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Hetch Hetchy Valley is a glacial valley in Yosemite National Parkmarker in Californiamarker. It is currently completely flooded by O'Shaughnessy Dammarker, forming the Hetch Hetchy Reservoirmarker. The Tuolumne River fills the reservoir. Upstream from the valley lies the Grand Canyon of the Tuolumnemarker. The reservoir supplies the Hetch Hetchy Aqueduct. The damming of the valley in the 1920s, and the creation of a reservoir, were at the time, and since, a major environmental controversy in the Western United States.

The Hetch Hetchy Road drops into the valley at the O'Shaughnessy Dam, but all points east of there are roadless, and accessible only to hikers and equestrians.


The name "Hetch Hetchy" comes from a grass with edible seeds that grows in the valley, in the Native American Sierra Miwok language . It was first used in the English language by Joseph Screech, who in 1850 became the first European to enter the valley. Screech noted that Paiutes had inhabited Hetch Hetchy and still gathered seeds, roots and acorns in and around it. Acorns are indeed available in the valley, but rare elsewhere in the high country.

Charles F. Hoffmann of the California Geological Survey conducted the first survey of the valley, in 1867 .

In 1906, after a major earthquake, San Francisco applied to the United States Department of the Interiormarker to gain water rights to Hetch Hetchy. This provoked a seven-year environmental struggle with the environmental group Sierra Club, led by John Muir. Muir observed:

Dam Hetch Hetchy! As well dam for water-tanks the people's cathedrals and churches, for no holier temple has ever been consecrated by the heart of man.

Proponents of the dam replied that the valley would be even more beautiful with a lake. Muir correctly predicted that this lake would deposit an unsightly ring around its perimeter, which would be visible at low water. Because the valley was within Yosemite National Parkmarker, an act of Congress was needed to start the project. The federal government ended the dispute in 1913, with the passage of the Raker Act, which permitted flooding of the valley.

Construction of the dam was finished in 1923. Water from the dam serves 2.4 million Californians in San Francisco, San Mateo, and Alameda Counties, as well as some communities in the San Joaquin Valley, and generates electricity for San Francisco. Environmental groups (including the Sierra Club) advocate removing the dam.

For more information on the controversial history of the dam and reservoir, see the O'Shaughnessy Dammarker article.


Like Yosemite Valleymarker, Hetch Hetchy was also sculpted by glaciers as recently as 10,000 years ago. The more recent glacier there was larger than the one in the paleo-Yosemite Valley. Today the Hetch Hetchy area is drier.

On the upper portion of the valley, beyond the reservoir, there is evidence of relatively young lava flows. One recent flow formed the Little Devils Postpilemarker which, as the name suggests, is a smaller version of the Devils Postpilemarker near Mammoth Lakesmarker to the southeast. Both formations are great examples of columnar basalt, a phenomenon that results from contraction of basaltic lava as it cools (forming hexagonal columns). Similar formations are found in the Giant's Causewaymarker in Ireland, and the New Jersey Palisadesmarker in the United States, as well as other places throughout the world.

See also

Another modern-day image of Hetch Hetchy Valley.


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