Tenkiller Lake is a Corps of Engineers reservoir operated by the Tulsa District located in Oklahoma. Because of concern over possible impacts to the reservoir of poultry waste applied to agricultural lands in the basin, a hydrodynamic and water quality model of Tenkiller Lake was constructed to evaluate how the reservoir would respond to changes in nutrient loading from the watershed. The CE-QUAL-W2 model was calibrated to field data over the period of January 1, 2005 through September 2007. Comparisons of field data to model predictions were made for water level, temperature, NH4-N, NO3-N, PO4-P, total N, Total P, chlorophyll a, and dissolved oxygen at multiple reservoir sites at various depths. The model was used to predict the response of the reservoir to changes in Total P loading in the watershed over a 50-year period. Several scenarios were run with the model including no changes in nutrient loading from the watershed, natural conditions, and cessation of further land application of poultry waste in the watershed. Results and recommendations for achieving water quality targets in Lake Tenkiller were outlined. The cessation scenario showed that even after 50 years, the reservoir would still not have recovered to a natural pristine state. High residual Total P loading in the basin from past agricultural practices would continue to degrade water quality.