Sites Reservoir is a potential new offstream reservoir that would be located about 78 miles northwest of Sacramento in the eastern foothills of the California Coast Range. It would harness winter flood flows from the Sacramento River, divert the water west and pump it into a deep, 14,000-acre reservoir formed in the Antelope Valley. The valley now is used for cattle grazing.
The concept is for Sites to be operated in coordination with other Northern California reservoirs such as Shasta, Oroville and Folsom to increase the flexibility, reliability and resiliency of the State Water Project (SWP) and federal Central Valley Project.
Water would arrive to Sites Reservoir via the existing Tehama-Colusa and Glenn-Colusa canals, as well as a new pumping station on the Sacramento River. The water would then be released into the Sacramento River to augment natural flows and releases from other reservoirs.
Proponents say they favor the Sites location because it is not on a major river so it wouldn’t directly affect fish migration and it is north of the Sacramento-San Joaquin Delta, meaning it could provide flexibility for water quality and environmental flows. Critics say diversions for the reservoir could take more than 60 percent of the Sacramento River flows at times, with potentially significant impacts to the river’s riparian and aquatic ecosystems and the many fish and wildlife species that depend on those ecosystems.
The total reservoir capacity would be between 1.27 and 1.81 million acre-feet (by comparison Folsom Reservoir fed by the American River has a 1 million acre-feet capacity). The estimated water yield would be between 470,000 to 640,000 acre-feet per year, depending on yearly rainfall and environmental regulations, according to California Department of Water Resources. (One acre-foot of water is 325,851 gallons – enough water to cover one acre of land at one foot deep and meet the annual needs of two to three urban households.)
In dry and critical years, Sites Reservoir would provide an additional 250,000 to 300,000 acre-feet of cold-water pools to help critically endangered salmon and improve water quality conditions, according to the Sites Project Authority, the group of regional entities, water agencies and counties formed in 2010 to pursue the development and construction of the project.
In addition to water storage, Sites Reservoir would be operated as a hydroelectric plant, helping in the generation of “power peaking” electricity for the Northern California grid by typically running only when there is a high demand — known as peak demand — for electric power.
The voter-approved Proposition 1 water bond of 2014 included $2.7 billion allocated to the public benefits of possible surface or groundwater storage projects. In 2018, the California Water Commission awarded $816 million of that money to help build Sites, which would cost an estimated $5.2 billion. Other governmental entities have also contributed.
The Sites Reservoir proposal first emerged as part of the second stage of the SWP in the 1980s. The first stage was comprised of Oroville Dam, the California Aqueduct and the associated hydroelectric plants and pumping stations. All this infrastructure was built during the 1960s to mid-1980s to provide an annual water yield of 2.23 million acre-feet.
SWP Stage II included Sites Reservoir along with a peripheral canal to divert water around the Delta and southward, and various other projects that would feature Northern California river diversions.
Renewed interest in the Sites Reservoir project has been linked to diminished water supply and delivery shortfalls due to drought, Delta pumping restrictions, population growth and climate change in California.
Sites Reservoir – officially referred to in studies by DWR and U.S. Bureau of Reclamation as the North-of-Delta Offstream Storage Project (NODOS) – is planned to improve water supply reliability during drought periods when operated in conjunction with existing reservoirs. In all, the primary objectives are:
- Improve water supply reliability for agricultural, urban, and environmental uses
- Increase survival of anadromous and endemic fish populations
- Improve environmental and drinking water quality in the Delta
- Provide flexible hydropower generation to support integration of renewable energy sources
Where is Sites?
Sites, a small community in Colusa County in Northern California, is surrounded by rolling hills and set in a basin of grasslands used primarily for grazing cattle. The town was named for John Sites, a pioneer rancher in the late 19th century. Although no township exists today, the community of a handful of families and ranchers still maintain a proud heritage.
And, even though a reservoir would inundate the basin, most of the residents support the water storage proposal.
If the reservoir were to be built, the surrounding 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. 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 hold in the north end of the lake, according to Reclamation.
Sites Joint Power Authority Board
The Sites Joint Power Authority Board is comprised of members representing water districts that have expressed interest in purchasing at least 20,000 acre-feet of water a year if the project is built. Those include: Colusa County Water District, Glenn County, Reclamation District 108, Colusa County, Glenn-Colusa Irrigation District, Maxwell Irrigation District, Orland-Artois Water District, Proberta Water District, Tehama-Colusa Canal Authority, Westside Water District and Yolo County Flood Control and Conservation Board.
In 2017, the Metropolitan Water District of Southern California’s board of directors unanimously authorized $1.5 million to join the first planning phase for Sites to potentially access as much as 50,000 acre-feet of annual water yield. The following year, the U.S. Department of Agriculture chipped in $449 million and in 2019 the federal Water Infrastructure Improvements for the Nation Act appropriated $6 million to the Bureau of Reclamation to advance Sites Reservoir.