In a normal year—or an abundant year such as this one—Zone 7 receives about 80 percent of the water through the Delta that it delivers to retailer water sellers (city of Livermore, city of Pleasanton, California Water Co. in Livermore and the Dublin-San Ramon Services District). Those water supplies, in dry or even normal years, have been interrupted by environmental laws concerning endangered fish species in the Delta.
Zone 7 is one of 29 agencies served by the State Water Project since the 1960s. The project starts with Lake Oroville (now being repaired after the near disaster with eroding spillways during the winter). Water then flows down the Feather River into the Sacramento River and is diverted through the Delta to the big pumps near Tracy. The north-south flows, when the Delta historically flows east-west, point out the problem with the State Project never being completed.
A Delta bypass always was in the plans and the twin tunnels to go under the Delta are the latest iteration. The plan calls for state-of-the-art fish screens to divert water into the gravity-flow tunnels that would transfer it to the pumping plants where it would go to the Bay Area (2.7 million customers) as well as Southern California farms and major agricultural districts in the San Joaquin Valley.
The current diversion system has functioned for more than 50 years and isn’t working for anyone. One measure of dysfunction—the current pumping levels are regulated by how fast two branches of the San Joaquin River are flowing backward to the pumps. Obviously, that’s no good for fish. The Delta habitat has been changed over the years so the water flows through channels instead of meandering through wetlands.
The tunnel plan received key approvals from federal fish agencies—decisions that were immediately challenged in court by environmental groups. There are more hurdles to go—including the economic one about users paying for it—but this was a key milestone.
So, Livermore Valley and Daughtery Valley residents: when you read about twin tunnels, remember it’s the water coming out of your tap that is at issue.
Incidentally, studies that Zone 7 has undertaken with other water agencies show that even the more aggressive program to diversify its water supply (highly treated wastewater, desalinated Delta water and more use of recycled water for irrigation) all continue to need imported Delta water to meet anticipated demand.
That’s particularly true for vineyards located on the east end of the valley that have limited access to ground water and rely on Delta water diverted from the South Bay Aqueduct.
I worked on these issues for many years as a consultant to Zone 7 working on educating customers about Delta issues.