL Call No.: 290.9-Am32P
 170. Statistical procedure for evaluating hydrologic/water
 quality models.
 Haan, C. T.; Allred, B.; Storm, D. E.; Sabbagh, G. J.; Prabhu, S. 
 Trans-ASAE v.38, p.725-733. (1995).
 Includes references.
 Descriptors: water-quality; simulation-models;
 performance-appraisals; hydrological-data
 Abstract: Input parameters are used in hydrologic/water quality
 models to describe specific situations. These input parameters
 are never known with certainty. The models, although largely
 physically based, are not capable of describing the exact
 hydrologic and chemical processes that take place under natural
 conditions. Evaluation of models by a comparison of observed and
 predicted results is fraught with ambiguities resulting from the
 large number of parameters that must be estimated and the
 inherent variability in natural systems. This article puts forth
 a model evaluation protocol based on a simulation procedure which
 transforms parameter uncertainty into prediction uncertainty
 using probability density functions. Confidence intervals are
 placed on model results and decisions regarding model
 acceptability are made based on the magnitude of measured data,
 confidence intervals, and performance criteria placed on the
 NAL Call No.: 290.9-Am32T
 171. Studying the role of old agricultural terraces on runoff
 generation in a small Mediterranean mountainous basin.
 Gallart, F.; Llorens, P.; Latron, J. 
 J-hydrol v.159, p.291-303. (1994).
 Special Issue: Field laboratory and modelling studies of flow and
 transport processing / edited by H.S. Wheater, P.A.C. Raats, and
 A.C. Armstrong.  Sciences Programme Session HS1 of the XVII
 General Assembly of the European Geophysical Society, April 6-10,
 1992, Edinburgh.
 Descriptors: terraces-; ditches-; drainage-channels; sediment-;
 drainage-water; storms-; runoff-; environmental-degradation;
 mountain-areas; agricultural-land; simulation-models; spain-
 Abstract: The small drainage basin of Cal Parisa was instrumented
 in early 1989 to study the hydrological and sediment routing
 behaviour of Mediterranean mountain areas formerly used for
 agriculture but now abandoned. Environmental changes produced by
 agricultural land use included the construction of terraces on
 the major part of the basin and subsequent artificial channelling
 of surface waters. Field observations and hydrological data
 suggest that storm runoff is generated by the contributing role
 of saturated areas, most of them originating from the terrace
 system. Modelling of the natural conditions before terracing,
 with the help of TOPMODEL, supports the hypothesis that terracing
 promotes the premature formation of saturated areas, increasing
 saturation overland flow at the expense of lower baseflow and
 actual evapotranspiration. Now, after land abandonment, the more
 relevant environmental hazard is linked to the spontaneous
 reorganization of the unmaintained artificial drainage network.
 NAL Call No.: 292.8-J82
 172. Substrate effects on the enhanced biotransformation of
 polychlorinated hydrocarbons under anaerobic condition.
 Doong, R. A.; Wu, S. C. 
 Chemosphere v.30, p.1499-1511. (1995).
 Includes references.
 Descriptors: chlorinated-hydrocarbons; chloroform-;
 carbon-tetrachloride; trichloroethylene-; microbial-degradation;
 anaerobes-; anaerobic-conditions; in-vitro; models-;
 bioremediation-; groundwater-pollution; acetic-acid; methanol-;
 glucose-; humic-acids; 1,1,1-trichloroethane-;
 NAL Call No.: TD172.C54
 173. Summary report Chesapeake Bay Watershed Model Workshop :
 15-16 December 1993, Annapolis, Maryland : final report. 
 Chesapeake Bay Watershed Model Workshop, 15-16 December 1993,
 Annapolis, Maryland.
 Deliman, P. N.; Chesapeake Bay Watershed Model Workshop (1993 :
 Annapolis, Md. 
 [Vicksburg, Miss.] : U.S. Army Corps of Engineers Waterways
 Experiment Station, [1994] v, 110 p. : ill., maps.
 "May 1994.".
 Descriptors: Watershed-management-Mathematical-models-Congresses;
 Chesapeake-Bay-Watershed-Md; -and-Va;
 NAL Call No.: GB991.A123C44--1993
 174. Sustainability of conjunctive water use for salinity control
 in irrigation areas: theory and application to the Shepparton
 regions, Australia.
 Prendergast, J. B.; Rose, C. W.; Hogarth, W. L. 
