Linking Watershed and Reservoir Models

Watershed nutrient management is essential in minimizing the eutrophication rate of reservoirs. A shortcoming in nutrient management of watershed-reservoir systems has been the lack of successful linking of watershed and water body models to evaluate impact of watershed management options on reservoir water quality. The objectives of this research were to 1) calibrate and validate a Soil and Water Assessment Tool (SWAT) watershed model for Beaver Reservoir Watershed; 2) calibrate and validate a CE-QUAL-W2 (W2) hydrodynamic and water quality model for Beaver Reservoir, 3) link the watershed and reservoir models, and 4) evaluate reservoir water quality changes with changing watershed management practices. Watershed management scenarios that were evaluated include: reductions in poultry litter application rates, reductions in commercial fertilizer rates, and reductions in waste water treatment plant (WWTP) effluent phosphorus (P) concentration. Scenarios were evaluated by comparing chlorophyll-a and PO4-P concentrations at two locations within the reservoir. Results indicated that chlorophyll-a and PO4-P concentrations were always greater at the transitional zone location than the lacustrian zone location. Predicted chlorophyll-a and PO4-P concentrations from scenarios evaluating reduction in commercial fertilizer and reduction in WWTP effluent P indicated generally less than 1% change at both reservoir locations. Scenarios simulating reduction in poultry litter applied in the watershed predicted a substantial decline in PO4-P concentrations. The linked SWAT and W2 modeling scheme provides a