Sites Reservoir

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Sites Reservoir
Coordinates39°21′18″N 122°20′29″W / 39.35500°N 122.34139°W / 39.35500; -122.34139Coordinates: 39°21′18″N 122°20′29″W / 39.35500°N 122.34139°W / 39.35500; -122.34139
TypeOffstream reservoir
Primary outflowsStone Corral Creek, Funks Creek
Managing agencyCalifornia Department of Water Resources
Max. length13 miles (21 km)
Surface area14,000 acres (5,700 ha)
Max. depth310 ft (94 m)
Water volume1,810,000 acre feet (2.23 km3)
(max. as proposed)
Surface elevation580 ft (180 m)

The proposed Sites Reservoir would be a large offstream reservoir in the Sacramento Valley in Northern California, a project of the California Department of Water Resources. Its primary purpose is to collect winter flood flows from the Sacramento River, diverting the water upstream of the Sacramento–San Joaquin River Delta and pumping it into an artificial lake located west of Colusa. The estimated water yield would be between 470,000 to 640,000 acre feet (580,000,000 to 790,000,000 m3) per year, depending on yearly rainfall and environmental regulations.[1]

The reservoir would be operated as part of the California State Water Project (SWP) and is projected to cost between $2.3–3.2 billion.[1] According to a 2013 Bureau of Reclamation study, it would provide economic benefits of between $248.8–276.2 million per year,[2] while annual operating costs would be in the range of $10–20 million.[3]

The state Department of Water Resources received an approval to study water storage north of the delta in 1996, and more funding was approved every several years since then. As of 2014, $52 million has been spent on studies.[4] On July 21, 2018 the state awarded $816 million in Proposition 1 funding to build the reservoir.[5]


The first proposals for Sites appeared in the 1980s as part of the State Water Project's Stage II. Stage I, which comprised the project's primary features, including the Oroville Dam, California Aqueduct and associated hydroelectric plants and pumping stations, was completed during the 1960s to mid-1980s, to provide an annual water yield of 2.23 million acre feet (2.75 km3). Stage II, which included Sites Reservoir, the Peripheral Canal and various proposals to divert other Northern California rivers was intended to bring the SWP to its full yield of 4 million acre feet (4.9 km3). Due to political and environmental opposition, these projects have not been built. Sites Reservoir went through federal review in 1996 but did not receive authorization.

However, the 21st century has experienced a growing threat of serious water shortfalls due to drought and rapid population growth in California; by 2020 the annual deficit of supply to demand could be as much as 3 million acre feet (3.7 km3).[6] Current studies refer to the reservoir officially as the North-of-Delta Offstream Storage Project.[7] The DWR has noted that between 2002 and 2011, SWP water supply delivery reliability declined, and that NODOS could improve water supply reliability during drought periods (when operated in conjunction with existing reservoirs).[8]

Cost and funding[edit]

The estimated cost of the reservoir is roughly $5.2 billion dollars.[9] Of that total, proponents have asked the state of California to provide roughly $1.7 billion in funding from California's Proposition 1, which requires that such state funding requires a benefit to the public at large.[9] As of February 2018, the California Water Commission estimates that benefit at roughly $662 million, roughly one billion dollars less than requested.[10] On July 21, 2018 the state awarded $816 million in Proposition 1 funding to build the reservoir.


The 14,000-acre (5,700 ha) reservoir would be formed by several dams located in the east foothills of the California Coast Ranges, flooding the long and narrow Antelope Valley. The main dams, Sites and Golden Gate, would be built across Stone Corral and Funks Creeks, respectively; the larger of the two, Sites, would stand about 310 feet (94 m) high. Six smaller saddle dikes would hold in the north end of the lake.[11] The total capacity would be between 1.27 to 1.81 million acre feet (1.57 to 2.23 km3), which could be further expanded in the future by raising the surrounding dikes.[11][12] Up to 5,900 cubic feet per second (170 m3/s) of water would be supplied to the reservoir via the existing Tehama-Colusa and Glenn-Colusa Canals as well as a new pumping station on the Sacramento River.[13]

Sites would be operated as a pumped-storage hydroelectric plant, similar to San Luis Reservoir in Central California's San Joaquin Valley, and as a result would be a net power generator. A hydroelectric power plant here would help in the generation of peaking power or grid energy storage for the Northern California grid.

Potential environmental impacts[edit]

Unlike other proposed reservoir projects in California, Sites would not directly affect fish migration because it is not located on a major river, and could be a source of additional cold water for fall-run chinook and coho salmon.[14]

However, diversions could take more than 60 percent of the Sacramento's flow at certain times, with potential harm to salmon and other migrating fish. The reservoir itself would affect habitat for 23 sensitive, threatened or endangered wildlife species.[13] The exposed location would also cause the annual evaporation of about 30,000 acre feet (37,000,000 m3) of water.[13]

The project would be operated in the interest of protecting fisheries, with such installations proposed as advanced fish screens at the pumping stations along the Sacramento River; potential modifications to upstream Shasta Dam to increase the supply of cold water available there; and modifications to the existing Tehama-Colusa and Glenn-Colusa Canal intakes that would be used by the project.[1]

See also[edit]


  1. ^ a b c "Sites Reservoir: Frequently Asked Questions" (PDF). California Department of Water Resources. September 2007. Archived from the original (PDF) on 2014-04-01. Retrieved 2014-03-16.
  2. ^ "Bureau of Reclamation releases progress report on Sites Reservoir". Maven's Notebook. 2013-12-31. Retrieved 2014-03-16.
  3. ^ "Our View: Sites Reservoir would sure come in handy this year". Appeal-Democrat. 12 January 2014. Retrieved 2014-03-16.
  4. ^ Hacking, Heather (2014-03-27). "Sites Reservoir: A long time in coming, a long way to go". Chico Enterprise-Record. Retrieved 2014-04-24.
  5. ^ Dale Kasler and Ryan Sabalow (2018-07-24). "California's largest reservoir project in decades gets an $800 million boost. But is it feasible?". Modesto Bee. Retrieved 2018-09-04.
  6. ^ "Water Supply". Trends and Challenges. Association of Bay Area Governments. Retrieved 2014-03-16.
  7. ^ Lien-Mager, Lisa (2013-12-30). "Report Outlines Progress on Sites Reservoir Studies". Water News. Association of California Water Agencies. Retrieved 2014-03-16.
  8. ^
  9. ^ a b "Water Storage Investment Program Project Review Portal". Retrieved 6 March 2018.
  10. ^ Boxall, Bettina. "Big dam proposals score low in contest for state money". Los Angeles Times. Retrieved 6 March 2018.
  11. ^ a b "North-of-the-Delta Offstream Storage Feasibility Investigation: Fact Sheet" (PDF). U.S. Bureau of Reclamation and California Department of Water Resources. Northern California Water Association. June 2011. Retrieved 2014-03-16.
  12. ^ "Surface Storage". Northern California Water Association. Retrieved 2014-03-17.
  13. ^ a b c Evans, Steven L. (August 2013). "Sites Offstream Storage Reservoir Fact Sheet" (PDF). Friends of the River. Retrieved 2014-03-17.
  14. ^ Zito, Kelly (2009-09-29). "Water interests argue new state dam proposals". SFGate. Retrieved 2014-03-17.