The Peripheral Canal is a recurring proposal to divert water from California's Sacramento River, around the periphery of the San Joaquin-Sacramento River Delta. It is currently proposed in the form of two tunnels to be constructed as part of the $25 billion Bay Delta Conservation Plan.
Currently, freshwater entering the Delta has to flow through a maze of river channels and sloughs before entering the Clifton Court Forebay north of Tracy, where water is pumped into the California Aqueduct and Delta-Mendota Canal. Large numbers of Delta smelt and other endangered species are killed by the pumping plants that provide water for the aqueducts. Freshwater flowing into the Delta displaces salt water entering from the San Francisco Bay. The freshwater/saltwater gradient has moved inland due to 5 to 7 million acre feet (6.2 to 8.6 km3) of water being exported each year to the Central Valley and Southern California. A peripheral canal would reduce the overall freshwater flow into the Delta and move the freshwater-saltwater interface further inland, causing damage to Delta agriculture and ecosystems.
Senator Dianne Feinstein, former California Governor Arnold Schwarzenegger and present Governor Jerry Brown have all declared their support for the Peripheral Canal. However, the Peripheral Canal proposal has been criticized because it would further reduce the amount of freshwater flowing through the Delta. Farmers in the Delta are among the most opposed to the project because it would decrease the amount of water available to them for irrigation.
Since the 1940s, various groups have lobbied for the construction of a Peripheral Canal to redirect water flowing from the Sacramento and San Joaquin rivers directly to the federal aqueducts that draw water from the southern end of the Delta. Because of drought and other low flow issues that cause ocean water to flow far enough into the aqueducts of both the state (California Aqueduct) and federal government (Delta-Mendota Canal) from pumping stations which are located at the southern edge of the Sacramento–San Joaquin River Delta, drinking and irrigation water, as well as fish and waterfowl are in danger. For this reason, both state and federal agencies proposed a plan in 1965 for the second phase of the California State Water Project creating a canal that would transport fresh water from the Sacramento River around the delta, instead of through it.
Voters defeated a ballot initiative to build a similar Canal in 1982.
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- Carle, David (2004). Introduction to Water in California. Berkeley, CA: University of California Press. pp. 42–43. ISBN 0-520-24086-3.
- Newton, Jim (2012-06-25). "Newton: Water ethics and a peripheral canal – Southern California needs the water, and Northern California has it. But let's not sacrifice the delta.". Los Angeles Times. Retrieved 2013-08-21.
- Matt Weiser (2104-08-28). "EPA says California’s Delta water tunnel project could violate federal law". Sacramento Bee.
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- Garone, Philip (2011). The Fall and Rise of the Wetlands of California's Great Central Valley. University of California Press. p. 242. ISBN 9780520266636.
- "The California Peripheral Canal: who backed it, who fought it". California Agriculture. 1983.
- Home page for the Bay Delta Conservation Plan, which includes Peripheral Canal-like tunnels.
- The Bay Delta Conservation Plan: An Overview and Local Perspectives in Western City.
- Bay-Delta Consevation from Save the Bay.