The realities of water distribution in California have caused regional strife over the years. Most of the state’s precipitation falls in the northern part of California, but the greatest demand for water is in the Central Valley and further south. So California engineered the country’s most complex plumbing system to send water hundreds of miles south, much to the chagrin of many of the state’s northern residents.

The lynchpin to this system is the Sacramento-San Joaquin Delta, a water source for 25 million people and 3 million acres (1.2 million hectares) of agricultural land. Pumps at the south end of the Delta divert water via aqueducts to farms and cities further south and west.

The Delta has more than 1,000 miles (1,600km) of waterways snaking between numerous islands, many of which support farms and small communities. The area also provides vital habitat for migratory birds and many fish species.

But the Delta is threatened. Many of its islands are below sea level (and sinking), relying on levees that are one strong seismic shake away from disaster. And the ecosystem itself faces serious challenges. The Delta needs enough fresh water to sweep away pollutants, limit saltwater intrusion and protect fish.

For decades, various interests have battled over how much water should be pumped out of the system for south-of-the-Delta water users. At the same time, federal regulators have stepped in to protect fish and place limits on pumping at certain times of the year.

Gov. Jerry Brown is championing a plan, California Water Fix, he says will protect the Delta’s ecosystem and deliver water more reliably to those south of the Delta. But first he needs buy-in from some of the state’s biggest water users. For the most part, support for the project has fallen along familiar regional lines, with the biggest proponents in the Central Valley and Southern California, and the biggest opponents in the north.

Silicon Valley residents may think of themselves as Northern Californians, but when it comes to water supply, they actually have more in common with Southern Californians. As of right now, Santa Clara Valley Water District – the water wholesaler for Santa Clara County that provides water for nearly 2 million people – is weighing whether or not to participate in California Water Fix, which has a hefty price tag. The district’s decision could affect more than just Silicon Valley.

Weighing the Costs and Benefits

When Barbara Keegan travels to Southern California she hears a lot about how crucial California Water Fix is to the future of the state. But when Keegan returns home to Santa Clara County, where she is the board chair of the Santa Clara Valley Water District, she hears her constituents talking about how Southern California is “trying to steal our water.”

“A lot of people like to characterize this as a battle of north versus south,” said Keegan. “What a lot of people don’t realize is that anyone who is south of the Delta, even if you’re in Northern California, you are dependent on that water.”

Santa Clara County imports more than half of its water and 40 percent of that comes through Delta conveyance.

“So we have a stake in finding a solution,” said Keegan. “Because if 40 percent of our water were to disappear, that would be a big problem.”

Few people disagree that the Delta is in trouble, but there is no easily agreed upon solution. Keegan said her water district has faced declining allocations over the years because of regulatory requirements, which has meant less water. If the district says no to the project, it doesn’t mean things stay the same, said Keegan. “Maintaining the status quo isn’t really maintaining the status quo because it means constantly diminishing water. It could also potentially mean further degradation of the Delta.”

The water district will likely be expected to take a position on the project by late fall. “We haven’t made up our minds yet,” she said. “We are still considering things and there are a lot of complex issues involved.”

For starters, the project is controversial. While Brown and his supporters say it will increase water reliability and protect the ecosystem, others are concerned that siphoning water at the north end of the Delta will mean worsening water conditions and less water flowing through the Delta farmers and wildlife.

But we’ve been here before with this deadlock. California Water Fix is actually a new name given to a pretty old idea. For decades water managers and politicians have been scheming over ways to bypass the Delta with a water conveyance system that would more directly deliver water to southern users. Back in the 1980s, Gov. Brown proposed the idea of a peripheral canal that would skirt the Delta. Voters soundly defeated the proposition in 1982.

Fast forward to 2006 when work first began on the Bay Delta Conservation Plan, conceived as an attempt to fund new water conveyance along with a massive restoration of the Delta’s ecosystem. When the 40,000-page draft of the plan was finally released in 2013, it didn’t get rave reviews. So last year, the Brown administration divided the plan, creating California Water Fix to address water conveyance issues and California Eco Restore, which pared down the habitat restoration efforts.

