By Brian Maffly
The Salt Lake Tribune
Page, Ariz. -- Federal water mangers and scientists Monday began ratcheting up releases from Glen Canyon Dam as part of a five-day experiment to push sediments down the Colorado River in hopes of restoring sandbars that play a vital ecological role in the river channel.
This week’s high-flow releases, designed to mimic the pre-dam natural flooding, mark "an historic milestone" for river management, according to Interior Secretary Ken Salazar.
"It was an honor to open the door to a new era for Glen Canyon Dam operations and the ecology of Glen Canyon National Recreation Area and Grand Canyon National Park — a new era in which we realize that the goals of water storage, delivery and hydropower production are compatible with improving and protecting the resources of the Colorado River," Salazar said after he personally triggered releases at noon through the dam’s outlet tubes that bypass the turbines.
The federal Bureau of Reclamation began experimenting with high flows in 1996; this week’s event is only the fourth experiment. The others occurred in 2004 and 2008.
But the frequency of future releases will increase — to the delight of conservationists — under protocols Salazar announced in May.
"We have been pitching Interior for years to do these as often as the sediment in the system warrants. They rejuvenate all the sediment-related resources," said Nikolai Lash, a program manager with the Grand Canyon Trust. Under the new protocols, high-flow releases are expected to occur as often as once or twice a year, depending on the accumulation of downstream sediments.
Scientists led by Utah State University geomorphologist Jack Schmidt will closely monitor the effects of these high flows for the next several years. Their findings will help guide a long-standing "adaptive management" strategy for the Southwest’s signature river, which has carved one of the world’s most scenic landscapes. Damming the river produced a windfall of electrical power, but it also wrecked the river’s ecology and pushed warm-water fish species toward extinction.
"By early 1990s, the scientific community recognized it would be impossible to restore native ecosystems without controlled floods because they reintroduce disturbance into the ecosystem," said Schmidt, who now works for the U.S. Geological Survey. A professor of watershed sciences, Schmidt remains on unpaid leave from his USU appointment while he leads the Grand Canyon Monitoring and Research Center in Flagstaff, Ariz.
By disturbance, Schmidt was referring to the massive floods that once roared through Glen and Grand canyons, with flows in excess of 50,000 cfs (cubic feet per second) occurring most years and in excess of 125,000 cfs every eight years on average. Before the 1966 completion of the 710-foot-high Glen Canyon Dam, which forms Lake Powell, the Colorado pushed millions of tons of eroded sediments downstream, creating a rich network of sandbars that supported fish and riparian communities along Grand Canyon’s floor, not to mention great camping spots for river runners.
The dam impounds 95 percent of the natural sediment flow, then releases water at a steady rate of 7,000 to 9,000 cfs, which prevents sediments building up at the mouths of tributaries from being pushed downstream, according Schmidt.