Report: Warming will shrink Colorado water supply |

Report: Warming will shrink Colorado water supply

Jerd Smith
Rocky Mountain News
Vail, CO Colorado

Colorado will likely heat up 2.5 to 4 degrees over the next 40 years, causing stream flows to shrink as spring and summer get hotter, according to a new study commissioned by the Colorado Water Conservation Board.

“There have been a lot of reports out there, (but) this one really focuses on Colorado,” said Jennifer Gimbel, director of the water conservation board.

Among the report’s findings:

– Summers will become extremely hot, registering as warm or warmer than the hottest 10 percent of summers between 1950 and 1999.

– Little change in annual precipitation will occur, but temperature increases alone are expected to have a significant impact on snow and water supplies.

– Stream flows in the Colorado River Basin will shrink from 5 percent to 20 percent, exacerbating water shortages already forecast because of population growth.

– Spring runoff will arrive earlier, altering the times when farmers and utilities can expect their water to arrive.

– Summer water demand by homeowners will rise due to temperature increases.

– Despite warmer winters, temperatures above 8,000 feet will remain well below freezing, helping preserve snowpack and mountain environments.

The report was compiled by the University of Colorado Western Water Assessment, a partnership between the university, the National Oceanic and Atmospheric Administration, the CU Cooperative Institute for Research into Environmental Sciences and the Colorado Climate Center at Colorado State University.

It comes as state officials prepare for a major drought conference Wednesday, a three-day meeting in Denver designed to help water utilities and policy officials explore ways the state can adapt to its warming climate.

Though it’s not clear how much less water the state’s streams will generate, state officials say water utilities must craft drought plans to cope with water supplies that will be less predictable and, often, less abundant.

“We’re recommending all suppliers have them,” Gimbel said.

Brad Udall, who directs the Western Water Assessment, says the report has important implications for how Colorado manages its remaining water supplies ” primarily those in the Colorado River that aren’t legally owed to other states, such as Nevada, Arizona and California.

“We need to be very careful about how we use our remaining Colorado River allocation,” Udall said. “That water is a moving target under climate change. We don’t know how much of it there is or how consistently we can expect it to be there.”

As a result, he said, Colorado needs to ensure it can keep enough water in the bank ” Lake Powell ” to ensure it can meet its obligations to downstream states while protecting Colorado’s portion.

Whether that means Colorado needs to build a major new reservoir here at home isn’t clear yet, Udall said.

“If flows decline, the storage we have may work more effectively and we won’t need more. Or you could make the case that we need to build storage in order to store more water,” he said.

Though water planners are concerned about climate change, there was some good news in the report. Colorado’s high country, because of its elevation, will still have very cold winters, a fact that will help high alpine landscapes retain their beauty.

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