Clean Coastal Waters Understanding and Reducing the Effects of Nutrient Pollution (2000) / Chapter Skim
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Appendix D Model Reviews
Appendix D Model Reviews
Pages 376-391
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From page 376... ...
Army Corps of Engineers, Hydrologic Engineering Center) might contribute to analysis of nonpoint source water quality in watersheds, only models with an explicit water quality simulation capability are described herein, and more specifically, the models must be capable of simulating nutrient loadings.
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From page 377... ...
The primary emphasis of the model is on nutrients, soil erosion, and sediment yield for comparing the effects of various best management practices on agricultural pollutant loadings. The AGNPS model can simulate sediment and nutrient loads from agricultural watersheds for a single storm event or for a continuous simulation.
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From page 378... ...
The assessment and planning module, working within GIS, allow users to quickly evaluate selected areas, organize information, and display results. The modeling module allows users to examine the impacts of pollutant loadings from point and nonpoint sources.
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From page 379... ...
Runoff flow rate, sediment loads, nutrients, pesticides, toxic chemicals, and other water quality constituent concentrations can be predicted. The model can simulate continuous, dynamic, or steady state behavior of both hydrologic/hydraulic and water quality processes in a watershed.
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From page 380... ...
Nonpoint loads are generated on the basis of land use and other data in a GIS format, coupled with simplified hydrologic techniques, but with complete coverage of the hydrologic cycle. Erosion processes are included in land runoff modules, as are integrated water quality fate and transport processes in riverine segments.
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From page 381... ...
381 U U 5- ~ Via ~ ~ U - ~ ~ o ~ CD ~ do ~ 3 ~ o ~ ~ to u 5_, 5°- ~ .
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From page 382... ...
Flow routing options range from simple to complete solution of the Saint-Venant equations in the Extran Block. Simulation of nonpoint source runoff quality may be performed by several options, including constant concentrations, regression methods and buildup and washoff functions.
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From page 383... ...
The equations were developed for three different hydrologic zones of the United States and utilize commonly available watershed characteristics as independent variables. If a single EMC or loading value is needed, this work remains the only comprehensive synthesis of thousands of samples of stormwater runoff from urban watersheds.
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From page 384... ...
Specific techniques contained in WQAM are the Fraction of Freshwater Method, the Modified Tidal Prism Method, Advection-Dispersion equations, and Pritchard's two-dimensional box model. Steady State and Tidally Averaged Steady state and tidally averaged simulation models generally use a box or compartment-type network and are difficult to calibrate in situations where hydrodynamics and pollutant releases are rapidly varying.
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From page 385... ...
Dynamic Simulation Models of One or More Dimensions Numerical one-dimensional and two-dimensional models that simulate variations in tidal height and velocity throughout each tidal cycle enable the characterization of phenomena varying rapidly within each tidal cycle, such as pollutant spills, stormwater runoff, and batch discharges. They also are deemed appropriate for systems where the tidal boundary impact is important to the modeled system within a tidal period.
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From page 386... ...
Primary physical processes included are surface heat transfer, shortwave and longwave radiation and penetration, convective mixing, wind and flow induced mixing, entrainment of ambient water by pumped-storage inflows, inflow density current placement, selective withdrawal, and density stratification as impacted by temperature and dissolved and suspended solids. Major chemical and biological processes in CE-QUAL-W2 include: effects on DO of atmospheric exchange, photosynthesis, respiration, organic matter decomposition, Vitrification, and chemical oxidation of reduced substances; uptake, excretion, and regeneration of phosphorus and nitrogen and nitrificationdenitrification under aerobic and anaerobic conditions; carbon cycling and alkalinity-pH-CO2 interactions; trophic relationships for total phytoplankton; accumulation and decomposition of detritus and organic sediment; and coliform bacteria mortality.
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From page 387... ...
CH3D-ICM CH3D-ICM is a linkage of CH3D, a hydrodynamic model, and CE-QUAL-ICM, a water quality model. CH3D is a three-dimensional, finite difference hydrodynamic model developed by Peter Sheng, recently modified for the Chesapeake Bay Program Johnson et al.1993)
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From page 388... ...
EFDC is a linked three-dimensional, finite difference hydrodynamic and water quality model developed at the Virginia Institute of Marine Sciences. EFDC contains extensive water quality capabilities, including a eutrophication framework based upon the ICM model.
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