Water Education Foundation

The Mokelumne (East Bay) Aqueduct

Posted by: Aquafornia on August 19, 2008 at 3:59 pm

The East Bay Municipal Utility District operates the Mokelumne Aqueduct, supplying water to the East Bay communities, including Oakland, Berkeley, Richmond, and parts of Alameda and Contra Costa County.   Established in 1923 to import water to serve the continually growing communities of the East Bay, EBMUD immediately began searching for a source to satisfy its growing service area,   soon settling on the Mokelumne River.

Bonds were authorized in 1924 and construction began in earnest in 1926. By 1929, Mokelumne River water reached the East Bay for the first time. Continued rapid growth in the East Bay communities led to a second pipeline for the aqueduct in 1949, and yet another in 1963.

Like the Hetch-Hetchy project, completion of this project also diverted water away from the Delta for consumptive use by piping the water across the Delta to the East Bay.

EBMUD's water system consists of a network of reservoirs, aqueducts, water treatment plants, pumping plants and distribution facilities. Water travels 91 miles from Pardee Reservoir through three steel pipeline aqueducts to the East Bay treatment plants and five terminal reservoirs. These reservoirs, located within EBMUD's service area, hold about 151,000 acre-feet and are used to regulate supply in winter and spring, augment supplies by capturing local runoff, provide an emergency source of supply, and provide environmental and recreational benefits to the residents of the East Bay.

About 90% of the water served by EBMUD comes from the Mokelumne River, with the remainder coming from local sources. The river's watershed collects water from the western face of the Sierra Nevada, encompassing a 577-square mile area of mostly national forest lands. The pristine watershed means that the water arriving in the East Bay requires only minimal treatment to meet health standards.

EBMUD holds rights to 364,000 acre-feet of water per year; this is enough to satisfy demand during normal years, but is insufficient during drought years. EBMUD is sometimes restricted from using its full entitlement due to upstream water use by prior right holds, downstream water obligations, and variability in rainfall and runoff.

To help meet demand in drought years, EBMUD has partnered with the Sacramento County Water Agency on the Freeport Regional Water Project, which will supply up to 112,000 acre-feet in a dry year, or 165,000 acre-feet over three years. Per the terms of the contract, this supply will only be available during years in which EBMUD's stored water supply is low. The project broke ground in 2007 and is targeted for completion in November 2009.

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