Climate change reducing Colorado River runoff

As climate warming shrinks the Colorado River Basin’s snowpack, runoff into the river will decrease by 9.5% per 1 degree C (Patrick Cone, National Parks Traveler)

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By mid-century, annual runoff into the Colorado River could be reduced by nearly a third as declining snowpack leads to greater evaporation of snowmelt, according to a new U.S. Geological Survey study.

That’s because as snowpack in the 100,000-square-mile river basin shrinks, it increasingly loses the ability to reflect solar radiation back into space, said Christopher Milly.

“We estimated that the warming effect alone (ignoring changes in precipitation) would, by the year 2050, reduce the flow by something in the range 14-31 percent, relative to historical 1913-2017 flows,” said Milly, who works in USGS’s Integrated Modeling and Prediction Division. “The loss would tend toward the higher end of this range for higher levels of greenhouse gases and toward the lower end for lower levels.”

The National Park Service is doing what it can but control is out of their hands. Rob Billerbeck is the NPS Colorado River Coordinator, and says their job is to “prevent unacceptable impacts to natural and cultural resources, and maintain natural processes. It’s really tough to answer questions of ecosystem health, and the condition of the park resources.”

But it now seems certain that there will be major deficits in Colorado River flows in the future, with unintended consequences to downstream users, hydroelectric power, recreation, fish, wildlife, water quality, flood control and all water-dependent ecological systems along the entire river. It all depends on whether the weather and the climate continue to change as predicted. And that’s a problem for everyone.

This series on the health of the Colorado River and its impacts on Canyonlands and Glen Canyon has been supported by a grant from The Water Desk, an independent journalism initiative based at the University of Colorado Boulder’s Center for Environmental Journalism.

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