Delta Tunnel

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 from the Delta Cross Channel 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 the Delta-Mendota Canal.[2] Large numbers of Delta smelt and other endangered species are killed by the pumping plants, which provide water for the aqueducts.[3] Freshwater flowing into the Delta displaces salt water entering from the San Francisco Bay. The freshwater to saltwater gradient has shifted inland because of 5 to 7 million acre feet (6.2 to 8.6 km3) increases in the amount of water being exported each year to the Central Valley and Southern California. The proposed 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 current 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. On August 28, 2014 the United States Environmental Protection Agency commented that the plan could violate the Clean Water Act and harm endangered fish species.[6]

Before 2015, the Bay Delta Conservation Plan had two coequal goals of habitat restoration and water supply improvement. In April 2015, the habitat restoration plan and the water supply improvement plan were separated. In effect, the 50-year guarantee to restore the Delta’s environment has been dropped.

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