Precipitation from the Eastern Sierra Nevada Mountains is one of the main water sources for four million Los Angeles residents. Snowpack from these mountains melt in the spring and summer, delivering water to Los Angeles through a 340-mile-long aqueduct.

Future availability of this water supply source is of critical importance to the Los Angeles Department of Water and Power to meet the needs of a growing population and large economy. Climate change is of concern because of changing precipitation amounts and because earlier snowmelt might reduce the amount of snowpack water storage in the Eastern Sierra.

Tetra Tech scientists assessed potential climate change impacts on these water sources using a mixture of modeling and analytical approaches, including dynamic and statistical downscaling of global climate models, and through evaluating the 80-year historical record in the basin. Tetra Tech used the analysis results to identify potential adaptation measures including the creation of additional ground water and surface water storage, conservation, and new water supplies.