 Irrig-sci v.14, p.177-187. (1994).
 Includes references.
 Descriptors: water-management; irrigation-water; water-use;
 groundwater-; surface-water; mixtures-; sustainability-;
 water-quality; salinity-; deterioration-; mathematical-models;
 Abstract: The long term sustainability of conjunctive water use
 for controlling irrigation salinity is affected by increase in
 groundwater salinity over time. This paper uses mass conservation
 of salt and water to assess groundwater degradation over long
 time scales. Management options which affect this rate of
 degradation are also examined. The groundwater model developed is
 illustrated using data from the Shepparton Irrigation Region in
 the Murray Basin, Australia. The model predicts rapid groundwater
 deterioration when conjunctive use is conducted over only a
 fraction of the area of influence of a groundwater pump. Where
 the pumped aquifer is underlain by deeper groundwaters, the rate
 of groundwater degradation is also affected by leakage into or
 out of the conjunctive use system. Surface redistribution of
 groundwater from pumps installed in zones of regional groundwater
 discharge to areas recharging the regional groundwaters, reduces
 excessive degradation in the zones of discharge. With optimal
 surface distribution of groundwater, the rate of degradation is
 low. The rate of groundwater degradation also depends on salt
 inputs from irrigation water and rainfall, and the average depth
 from the soil surface to the base of the aquifer. The rate of
 degradation resulting from applied salts in surface water and
 rainfall is typically about 0.01 dSm-1 per year for shallow
 aquifers in the Shepparton region, but the rate is lower where
 deeper aquifers are pumped. Partial irrigation also reduces the
 rate of degradation because of the reduced rate of salt inputs.
 Where poorer quality groundwater lies within the area of
 influence of the groundwater pump, a greater rate of
 deterioration.  mixing. In some irrigation regions limited export
 of groundwater through surface water conveyance structures to a
 river is possible. so that a regional surface salt balance could
 be maintained. However, salt exports made equal to the rate of
 surface imports into the irrigated area will only significantly
 impact groundwater salinity in the very longterm, or where only
 shallow aquifers.
 NAL Call No.: S612.I756
 175. Sustainability of sewage sludge land application to northern
 hardwood forests.
 Crohn, D. M. 
 Ecol-appl v.5, p.53-62. (1995).
 Includes references.
 Descriptors: sewage-sludge; organic-amendments;
 application-to-land; broadleaved-deciduous-forests; forest-soils;
 simulation-models; monte-carlo-method; application-rates;
 nitrogen-; nitrate-; leaching-; groundwater-pollution;
 soil-fertility; humus-; growth-; biomass-production;
 nutrient-uptake; new-hampshire; fortnite-; forsento-
 NAL Call No.: QH540.E23
 176. Technical analysis of response of Chesapeake Bay water
 quality model to loading scenarios.  Response of the Chesapeake
 Bay water quality model to loading scenarios.
 Thomann, R. V.; United States. Environmental Protection Agency.
 Chesapeake Bay Program. Modeling Subcommittee. 
 Annapolis, MD : U.S. Environmental Protection Agency, Chesapeake
 Bay Program Office, [1994] 1 v. (various pagings) : ill., 1 map.
 "Principal authors: Robert V. Thomann ... [et al.]"--P. after
 Descriptors: Water-quality-Chesapeake-Bay-Md; -and-Va;
 -Mathematical-models; Eutrophication-Chesapeake-Bay-Md; -and-Va
 NAL Call No.: TD223.1.T43--1994
 177. Technology as an agricultural pollution control policy.
 Abler, D. G.; Shortle, J. S. 
 Am-j-agric-econ v.77, p.20-32. (1995).
 Includes references.
 Descriptors: maize-; agricultural-chemicals; pollution-control;
 technical-progress; environmental-policy; low-input-agriculture;
 innovation-adoption; elasticities-; mathematical-models; usa-
 Abstract: In this paper we consider the market-level impacts of
 factor-augmenting innovations designed to reduce the use of
 fertilizers and pesticides, first within the context of a simple
 two-factor model, and then through a simulation model of the U.S.
 corn market. In both models, the impacts depend on the output
 demand elasticity and input substitution elasticities. The
 principal conclusion of the simulation analysis is that the
 potential for new techniques to reduce the use of agricultural
 chemicals is limited. Capital-augmenting innovations would
 actually raise fertilizer and pesticide usage. Land-augmenting
 innovations would also tend to increase pesticide usage.
