Reservoirs

Seven major stream systems originate in the mountains of San Diego County and drain into the Pacific Ocean. Runoff from these seven watersheds supplies 24 reservoirs – that have a combined capacity of about 723,000 acre-feet. In addition, San Diego County ratepayers have invested in reservoirs owned by the Metropolitan Water District of Southern California, and the Water Authority is seeking a storage account in Lake Mead as a low-cost way to increase reserves and provide water to this federal drought-stricken reservoir.

The last major increase in San Diego regional water storage capacity occurred in 2014 when the San Vicente Dam Raise was completed, adding 157,000 acre-feet of capacity. While the region’s reservoirs were built mainly as water supply projects, they also provide other benefits such as recreation, flood reduction and hydroelectric generation.

Each reservoir has unique characteristics that define its role in meeting the region’s water supply needs. Some reservoirs are important from a regional water reliability standpoint, while others are primarily used by local agencies for operational flexibility.

Since the major statewide drought of 1976-1977, annual surface water use from local reservoirs has ranged from 4,100 acre-feet in fiscal year 2015 to 140,300 acre-feet in fiscal year 1984. Over the past 10 years, an average of about 8 percent of the region’s total annual water supply came from local surface water.