Lake Powell. Photo: Wolfgang Staudt / Wikimedia

By Brittany Patterson
27 October 2017

GLEN CANYON NATIONAL RECREATION AREA, Utah (Scientific American) – Like many places across the West, Lake Powell seems impossibly large, mythical almost, with its rich red rock canyon walls standing in dramatic juxtaposition to the expanse of cerulean below that seems to stretch on forever.

Dramatic is an apt way to describe the second-largest man-made reservoir in America.

When it was formed in 1963, following the construction of Glen Canyon Dam in northern Arizona, Lake Powell was designed to hold a massive quantity of water—26,215,000 acre-feet—that flows down mostly in the form of melted snowpack from the Upper Colorado River Basin states of Colorado, Utah, Wyoming and New Mexico. One acre-foot is enough water to serve a family of four for a year.

White calcium carbonate deposits, which form a striking bathtublike ring along the canyon walls, show the lake's steep drop in water levels over the last decade and a half due to a combination of overuse and the worst 16-year drought in over a century.

Now, a controversial proposal—to allow Lake Powell to become a "dead pool," meaning there is no longer enough water to generate hydropower at the nearby 710-foot-tall Glen Canyon Dam—is no longer dismissed as unthinkable. Under that plan, Powell's sister, Lake Mead, would serve as the main reservoir. […]

Between the drought years of 2000-2005, Lake Powell lost 13 million acre-feet of water and dropped almost 100 feet, about one-fifth of its maximum depth. A repeat dry spell could decimate what remains. […]

Over the last 10 years, the Colorado River has put out approximately 15.34 million acre-feet on average. The imbalance between what the river actual provides and what's outlined in the compact is often referred to as a "structural deficit." Experts believe the shortfall ranges between 1.5 million and 2.5 million acre-feet.

"There's not enough water in the river," said Daniel McCool, a political science professor at the University of Utah. "What may have worked as a solution in 1922 is now a really bad way of looking at river basins." […]

A study published this year by Bradley Udall, senior water and climate research scientist with the Colorado Water Institute at Colorado State University, and Jonathan Overpeck, professor of hydrology and atmospheric sciences at the University of Arizona, found that during the drought years of 2000-2014, the river surrendered a third of its flow because of higher temperatures in the upper basin. They were 0.9 degree Celsius above the 1906-1999 average. […]

Lake Powell almost fulfilled the worst fears of water managers this year.

"If we had not had a really wet snow year this year, we'd be approaching the point where Lake Powell dropped below hydropower levels," McCool said. "One really fat year delayed the inevitable." [more]

Should Iconic Lake Powell Be Drained?

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