 NAL Call No.: 280.8-J822
 178. Thermal venting to recover less-volatile hydrocarbons from
 the unsaturated zone. II. Model applications.
 Mesbah Ul Islam, K. M.; Kaluarachchi, J. J. 
 J-contam-hydrol v.17, p.313-331. (1995).
 Second of a two part series.
 Descriptors: hydrocarbons-; contaminants-; volatile-compounds;
 groundwater-pollution; techniques-; simulation-models
 NAL Call No.: TD426.J68
 179. Transport of a nonreactive solute in soils: a two-flow
 domain approach.
 Ma, L.; Selim, H. M. 
 Soil-sci v.159, p.224-234. (1995).
 Includes references.
 Descriptors: solutes-; transport-processes; mathematical-models;
 soil-types-genetic; solute-transport-models
 NAL Call No.: 56.8-So3
 180. Transport of acridine in saturated porous media.
 Matzner, R.; Bales, R. C. 
 Chemosphere v.29, p.1755-1773. (1994).
 Includes references.
 Descriptors: acridines-; transport-processes; silica-;
 adsorption-; ph-; models-; groundwater-pollution
 NAL Call No.: TD172.C54
 181. Transport of bacteria in an aquifer sand: experiments and
 model simulations.
 Tan, Y.; Gannon, J. T.; Baveye, P.; Alexander, M. 
 Water-resour-res v.30, p.3243-3252. (1994).
 Includes references.
 Descriptors: soil-bacteria; sand-; porous-media; aquifers-;
 transport-processes; mathematical-models; simulation-models
 Abstract: Experiments were carried out to determine the
 breakthrough of bacteria through a saturated aquifer sand at
 three flow velocities and three cell concentrations. Bacteria
 were either suspended in deionized water or 0.01 mol L-1 NaCl
 solution. Bacterial transport was found to increase with flow
 velocity and cell concentration but was significantly retarded in
 the presence of 0.01 mol L-1 NaCl. A mathematical model based on
 the advection-dispersion equation was formulated to describe
 bacterial transport and retention in porous media. The transport
 equations for bacteria were solved using the finite difference
 Crank-Nicolson scheme combined with Newton-Raphson iterations.
 The best fit of the numerical model to the experimental data was
 obtained using the downhill simplex optimization technique to
 minimize the sum of the squares of deviations between model
 predictions and experimental data by varying three parameters.
 This numerical model was found to describe the experimental data
 very well under all the experimental conditions tested. An
 alternative model (also based on the advection-dispersion
 equation) was tested against all the experimental data sets, but
 it did not represent the experimental data as well as the model
 proposed in this paper.
 NAL Call No.: 292.8-W295
 182. Transport of chlorsulfuron through soil columns.
 Veeh, R. H.; Inskeep, W. P.; Roe, F. L.; Ferguson, A. H. 
 J-environ-qual v.23, p.542-549. (1994).
 Includes references.
 Descriptors: chlorsulfuron-; transport-processes; leaching-;
 persistence-; unsaturated-flow; silt-loam-soils; clay-loam-soils;
 Abstract: Chlorsulfuron
 amino]carbonyl]-benzenesulfonamide] is an anionic sulfonylurea
 herbicide with high soil persistence; consequently, there is
 interest in predicting its mobility in agricultural soils. The
 objectives of this study were to determine the transport
 characteristics of chlorsulfuron in disturbed and undisturbed
 soil columns and evaluate the capabilities of LEACHM (Leaching
 Estimation and Chemistry Model) for predicting chlorsulfuron
 transport. Soil column experiments were conducted with two
 Montana soils (Amsterdam silt loam, fine-silty, mixed Typic
 Haploboroll, and Haverson silty clay loam, fine-loamy, mixed
 (calcareous), mesic Ustic Torrifluvent) under unsaturated flow
 conditions. Unit gradient was established in all columns by
 balancing surface water input to outflow at the bottom of each
 column through a stainless steel porous plate connected to a
 vacuum chamber containing a fraction collector. A nonlinear least
 squares approach (CXTFIT) was used to fit breakthrough curves
 (BTCs) for Br- and 14C-labeled chlorsulfuron using the linear
 equilibrium adsorption model (i.e., local equilibrium assumption
 or LEA model) and the bicontinuum model (i.e., nonequilibrium
 assumption). Observed Br- BTCs were best described by the
 bicontinuum model indicating physical nonequilibrium due to
 immobile water regions. Observed chlorsulfuron BTCs demonstrated
 both chemical and physical nonequilibrium during transport. The
 best fit to observed chlorsulfuron BTCs was obtained with the
 bicontinuum model using the dispersion coefficient optimized
 (i.e., fixed) from the Br- BTCs. LEACHM was used to generate
 predicted BTCs for chlorsulfuron utilizing independently.  BTCs
 utilizing the Br- derived dispersion coefficient (D) and the
 bicontinuum model-derived partition coefficient (Koc) did not
 adequately reflect observed BTCs primarily because the current
 version of LEACHM has no capability for accepting input
 parameters relating to nonequilibrium conditions. The D and Koc
 vales for chlorsulfuron BTCs derived from the LEA model improved
 predictions; however, it is important to note that LEA-derived D
 and Koc values for chlorsulfuron BTCs essentially compensate for
 nonequilibrium behavior. Finally, the experimentally determined
 chlorsulfuron BTCs confirmed the high mobility of this chemical
 at neutral soil pH values.
