SALT LAKE CITY, Feb. 10 (UPI) -- Manmade floods from an Arizona dam can rebuild critical Grand Canyon sandbars if timed properly, but could kill endangered fish if they're not, a report says.
The U.S. Geological Survey report said the latest of three intentional floods from the Glen Canyon Dam, unleashed in March 2008, created lasting Colorado River sandbars to benefit fish, wildlife and river-running campers, The Salt Lake Tribune reported Thursday.
However, the spring flood caused a population explosion in non-native rainbow trout that eat and compete with the endangered humpback chub, the report said in suggesting the U.S. Bureau of Reclamation consider fall floods in the future.
Sandbars on the river have dwindled since the government finished Glen Canyon Dam in 1963. Where still present, they form pools for native fishes and beaches for wildlife and recreation.
Short floods from the dam can help, the report says.
Of 34 river sandbar study sites, researchers say, 31 were larger just after the spring 2008 flood.
"It does seem to be somewhat encouraging," said Ted Melis, deputy chief of the USGS Grand Canyon Monitoring and Research Center.
Interior Secretary Ken Salazar has ordered the Bureau of Reclamation to prepare a protocol to spell out conditions under which it will repeat the floods, and to also prepare a plan to keep rainbow trout in check.