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FLAMING GORGE, Daggett County — The Bureau of Reclamation opened bypass tubes at Flaming Gorge Dam on Friday, catching some weekend boaters by surprise.
The increased outflow caused minor flooding to rural areas downstream. Sections of the Little Hole National Scenic Trail, commonly used by anglers on the riverside, are currently under water. The U.S. Forest Service closed the trail between the Spillway Road and Little Hole on June 5.
On May 29, the Bureau listed releases from Flaming Gorge at 814 cubic feet per second. By June 7, that number climbed to 8,444 cfs. That indicates flow into the Green River below the dam is now more than 10 times greater than it was less than two weeks ago.
As a result, the National Weather Service office in Grand Junction posted a flood advisory for Daggett County, Utah and Moffatt County, Colorado lasting until Monday at 12:30 p.m.
The bypass tubes allow water to circumvent hydropower generators inside the dam. Combined releases from both the generators and bypass tubes reach an approximate maximum at 8,600 cfs. Emergency releases can be made through the dam's spillway, though that's not being done currently.
The Bureau anticipated the increases in late May, noting scientists had detected the presence of larval razorback sucker along the Green River. The razorback sucker is an endangered species that was once abundant in Colorado River drainage system.
The increased outflows simulate spring run-off conditions that would have existed prior to the dam's construction. The goal, according to a news release, is to reach combined flows at or above 18,600 cfs below the confluence of the Green and the Yampa rivers in Dinosaur National Monument. That would transport razorback sucker larvae into nursery habitat in the river's floodplain wetlands.
The Yampa flows out of Colorado's Rocky Mountains and, unlike the Green, is not dam-regulated. Its spring run-off flows started tapering earlier than expected, prompting the spike in releases from Flaming Gorge.
Lake Powell also stands to benefit. Even before the bypass tubes opened at Flaming Gorge, Lake Powell was rising roughly a foot per day. The Bureau's website currently says the elevated "releases will remain at bypass capacity until further notice."