Duel Conveyance: Delta Tunnel Dilemmas

by Jay Lund

A new option has entered public discussion of Delta water supplies, having only one cross-Delta tunnel instead of two. The official State WaterFix proposal is for two tunnels (totaling 9,000 cfs capacity) under-crossing the Delta for 35 miles to allow up to 60% of Delta water exports to be directly from the Sacramento River for a variety of water supply, water quality, and Delta fish benefits.  Implementing such a major project requires extraordinary political and financial support.  For more than a decade, the group of Delta export water users involved in WaterFix has often lacked internal consensus on the project and its funding.  This is clear today, as cities and water user groups vote differently on WaterFix financing.  Apparent awkwardness of federal water contractor support for WaterFix and the recent Santa Clara Valley Water District vote have again raised the idea of a single smaller Delta tunnel.

In the mid-2000s a single Delta tunnel of 2,500 cfs was proposed to serve urban water agencies.  And in 2013, a group of environmental and urban agencies suggested a single 3,000 cfs tunnel combined with a portfolio of other actions, which was bruskly rejected by the state.  The WaterFix effort’s EIR in 2013 also included a single 3,000 cfs tunnel which was not recommended.  A Public Policy Institute of California op-ed last year suggested one tunnel as a promising alternative, as has a recent Los Angeles Times editorial.  Some suggestion is made that a single tunnel might make additional tunnels in the future easier, if needed.

California needs a viable Delta water supply strategy, given worsening endangered species conditions, the coming end of supplies from groundwater overdraft, sea level rise, continued land subsidence, and the Delta’s inherent structural fragility.  Any Delta water supply solution will be expensive and will need to be paid for.  Many regard the two tunnel proposal as too expensive for its benefits.  Here are some dilemmas for Delta conveyance capacity.

One 3-5,000 cfs tunnel is enough capacity to provide Bay Area and southern California cities with higher water supply reliability and better water quality.  This option has clear water supply and financial benefits for cities and reduces construction and other impacts within the Delta.  If the current state-led effort collapses, a consortium of urban agencies could conceivably embark on their own tunnel project, essentially a peripheral garden hose for urban users.

But one tunnel is not enough capacity to greatly improve water reliability and quality for agricultural water users in the southern Central Valley.  It is also not large enough to greatly reduce unnatural reverse river flows in the central and southern Delta that harm native fish unless accompanied by great reductions in agricultural water use in the southern Central Valley.

The coming end of groundwater overdraft under the Sustainable Groundwater Management Act will likely lead to substantial land fallowing and increased agricultural pressure to maintain or expand Delta exports, commensurate with current attention to recharging aquifers with floodwaters.  Even if federal arrangements continue to disrupt CVP contractors’ ability to financially support WaterFix through the CVP, some more prosperous contractors and groundwater-dependent San Joaquin Valley farmers might see financial benefits from improved Delta export reliability as new State Water Project contractors, sub-contractors, or water or conveyance capacity purchasers.

Another aspect is that many Delta land owners depend on water project pumping from the southern Delta to bring fresher Sacramento River water to the central and southern Delta.  (The Delta has two major salinity sources, seawater to the west and drainage from the San Joaquin River.)  State subsidies for Delta levees are easier if the state has an interest in these levees for maintaining through-Delta water exports.  Larger tunnels could reduce outside water and financial subsidies for in-Delta water quality and levees.

Would solving Delta water supply problems for cities reduce their involvement in finding solutions for the environment, Central Valley agriculture, and Delta levees and make solving overall Delta problems harder?

The state needs effective Delta policies in three areas – water supply for urban, agricultural, and in-Delta users, environmental management for declining native species, and levee protection or retreat for subsided islands which are uneconomical for landowners.  These policies often interact for good and ill.  State agencies continue to work on these strategies fitfully, across many agencies and programs, with more focused attention than in past decades.  Levee conditions have been improving, but environmental and water supply conditions continue to deteriorate.

