YOSEMITE valley's long-lost twin could be restored to its former glory. This week, San Francisco voted on plans to drain the Hetch Hetchy reservoir and restore the valley to its original majesty.
The reservoir was created in 1923, when the river that flows through the Yosemite National Park was dammed. As a result, the Hetch Hetchy valley was turned into a giant basin that now supplies 85 per cent of San Francisco's water.
Proposition F was on the same 6 November ballot in San Francisco as the presidential election. Votes were still being cast as New Scientist went to press. If they come out in favour, the city will spend $8 million on drafting a plan to restore the valley.
Hydrologists say water supplies should not be affected, as the nearby Don Pedro reservoir holds more than twice as much water as Hetch Hetchy. Sarah Null of Utah State University in Logan says losing the reservoir would cause only minor additional shortages in the San Francisco Bay Area, even in a worst-case climate scenario.
Restoring the valley to its original state is possible, says Joy Zedler of the University of Wisconsin in Madison, but not easily. There's little record of which species lived in the valley before it was flooded. Models suggest meadows and wildlife could return within a few years. Forests could be restored within 50 years, but it could take a century for lichens to return to the rocks.
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