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Kiefer: Dams provide large amounts of power
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Any movie collector can recall the incredible “dam jump” scene in “The Fugitive.” Dr. Richard Kimble is pursued by a federal marshal. Trapped on the dam’s high side, he jumps, rides a column of water down the spillway, splashes into the river and escapes.

This was filmed at Cheoah Dam on U.S. 129, near Robbinsville, N.C. No actor actually did the jump. A 220-foot drop, almost 40 feet higher than Niagara Falls, isn’t survivable.

Scenic lakes like Cheoah Reservoir or Hall County’s Lake Lanier owe their existence to dams constructed by the U.S. Army Corps of Engineers. No glaciers carved out lake beds during the Ice Ages, so all the lakes in North Georgia and adjacent areas in North Carolina and Tennessee are artificial.

Their primary purpose is to regulate river flow and prevent flooding. But they also produce electricity. At Cheoah, which was billed as the world’s tallest dam in 1919, it’s rare to see water rushing down the front, because it won’t do any work that way.

The lake drains through a large pipe connecting the dam with the powerhouse. Called the penstock, it forces water into turbines, where power-producing rotors spin up to 2,000 rpm. Hydroelectric power is renewable energy because no water is consumed or altered in any way.

But their electric output doesn’t match that of nuclear or even coal-fired plants. On the other hand, there is no waste product and no worry about the bird kills that can happen with wind turbines and focused array (“heat ray”) solar plants.

In our area, Buford Dam holds 63,000 acres of Lake Lanier in place. Unlike many others, it’s an earthen dam, not a curved concrete wall. Earth dams are resistant to movement of the ground, most prominently in California where minor earthquakes are common.

But the lake must be prevented at all cost from overflowing the top. Even a minor breach in an earth dam can cause disaster. The 1889 Johnstown, Pa., flood killed 2,200 people when a private earth dam was overrun by flood waters.

Buford Dam is free of such worries because there is a huge overflow channel, lower than the dam’s top, at Lanier Park. In addition to the lake’s value as a drinking water reservoir and recreation facility, the dam produces 73 megawatts of power. That’s enough to power up to 50,000 homes.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.

 

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