Dear Deeply Readers,

Welcome to the archives of Water Deeply. While we paused regular publication of the site on November 1, 2018, we are happy to serve as an ongoing public resource on water resilience. We hope you’ll enjoy the reporting and analysis that was produced by our dedicated community of editors and contributors.

We continue to produce events and special projects while we explore where the on-site journalism goes next. If you’d like to reach us with feedback or ideas for collaboration you can do so at [email protected].

Delta Water Tunnel Project Revised Again, But Concerns Linger

Two massive tunnels proposed under the Sacramento-San Joaquin Delta could help ease future droughts, but some say the risks are too great.

Written by Robin Meadows Published on Read time Approx. 6 minutes

Just last year, the public was invited to have its say on the Bay Delta Conservation Plan (BDCP), the state’s long-contested proposal to pipe water under the Sacramento-San Joaquin Delta. Now the twin tunnels are back under a new name – California WaterFix – with the key difference that the tunnels are no longer linked to extensive habitat restoration. We have until October 30 to get our comments in.

Here we go again.

The project is important because about half of California’s freshwater flows through the delta, the largest estuary on the West Coast of the Americas. The delta supplies about 13 percent of the total water used throughout California, providing at least part of the drinking water for 22 million people and irrigating 3 million acres of farmland, mostly in the San Joaquin Valley.

If the proposed tunnels work as promised, they might help ease future droughts by taking larger “gulps” of water from the Sacramento River in wet winters or during big storms. That water could then be stored in reservoirs or aquifers to help ease dry times.

The delta has been heading for trouble since people diked its many islands for agriculture more than 100 years ago. Today, those levees are in questionable shape and, according to the Legislative Analyst’s Office, breaks big enough to threaten water supplies are likely. The region is also threatened by sea level rise, which could overwhelm levees and render delta waters undrinkable.

The estuary is also a major thoroughfare for California’s salmon. Two-thirds of them migrate through the delta, and several salmon runs are threatened or endangered. Other at-risk fish include the famous delta smelt, the less-known longfin smelt and the green sturgeon.

What these fish have in common, aside from the misfortune of their deteriorating ecosystem, is that they live in salty water as adults but migrate back to freshwater to spawn. And this is part of their undoing in today’s delta.

At the southern tip of the delta, two sets of pumps drain water into state and federal water projects. Sucking water south through the delta disturbs the natural east–west flow of water between the rivers and the sea. “The south delta is more like a lake,” said U.C. Davis fish biologist Peter Moyle, explaining that migratory fish navigate by tidal currents. “It’s confusing to the fish; they don’t know where to go.” Another problem is that the pumps crush fish.

Supporters say the proposed tunnels could help solve both problems. About 30 miles long, 40 feet across and up to 150 feet underground, the tunnels would carry water from the northern tip of the delta to the pumps in the south. “Moving water directly to the pumps could be less confusing to the fish,” Moyle said. “That’s the theory, anyway.”

The tunnel intakes would be like three gigantic mouths on the Sacramento River, each capable of gulping up to 22,000 gallons per second. While the plan also calls for screens designed to protect fish, the intakes could still be risky for fish. So the project can’t go forward without “incidental take” permits for endangered fish from wildlife agencies; these permits allow harm to listed species or their habitat in exchange for habitat conservation.

Permitting the earlier vision for the tunnels, as proposed under the Bay Delta Conservation Plan, looked unlikely, in part given the U.S. Fish and Wildlife Service’s 30 pages of “red flag” comments.

BDCP was a 50-year plan that bundled the tunnels with large-scale restoration to meet the 2009 Delta Reform Act’s goals of water reliability and ecosystem restoration. According to the state, combining the two projects was a major holdup to permitting the tunnels. Wildlife biologists thought the long-term impact on endangered species was too uncertain, and doubted that the BDCP could deliver the extensive habitat restoration it promised.

Now the state has split BDCP into California WaterFix and California EcoRestore. This means the tunnels are no longer linked to a 50-year permit and large-scale restoration. The new plan does include up to 15,600 acres of habitat restoration and protection, but this is only about a tenth of what BDCP promised. While separating BDCP into two parts may facilitate permitting the tunnels, critics are as vocal as ever.

Doug Obegi, an attorney with the Natural Resources Defense Council’s Water Program, said the NRDC is open to rerouting water from the north delta to the south. But he doesn’t like the state plan. “Moving the point of diversion doesn’t address the primary problem that outflows from the delta are too low,” he said, adding that outflow to the sea correlates with the health of delta fish populations. “New intakes would increase the potential to take water from the delta, and the State Water Resources Control Board has waived a lot of environmental flows during the drought.”

The board acknowledged in a 2010 report that recent delta outflows are too low for fish. According to the report, we would ideally let 75 percent of the delta’s water flow through it and out to sea during the rainy season. But in dry years, outflows have been as low as 30 percent. By law, the board must balance environmental water needs with those of cities, agriculture and recreation.

Fish need water most during dry years. “When flow is high, salmon just pass through the delta,” said Jeffrey Mount, a fellow at the Public Policy Institute of California’s Water Policy Center. “When flow is low, it’s hard for them to get through without being picked off by non-native predators,” which include two species of catfish and several species of bass.

Mount understands why the state is moving forward with the twin tunnels. “The current strategy has not worked and the state needs to work toward a decision,” he said. And uncertainty over the tunnels is unavoidable. “It’s a big experiment, and we don’t really know what the environmental benefits will be,” he added, explaining that it’s hard to predict how climate change will affect future droughts and sea level rise.

As long as we use water from the delta, we are in for an engineering fix one way or another, Mount said.

“It’s an engineered landscape – we have eliminated all of the original delta,” Mount said. “An engineering solution is inevitable.”

A key question is whether we will get to choose how and when to do it, or whether we will let a catastrophe like levee failure dictate the terms. Either way, people will survive. But we’ve been getting nowhere on a fix for decades and the longer we delay, the closer the delta’s endangered fish slide toward extinction.

That said, Mount is “agnostic” on California WaterFix, citing its colossal expense. Costs could run to $15 billion, according to the California Department of Water Resources, the lead state agency on California WaterFix.

The primary permits for the project are issued by federal and state wildlife agencies, the U.S. Army Corps of Engineers and the state water board. Funding is up to the water users, who are mostly Central Valley farmers and Southern California water agencies.

We can’t vote on the latest incarnation of the twin tunnels, but we can make our voices heard. You can learn more about California WaterFix at and can send comments to [email protected] or BDCP/California WaterFix Comments, P.O. Box 1919, Sacramento, CA 95812.

Robin Meadows covers water issues for the Bay Area Monitor, where this article originally appeared.

Top image: An aerial view of a portion of the Sacramento-San Joaquin Delta. (

Suggest your story or issue.


Share Your Story.

Have a story idea? Interested in adding your voice to our growing community?

Learn more
× Dismiss
We have updated our Privacy Policy with a few important changes specific to General Data Protection Regulations (GDPR) and our use of cookies. If you continue to use this site, you consent to our use of cookies. Read our full Privacy Policy here.