Local Supplies Enhance Supply Reliability

Coordinating with 23 member agencies to develop local water resources is a key component of the Water Authority’s mission to provide a safe and reliable water supply. In fact, a growing number of local water sources across the San Diego region are managed by member agencies — and they are critical to ensuring long-term water supply reliability. Local projects reduce demand and reliance on imported supplies and provide local agencies with more control over costs.

Before 1947, the San Diego region relied heavily on local surface water runoff in normal and wet years, and on groundwater pumped from local aquifers during dry years when stream flows shriveled. As the economy and population grew exponentially, local resources became insufficient to meet the region’s water supply needs and the region increasingly turned to imported water supplies.

Local Sources

In recent years, local water agencies have increasingly invested in local supplies such as brackish groundwater, recycled water and water purification. The Water Authority has also invested in seawater desalination. Water supplies from these projects is considered drought-resilient since the projects are primarily independent of precipitation. Today, about 30 percent of the water used across the region is from local supplies – and that number is expected to grow as more water purification projects come online.

drinking water stoarge tanks at desalination plant
Seawater Desalination

The Water Authority added desalinated seawater to its supply portfolio in 2015 with the start of commercial operations at the nation’s largest seawater desalination plant – the result of a public-private partnership in northern San Diego County.

Sweetwater Authority Groundwater Desalination Facility

Groundwater is small but growing and important resource, especially in places like the South Bay where the aquifers are relatively large. Overall, it accounts for about 5 percent of the region’s water supply portfolio.

Water Recycling

Water and wastewater agencies across San Diego County are developing or expanding water recycling projects, because every gallon of recycled water reduces the need to import or develop other supplies.

East County Advanced Water Purification Facility
Water Purification

In coming years, potable reuse projects are expected to help water agencies optimize existing infrastructure, increase locally controlled water supplies, and provide environmental benefits while continuing to protect public health.

lake with traffic mitigration
Surface Water

Runoff from local rainwater that flows into reservoirs represents a vital but small portion of San Diego County’s water supply needs.