Predicting Sediment and Phosphorus Loads in the Rock River Basin Using Swat

The Rock River is considered degraded from excessive amounts of phosphorus. Individual programs are ongoingto reduce phosphorus from point and nonpoint sources. However, a comprehensive phosphorus management approach mayprove more cost effective and beneficial. To be successful, such an approach must take into consideration phosphorus fromall sources and seek geographically targeted, costeffective, and holistic solutions. This study utilized the SWAT (Soil andWater Assessment Tool) model to quantify phosphorus sources throughout the basin and quantify impacts from the applicationof basinwide BMPs. Results of this study indicate that, under existing land use and management conditions, an averageannual phosphorus load of approximately 764,000 kg enters the Rock River and it tributaries. Point sources account for 41%of this value, and nonpoint sources account for 59%. Model results show that, under existing conditions, approximately160,000 tons of sediment is delivered to the streams and surface water bodies on an average annual basis. Modeling resultsindicate that implementation of improved tillage practices (predominantly conservation tillage) can reduce sediment yields by almost 20%.