California is leaving no stone unturned in its quest to generate water; the Golden State has considered ways to conserve, store, reuse, and desalinate water. As it continues to experience intense and on-going drought, and climate change produces rising sea-levels that threaten water sources, the need to protect those sources and deliveries becomes paramount. To aid in both of those objectives, Governor Gavin Newsom recently revived plans for a tunnel around the Sacramento-San Joaquin Delta.    

The Delta Conveyance Project, as dubbed by the Newsom administration, is not a new idea, nor is it without controversy. The Sacramento-San Joaquin Delta is the largest freshwater estuary on the west coast and is considered the “hub” of California’s surface water delivery systems, the State Water Project, and the Central Valley Project. In combination, the three create a water conveyance system that supplies water to over 29 million people, at least in part, and irrigation to a large percentage of the state’s agriculture industry.[1] Yet its role as a hub is often in conflict with its role as an ecosystem, home to many endangered species.

The tunnel idea originated in the 1940s as a “Peripheral Canal” to divert water from the Sacramento River around the San Joaquin-Sacramento Delta to the south. In 1982, during Gov. Jerry Brown’s first term, he formally proposed the Peripheral Canal Act which voters rejected. The idea was rekindled by Gov. Arnold Schwarzenegger in 2007 but faced blistering environmental concerns, particularly related to fish and wildlife of the Delta, and consequently did move forward. In 2011, during Gov. Brown’s second term, the concept was re-introduced as two tunnels that would run under the Delta, but the idea continued to generate intense environmental scrutiny that was unresolved when he left office. In 2019, the twin tunnel concept was withdrawn by Gov. Gavin Newsom, in favor of a scaled back, single-tunnel version which he recently unveiled.

Newsom’s proposed tunnel would measure 36 feet in diameter with a maximum capacity of 6,000 cubic feet per second, transporting water 45 miles from the Sacramento River and delivering it to the State Water Project pumps located at Bethany Reservoir. The tunnel’s capacity is roughly fifty percent less than Gov. Brown’s proposed project and is estimated to cost only $3 billion less than Brown’s tunnels, still coming in with a price tag of approximately $16 billion.[2]

Advocates of the plan claim the tunnel will protect water transport for the future (from earthquakes), address threats to the Delta stemming from rising sea levels and saltwater intrusion brought on by climate change, and improve the environment through the watershed restoration that is incorporated into the plan. However, Newsom faces a difficult battle moving forward, much as his predecessors did. The California Department of Water Resources released a Draft Environmental Impact Report stating the Delta Conveyance Project would cause “unavoidable” impacts to delta farms, and although the fish and wildlife of the Delta are increasingly endangered by climate change impacts, most argue the tunnel will create an even worse situation. If permitted, the project is certain to face court challenges related to endangered species laws.

[1] “Sacramento-San Joaquin Delta.” Water Education Foundation,

[2] Rust, Susanne. “California Officially Shrinks Delta Water Diversion Plan from Two Tunnels to One.” Los Angeles Times, Los Angeles Times, 28 July 2022,