GRAND CANYON NATIONAL PARK, Ariz. (AP) -- A surge of water up to four times greater than normal would cascade through the Grand Canyon in March if plans being completed by federal officials are approved.

The release of water from the Glen Canyon Dam upstream of the canyon is designed to scour sand from the bed of the Colorado River and rebuild beaches that support wildlife and are used for camping by rafters. Bigger sandbars also provide habitat for endangered native fish and will protect archaeological sites, according to the Interior Department.

The Glen Canyon Dam was completed in the early 1960s and cut natural flood cycles that ranged from heavy springtime flooding that cleansed the river's sand and gravel bars to slow late fall flows. In the past decade, half the camping sites in the canyon have been lost to shrinking beaches.

If environmental reviews of the project are approved as expected and the releases happen, it would be the third time the dam has been opened beyond power-generating capacity. Similar experiments were done in 1996 and 2004.

This year's high-flow test is expected to be more successful than the previous efforts because federal scientists have determined that much more sand is available in the riverbed.

The Bureau of Reclamation operates the dam and plans to open bypass gates and run the maximum amount of water possible through the dam's powerplant, bureau officials said Thursday. Flows would increase to 41,000 cubic feet per second for nearly three days, up from the normal of 8,000 cfs to 20,000 cfs.

The river will rise significantly, affecting rafting and campsites alongside the river.

A full environmental assessment is expected to be released early next month by the Bureau of Reclamation and a final decision made by the end of February. A series of scientific studies will be done during and after the high flows to gauge their effect on beaches, wildlife habitat and fish.

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On the Net:

Grand Canyon National Park: http://www.nps.gov/grca ..

Bureau of Reclamation: http://www.usbr.gov/

Grand Canyon Monitoring and Research Center: http:http://www.gcmrc.gov/research/high-flow/2008/

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