The heart of the California Water Fix is now twin tunnels that go under the Delta. The tunnels would be a massive 40ft (12m) in diameter and sunk up to 150ft (46m) underground. They’d siphon water from the Sacramento River and deliver it to export facilities in the South Delta. It would eliminate the need to pump all the exported water out of the South Delta, as is done now, which has caused river flows to be reversed and proved a danger to fish species that are caught in the pumps or pulled off their migration course.

The plan comes with a hefty price tag, calculated right now at $15 billion for capital design and construction, and closer to $17 billion with mitigation, operations and maintenance costs figured in. Keegan said her agency would be on the hook for about 5 to 6 percent of the project, which puts the minimal cost for Santa Clara County around $1 billion. But it’s not the initial price tag that has her worried.

“I’m a civil engineer by trade and I know the history of large infrastructure public works projects,” she said. “There are very few of them that come within budget. A successful project could be one that only goes over by 50 percent or doubles.”

It is not yet clear to the water district’s board if the plan would be cost-effective for Santa Clara County, she said. There are still a lot of unknowns. “What if costs increase? What if some of the other partners drop out?” she questioned. “Could our county end up having to pay a disproportionate share of the project?”

And how to pay for the project is another issue. The district receives Delta water through the State Water Project, which is paid for through property taxes. But raising property taxes to pay for the tunnels project might not be possible. The Howard Jarvis Taxpayers Association has cautioned the water district that raising property taxes without a public vote to fund the project would be illegal since it was not part of the original State Water Project infrastructure.

Keegan said she has heard positions contrary on that issue, but whether it is legal is only one matter; whether it’s the right thing to do is another. “If we participate in this then the people who live here are going to be paying for it,” she said.

Brian Schmidt, a former district director and vice chair of the Santa Clara Valley Water District, said he believes that cost overruns are a serious concern. “I don’t see a way in advance to reduce that risk to a level we can ignore,” he said.

Other Options?

Rita Norton, a member of the water district’s environmental advisory committee, called the “slice and dice” separation of the project into two initiatives a politically astute move by its proponents, but worries about whether the environmental portion will ever be funded, even if the infrastructure project does get approval.

And she sees other implications if Santa Clara Valley Water District does participate. “How much indirectly by supporting this project is the water district continuing unsustainable water use in the Central Valley?” she asked. “It’s being sold as a water reliability project, but what else is good for water reliability? How else could these dollars be spent?”

Right now, Delta water is a vital supply for Santa Clara County, but could that change in the future? Keegan said that the district is invested in the idea of recycled water. It recently completed an Advanced Water Purification Center that can treat wastewater to drinking water quality standards, although so far it’s only used for non-potable uses.

“We plan to aggressively expand that,” she said. “A lot of times with projects your limitations are financial or just the time that it takes to do certain things. In this case one of the limiting factors is really getting public acceptance.”

Faced with paying more money to import water, will Santa Clara County residents embrace drinking recycled water?

Schmidt hopes so.

“I think the tunnels would reduce the incentive to greater self-sufficiency through increased direct and indirect potable reuse,” said Schmidt. “I see potable reuse as the real future for Silicon Valley with imported water serving primarily as backup sources.”

A decision is likely coming this fall from the water district on whether or not it will participate. Keegan said the district will hold more workshops and public meetings, and welcomes input from residents. But, she said this fall’s decision may not be a definitive yes or no. It’s possible that they will move forward with helping to fund more studies to determine the preliminary engineering and whether cost estimates are in fact realistic. Already, the district has contributed $9 million to studies on the project.

There is likely to be a lot of pressure from project proponents to get Bay Area water districts like Santa Clara Valley on board so that the project has enough critical mass and money to move forward.

“My own opinion is that we are sort of like a swing vote on this,” said Norton. “We are quite influential.”

How key Santa Clara County will be to the project remains to be seen, but minimally its involvement would be symbolic. “We are a Northern California water agency, the fact that if we choose to buy into this and partner with it, that sends a message,” said Keegan.

But ultimately, she said, “We want to see a cost-effective comprehensive and reliable long-term solution for the Delta that also includes something that meets the environmental needs. So, maybe that is an impossible challenge, but that’s what we are looking for.”

Water Deeply is an independent digital media project dedicated to covering California’s water crisis. The project is part of News Deeply, a new media startup and social enterprise based in New York.