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Scientists say Lake Powell sediment holds clues to managing the shrinking reservoir

 Researchers near Calf Canyon studying thick deposits of sediment.
Courtesy Cari Johnson
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Researchers near Calf Canyon studying thick deposits of sediment.

As Lake Powell water levels continue to fall, it’s not just side canyons that are being exposed. A new report looks at the history of the sediment that has been left behind.

Researchers are learning more about the layers of sand and mud deposited by the Colorado River in Lake Powell. They’re studying canyons left dry after the reservoir receded from its peak 1983 water level. Cari Johnson, an author on the report and a geology professor at the University of Utah, said they’re used to studying sedimentary formations much older.

She said the extensive data on water levels for the reservoir give them an advantage in their research.

“If we're going back and looking in deep time, millions-of-years old rocks, we're kind of guessing at what the formative conditions were,” Johnson said. “But here we know what the formative conditions were down to monthly scales or better.”

Lake Powell first started filling up in 1963, with the completion of the Glen Canyon Dam. Since 2000, water levels have been declining because of the megadrought in the region. In 2021, it reached a historic low level, and this year, it continues to drop.

Sediment accumulation has already led to a decrease in reservoir capacity — since 1963, it’s gone down almost 7%, according to a report released last month. Currently, the reservoir sits just under 24% or about 177 feet below full pool.

Understanding how sediment has moved into the landscape will help with future management of the area, according to report co-author Scott Hynek of the United States Geological Survey Utah Water Science Center.

“This is kind of one of the keys to managing this sediment in the Colorado river system now, because if we have permanently lower lake levels, all of this sediment is going to be moving out of the system and into new places,” he said.

Johnson said people managing the reservoir can’t just think of water, they need to think about sediment too, which has “largely been ignored as a piece of that really big, complex puzzle.”

She added it’s humbling to study how people have shaped the landscape in and around Lake Powell.

“There is a legacy of Lake Powell and the footprints left behind in our own decisions on this landscape, and you can see it,” she said.

Produced with assistance from the Public Media Journalists Association Editor Corps funded by the Corporation for Public Broadcasting, a private corporation funded by the American people.

Copyright 2022 KUER 90.1. To see more, visit KUER 90.1.

Lexi Peery
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