Climate change has reduced Colorado River's flow by 1/5, and federal researchers say the trend is likely to continue

U.S. Bureau of Reclamation map; for a larger version, click on it.

The flow of the Colorado River, which is essential to life in the desert Southwest, has declined more than 20 percent because a warming climate is making snowpack evaporate instead of run off, U.S. Geological Survey senior resource scientist Chris Milly and physical scientist Krista A. Dunne have concluded. And they say the phenomenon is likely to accelerate.

"Less snow means less heat is reflected from the sun, creating a feedback loop known as the albedo effect, they say," reports Juliet Eilperin of The Washington Post. "The new findings are significant because about 40 million Americans living across the West depend on water from the Colorado River, which supports $1 trillion in economic activity each year. The water is shipped as far away as California’s Imperial Valley and central Arizona, where farmers use it to irrigate crops, as well as across the Rockies to supply drinking water for Colorado’s biggest cities."

Eliperin writes, "The region is poised to warm even more in the years ahead, Milly said, and it isn’t 'likely' that precipitation can compensate for these hotter and drier conditions," Comparing the Colorado River’s historic flow between 1913 and 2017 to future conditions, he added: 'That flow, we estimate, due to the warming alone would be reduced anywhere from 14 to 31 percent by 2050.' Colorado State University senior scientist Brad Udall, who has written two papers attributing half of the Colorado River’s lower flows to warming temperatures, said in a phone interview that researchers now 'have multiple lines of evidence pointing to a very similar number.' . . . Udall said of the new study, 'I would say eye-popping.'"