Hetch Hetchy Valley

Hetch Hetchy Valley is a glacial valley in Yosemite National Park. In its original state, it was said to rival Yosemite Valley in its beauty. Then, in 1923, the City of San Francisco, California finished O'Shaughnessy Dam, which blocked the Tuolumne River and flooded the valley. The 430-foot-high dam provides San Francisco with high-quality water and electricity. The depth of lake is about 300 feet and the highest point in the valley is 2700 feet from the bottom of the valley.

History

In 1903, San Francisco applied to the United States Department of the Interior to gain water rights to Hetch Hetchy. This provoked a 10 year struggle with the Sierra Club, which ended in 1913, with the passage of the Raker Bill, which permitted flooding of the valley. It is said that the passage of the bill broke John Muir's heart: he died the following year.

Construction of the dam was finished in 1922 but was later raised an additional 86 feet. Proponents of the dam said that the valley would be even more beautiful with a lake. Muir stated that this lake would deposit an unsightly ring around the lake, which exists today.

The Sierra Club is currently advocating removing the dam, but the city of San Francisco is resisting. The cost of deconstructing the dam will be about 65 million dollars, which is a fraction of the 8 billion dollars needed to upgrade the water system of San Francisco. This dam is also a hydroelectric facility but the electrical generation equipment and lines are well-hidden.

Geology

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

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 Postpile which, as he name suggests, is a smaller version of the Devils Postpile near Mammoth Lakes to the south. Both formations are great examples of columnar jointing which is a phenomenon that results from contraction of basaltic lava as it cools (forming hexagonal columns).

External links

• Restore Hetch Hetchy web site
• San Francisco Public Utilities Commission, Department of Hetch Hetchy Water and Power