Modeling Water Quality Impacts in a Rural Watershed in Delaware

The SWRRB model was used to model agricultural BMPs for the Delaware Inland Bays. Corn, soybeans and wheat were the crops used in the simulation. Conventional tillage with a winter cover crop along with minimum tillage and no-tillage with and without a winter cover crop were simulated as BMPs. The model was calibrated with water quality and flow data from Stockley Branch, a 1359 ha watershed. The model could not be accurately calibrated for the watershed. There was considerable variation in the month to month simulated and measured runoff volumes. Nitrate loadings were under predicted for the different seasons. For the BMP simulations, winter cover crops had a large effect in reducing nitrogen and phosphorus loads regardless of tillage.