The nutrient budget of the Lake Diefenbaker reservoir (SK, CAN) is being developed as part of a larger multi-faceted trophic status study. However, it is currently unknown if shoreline erosion from the near vertical banks serves as a source of nutrients to the reservoir. Thus, the objective of this study was to quantify the annual nutrient loading to the reservoir through shoreline erosion, and the relative magnitude of erosion-derived inputs versus nutrient loading through the major tributary, the South Saskatchewan River (SSR). Nutrient status measurements indicate that Lake Diefenbaker algal populations would be responsive to additional inputs of phosphorus (P). We measured the total carbon (TC), total nitrogen (TN), Mehlich 3 P, and iron oxide strip extracted (FeO) P nutrient content by weight in the bank soils along the reservoir. Combined with shoreline erosion rates and lengths, the mean annual nutrient inputs for TC, TN, M3P, and FeO P were 57,500kgyear−1, 2100kgyear−1, 49.8kgyear−1 and 30.0kgyear−1, respectively. We also compared nutrient content and inputs across bank classifications and land uses to identify factors contributing to nutrient loading through erosion and to determine potential areas for mitigation efforts. Relative to the primary nutrient loading from the SSR, bank soils represent less than 1% of the overall load. These measurements of nutrient inputs will allow us to assess the relative contribution of soil nutrients to prairie reservoirs and will serve as important baseline data for the reservoir.