Evaluation of Nutrient Loadings in an Agricultural Watershed using AnnAGNPS.

Skaneateles Lake is the primary source of drinking water for the Syracuse metropolitan area. Continued maintenance of water quality is critical because the water is withdrawn from the lake and used without filtering. Implementation of agricultural best management practices (BMPs) is considered to be a critical component to insure continued use of unfiltered water. The ultimate effectiveness of BMPs can be assessed by monitoring stream chemistry and sedimentation in combination with use of hydrologic and water quality models. These are essential tools for improving our current understanding of agricultural non-point source pollution. This study presents the calibration of AnnAGNPS for nutrient loadings in the watershed and its application in evaluating BMP effectiveness. Six sub-watersheds were selected to calibrate AnnAGNPS model using data collected from storm events and base flow during the period of April to November, 2007. Nitrogen and phosphorus loadings were calibrated for year 2007 and will be validated for year 2008. Model predictions are conducted on both an annual and monthly basis. Comparison of subwatersheds dominated by forest land use with those dominated by agriculture suggests that water quality has not been compromised.