Modeling the impact of land use changes on runoff and sediment yield in the Le Sueur watershed, Minnesota using GeoWEPP

Sediment delivery from the Le Sueur River watershed is a major concern in the turbidity-impaired Minnesota River. As part of a broader effort to develop a sediment budget for the Le Sueur River, this study implemented a process-based watershed hydrology and upland erosion model, Water Erosion Prediction Project (WEPP), to simulate hydrology and sediment dynamics in several land-use/land-cover scenarios. The Geo-spatial interface for WEPP (GeoWEPP) was used to characterize upland overland flow elements based on their land use/land cover, soil, and slope profiles. These characteristics were used as inputs for the WEPP model to estimate runoff fluxes, soil loss rates, and sediment delivery ratio (SDR) for three environmental scenarios: current land-use/land-cover with agricultural lands under fall mulch till management (scenario 1), current land-use/land-cover with agricultural lands under no till management (scenario 2), and pre-settlement land-use/land-cover (scenario 3). Over a simulated 30-year period (1979–2008), the runoff depth, soil loss rate and SDR were estimated to be 86 mm, 2.6 T/ha, and 0.84 for scenario 1; 73.8 mm, 0.5 T/ha, and 0.9 for scenario 2; and 70.9 mm, 0.2 T/ha, and 0.73 for scenario 3.