Evaluation of BMPs in Flatland Watershed with Pumped Outlet

The effectiveness of existing and potential best management practices (BMPs) to cropped lands in the Jeannette Creek watershed (Thames River basin, Ontario, Canada) in reducing P loads at its pumped outlets was assessed using the Soil and Water Assessment Tool (SWAT). Existing BMPs consisted of banded, incorporated, and variable phosphorus (P)-rate application, conservation tillage, cover crops, and vegetative buffer strips. Potential BMPs consisted of banded P application, no-till, and a cover crop following winter wheat. Two separately delineated sub-watersheds, J1 and J2, characterized by a flat topography and distinct pumped outlets, were selected for analysis. Despite challenges in delineation, the SWAT model was successfully set up to assess the impact of BMPs in reducing P loads in these sub-watersheds. Each BMP was systematically removed, and the resulting simulated P loads were compared with the baseline scenario. Compared to cover crops or vegetative buffer strips, the implementation of conservation tillage and no-till, along with altering the mode of P application, offered superior effectiveness in reducing the P load. On average, the annual reduction in total P (Ptot) loads under existing BMPs was 9.2% in J1 and 11.3% in J2, whereas, under potential BMPs, this reduction exceeded 60% in both watersheds.