The Science Of Draining Hetch Hetchy - SacBee

[hatrack]

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A team of scientists from U.S. Fish and Wildlife Service, the California Department of Fish and Game and the National Park Service came together in 1988 to study the matter. Their job was to examine a controversial proposal by Donald Hodel, President Reagan's secretary of the interior. Hodel wanted Hetch Hetchy restored for the national park.

San Francisco leaders howled in protest. Hodel got nowhere with his idea. But credit him and the scientists who prepared the Interior Department report. They figured out the science of the restoration if not the politics.

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* The dam must stay, or at least a very large section of it must remain. San Francisco dug 118 feet below the riverbed to build the foundation for the dam. "The removal of the lower 118 feet of the dam would vastly change the river gradient at the narrow lower end of the valley and would probably lead to rapid erosion of the meadows in the lower chamber of Hetch Hetchy," the scientists said.

* The sediment isn't as big a problem as one might think. On many rivers, a dam will capture tons of loose dirt and small rocks and transport the sediment toward the sea. That didn't happen at Hetch Hetchy, which is a good thing. If it had, the valley would be more dead than alive. The sediment load "appears quite low," the scientists said. "The Tuolumne River descends from a watershed comprised largely of thin soils and great expanses of exposed and glaciated rock." (In 1991, barely an inch of sediment covered the floor.)

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* Two options exist for grasses, plants and trees. Let nature do the job, or manage what grows back. By leaving things alone, "within two years extensive areas on the floor of Hetch Hetchy valley would be covered with grasses, sedges and rushes. ... Willows would begin to colonize the riverbanks." The drawbacks: Grasses wouldn't be native grasses, and the native pines and oaks might face some competition. If the valley were managed, after five years, "conifers would be up to 15 feet high and black oaks would be about six feet high in areas planted the first year."

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http://www.sacbee.com/content/opinion/story/10800900p-11718855c.html

[phantom power]

1. Science schmience... fetch me the C4!

[NNadir]

2. I always remembered it as being James Watt who proposed this.

He was the Reagan Secretary of the Interior who claimed Jesus would be mad if he came back and there was still some oil in the ground.

Anyway, this was the only good environmental idea to come out of the Reagan freaks.