The Glen Canyon Dam’s Jet Tubes Are Opened For a Grand Science Experiment

On March 5, 2008, when Secretary of the Interior Dirk Kempthorne opened the jet tubes at Reclamation’s Glen Canyon Dam, he released about 41,500 cubic feet per second of Colorado River water into the Grand Canyon, and launched a scientific experiment aimed at learning more about how to improve the river for wildlife and visitors.

“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,” Secretary Kempthorne said. “The water will be released at a rate that would fill the Empire State Building within twenty minutes. It will transport enough sediment to cover a football field 100 feet deep with silt and sand.”

The experiment – a 60-hour high flow test – is expected to push sand built up at the confluence of the Paria River downstream
of the dam into a series of sandbars and beaches along the river. Most sediment entering Grand Canyon National Park now arrives from the Paria River and upper Marble Canyon tributaries below the dam.

The test is similar to the previous high-flow experiments conducted in 1996 and 2004, but the amount of sediment available is considerably larger. In the 17 months preceding the March 2008 experiment, tributaries below the dam provided more sand to the system than had been available at any time in the past ten years- about two times greater than the supply that preceded the 2004 experiment.

Data will also be collected to determine the total amount of sediment in the system and its availability for restoring sandbars and camping beaches, which provide habitat for wildlife and supply sand needed to protect archaeological sites. Interpreting this large volume of information could take from months to years. It will then be used to improve the predictive capabilities of the existing sediment model and determine the optimal peak flows of future high-flow experiments.

“With more than 100 federal, state and university researchers collecting data on behalf of this experiment, it will take some time to interpret the data and reach final conclusions on what has been learned,” said John Hamill, U.S. Geological Survey (USGS) Grand Canyon Monitoring and Research Center Chief. “The effects of the high-flow experiment on various resources in Glen and Grand Canyons will be evaluated in the field through the fall of 2008.”

In addition, high flows create areas of low-velocity flow, or backwaters, used by young native fish. USGS scientists will be monitoring how the high-flow releases affect the survival of a population of young humpback chub. The humpback chub is one of four remaining native fish in the Grand Canyon.

USGS anticipates that initial reports from the experiment will be provided to the public in late 2008 and 2009; with a complete synthesis of the results, including comparisons with the 1996 and 2004 tests, to be provided in 2010.

The high flow experiment is an inter-agency research effort conducted by the USGS, Reclamation, which operates Glen Canyon Dam on the Colorado River; and the National Park Service, which manages Grand Canyon National Park.

Dave Walsh | PN Region

Andy Pernick, LC Region

Tami Heilemann | DOI

Tami Heilemann | DOI

Andy Pernick | LC Region

Dave Walsh | PN Region