A Modeling Approach to Evaluate the Effectiveness of Agricultural Best Management Practices.

The Sassafras River watershed, which is located in Cecil and Kent County Maryland, and New Castle County Delaware, is comprised of 57% agricultural land and about 5% residential or industrial land. The Sassafras River Association has documented that the Sassafras River is challenged by nutrient and sediment loading from agricultural runoff. The implementation of best management practices (BMPs) could potentially reduce the loading of pollutants into the Sassafras River.  Environmental modeling applications make it possible to predict the reduction of nutrient loading that would result from the usage of best management practices. The objective of this research was to use the Spreadsheet Tool for Estimating Pollutant Load (STEPL) model in the planning of BMPs of cropland. Inputs for this model include the acreage of all land uses in the watershed. A BMP can then be applied to each land use, resulting in the simulations of nitrogen, phosphorus, biochemical oxygen demand, and sediment loading. The BMPs tested were contour farming, diversion, filter strips, reduced tillage farming, stream bank stabilization and fencing, and terrace farming. For all BMPs simulated, there was a linear decrease in loading at all percentage levels of implementation. Reduced tillage and filter strips were equally effective in reducing all simulated pollutant loadings. Stream bank stabilization and terrace farming generally showed the largest reduction of nutrient and sediment loading, however, implementation of these BMPs may require costly installation procedures. This project was supported by Delaware EPSCoR, through National Science Foundation Grant EPS-0447610 and Wesley College.