PAGE, ARIZ.—On March 5, 2008, Secretary of the Interior Dirk Kempthorne opened jet tubes at Glen Canyon Dam to release about 41,500 cubic feet per second (cfs) of Colorado River water into the Grand Canyon. The experiment is a 60-hour high-flow test. The additional water is expected to push sand built up at the bottom of the river’s channel into a series of sandbars and beaches along the river.
Secretary of the Interior Dirk Kempthorne opened jet tubes at Glen Canyon Dam to release about 41,500 cubic feet per second of Colorado River water into the Grand Canyon as part of a 60-hour high-flow test.
"This experiment has been timed to take advantage of the highest sediment deposits in a decade and designed to better assess the ability of these releases to rebuild beaches that provide habitat for endangered wildlife and campsites for thousands of Grand Canyon National Park tourists," Kempthorne said. "The water will be released at a rate that would fill the Empire State Building within 20 minutes. It will transport enough sediment to cover a football field 100 feet deep with silt and sand."
The experiment is an inter-agency research effort conducted by three Department of the Interior bureaus—the U.S. Geological Survey; the Bureau of Reclamation, which operates Glen Canyon Dam on the Colorado River; and the National Park Service, which manages Grand Canyon National Park.
Evaluation of the results of the release will be part of an effort to fashion a long-term, science-based adaptive management process. Scientists hope to gain a better understanding about whether higher flows created by releasing water from the dam can be used to rebuild eroded beaches downstream. These Colorado River sandbars within Grand Canyon not only provide habitat for wildlife and camping beaches for recreationists, but also supply sand needed to protect archaeological sites. High flows also create areas of low-velocity flow, or backwaters, used by young native fishes, particularly endangered humpback chub. Most sediment entering Grand Canyon National Park now arrives from the Paria River and upper Marble Canyon tributaries below the dam.
The 2008 test is different than previous high-flow tests conducted in 1996 and 2004. In particular, scientists have concluded that more sand is needed to rebuild sandbars throughout the 277-mile reach of Grand Canyon National Park than was available in 1996 or 2004. Currently, sand supplies in the river are at a 10-year high with a volume about three times greater than the volume available in 2004 because of tributary inflows below the dam during the last 16 months.
"The water released during the test will not change the amount of water to be released over the course of the 2008 water year," said Larry Walkoviak, regional director of Reclamation’s Upper Colorado Region. "The current plan of operations calls for releasing 8.23 million acre-feet of water from Glen Canyon Dam. That water flows downriver to Lake Mead for use by the Lower Colorado River Basin States and Mexico. The experimental flows are included within this annual volume. Monthly releases later in the year will be adjusted downward to account for the water released during the experiment."
More information about the experimental high flow is available on the Grand Canyon Monitoring and Research Center website.