 NAL Call No.: QH540.J6
 183. Transport of reactive solutes in soils: a modified
 two-region approach.
 Selim, H. M.; Ma, L. 
 Soil-Sci-Soc-Am-j. [Madison, Wis.] Soil Science Society of
 America. Jan/Feb 1995. v. 59 (1) p. 75-82. 
 Includes references.
 Descriptors: solutes-; transport-processes; adsorption-;
 retention-; release-; mathematical-models; clay-soils; atrazine-;
 Abstract: A modified two-region approach that accounts for
 chemical and physical nonequilibrium of solute behavior in soils
 was developed. Chemical nonequilibrium was described by a
 second-order two-site model, while physical nonequilibrium was
 represented by a two-region (mobile-immobile) approach. Model
 validity was based on predictions of atrazine
 [2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine] miscible
 displacement experiments in a Sharkey clay soil (very fine,
 montmorillonitic, nonacid, thermic Vertic Haplaquept) for
 different aggregate sizes, flow velocities, column lengths, and
 flow interruption. Independently measured model parameters from
 kinetic batch experiments were used in model validation. Two
 model formulations were evaluated. Model I was based on the
 classical two-region approach where the soil matrix was divided
 into two fractions. In Model II, we assumed that the rate of
 reaction within each soil region was a function of the total
 number of vacant sites in the soil. Thus, the partitioning
 coefficient f of the two-region concept, which is difficult to
 measure, need not be specified and the amounts retained by each
 soil region is solely a function of reaction rate coefficients.
 Model I with f = F (F = mobile/total water contents) provided the
 worst atrazine predictions. Moreover, based on Model I
 predictions with f = 1 and f = 0, the significance of physical
 nonequilibrium was dependent on experimental constraints such as
 aggregate size and flow velocity. Based on root mean squares,
 however, the best overall predictions were obtained using Model
 II. We concluded that Model II, which requires fewer parameters,
 is superior to Model I in its prediction.
 NAL Call No.: 56.9-So3
 184. Using curve numbers to determine baseline values of
 green-ampt effective hydraulic conductivities.
 Risse, L. M.; Liu, B. Y.; Nearing, M. A. 
 Water-resour-bull v.31, p.147-158. (1995).
 Includes references.
 Descriptors: infiltration-; hydraulic-conductivity; runoff-;
 green-and-ampt-equation; water-erosion; prediction-;
 mathematical-models; water-erosion-prediction-project
 Abstract: Since the trend in infiltration modeling is currently
 toward process-based approaches such as the Green-Ampt equation,
 more emphasis is being placed on methods of determining
 appropriate parameters for this approach. The SCS curve number
 method is an accepted and commonly used empirical approach for
 estimating surface runoff, and is based on numerous data from a
 variety of sources. The time and expense of calibrating
 process-based infiltration parameters to measured data are often
 prohibitive. This study uses curve number predictions of runoff
 to develop equations to estimate the "baseline" hydraulic
 conductivities (Kb) for use in the Green-Ampt equation. Curve
 number predictions of runoff were made for 43 soils. Kb values in
 the Water Erosion Prediction Project (WEPP) model were then
 calibrated so that the annual runoff predicted by WEPP was equal
 to the curve number predictions. These calibrated values were
 used to derive an equation that estimated Kb based on the percent
 sand, percent clay, and cation exchange capacity of the soil.
