Modeling a Basin-Wide Extrapolation of Stormwater Management Activities: A Case Study of the Lake Tahoe Clarity TMDL Implementation Plan for Developed Areas

Lake Tahoe is a designated Outstanding National Resource Waterbody. However, lake clarity has dropped at a rate of 9 inches per year since the late 1960s, with ultra-fine sediment and nutrient driven algae production as the primary stressors. About 70% of the total fine sediment particles are estimated to come from developed areas, which make up 10% of this largely rural watershed. With more than $1.5 billion estimated as the cost to restore lake clarity, a premium has been placed on developing informative decision support analyses. A detailed watershed model was developed to represent the unique orography and hydrology of the Lake Tahoe Basin, predict loads by land use source, and calculate TMDLs allocations. This paper highlights a methodology that informs the watershed model regarding pollutant load reductions achieved from implementation of Best Management Practices (BMPs) under different physiographical settings for developed land in the Lake Tahoe Basin.