San Diego County’s semi-arid climate means dry years are very common and wet years are few and far between – which results in extreme variability in this supply source. During rare wet years, surface water supplies can represent the largest single local resource in the Water Authority’s service area. Since 1976, the amount of local surface water used to help meet annual demand has ranged from a high of 140,300 acre-feet, down to a low of 4,100 acre-feet.
Although average annual runoff into local surface water reservoirs varies significantly, it plays a vital role in San Diego County’s water supply. Over the last 10 years, an average of about 7 percent of the region’s total annual water supply came from local surface water.
Today, the Water Authority and its member agencies have 24 reservoirs that store imported and local runoff water for normal use, emergency conditions and imported water shortages. Combined water storage capacity now totals approximately 723,000 acre-feet. This is a 30 percent increase since 2003, created by the Water Authority’s $2 billion Capital Improvement Program to improve the region’s water infrastructure.