The proposed Sites Reservoir would be an off-river storage basin on the west side of the Sacramento Valley, about 78 miles northwest of Sacramento. It would capture stormwater flows from the Sacramento River for release in dry and critical years for fish and wildlife and for farms, communities and businesses.
The water would be held in a 14,000-acre basin of grasslands surrounded by the rolling eastern foothills of the Coast Range. Known as Antelope Valley, the sparsely populated area in Glenn and Colusa counties is used for livestock grazing.
The reservoir would be owned by the Sites Project Authority, a group of Sacramento Valley agricultural interests, cities and water districts, and operated in coordination with other Northern California reservoirs such as Shasta, Oroville and Folsom.
Proponents say they favor the project because it would increase the flexibility and reliability of the State Water Project and federal Central Valley Project. Though Site Reservoir would not dam a river or block fish migration, critics say diversions for the reservoir could at times take more than 60 percent of the Sacramento River flows, potentially harming the river’s riparian and aquatic ecosystems and the many fish and wildlife species that depend on them.
In dry and critical years, the reservoir would help preserve the colder water in Lake Shasta to help critically endangered salmon and improve water quality in the Sacramento River, according to the Sites Project Authority.
Sites Reservoir is designed to achieve the following objectives when operated in coordination with existing Northern California reservoirs:
- Improve water supply reliability for agricultural, urban and environmental uses
- Increase anadromous and endemic fish populations
- Improve environmental and drinking water quality in the Delta
In 2020, the Sites proposal was modified, with estimated costs reduced from $5.1 billion to $3 billion. The revised plan decreases the reservoir capacity from 1.8 to 1.5 million acre-feet, dropping the reservoir’s average delivery capacity from 505,000 to 243,000 acre-feet a year. In 2023, the Sites Project Authority estimated the costs at $3.5 billion.
The modified plan also eliminates an 18-mile pipeline to the Sacramento River. Instead, the river would be diverted to the reservoir through the Tehama-Colusa and Glenn-Colusa canals and released back into the river to augment natural flows and releases from other reservoirs.
Sites reached two procedural milestones in late 2023. The federal Bureau of Reclamation completed the project’s final environmental impact report and statement. Just days later, California Gov. Gavin Newsom used a new state law to shorten the window for filing environmental challenges against the project.
If the reservoir is built, the foothills would provide a natural barrier to the basin and facilitate the flooding of the long and narrow Antelope Valley. The reservoir would be fortified by several dams connecting the hills. The main dams, Sites and Golden Gate, would be built across Stone Corral and Funks creeks. Sites Dam, the larger of the two, would stand about 310 feet high. Six smaller saddle dikes would be built at the north end of the lake, according to Reclamation.
The reservoir takes its name from a small community in the basin that was home to John Sites, a pioneer rancher in the late 19th century. Though the reservoir would inundate the basin, many of its residents support the water storage proposal.
First conceived in the 1950s, Sites Reservoir emerged in the 1980s as part of a proposed second stage of the State Water Project, but the plan was abandoned.
Interest in the reservoir renewed in the 2000s as the frequency and severity of droughts grew under climate change and declines in native fish populations led to tighter restrictions on exporting water from the Sacramento-San Joaquin Delta.
Sites Project Authority Board
The board consists of representatives of Sacramento Valley water interests, including Colusa and Glenn counties, the Colusa County Water District, Glenn-Colusa Irrigation District, Tehama-Colusa Canal Authority, Westside Water District, Reclamation District 108, the cities of Roseville and Sacramento, Sacramento County Water Agency and Placer County Water Agency.
The project includes a reservoir committee made up of water agencies and irrigation districts across the state that are investing in a share of the water.
Since 2017, the Metropolitan Water District of Southern California’s board of directors has authorized $5.7 million in investments to access as much as 50,000 acre-feet of annual water yield from the Sites project.
In 2018, the project received $816 million from the Proposition 1 water bond and secured a $449 million loan from the U.S. Department of Agriculture. As of July 2023, $233 million in federal contributions had been made to the project.