Celebration and Concern: Hetch Hetchy Reservoir Turns 100, However Local weather Change Complicates its Future

But water experts believe the next 100 years of providing millions of people with a finite resource will be far more complicated than storing water in a mountain bathtub and channeling it into the bay. Water authorities need to save more and possibly make technical improvements to allow the system to store more water.

The Hetch-Hetchy system has been able to handle recent severe droughts and this winter’s powerful storms, but Newsha Ajami, the president of the SFPUC, said “some of it was luck driven.”

“We have one of the lowest water usage rates in the state,” she said. “San Franciscans consume about 40 gallons per person per day, which is very little.”

The SFPUC operates the reservoir and expects the Hetch Hetchy system to be tested by even more extreme drought and flooding.

“This year was one of the wettest years we have ever seen. Just before we had the driest three-year sequence we’ve ever seen,” Graham said. “We’re seeing what the climate models are predicting, wetter rainy seasons and drier dry spells, which makes managing all of that a little more difficult.”

Water supplies may appear stable in a wet year, Graham said, but managing runoff from a massive Sierra snowpack requires constant attention, especially with no guarantee future years will be wet either. In August, he said, the reservoir will remain glassy and brimming.

“Right now I’m just trying to maximize what we have and the storage capacity that we have,” he said. “Climate change will make managing this water supply significantly more difficult.”

San Francisco Mayor London Breed looks out over the Hetch Hetchy Reservoir from O’Shaughnessy Dam during Tuesday’s centenary celebrations. (Beth LaBerge/KQED)

While San Franciscans don’t use much water, other parts of the Bay Area overuse the resources. Laura Feinstein of the nonprofit political group SPUR analyzed water use within the system and found that communities like Hillsborough in San Mateo County that receive water from the Hetch Hetchy system use 190 gallons of water per person per day.

“Even in winter when it rains, they use water liberally,” she said of the residents, who continue to water large yards and landscapes regardless of the season. “This kind of inefficiency puts a lot of pressure on the system. Making communities like this more water efficient would mean a lot of savings and make the whole system more climate resilient.”

Hetch Hetchy’s success will depend on how it’s used

Susan Leal wants to ensure that Hetch Hetchy exists as a thriving water resource in the face of human-caused climate change. She is a former executive director of the SFPUC.

She sees three possibilities for the future of water from Hetch Hetchy: it becomes more expensive over time, the authorities start recycling it on a large scale, or they increase the level of the reservoir.

Regarding water recycling, Leal said there was “no alternative,” and city officials need to give serious thought to creating more recycled water facilities this year. Treated water, she said, costs more but could take some strain off the system.

“To discourage people from bottled water, we kept telling them how good their Hetch Hetchy water was,” she said. “We need to make people understand that recycled water is like distilled water. It is very pure water.”

O’Shaughnessy Dam holds back the Tuolumne River and forms the Hetch Hetchy Reservoir in Yosemite National Park. (Beth LaBerge/KQED)

Another way to increase the water supply is to raise the dam to store more water. In 1938 officials increased it from 227 feet to 312 feet. Leal said the O’Shaughnessy Dam, which will hold back the Tuolumne River, could be built 55 feet higher than it is today.

“We may have to build the dam higher to hold more water,” she said. “We have to take that into account because we never planned the extreme storms.”

Raising the dam and increasing the storage capacity of the reservoir would likely face significant opposition from environmentalists and likely face lawsuits.

“I don’t know if it’s being considered, but if it’s recycling or impounding more water at Hetch Hetchy or other dams, all of those things have had to be thought about since yesterday,” she said.

100 years marks the “victim of the environment”

The story of Hetch Hetchy isn’t just about free-flowing, clean drinking water, and its construction sparked one of the first major U.S. struggles over land use and conservation. When officials were building Hetch Hetchy, the reservoir cut off waterways to fish, plants, and other animals that depended on running water, most of which is now stored behind a cement wall deep in the Sierra Nevada.

UC Davis’ Sandoval Solis said the construction of the reservoir, while good for many people in the Bay Area, has destroyed the freshwater ecosystems on the shores.

“The environment has been at risk for 100 years,” said Sandoval Solis. “The centenary also marks the centenary of endangering or sacrificing the environment and some of the Indigenous communities who were displaced for the benefit of the people living in San Francisco.”

Hetch Hetchy is the ancient home of up to a dozen indigenous peoples; Throughout Yosemite, many were forcibly displaced or killed in the mid-1800s.

The Hetch-Hetchy Valley has been inundated with water since the construction of the O’Shaughnessy Dam 100 years ago. (Beth LaBerge/KQED)

Damming rivers in the Sierra Nevada, such as the Tuolumne River at Hetch Hetchy, have bifurcations into the river systems that join the San Joaquin River, empty into the San Joaquin-Sacramento Delta, and enter the Bay.

The large amounts of fresh water that once flowed helped mix natural algae into the salty water. Still, lower inflows into the bay mean the seaweed sits atop the water, creating the perfect habitat for toxic algal blooms. Olivia Yip, an associate professor at San Jose State University who studies algal blooms, said the latest eruption, which killed thousands of fish, was partly due to reduced freshwater flows.

“Imagine some seaweed floating around in the bay,” Yip said. “With more mixing, it’s less likely to just sit on top and grow like crazy.”

The future of the system must include an equitable use of water, proponents say

The Hetch-Hetchy Pipeline runs through communities in the Central Valley and Bay Area that need clean drinking water of their own. UC Davis’ Sandoval Solis said access to safe drinking water “should not be a luxury because it is a human right.”

“The pipes run right through their communities, but they can’t use them,” he said. “I don’t think providing clean water to disadvantaged communities should be a problem.”

About two-thirds of the Bay Area’s pure Hetch-Hetchy water is used outside of San Francisco’s borders.