 Estimated values of Kb from this equation compared favorably with
 measured values and values calibrated to measured natural runoff
 plot data. WEPP predictions of runoff using both optimized and
 estimated values of Kb were compared to curve number predictions
 of runoff and the measured values. The WEPP predictions using the
 optimized values of Kb were the best in terms of both average
 error and model efficiency. WEPP predictions using estimated
 values of Kb were shown to be superior to predictions obtained
 from the curve number method. The runoff predictions all tended
 to be biased high for small events and low for larger events when
 compared to the.  annual and event basis were also developed for
 the WEPP model.
 NAL Call No.: 292.9-Am34
 185. Using GLEAMS to select environmental windows for herbicide
 application in forests.
 Smith, M. C.; Michael, J. L.; Knisel, W. G.; Neary, D. G. 
 Environmentally sound agriculture  proceedings of the second
 conference  20-22 April 1994 / p.506-512. (1994).
 Includes references.
 Descriptors: forest-management; herbicides-; application-date;
 timing-; determination-; simulation-models; mathematical-models;
 environmental-protection; climatic-factors;
 NAL Call No.: S589.7.E57-1994
 186. Using ISC & GIS to predict sulfur deposition from power
 Lopez, J. I.; Beene, J. S.; Parnell, C. B. Jr. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (934059) 22 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: air-quality; grazing-; models-; cattle-
 NAL Call No.: 290.9-Am32P
 187. Utilizing GIS and GLEAMS to prescribe best management
 practice's for reducing nonpoint source pollution.
 Searing, M. L. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-3558) 20 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 14-17, 1993, Chicago, Illinois.
 Descriptors: watersheds-; water-pollution; feasibility-;
 geographical-information-systems; simulation-models;
 pollution-control; maryland-; frederick-county,-maryland
 NAL Call No.: 290.9-Am32P
 188. Validation of EPIC for land applied animal waste.
 Coffey, S. W.; Stone, K. C.; Line, D. E. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Winter 1993. (93-2531/93-2550) 14 p. 
 Paper presented at the "1993 International Winter Meeting
 sponsored by the American Society of Agricultural Engineers,"
 December 12-17, 1993, Chicago, Illinois.
 Descriptors: animal-wastes; application-to-land;
 nitrate-nitrogen; leaching-; simulation-models
 NAL Call No.: 290.9-Am32P
 189. Validation of GLEAMS nutrient component for midwestern
 Mamillapalli, S.; Engel, B. A.; Kladivko, E. J. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1994. (94-2066/94-2090) 27 p. 
 Paper presented at the "1994 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers,"
 June 19-22, 1994, Kansas City, Missouri.
 Descriptors: water-quality; ammonia-; nitrate-
 NAL Call No.: 290.9-Am32P
 190. Validation of leaching model on actual structures.
 Wegen, G. v. d.; Plas, C. v. d. 
 Stud-environ-sci. Amsterdam ; New York, Elsevier Scientific
 Publishing Co. 1994. (60) p. 55-62. 
 In the series analytic: Environmental aspects of construction
 with waste material / edited by J.J.J.M. Goumans, H.A. van der
 Sloot and T.G. Aalbers.  Implications of Construction Materials
 and Technology Developments," held June 1-3, 1994, Maastricht,
 The Netherlands.
 Descriptors: cement-; concrete-; bitumen-; slags-; fly-ash;
 building-materials; leaching-; soil-; pollution-;
 environmental-factors; copper-
 NAL Call No.: QH540.S8
 191. Validation of the GLEAMS-WT and GLEAMS-SWAT erosion
 Reyes, M. R.; Fouss, J. L.; Bengston, R. L.; Carter, C. E. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932088) 11 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers, and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: erosion-; runoff-; prediction-; simulation-models;
 losses-; water-table; subsurface-drainage; louisiana-
 NAL Call No.: 290.9-Am32P
 192. Variability in Green-Ampt effective hydraulic conductivity
 under fallow conditions.
 Risse, L. M.; Nearing, M. A.; Zhang, X. C. 
 J-hydrol v.169, p.1-24. (1995).
 Includes references.
