ANSWERS-2000: Runoff and Sediment Transport Model.

A non–point source pollution management model, ANSWERS-2000, was developed to simulate long-term average annual runoff and sediment yield from agricultural watersheds. The model is based on the event-based ANSWERS model and is intended for use without calibration. The physically based Green-Ampt infiltration equation was incorporated into ANSWERS-2000 to improve estimates of infiltration. An evapotranspiration submodel was added to permit long-term, continuous simulation. The model was validated without calibration using data from the field-sized P2 and P4 watersheds in Watkinsville, Ga. Additional validation with limited calibration was done on the Owl Run watershed in Virginia. Model predictions of cumulative sediment yield were within 12% and 68% of observed values. Predicted cumulative runoff volumes ranged from 3% to 35% of observed values. Predictions of sediment yield and runoff volume for individual storms were less accurate, but generally within 200% of observed values. In a practical application, the use of the model in agricultural non–point-source pollution control planning was demonstrated. [ABSTRACT FROM AUTHOR]