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Sacramento-San Joaquin Delta Canal/Tunnels Proposals

Sacramento-San Joaquin Delta Canal/Tunnels Proposals

The Sacramento-San Joaquin Delta has been the hub of California’s water system for more than 50 years and  along the way water experts have struggled to balance the many competing demands placed on the estuary—the largest on the West Coast.

Those demands include meeting the needs of agricultural communities in the Central Valley, water deliveries through the Delta to the Bay Area and arid Southern California, and providing habitat for plants and wildlife.

Water leaders for decades have discussed building a peripheral canal or tunnels to convey export water around the Delta (instead of through the Delta using natural channels). A proposed canal was defeated by California voters in 1982. California Gov. Jerry Brown brought those talks to the forefront again in 2012, recommending through the Bay Delta Conservation Plan the construction of two 37-mile tunnels to move some export water while also working to restore the ecological health of the Delta.


The use of Delta channels as conduits for transporting water began in 1940 with completion of the Contra Costa Canal, the first unit of the Central Valley Project. With the 1951 completion of the Delta-Mendota Canal, the Delta became part of a vast water export system and pumping plant.

Also in 1951, the Delta Cross Channel was constructed near Walnut Grove to facilitate the transfer of water from the Sacramento River across the Delta to CVP export pumps located near Tracy.

Meanwhile, officials have discussed a possible peripheral canal or other means of water around and through the Delta because of concerns with water quality and fish being killed by the pumps.

In 1977, for instance, California’s Department of Water Resources backed earlier studies that said a peripheral canal would be the best facility to move water to the Delta export pumps.

However, voters defeated Proposition 9, which included a peripheral canal, in 1982.

Currently, two proposed tunnels would be constructed as part of the Bay Delta Conservation Plan, with intakes just south of Sacramento. The controversial BDCP tunnels proposal is expected to be available for public comment Oct. 1, 2013.


Proponents of an isolated water conveyance facility acknowledge that while not a panacea to the state’s water challenges, a canal or tunnel is a necessary part of a broader solution to California’s water future because it is necessary to break the gridlock that is often the hallmark of Delta convey­ance issues. Currently, restrictions on pumping can result in reduced supplies to State Water Project and Central Valley Project contractors south of the Delta. Under the current BDCP proposal, some water would be conveyed through the tunnels and some would still be allowed to flow through the Delta’s existing channels to the pumps located in the South Delta through what is referred to as dual conveyance.

But the idea of constructing an alternative conveyance system has its detractors who say such an apparatus would lead to greater water exports while depriving the Delta environment of much-needed fresh water inflow.

As outlined in preliminary discussions, the BDCP aims to recover and conserve at-risk native species in the Delta while rehabilitating the ecosystem to better support aquatic and riparian and floodplain communities.

According to environmental groups and some federal scientists, however, a Sacramento-San Joaquin Delta water conveyance system would be significant barrier to this environmental restoration. The Natural Resources Defense Council and others are advocating a “portfolio” alternative to the BDCP calls for a single, 3,000-cfs North Delta diversion facility. The financial savings associated with such a project, they say, could be used for new south of Delta storage, levee improvements, and habitat restoration.

Next Steps

The list of negative developments in the Delta—from revelations of earthquake vulnerability to poor water quality and crashing fish populations— has produced near unanimous agreement that maintaining the current course is not a reasonable solution for the ecosystem or water supply.

Court decisions and regulatory actions have also highlighted the poor condition of Delta fish species such as the Delta smelt and the extent to which pumping operations affects their survival.

But others say old arguments against additional Delta conveyance have been trumped by the reality that maintaining the existing system is not sustainable.

Ultimately, all involved in the process acknowledge any conveyance system will have to be legally valid and have political support before becoming a reality. It is also a given that any approved project will immediately draw a legal challenge.

Under Gov. Brown’s proposal, there would be no vote on the construction of the roughly $25 billion tunnels.

The proposal was amended in summer of 2015 to dramatically reduce the habitat restoration portion of the plan from 100,000 acres to 30,000 acres to make permitting the project easier.

The project proposes building two underground tunnels, 40 feet across and 30 miles long, to send water from the Sacramento River around the Delta.

In 2017 a biological opinion by the U.S. Fish & Wildlife Service and the National Marine Fisheries Service said the tunnels would not jeopardize the continued existence of the Delta smelt, Chinook salmon, steelhead and other imperiled species. The state of California also signed off on the project by finalizing its environmental review. In their opinion, the construction and operation of the tunnels complies with the California Environmental Quality Act.

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