How Water Shaped Yosemite

Show Summary - March 30, 2009

Guest: Scott Gediman

Scott Gediman (Yosemite, CA), Yosemite National Park, "Water's Effects on the Yosemite Environment"

Scott Gediman, the second guest, talked about California's Yosemite National Park, where he works as Head of Interpretation. Regarding water, he noted that Yosemite encompasses two major watersheds, the Tuolumne and the Merced Rivers, both of which flow westward into the San Joaquin River. Eastward, the park ends at the crest of the Sierra Nevada Mountains (Mt. Dana, 13,061 feet, is the highest point on the Sierra divide within the park. The park's highest summit, Mt.Lyell, 13,120 feet, lies on the Merced/Tuolumne divide). None of the eastern Sierra Nevada slope, which drains into the Nevada desert, lies within the park.

Hetch-Hetchy Reservoir and O'Shaughnessy Dam, on the Tuolumne River, supplies 80% of San Francisco's drinking water, plus agricultural irrigation water. The California Central Valley is one of the most productive agricultural areas in the world and depends entirely on irrigation.

The dam, completed in 1923, was and is extremely controversial due to the geology and scenic qualities of the Hetch-Hetchy Valley, which it floods. The valley is similar to Yosemite Valley but smaller, more isolated, and some say, even more beautiful. The battle to prevent the dam was the last conservation fight of famed Yosemite naturalist, John Muir (who died in 1914).

The park has the option of withholding water back during drought years.

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Categories: U.S. national parks, monuments; water and sanitation