Where does our water come from?

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Our Primary Water Sources

Water Journey beginning with Sierra Nevada Snowmelt providing water to the California Delta, connecting the South Bay aqueduct with Patterson Pass Water Treatment Plant, Del Valle Water Treatment Plant and Lake Del Valle. Another water source is the Livermore Valley groundwater basin and well field to Mocho Groundwater Demineralization plant. The water from the treatment plans then are overseen by Zone 7 Water Agency who provides the water to retailers and the homes and businesses

The water that flows from your tap originated from a number of sources including snowpack, rainfall and underground aquifers.

Imported Surface Water

Blue lake with green grass, surrounded by tall trees and Sierra Nevada mountains in the background

More than three-quarters of our water supply originates high in the Sierra Nevada mountains as snowmelt. The water flows downstream where it is pulled into infrastructure created by the State Water Project (SWP) that allows it to distribute or convey the water throughout the entire state.

The SWP conveys the water through the California Delta, its first major stop where the water is divided between two major aqueducts. The majority of the water that comes to Zone 7 is conveyed via the South Bay Aqueduct to the Tri-Valley area. We purchase this water from the SWP, and invest in the infrastructure that helps bring the water to our community.

Local Surface Water

Aerial view of Lake Del Valle surrounded by mountains

A small portion of our water supply comes from local rain runoff which is stored in Del Valle Reservoir. This amount fluctuates each year depending on how much rain we receive. During rainy years, local surface water helps offset the amount we purchase from the SWP. During dry years, we have less local surface water available and need to rely more on imported surface water.

Local Groundwater

Aerial view of the Delta surrounded by brown and green landscape

Our local groundwater basin is carefully managed by Zone 7. This critical water supply is stored within the aquifer under the Livermore-Amador Valley, and comes primarily from strategic recharges made with imported water during wet years, so that we have it available as a resource during dry years.