Damming Yosemite Park's Hetch Hetchy Valley - My Yosemite Park

Damming Yosemite Park's Hetch Hetchy Valley

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Yosemite's Hetch Hetchy Valley is now a reservoir created by the O’Shaughnessy Dam.

Yosemite's Hetch Hetchy Valley is now a reservoir created by the O’Shaughnessy Dam.

In the least crowded corner of Yosemite National Park, debates about the future of Hetch Hetchy Valley have been going on for over 100 years.

When naturalist and conservationist John Muir first visited the valley, he wrote that is was "a grand landscape garden, one of Nature's rarest and most precious mountain temples." Even after Muir won the fight to preserve Yosemite as a national park in 1890, and later to expand that protection to the Sierra Nevada high country, in the end he couldn't save the Hetch Hetchy Valley.

In 1906 an earthquake struck San Francisco, resulting in many terrible fires. After the flames had been put out, the city began looking for a higher capacity water source. They found a solution in damming the Tuolumne River and flooding the Hetch Hetchy Valley. Secretary of the Interior at the time James R. Garfield (President Garfield’s son) granted San Francisco development rights in 1908 to move the project forward. That permission came much to the outrage of the Sierra Club and Muir, who fought vehemently against the decision only to be defeated.

Since the dam was to be built on federal land, an act of Congress was required to authorize the project. Their approval came in 1913 when the Senators and Representatives passed the Raker Act, which allowed flooding of the valley. President Woodrow Wilson signed the bill sealing the Hetch Hetchy Valley’s fate.

Construction of the O’Shaughnessy Dam began in 1919 and four years later the valley was completely underwater.

The O’Shaughnessy Dam at Hetch Hetchy Valley. Photo by Gloria Wadzinski

The O’Shaughnessy Dam at Hetch Hetchy Valley

Some environmentalists including the Sierra Club have never given up Muir's fight to save Hetch Hetchy, and many still dream of returning the valley to its natural state. After much political wrangling, the issue went on the ballot for California voters to decide in late 2010 and was defeated.

But even if it is still too late to save Hetch Hetchy, what happened there did help turn the tide against damming rivers elsewhere in the West, including at Kings Canyon in the Sierra Nevada and the Grand Canyon in Arizona, where dams were never built.

Hetch Hetchy by the Numbers


is the year president Woodrow Wilson signed the Raker Act, allowing San Francisco to Build a Dam in the Hetch Hetchy Valley.


is the year the O'Shaughnessy Dam was completed.


feet is the area's elevation, making for a long hiking season.

2.4 million

San Francisco area residents rely on the dam for water.

38 miles

is how far it is from Yosemite Valley.

Source: National Park Service