 Descriptors: hydraulic-conductivity; rain-; infiltration-;
 runoff-; temporal-variation; soil-water-content;
 green-and-ampt-equation; fallow-; simulation-models;
 Abstract: Hydraulic conductivity of the soil matrix dynamically
 responds to changes in the surrounding environment. Therefore,
 infiltration parameters for the Green-Ampt equation should change
 for each storm event in continuous simulation models. This study
 focused on improving Water Erosion Prediction Project (WEPP)
 model estimates of runoff using over 220 plot-years of natural
 runoff plot data from 11 locations. By optimizing the effective
 Green-Ampt hydraulic conductivity. Ke, for each event within the
 simulation, a method of correlating hydraulic conductivity on any
 given day to many other parameters was established. Factors with
 significant correlation to optimized values of Ke fell into three
 distinct categories; (1) factors related to soil crusting and
 tillage; (2) factors related to event size; (3) factors related
 to antecedent moisture conditions. Equations were developed to
 represent the temporal variability of hydraulic conductivity for
 each group. The equation describing the decrease in hydraulic
 conductivity owing to crusting used an exponential decay function
 based primarily on cumulative rainfall kinetic energy since last
 tillage, a soil stability factor, and a crust factor. The
 relationship between hydraulic conductivity and event size was
 characterized using an exponential relationship with total
 rainfall kinetic energy. The final adjustment used the moisture
 content immediately below the infiltration zone to account for
 the influence of antecedent moisture conditions on optimized
 hydraulic conductivities. All three adjustments were
 incrementally incorporated into WEPP and each improved the
 average model efficiency.
 NAL Call No.: 292.8-J82
 193. Verification and adjustment of regional regression models
 for urban storm-runoff quality using data collected in Little
 Rock, Arkansas.
 Barks, C. S.; Little Rock (Ark.). 
 Little Rock, Ark. : U.S. Dept. of the Interior, U.S. Geological
 Survey ; Denver, CO : Earth Science Information Center, Open-File
 Reports Section [distributor], 1995. v, 12, 25 p. : maps.
 Chiefly tables.
 NAL Call No.: GB701.W375--no.94-4216
 194. Water budget analysis for the Everglades Agricultural Area
 drainage basin.
 Abtew, W.; Khanal, N. 
 Water-resour-bull v.30, p.429-439. (1994).
 Includes references.
 Descriptors: agricultural-land; water-budget; drainage-;
 irrigation-; runoff-; water-use; water-quality; rain-;
 seasonal-fluctuations; mathematical-models; florida-
 Abstract: Water budget studies are essential for water resources
 and environmental management. In this study, a water budget
 analysis is presented for the Everglades Agricultural Area (EAA)
 in South Florida for the period from 1973 to 1991. The EAA is a
 highly productive irrigation/drainage basin that has a high water
 table and organic soils. Water quality problems are associated
 with the drainage discharge from the basin. During dry periods,
 supplemental water is used for irrigation and in rainy periods
 excess water with relatively higher phosphorus content is pumped
 out of the basin to Lake Okeechobee and the Everglades ecosystem.
 Elevated concentrations of phosphorus in the runoff/drainage that
 is discharged from the EAA basin have created water quality
 problems. The mean surface water inflow to the basin was 63,990
 ha-m, and the outflow was 131,447 ha-m per year. On the average,
 supplemental surface water use was 47,411 ha-m, and
 runoff/drainage was 114,816 ha-m per year. The mean annual basin
 rainfall was 120.9 cm. A general trend in the decline of the wet
 season rainfall is observed.
 NAL Call No.: 292.9-Am34
 195. WEPP watershed model: applications and progress.
 Ascough, J. C. II.; Tiscareno Lopez, M.; Zweep, R. A. v. d.; Deer
 Ascough, L. A.; Livingston, S. J. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932106) 34 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: erosion-; prediction-; watersheds-; water-quality;
 simulation-models; water-erosion-prediction-project
 NAL Call No.: 290.9-Am32P
 196. WEPP watershed model: background and processes.
 Ascough, J. C. II.; Zweep, R. A. v. d.; Deer Ascough, L. A.;
 Livingston, S. J.; Laflen, J. M. 
 Pap-Am-Soc-Agric-Eng. St. Joseph, Mich. : American Society of
 Agricultural Engineers,. Summer 1993. (932105) 13 p. 
 Paper presented at the "1993 International Summer Meeting
 sponsored by The American Society of Agricultural Engineers and
 The Canadian Society of Agricultural Engineering," June 20-23,
 1993, Spokane, Washington.
 Descriptors: erosion-; prediction-; watersheds-; water-quality;
 simulation-models; water-erosion-prediction-project
 NAL Call No.: 290.9-Am32P

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