Watershed Application of WEPP to a Michigan Water Quality Problem

Abstract

The USDA Water Erosion Prediction Project (WEPP) model allows simulation of overland flow and soil erosion processes at the small watershed scale. Capabilities within WEPP allow evaluation of various parameters influencing water quality. The WEPP model was applied to a small agricultural watershed in southern Michigan to test the feasibility of using its hydrologic and sedimentation outputs to estimate phosphorous loadings at the mouth of the watershed. WEPP provides detailed daily estimates of runoff, soil loss, sediment delivery and sediment particle size distributions. Simple techniques are available to correlate phosphorous loadings to sediment yield and discharge volumes from a watershed and its individual components. Using procedures provided by the Michigan Department of Environmental Quality and outputs from WEPP, we can predict phosphorous loading at the mouth of the watershed, and identify areas within the basin making the highest contributions to the total phosphorous load. With the new user-friendly WEPP Windows interface, users can test the effectiveness of different management systems to reduce runoff and sediment delivery, thereby reducing sediment-bound and soluble phosphorous delivered to the mouth of a watershed.