100 years of that divine Hetch Hetchy water

Come on in, the water here in San Francisco is fine.

What's happening: San Francisco city officials, including Mayor London Breed, visited the Hetch Hetchy Reservoir in Yosemite National Park this month to celebrate the centennial of the O'Shaughnessy Dam.

Why it matters: That 430-foot-high dam is at the heart of the Hetch Hetchy Water and Power system, the infrastructure that provides San Francisco Bay Area residents and businesses with water.

What they're saying: Breed called the dam "a testament to the creativity, and the innovation of San Franciscans," a reference to the fact that the water system solely uses gravity to deliver water through a 167-mile pipeline to the Bay Area.

• The water from Hetch Hetchy also doesn't require filtration due to its natural cleanliness, according to the San Francisco Public Utilities Commission. It is, however, treated.

Flashback: Construction of the O'Shaughnessy Dam began in 1919 and was completed in 1923, according to the SFPUC.

• Its construction was in response to the 1906 earthquake and subsequent fire that highlighted the issues with San Francisco's existing water infrastructure, the San Francisco Chronicle reports.
• The reservoir filled for the first time in May 1923, according to the SFPUC.
• The project was not without controversy. Environmentalists opposed the dam and reservoir, arguing that nature should be protected from human interference.
• Of note: Hetch Hetchy was once home to nearly a dozen Indigenous peoples, such as the Sierra Miwok, Washoe and Western Mono. Many across Yosemite Valley, however, were forcibly displaced or killed in the mid-1800s, KQED reports.

By the numbers: The water system serves drinking water to 2.7 million residents and thousands of businesses across four Bay Area counties, according to the mayor's office.

• The 8-mile-long reservoir holds about 117 billion gallons of water with a maximum depth of 306 feet, according to the San Francisco Public Utilities Commission (SFPUC), which manages the reservoir.

• Hetch Hetchy accounts for 85% of the water in the Bay Area Water Supply and Conservation Agency (BAWSCA), according to BAWSCA.

Yes, but: Climate change threatens the system due to concerns about its ongoing reliability, KQED reports.

• The back-and-forth between drought and flooding will continue to challenge the system, and while the utility commission is trying to maximize storage capacity, "climate change is going to make managing this water supply much more difficult," Christopher Graham, a manager with SFPUC, told KQED.

What to watch: SFPUC General Manager Dennis Herrera, in a press release, said SFPUC is committed to making the infrastructure investments required to "ensure the system serves the people for another 100 years."

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