FLAGSTAFF, Ariz. — Federal officials are considering releasing a large amount of water from the Glen Canyon Dam into the Grand Canyon early next year in an effort to rebuild beaches and aid endangered fish.

If approved by the Interior Department, water released from the dam just south of the Arizona-Utah border would scour sand from the river bottom and deposit it on beaches. Shrinking beaches have led to the loss of half the camping sites in the canyon in the past decade.

The Glen Canyon Dam cut the natural flood cycles that had maintained the ecosystem for millions of years. Before it was dammed in 1963, flows ranged from heavy springtime flooding that cleansed the river's sand and gravel bars to slow late fall flows.

If the project is approved, it would be the third time the dam was opened beyond power-generating capacity. Similar experiments were done in 1996 and 2004.

Scientists plan to conduct $2 million in experiments on how the flood affects food sources, trout, water quality and sandbars.

More broadly, it is a test of ways to better manage the ecosystem of the Grand Canyon to offset impacts from the dam, required under a 1992 law.

Scientists contend that with periodic floods it might be possible to allow fish and plants that thrived in the canyon before the dam was built to recover.

Ninety percent of the sediment that used to flow into the Grand Canyon now settles out in behind the dam in Lake Powell, researchers say. Lack of rapid springtime flows also has led to silt buildup in tributaries.

"The idea behind these high flows is you're trying to take the sand that's in the bottom of the channel and wash it up on the beaches," said John Hamill, chief of the Grand Canyon Monitoring and Research Center at U.S. Geological Survey in Flagstaff.

The planned flooding would be less than half as powerful as some of the pre-dam floods that sometimes tossed around house-sized boulders.

More sandbars should aid reproduction for the endangered humpback chub, said Andrea Alpine, a biologist and director of the Southwest Biological Science Center at USGS.

The chub population, repeatedly a source of litigation, has increased by up to 25 percent in the last five years, to 6,000 adult fish, Alpine said. Researchers aren't certain about why.

A project to kill nonnative trout near where the chub live has been in place for several years, removing a primary competitor.

The flooding plan is opposed by the Federation of Fly Fishers, which says the floods harm aquatic plants, fish and the food supply in the river.

"It's the Grand Canyon magic sand show, that's what it is," said Mark Steffen, of the Fly Fishers. "It's a whole bunch of scientists (who) want to get together and see what happens to the sand. That's really all it's about."