resevoir with bouy

Surface Water Varies Wildly By Year

San Diego County’s semi-arid climate means that wet years are few and far between, and dry years are very common. However, rare extreme wet years can result in surface water supplies representing 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 been as high as 140,300 acre-feet and as low as 4,100 acre-feet.

Consequently, average annual runoff that flows into local reservoirs represents a small but vital portion of San Diego County’s water supply. Over the past 10 years, an average of about eight percent of the region’s total annual water supply came from local surface water.

Storage Capacity

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.