Experimental floods aid Grand Canyon sandbars

Brandon Loomis - 

Experimental floods from Glen Canyon Dam have proved effective at rebuilding environmentally critical Grand Canyon sandbars when timed properly, but could kill endangered fish when they're not, according to a new U.S. Geological Survey report.

The latest of three such floods, unleashed in March 2008, created lasting Colorado River sandbars to benefit fish, wildlife and river-running campers, said this week's report. It also caused an explosion in nonnative rainbow trout, which eat and compete with the endangered humpback chub.

The results will help river managers craft a plan to govern more experiments in the coming decade, and the researchers say it might make sense to release a burst of water at least once a year whenever tributaries below the dam deposit enough sand. In dry years, when Utah's Paria and Arizona's Little Colorado don't add enough sediment, scientists say it might not make sense to do any so-called grand flushes.

Sandbars and beaches have dwindled since the government finished Glen Canyon Dam in 1963. Where still present, they help form warm pools for native fishes(refugees from the cold waters released from Lake Powell's depths) and beaches for wildlife and recreation. The sands also help protect archaeological sites from erosion or vandalism.

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