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How Reliable Are Silicon Valley Water Sources?

Depending on where you live in San Mateo or Santa Clara counties there are many places your water could come from – and, as the drought has shown, some of those sources are more reliable than others. Here’s a look at the pros and cons of the most important sources.

Written by Published on Read time Approx. 8 minutes
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SAN MATEO, California – Tucked in the woods off Cañada Road in Redwood City is an unusual part of California’s water system. The Pulgas Water Temple is a Beaux Arts style pavilion with fluted columns that pay homage to ancient Rome. It’s a fitting tribute because the temple itself is a monument not just to water, but to water engineering – something for which the Romans are lauded.

A Biblical inscription at the top reads, “I give waters in the wilderness and rivers in the desert, to give drink to my people.”

The temple marks the terminus of the aqueduct that stretches more than 160 miles (255km) from the Sierra Nevada to San Mateo County. This is known as Hetch Hetchy water – named after the controversial project enabled by the Raker Act in 1913 that let San Francisco dam a valley in Yosemite National Park to capture the pristine snowmelt and runoff that flows into the upper reaches of the Tuolumne River.

The flooding of Hetch Hetchy valley for the reservoir was decried by many at the time, including famed environmentalist John Muir, but today as water stress has increased in California, most view the project as a great boon for San Francisco.

But the City by the Bay and its 837,000 residents are not the only benefactors. In fact, 2.6 million people in the Bay Area drink from the Hetchy system, among them many residents of San Mateo County and Santa Clara County.

As important as Hetchy is, though, it’s not the only source of water in these Silicon Valley counties. Depending on which town you live in, your water may come from Hetchy, the State Water Project, the federal Central Valley Project, groundwater, recycled water or local surface water. In some cases it’s a combination.

Each of the water sources has pluses and minuses, which are becoming more apparent as California’s drought continues. How each community weathers this drought (and future ones) depends on the reliability of its water system – and that can vary by town.

For those towns in San Mateo County, understanding the reliability of the water system means understanding how the Hetchy system works because 90 percent of the water supply for the county comes from Hetchy.

But the San Francisco Public Utilities Commission (SFPUC), which runs that system, doesn’t supply water directly to residents in San Mateo County as it does in San Francisco. Instead the SFPUC sells to 16 different agencies in San Mateo County, which then supply the water to local residents and businesses. A few of these agencies are run by private water companies, but most are run by water districts or municipalities themselves. This means that even though the water supply may be the same in most places, rates can vary. At the wholesale level, Hetchy water can be among the most expensive in the state, but for good reason.

The water, which travels from the mountains to the Bay Area via a gravity-fed system, is known for being good quality and also a reliable source. One of the advantages is that it’s draining snowmelt from high mountain elevations. The higher up you are, the better chances are that precipitation will fall as snow, instead of rain, which means more water in the warmer months when demand is high. Some other California water systems rely on mountain runoff too, but from headwaters much lower in elevation.

SFPUC and the other water agencies using Hetchy water also have kicked in $4.6 billion of capital improvements to the system especially aimed at increasing reliability and resistance to earthquakes. But the system does have one big potential weakness – 85 percent of the water comes from the Tuolumne River, which means the vast majority is from one source. Sounds problematic, right?

“We used to think that the single-source agencies would be more vulnerable because they only had one supply, but with this drought, because of the way it hit the state systems harder, it turns out the agencies with multiple sources ended up having to take a greater reduction,” said Nicole Sandkulla, CEO and general manager of the Bay Area Water Supply and Conservation Agency (BAWSCA). Her organization represents the 26 member agencies in San Mateo, Santa Clara and Alameda counties that are served by the Hetch Hetchy system.

“So the theory didn’t prove in practice,” she said and explained that while some water providers (like those in Santa Clara County) had cutbacks to their allocations because of drought, the SFPUC didn’t. It did ask for 10 percent voluntary reductions from retailers, but its rather meager request was overshadowed by the 25 percent cuts mandated statewide by Gov. Jerry Brown.

As good as all this seems, that doesn’t mean that San Mateo County residents are happy to sit back and watch the water flow down from the mountains. There are still other issues to contend with.

“The supply that we have from Hetch Hetchy is pretty reliable, and in normal years is a pretty comfortable feeling,” said Adrienne Etherton, executive director of the nonprofit Sustainable San Mateo. “But this extended drought has really made people start to think about it a lot more and the people who are really in the know are really pushing to try and diversify and find new sources.”

