A Lumped Parameter Watershed Water Quality Model for Total Maximum Daily Loads (TMDLs) in the Watershed Modeling System (WMS)

The Watershed Modeling System (WMS) is a comprehensive graphical user environment for conducting watershed hydrologic analysis. The model was developed by the Engineering Computer Graphics Laboratory of Brigham Young University in cooperation with the U.S. Army Engineering Research and Development Center, Waterways Experiment Station. Features of the WMS include pre- and post-processing support, GIS/CADD links, finite difference/finite element grid generation, 2D data interpolation/visualization, AVI video file animation, use of NEXRAD radar of Battlescale Forecast Models as inputs to 2D spatial models, and the ability to import digital terrain data. Models included within this system are HEC1, TR20, TR55, NFF, and CEQUAL- W2. Watershed water quality models in the system which can be utilized in the determination of Total Maximum Daily Loads (TMDLs) are CASC2D and the Hydrologic Simulation Program- Fortran (HSPF). HSPF is one of the most widely used lumped parameter watershed water quality models currently used in the country while CASC2D is a newly developed distributed watershed model. This paper describes the application of the lumped parameter watershed water quality model HSPF to a basin in the Upper Mississippi River Watershed. Results from the study yield insight into the advantages and disadvantages of utilizing the WMS for determination of TMDLs and watershed assessments including the evaluation of Best Management Practices (BMPs).