Environment

Flooded at Last

By Fenella SaundersJan 1, 1997 12:00 AM

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The grand canyon was dying of thirst for 33 years. With the unveiling of the Glen Canyon Dam in 1963, up to 80 percent of the Colorado River’s flow was cut off, not to mention 100 percent of the annual spring floods. The floods used to drop sediment on beaches and sandbars in the canyon that serve as homes for nesting birds; they also stirred up nutrients and washed away clogging vegetation to keep the canyon’s marshes suitable as breeding grounds for fish. Thanks to the dam, the canyon was losing its beaches and its marshes were stagnating.

In response, the Bureau of Reclamation opened the dam for a week at the end of last March, releasing more than 117 billion gallons of water; only a quarter of a natural spring flood. Bureau ecologists had decided the canyon couldn’t handle any more in its fragile state. The flood nonetheless rebuilt some 50 beaches that had completely disappeared, enlarged 70 percent of the existing ones, and rejuvenated marshes and backwaters. Some of the canyon’s endangered birds, such as the southwestern willow flycatcher, began to use the new habitat, and endangered fish like the humpback chub have been spawning.

To keep the canyon from degenerating, the bureau will have to flood it again, but it doesn’t plan to approximate nature with annual floods. There’s not enough sand to move around, says bureau ecologist Chris Brod. Besides stopping the floods, the dam traps 90 percent of the sediment that used to enter the canyon. The only beach-building material to work with is the sediment deposited in the river by streams below the dam. It will take at least seven years for them to bring in another supply.

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