It is good to see middle ground alternatives come forward, but there will be no perfect solutions for the Delta’s problems.  Imperfections will be seen differently by different interests.  We remain largely in a game of chicken, where each interest refrains from public compromise (or maintains that it has already compromised enough) 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 conflicting interests.

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

Further readings

BDCP (2010), “Analysis of Tunnel Sizing, BDCP Steering Committee, New Conveyance Sizing,” powerpoint presentation July 1, 2010, http://baydeltaconservationplan.com/Libraries/Dynamic_Document_Library_-_Archived/7_1_10_BDCP_Sizing_Presentation.sflb.ashx

CCWD (2008), Comment letter on ‘Notice of Intent (April 15, 2008) and Notice of Preparation (March 17, 2008) of the Environmental Impact Report/Environmental Impact Statement (EIR/EIS) for the Bay Delta Conservation Plan (BDCP)’, May 30, 2008, Contra Costa Water District, CA.  http://www.ccwater.com/DocumentCenter/Home/View/1972

CCWD (2009), Comment letter on December 17,2008 Draft of ‘An Overview of the Draft Conservation Strategy for the Bay-Delta Conservation Plan’, July 2, 2009, Contra Costa Water District, CA. http://www.ccwater.com/DocumentCenter/Home/View/1976

Green, E., “Sorry, my fellow environmentalists, we have to build the delta tunnels,” Los Angeles Times, op-ed, 9 October 2017.

Lund, J., “Delta “chicken” – A tragedy, CaliforniaWaterBlog.com, 15 February 2011

Lund, J., E. Hanak, W. Fleenor, R. Howitt, J. Mount, and P. Moyle, Envisioning Futures for the Sacramento-San Joaquin Delta, Public Policy Institute of California, San Francisco, CA, 300 pp., February 2007.

Lund, J., E. Hanak, W. Fleenor, W. Bennett, R. Howitt, J. Mount, and P. Moyle, Comparing Futures for the Sacramento-San Joaquin Delta, University of California Press, Berkeley, CA, February 2010.

Moyle, P. and J. Hobbs, “California WaterFix and Delta Smelt,” CaliforniaWaterBlog.com, August 13, 2017

Nelson, T., H. Chou, P. Zikalala, J. Lund, R. Hui, and J. Medellin-Azuara, “Economic and Water Supply Effects of Ending Groundwater Overdraft in California’s Central Valley,” San Francisco Estuary and Watershed Science, Volume 14, Issue 1, 2016.

NRDC, “Portfolio-Based Conceptual Alternative for the Bay-Delta, Overview,” Natural Resources Defense Council, January 16, 2013  https://www.nrdc.org/resources/portfolio-based-conceptual-alternative-bay-delta

Weisser, M. (2017), “Could a Simpler Delta Tunnel Solve Years of California Water Conflict?”, Water Deeply, 31 October 2017.

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1 Response to Duel Conveyance: Delta Tunnel Dilemmas

  1. One 40 foot diameter tunnel traveling 37 miles with a 150 foot drop has the capacity to move 14.8 Million Acre Feet (MAF) of water a year. See link to do the calc yourself @ http://www.calctool.org/CALC/eng/civil/hazen-williams_g FYI… Increasing the depth where the water is pumped up and into forebay will quickly increase volume of water that can be moved.

    14.8 MAF of water is still a lot of water. But why get water from Sacramento 37 miles away instead of 19 miles to the North Side of Sherman Island? The tunnel could follow the Rail Road track and highway all the way to Sherman Island. 1/2 the distance may not me 1/2 the cost, but certainly a lot cheaper. Getting the water after the Delta will eliminate most of the Delta objections.

    ZeeWeed or similar product can extract only the water leaving the sediment in river at extraction point, much better than fish screens. Membrane extraction is a ZERO loss of life in extraction of water verses screens which require settling ponds.

    Replace the 1.5 mile levee at Clifton Court Forebay (CCF) with a fish a 1.5 mile fish screen or ZeeWeed and you will have your flow and never kill fish in exporting water south..

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