Beyond its aesthetic and recreational appeal, the Eastern Sierra snowpack plays a vital role as the primary water source for more than 3.5 million City of Los Angeles residents. The rest of Los Angeles' water supply comes from the Colorado River, California's Central Valley and groundwater sources within the Los Angeles city limits. Because Los Angeles relies upon the Eastern Sierra for most of its water, accurate snow measurements are vital in order to forecast each year's water supply. Each winter, DWP hydrographic crews provide the data needed for forecasting by conducting snow surveys. By actually measuring the depth of snow and amount of water content in the snow at specific locations over a period of many years, forecasters can accurately predict the amount of runoff each year.
Many important decisions depend upon accurate water supply forecasting.
The availability of water for irrigation needs, reservoir storage and operation, groundwater pumping levels, hydroelectric generation, maintenance programs, recreation availability and even the possible need for water rationing all rely on accurate water supply forecasting.