Three months ago, Santa Clara County’s largest water agency voted to kill a $3.2 billion plan to build a huge new reservoir in the southern part of the county near Pacheco Pass.
The Pacheco Reservoir would have been the largest new reservoir built in the Bay Area since 1998 when Los Vaqueros Reservoir was constructed in eastern Contra Costa County.
But soaring cost overruns, a lack of interest among other water agencies to help pay construction costs and share the water, and a decision by the federal Bureau of Reclamation not to allow water from federal projects to be stored in the reservoir, marked the end.
Now the Santa Clara Valley Water District is back with new plans to boost water storage. This week, the district, a government agency in San Jose that provides water to 2 million South Bay residents, approved a roadmap for the next 25 years that combines new reservoir projects, groundwater storage and recycled water. The price tag: $3.9 billion.
“When I meet people in groups, I’ll say ‘raise your hand if you’ve ever worried that clean, safe water won’t come out when you turn on your tap,’” said Shiloh Ballard, a water district board member. “Almost no hands go up. Our job is to make sure you never have to worry.”
Unknown to many people, Santa Clara County — like Los Angeles and most other urban areas in California — has seen its overall water use drop in recent decades, even as population has grown. Total water use in Santa Clara County has fallen 20% since 2000, while population grew by 25% over the same time.
The reason: The district has spent millions of dollars to pay people to remove lawns and replace them with water-efficient landscaping, and on rebates for low-water appliances. New statewide building codes also have required low-flush toilets, showerheads, and other water-saving plumbing.
“Most water use is outdoors,” said Kirsten Struve, the water district’s assistant officer for water supply. “As we see fewer lawns and improved technology indoors, water use goes down.”
Even though there has been significant development, she noted, new condominiums and apartments use far less water than older single-family homes, which often have landscaped yards, leaky plumbing and aging appliances.
So why add new storage at all? Fear of extreme droughts, water officials say.
“I’m an optimist,” Ballard said. “But we are responsible for making sure people have water. We have to plan for extreme scenarios and be paranoid. We have to anticipate the worst.”
Right now, times are good. Northern California has had three wet winters in a row. Levels in reservoirs and many underground aquifers are above average.
But since 2007, as any longtime resident knows, California has suffered through three big droughts — in 2007-2009, 2012-2016, and 2020-2022, with severe heat waves and wildfires made worse by rising temperatures from climate change.
The Santa Clara Valley Water District’s planners estimate that current countywide water use of about 285,000 acre feet a year will rise 16% to 23% by 2050 as the population grows and new industries like AI data centers use more water. Complicating matters, the Sierra snowpack, a major source of water, is projected to melt earlier as temperatures continue to rise. In a severe 6-year drought, they say, Santa Clara County could be 69,000 acre-feet short. An acre-foot is about 325,851 gallons, or the amount 10 people use in a year.
On Wednesday, the district’s board approved a 428-page document called the “Water Supply Master Plan 2050” to try and reduce future shortages.
A key part of the plan is to continue conservation measures, even in wet years, such as the current program of paying homeowners $2 a square foot to voluntarily remove their lawns. The plan also includes five major projects:
1) Raising the dam at San Luis Reservoir. Eight water agencies and the federal government signed an agreement last November to spend $1 billion to raise the dam at one of California’s largest reservoirs, San Luis Reservoir between Gilroy and Los Banos, by 10 feet. That would create 130,000 acre feet of new storage. The Santa Clara Valley Water District could get up to 60,000 acre feet of that. Pros: There is little environmental opposition. Cons: Caltrans would have to move parts of Highway 152, which could cost $400 million or more.
2) Delta tunnel. The Santa Clara Valley Water District, along with the Metropolitan Water District of Southern California and others, supports a $20 billion plan by Gov. Gavin Newsom to build a 45-mile long tunnel under the Sacramento-San Joaquin Delta to make it easier to move water from Northern California to Southern California. Pros: It could provide the district 14,000 acre feet of new supply a year. Cons: The project is highly controversial, has been the subject of lawsuits since the 1980s and may never be built.
3) Pure Water Silicon Valley. The district is in talks with San Jose city leaders to recycle more wastewater from the sewage treatment plant at Alviso — which now provides 5% of the district’s supply for irrigation and industrial uses — at cleaner levels and put that water into underground aquifers or send it directly to drinking water treatment plants. Pros: It’s a local, drought-free supply. Cons: Public acceptance and a relatively high cost.
4) Groundwater storage: The plan calls for the district to store 250,000 acre-feet underground. Right now it has more: 305,000 acre feet stored at Semitropic Water Storage District in Kern County, a deal it struck in 1997. Pros: Groundwater storage is cheaper and less controversial than new dams. Cons: New state laws to reduce groundwater overdraft in the Central Valley could jeopardize some supplies.
5) South County recharge: The district would build new percolation ponds and other projects to increase groundwater storage in Southern Santa Clara County. Pros: Local supply at a relatively low cost. Cons: It needs support from farmers and other landowners.
The district also is studying a desalination plant for the South Bay. That would provide a local supply, but could run into problems with fish and wildlife in San Francisco Bay. And the agency continues discussions in a partnership to build Sites Reservoir, a huge $6.2 billion project in Colusa County that could break ground as soon as next year.
Environmentalists say they prefer conservation, groundwater storage and recycled water.
“The Delta tunnel is a huge mega-project like high speed rail,” said Katja Irvin, with the Sierra Club’s Loma Prieta chapter. “It’s going to continue to have problems. The cost is going to continue to go up. It’s unclear if water agencies are ever going to want to pony up to pay for it.”
Jay Lund, vice director a professor at UC Davis’ Center for Watershed Sciences, said many huge water projects fail because water agencies find cheaper solutions, like conservation and groundwater storage.
“Water management is a very long-term issue,” he said. “There are all kinds of changes and unexpected things that happen over periods of decades. But these kinds of plans are a necessary way to focus the conversation.”
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