A shrunken Delta tunnels project? Decision time is upon California

Delta Tunnels proposed intake location in Clarksburg. Image is looking south along the River Road at right.
Delta Tunnels proposed intake location in Clarksburg. Image is looking south along the River Road at right.

A new option has entered the discussion of Delta water supplies: one cross-Delta tunnel instead of two.

For now, California’s WaterFix proposal, pushed by Gov. Jerry Brown, is for two tunnels under-crossing the Delta for 35 miles, allowing up to 60 percent of Delta water exports to come from the main channel of Sacramento River. Implementing such a major project requires extraordinary political and financial support that so far is lacking.

Delta water users involved in WaterFix have failed to reach consensus on the project and how it would be funded. The Westlands Water District voted against funding the WaterFix and the Santa Clara Valley Water District voted for a scaled-back project. President Donald Trump’s Interior Department offered an ambivalent statement on the project Wednesday, further adding to the confusion.

Under these conditions, the WaterFix project could shrink to become a single-tunnel state-only project supported mostly by urban water users and some Tulare basin agricultural contractors.

We’ve been here before. In the mid-2000s, a single Delta tunnel of 2,500 cubic feet per second was proposed to serve urban water agencies. In 2013, environmentalist and urban agencies suggested a single tunnel combined with other actions, which the state bruskly rejected.

The WaterFix effort’s EIR in 2013 also included a single 3,000-cubic feet per second tunnel, but didn’t favor it. A Public Policy Institute of California op-ed also suggested one tunnel.

Much of California depends on a long-term Delta water supply. But that supply is threatened by worsening endangered species conditions, sea level rise, continued land subsidence, and the Delta’s structural fragility. At the same time, 2014 state legislation will leave San Joaquin Valley agriculture with less groundwater, making it even more dependent on Delta water.

Here are some dilemmas for Delta conveyance capacity:

One 3,000-5,000-cubic feet per second tunnel would provide enough water for the Bay Area and Southern California. This option has clear benefits for cities and would reduce construction impacts within the Delta. The state could more readily justify subsidies to fortify Delta levees if these levees are needed to maintain through-Delta water exports.

However, one tunnel would leave most agricultural water users in the southern Central Valley dependent on the existing southern Delta diversions. These diversions provide poorer water quality and reliability and unnaturally reverse river flows, harming native fish.

Another twist is that many Delta land owners rely on water project pumping from the southern Delta to bring cleaner Sacramento River water to the central and southern Delta.

Solving Delta water supply problems for cities with a single tunnel could reduce urban involvement in finding solutions for the environment, Central Valley agriculture, and Delta levees. That could make solving overall Delta problems harder.

The state needs effective Delta policies in three areas: water supply for urban, agricultural, and in-Delta users; for declining native species; and levee protection, or a lack of protection, for islands that provide insufficient economic value.

State agencies work on these strategies fitfully, though they’ve been more focused in recent years. Levee conditions have been improving, but environmental and water conditions continue to deteriorate.

There are no perfect solutions. We remain largely in a game of chicken, in which each interest refrains from public compromise to avoid weakening its negotiating position. But time is passing, and fish conditions worsen. Sustained state leadership is needed to craft imperfect but workable solutions among the Delta’s many conflicting interests.

Jay Lund is a Professor of Civil and Environmental Engineering and Director of the Center for Watershed Sciences at UC Davis,

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