Our Connection to Oroville

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Lake Oroville Stores Most of Our Water

  Damage to Lake Oroville Dam spillway February 2017

Click on this image to view a series of amazing videos (posted on www.imgur.com) capturing the Oroville spillway incident that began February 7, 2017. Photo courtesy of California Department of Water Resources.

Images of the damaged spillway at Oroville Dam have been mesmerizing and sobering. While we and our water customers are far from the evacuation zone, we have a direct link to the water stored behind the dam.

Lake Oroville is a critical part of our water system. It is the largest reservoir in the State Water Project, which supplies about 80 percent of the Tri-Valley’s water in a typical year. Zone 7 Water Agency purchases about two percent of the water released by the State Water Project, treats it to drinking water standards, and resells it to DSRSD and other Tri-Valley water utilities.

Crews are working 24 hours a day on emergency repairs to Lake Oroville's spillways, which have cost about $250 million through April. DWR also has awarded a $275 million contract for the first phase of permanent repairs.

For updates on the Oroville spillway repairs, visit the California Department of Water Resources news site.

160-Mile Journey to the Tri-Valley

Our water’s journey starts in the northern Sierra Nevada as rain and melting snow flowing into Lake Oroville. Through California’s long, dry summer, the water is released gradually through the dam’s hydroelectric generating plants. It flows into the Feather River, down the Sacramento River, and through the Delta. Near Tracy, the Banks Pumping Station pumps the water into the 444-mile long California Aqueduct. Some of this water is diverted into the South Bay Aqueduct; the rest continues south to supply Central Valley farms and southern California cities.

  Map showing how far water must flow from Lake Oroville to supply DSRSD customers
  Water from Lake Oroville travels via rivers, the Delta, and State Water Project aqueducts to DSRSD and other Tri-Valley water agencies.

The South Bay Aqueduct serves Zone 7 Water Agency, Alameda County Water District, and Santa Clara Valley Water District. The water may be stored temporarily in Lake Del Valle, another State Water Project reservoir, where it mixes with local rainfall.

Local Sources Increase Reliability

Zone 7 carefully manages the amount of water it stores, imports, treats, and delivers to DSRSD, Pleasanton, Livermore, and California Water Service-Livermore. A key responsibility is releasing some of the imported water into local arroyos and lakes to recharge the groundwater stored under our valley. Groundwater is a vital local water bank. When State Water Project allocations were severely restricted in the 2014-15 drought, most of our water came from groundwater.

DSRSD purchases all of its potable (drinkable) water from Zone 7 and delivers it to 20,000 water customers in Dublin and the Dougherty Valley area of San Ramon. After it’s used, about 75 percent of this water is cleaned and released into the San Francisco Bay. But the rest--25 percent--is recycled into irrigation water, reducing the amount of water that must make the long journey from Oroville to our taps.

Updated May 3, 2017