Modeling and assessment of agricultural best management practices on sediment and nutrient load reductions in the Upper Medway watershed of the Lake Erie Basin

Abstract

The Upper Medway watershed is a representative rural upland watershed of the Lake Erie Basin with an undulating landscape dominated by agricultural land use activities. Various agricultural best management practices have been implemented in the study area over time to reduce sediment and nutrient loadings from the watershed. The purpose of this study was to assess the effectiveness of these practices at field and watershed scales by using a process-based hydrologic model. Higher effectiveness was found for vegetative buffer strips and wetland restoration in reducing sediment and phosphorus loadings. Controlled tile drainage was found more effective in reducing nitrogen loadings compared to other best management practices. Grassed waterways and water and sediment control basins were more effective in reducing sediment loading but less effective in reducing nutrient loadings. Fertilizer incorporation was more effective compared to conservation tillage and cover cropping in reducing nutrient loadings from the tile-drained fields. It was estimated that all existing best management practices present in the watershed, reduced sediment, total phosphorus, and total nitrogen by 21.6%, 12.9%, and 20.0% respectively at the watershed outlet. The study showed that watershed modeling, in combination with field monitoring, can be a useful technique for evaluating the effectiveness of various land management practices in improving rural water quality. Findings of these practices' effectiveness in the Upper Medway watershed modeling study can be a valuable reference for similar studies in the Lake Erie Basin. However, more field monitoring data is required to improve the model's performance and to reduce the uncertainty of best management practices assessment.