Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2002
Publication Date: 12/15/2002
Citation: KIRSCH, J., KIRSCH, A., ARNOLD, J.G. PREDICTING SEDIMENT AND PHOSPHORUS LOADS IN THE ROCK RIVER BASIN USING SWAT. TRANSACTIONS OF THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. 2002. v. 45(6). p. 1757-1769.
Interpretive Summary: The Rock River in south central Wisconsin is polluted by excessive amounts of phosphorus. Excess phosphorus can cause odor, fish kills, habitat destruction and a general degradation of the aesthetic and recreational value of the natural environment. A watershed model called SWAT (Soil and Water Assessment Tool) was used to determine the impact of several proposed management scenarios on phosphorus concentrations in the Rock River. Scenarios simulated by the model included: conservation tillage, reducing fertilizer applications, and reducing phosphorus concentrations from the wastewater treatment plants. Results from the model are being used by the Rock River Partnership to develop an integrated watershed-based approach to solving the phosphorus problem. Results indicated that nutrient trading or pollutant trading was a viable option to meet the water quality objectives of the Rock River Basin. Members of the Rock River Partnership include state agencies, municipal wastewater operators, industries, private citizens, and environmental organizations.
Technical Abstract: The Rock River is considered degraded from excessive amounts of phosphorus. Individual programs are ongoing to reduce phosphorus from point and nonpoint sources. However, a comprehensive phosphorus management approach may prove more cost effective and beneficial. To be successful, such an approach must take into consideration phosphorus from all sources and seek geographically targeted, cost-effective, and holistic solutions. This study utilized the SWAT (Soil and Water Assessment Tool) model to quantify phosphorus sources throughout the basin and quantify impacts from the application of basin-wide BMP practices. Results of this study indicate that under existing land use and management conditions an average annual phosphorus load of approximately 764,000 kg enters the Rock River and its tributaries. Point sources account for 41 percent of this value, and 59 percent is from nonpoint sources. Model results show that under existing conditions, approximately 160,000 tons of sediment is delivered to the streams and surface water bodies. Implementation of improved tillage practices (predominantly conservation tillage) can reduce sediment yields by almost 20 percent.