Is This Worth a Dam?

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Which set of concerns should take precedence? That question has been coming up with increasing regularity in both Western and Eastern states. Just last month, for example, the Arizona Public Service Company shut down two aging hydropower plants that no longer produced much electricity and opened the gates of a small diversion dam that for nearly a century had shunted water away from Arizona's Fossil Creek, a spring-fed tributary of the Verde River. As a thin ribbon of water trickled through, Dr. Robin Silver of the Center for Biological Diversity cheered. "In four to five years, the whole face of this stream will change," he predicted. Among other things, Silver expects young cottonwoods to take root along the banks and native fish like speckled dace, roundtail chubs and Sonoran suckers to thrive and multiply.

That many good things can happen when dams are removed is well documented. In 1999, for example, when a deconstruction crew took a wrecking ball to the Edwards Dam on Maine's Kennebec River, the results stunned even those who had lobbied for the dam's removal. Important fish species that used to swim from the ocean to spawn upstream--Atlantic salmon, alewives, sturgeon and shad--didn't just come back, marvels Pete Didisheim, advocacy director of the Natural Resources Council of Maine, "they surged back." The next year, almost a million alewives were massing in the river. Fish are also rebounding in Virginia's Rappahannock River after the U.S. Army Corps of Engineers blasted a gaping hole in the Embrey Dam last year.

The Edwards and Embrey dams (each hundreds of feet long and more than 20 ft. high) are among the most imposing structures that America's dam busters have tackled to date. But while a handful of large dams are scheduled to come down soon, those involved in their demolition are proceeding with caution, wary of what hazards they might unleash. As University of Utah political scientist Daniel McCool puts it, "We don't know how to remove big dams yet. We're still learning."

Shaping up as an important milestone is the demolition of two large dams in Washington State's Elwha River, which flows from the mountains of Olympic National Park into the Juan de Fuca Strait. Their removal, scheduled to begin in 2008, would occur in stages, and if it goes as planned, the Pacific Northwest will lose only a tiny amount of hydropower and regain a legendary salmon fishery. But there could be problems. Behind the Elwha dams are some 18 million cubic yards of accumulated sediment, enough to fill four superdomes, and if a lot of that sediment starts to move downstream at once, the ecological consequences could be severe.

What about even bigger, more significant dams? Well, no one has seriously suggested demolishing the Grand Coulee Dam on the Columbia, but a coalition of environmental groups has taken aim at four dams on the lower Snake River--and stirred up a storm of controversy. The damage those dams have done is clear. Since they were built in eastern Washington State from 1955 to 1975, the salmon population in the Snake has gone into free fall. But the benefits the dams provide are also clear: inexpensive barge transport for wheat farmers, irrigation water for fruit growers and a small but still useful amount of hydropower.