California Agriculture

Lake Tahoe is a high-altitude (6,227 feet) lake located in the northern Sierra Nevada at the California-Nevada border. During the second half of the 20th century, the decline in Lake Tahoe’s water clarity and degradation of the basin’s air quality became major concerns. The loading of gaseous and particulate nitrogen, phosphorus and fine soil via direct atmospheric deposition into the lake has been implicated in its eutrophication. Previous estimates suggest that atmospheric nitrogen deposition contributes half of the total nitrogen and a quarter of the total phosphorus loading to the lake, but the sources of the atmospheric pollutants remain unclear. In order to better understand the origins of atmospheric pollutants contributing to the decline in Lake Tahoe’s water clarity, we reviewed a series of studies performed by research groups from the U.S. Department of Agriculture’s Forest Service, UC Davis and the Desert Research Institute. Overall, the studies found that the pollutants most closely connected to the decline in Lake Tahoe’s water quality originated largely from within the basin.