Los Vaqueros Project History


Los Vaqueros was designed and built with water quality as the first priority. Our main water source is the Sacramento-San Joaquin Delta. During the late winter and spring months, when the Sierra Nevada snow pack melts and flows into the Delta, the quality of the water in the Delta is very high.

But in the late summer and early fall, high levels of salt often creep into the Delta from the San Francisco Bay and cannot be treated. Los Vaqueros allows us to pump high quality water into the reservoir and save it. When water in the Delta gets salty, we blend water from the Delta with the quality water from Los Vaqueros, lowering the salt content dramatically.

Project Benefits

  • Improve water quality for our customers.
  • Provide a 1-to-3 month supply of emergency water storage.
  • Other benefits include recreation, flood control, and protection of rare natural and historic resources within the watershed.


In 1988, voters approved authorization funding of the $450 million Los Vaqueros Reservoir project. The measure won with 68 percent of the vote. After a thorough and deliberate design phase, construction began in 1994. The reservoir was completed in 1998, at the height of 192 feet and could store up to 100,000 acre feet of water. Then in 2012, we invested another $120 million to raise the dam 34 feet and expand the capacity to hold 160,000 acre-feet of water. The dam is now 226-feet high (from toe to crest).

Project Timelines

  • Construction started 1994
  • Project completed 1997
  • Project dedicated 1998
  • Expansion started April 2011
  • Expansion completed/dedicated July 2012

Original Project Details

Los Vaqueros was a massive project. We secured nearly 20,000 acres land for the dam and the watershed, and relocated and installed several necessary facilities. We made a commitment to preserving the environment and respecting Native American and other historical sites in the watershed. As part our ongoing environment protection program in the watershed, we planted more than 9,000 valley and blue oak seedlings.

2012 Expansion Details

The additional water storage helps to ensure high-quality water deliveries to customers, reliability during drought and protections for Delta fisheries and the environment. In addition to enlarging the dam, we purchased more than 5,000 acres of land in Contra Costa, Alameda and San Joaquin counties to provide habitat for several endangered species. Learn about the Phase 2 Los Vaqueros Reservoir Expansion Project.