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(Trying to be) a force of nature

Water is blasted through the Grand Canyon to spread nature's nourishment.

Reshaping the canyon's banks: For 60 hours starting Wednesday, the Colorado River is reclaiming some of its former glory, swelling with floodwaters that will reshape miles of sandy banks on the floor of the Grand Canyon. The flood, released at the Glen Canyon Dam near the Arizona-Utah border, is meant to mimic natural ones that used to nourish the ecosystem by spreading sediment. The water level in the canyon will rise only a few feet, but officials hope that will be enough to restore sandbars. It's the third such experiment along the river in a dozen years, repeating tests in 1996 and 2004.

A rush of water: More than 300,000 gallons of water per second - enough to fill the Empire State Building in 20 minutes - are being released from Lake Powell through the dam. That's four to five times the usual flow. No water will be lost from the Colorado River system. The amount released will be stored in Lake Mead at the other end of the canyon.

Then and now: Before the dam was built in 1963, the Colorado River was warm and muddy, and natural flooding built up sandbars that are essential to native plant and fish species. The river is now cool and clear, with 98 percent of its sediment blocked by the dam, according to Grand Canyon National Park superintendent Steve Martin. The change helped speed the extinction of four fish species and push two others, including the endangered, 3.5-million-year-old humpback chub, near the edge. The humpback chub has recovered some of its lost numbers since the last flood.

[Last modified March 6, 2008, 01:01:29]