The Colorado River will gush at flood stage starting Sunday night (Nov. 18), giving rafters a rare thrill and hopefully restoring beaches and native fish habitat in the Grand Canyon.
The six-day-long water release from Glen Canyon Dam is the first of many floods planned by the Department of the Interior through 2020. The floods, or "high-flows," are an effort to restore the river's natural environment for both tourists and wildlife.
"The high-flow does mimic a natural event, and that is a good thing for the ecosystem," said Glen Knowles, chief of the adaptive management group at the Bureau of Reclamation's Salt Lake City office.
Since the dam was completed in 1966, the Colorado River, once copper-colored with sediment, now runs clear. While sand and mud piles up behind the concrete barrier, natural beaches and sandbars have disappeared, allowing predatory non-native fish such as rainbow trout to flourish. Bushes and trees, once buried or ripped away during periodic floods, now choke popular camping sites for river rafters. [Top 10 Most Visited National Parks]
Deluge to build new beaches, habitat
The goal of the flood is to park sediment high along the walls of the Grand Canyon.
"The beaches have changed rather dramatically since the dam was put into place, and we can rebuild those beaches to an extent," said Knowles, who was involved in planning and developing the high-flow release protocol. "The same sandbars that create the beaches also create backwater habitat for native fish," he told OurAmazingPlanet.
The high-flow release plan was announced in May by Secretary of the Interior Ken Salazar. Developed after more than 16 years of planning and testing, the strategy allows flood releases on short notice, without extensive environmental review or planning, through 2020. The order calls for flows from 31,500 to 45,000 cubic feet (892 to 1,274 cubic meters) per second for up to 96 hours in March-April and October-November,.
Flood tests were conducted in 1996, 2004 and 2008. These three blasts helped rebuild beaches and protect native fish such as the federally threatened humpback chub, but the newly deposited sediment quickly eroded. Researchers also found that without sufficient sediment below the dam dumped by the Paria and Little Colorado rivers the reservoir water was too cold for the humpback chub to spawn.
The new plan authorizes dam releases when enough sediment has been deposited by the free-flowing Paria and Little Colorado, Knowles said. Tests by the U.S. Geological Survey found the Paria River dropped 538,000 metric tons of sand into the Colorado River between late July and the end of October, so there's enough sediment to merit a flood now. [Related: The Grand Canyon in Pictures]
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Restorative Flood in Grand Canyon Starts Sunday Night