East Palo Alto, for example, gets its water from the Hetchy system but the town’s needs exceed their supply allotment and without more water, growth will be hard. So East Palo Alto is in the process of redeveloping a groundwater well previously shuttered because of water quality issues.

A project is also underway in the northern part of the county with Daly City, San Bruno and the California Water Service Company to use a local groundwater basin to “bank” water in wet years.

“We are looking at new investments in other supplies that increase that reliability in dry years, things like doing a water transfer, looking at a brackish groundwater project locally, those types of projects,” said Sandkulla. “There is also huge interest in the region in onsite reuse and lots of talk about indirect and direct potable reuse.”

While most of San Mateo County has some tie to the Hetchy system, residents of Montara, just south of Pacifica on the coast, are in another boat entirely. They are served by the Montara Water and Sanitary District, which relies entirely on local sources – about 85 percent of which is groundwater, while the remaining 15 percent is surface water.

Clemens Heldmaier, the district’s general manager, says that despite drought, “we didn’t have any water supply issues in the past years and we don’t foresee any water supply issues in the coming years, even if the drought continues.”

But, he cautioned that no one knows how severe the drought will be and when it will end. “We have access to different aquifers and some of those are fairly drought proof,” he said. “But what ‘drought proof’ means, is not 100 percent clear.”

For Santa Clara County’s nearly 2 million residents, things are even more complicated. Just over half of the water is imported and 15 percent of that is Hetchy water. This makes up part of the water supply for eight towns: Alviso, Los Altos Hills, Milpitas, Mountain View, Palo Alto, San Jose, Santa Clara and Sunnyvale.

None of the 17 water agencies in Santa Clara County rely on a single source of water. The biggest amount of water, 40 percent, is pumped through the Sacramento-San Joaquin Delta from Sierra runoff and is delivered through either the State Water Project or the federal Central Valley Project, which also supplies water to millions of Californians across the state and much of the agricultural interests of the San Joaquin Valley. All but two water agencies in the county rely on the Delta for at least some portion of their water supply.

One of the biggest vulnerabilities of relying on water supplied by the state and federal projects through the Delta is that there are more competing interests for the water. And that makes a string of consecutive drought years especially tough. The Delta’s water issues are a political tangle as farmers, fishermen, environmentalists and urban water users jockey for limited resources.

Many farmers saw their water deliveries severely cut or eliminated altogether last year, and even the Santa Clara Valley Water District (SCVWD), a wholesaler that helps supply and manage water in Santa Clara County, received a cut in allocation.

“We had the lowest combined allocation of state and federal water in all of the years that we’ve been taking it – since the early 60s,” said SCVWD’s deputy operating officer Garth Hall.

Because of the reduction in imported water from the Delta, SCVWD’s board called on its retail members across Santa Clara County to reduce water use by 20 percent in 2014 but members achieved only 13 percent reductions that year.

Shortfalls of Delta water were complemented by 10 local reservoirs and a large groundwater basin. But that, too, had its limits. “The retailers in north county resorted to groundwater pumping because our treated water supplies were reduced in 2014,” said Hall. “The net result was that we had a fairly severe depletion of our groundwater basin.”

Roughly 20 percent of the total annual water supply of the entire county was pulled from the groundwater in excess of what was being replenished. “So the water levels in the ground fell quite badly,” he said.

In 2015 SCVWD called for 30 percent conservation, which exceeded even the governor’s statewide mandate, and customers stepped up big this time, reducing water use by 27 percent, which paid off.

“We managed to halt the decline in water levels in our basin so we ended up at the end of 2015 with groundwater levels that were no worse and possibly the same as 2014.”

The focus for the county continues to be on improving reliability and increasing supply for the future. Hall said they are considering whether to participate in California Water Fix, a $15 billion plan by the governor to build two tunnels underneath the Delta in an effort to increase the reliability of water deliveries.

Closer to home there is also an $800 million project underway to expand a water recycling facility to produce potable water that could be mixed with groundwater. It’s in the planning phase now, said Hall, but they are hoping by 2020 it will provide 10 percent of the county’s water supply. It will be more expensive per acre-foot than Delta water, but more reliable.

Water recycling is an effort Sustainable San Mateo’s Etherton hopes gains more traction in Silicon Valley communities. “I think it’s really an opportunity that we need to be putting more effort behind and trying to speed along,” she said. “If we get some more rains, I hope it doesn’t end that progress.”

Top image: Menlo Park resident Robert Wilkins stops on a bicycle ride to fill his water bottle from a fountain at Pulgas Water Temple in Redwood City, Calif. (Tara Lohan)

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