Excessive phosphorus has lead to Lake Simcoe's inability to support cold-water fisheries and atmospheric deposition is responsible for roughly one-third of this phosphorus. The objectives of this research were to develop a method for calculating atmospheric phosphorus deposition using weather radar data (compared to local rain gauges) over Lake Simcoe, conduct a statistical analysis on atmospheric bulk collector data, and develop a management tool (CALPUFF) to quantify the contribution of local sources to atmospheric deposition. By accounting for the spatial variability of rain quantity and quality differences in phosphorus loads ranged between 1-88% when not accounted for. Statistical analysis of the bulk collectors found a significant difference in phosphorus loads indicating the large impact local air pollution sources have on TP deposition versus distant sources. It was also found that CALPUFF is a powerful tool to quantify bulk atmospheric phosphorus deposition for Lake Simcoe; however more in-field data is required.