Suwannee River -- Watershed Assessment Project

The purpose of the GIS watershed assessment project was to develop specific criteria to determine the relative impacts of land use, soils, hydrography, and other parameters on the discharge water quality, wetland value, and flood impact. Watershed assessment models have two roles in the overall assessment process: source identification and plan evaluation.

WAM (Watershed Assessment Model) is a GIS-based tool for determining the spatial influence of land uses and soils on the water quality and quantity throughout a watershed. The modeling approach is to overlay land use and soil ARC/INFO Grid coverages (one hectare cell size) to locate every unique soil/land use combination within a watershed. The surface and ground water discharges and their total suspended solids (TSS), nitrogen and phosphorus contents from every cell are then simulated using a land use specific cell model. The USDA GLEAMS model is used for non-wetland and non-urban areas. Wetland and urban areas are handled with separate models. The individual cell discharges are then routed through the watershed based on the GIS hydrography coverage.

Two separate versions of WAM are available for predicting either very detailed hourly discharges (WAM-D) or long-term annual average responses (WAM-A). The WAM-D simulates water depths and flows throughout the stream network, but it requires much more data and longer run-times than WAM-A. WAM-A is normally preferred unless the actual time series of constituent loads and flow to a receiving water body is needed for assessments.
A menu driven interface allows the user to easily view the input and output data. Graphical land use editing and management assignment tools allow the user to modify land uses for comparisons to existing conditions. Different best management practices (BMPs) can be easily assigned to land uses to directly assess pollution abatement strategies. Dual screen graphical displays and tabular ranking tables provide both visual and quantitative comparisons of a test scenario.

WAM also provides a simple indexing model for the spatial assessment of BOD, toxins, and coliform bacteria sources, as well as the pollutant assimilative capacity and wildlife diversity of wetlands within a watershed.

Example Interface Screen for the Suwannee River Watershed Assessment Model