New Study Examines Colorado River Flows, Loss Of Beaches

By Ron Dungan
Published: Wednesday, February 10, 2021 - 8:29am

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A night view of an experimental high flow at Glen Canyon Dam in 2012.
Andy Pernick/U.S. Bureau of Reclamation
Glen Canyon Dam.

A recent study looks at how Grand Canyon has changed since the construction of Glen Canyon Dam.

Before the dam was built, the Colorado flowed erratically, with high runoff in the spring and low flows the rest of the year. A research team led by Alan Kasprak, of Fort Lewis College in Colorado, has found that changes to the river have reduced the amount of sand by about half.

Although previous studies have shown the importance of high flows in the Colorado River ecosystem, Kasprak’s team found that low flows play an important role as well.

"The recognition of the importance of low flows is a little bit, is something that we’ve recently come to discover," Kasprak said. "It’s sort of the other part of the flow regime of the Colorado River that’s been lost as a result of Glen Canyon Dam operation."

The study also found that current flows have led to increased tamarisk growth, which is likely to continue over the next couple of decades, causing further loss of beaches.

Bare sand lines the channel and uplands of the Colorado River
Joel Sankey/U.S. Geological Survey
Bare sand lines the channel and uplands of the Colorado River about 85 miles downstream from Glen Canyon Dam in Grand Canyon National Park.

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