Research Warns of Coming Water Shortages in the Colorado River Basin

The 40 million people who rely on Colorado River water need to prepare for a drier future.

Global warming is shrinking the Rocky Mountain snowpack that feeds the river and flows are declining at a rate of about 9.3 percent for every 1.8 degrees Fahrenheit increase in temperature, according to a new study that "identifies a growing potential for severe water shortages in this major basin."

The decline is "mainly driven by snow loss and consequent decrease of reflection of solar radiation," a pair of scientists with the U.S. Geological Survey wrote in a new paper published Thursday in the journal Science. The study helps resolve a "longstanding disagreement in previous estimates of the river's sensitivity to rising temperatures."

The study links dwindling flow of water with the loss of albedo, a measure of the snowpack's reflective quality. Like ice in the Arctic, white snow reflects solar radiation back to space. But as the snowpack in the Colorado River declines, the ground and, crucially, the air directly above the ground, warm up. Water from the melting snow or from rain evaporates from the soil, rather than trickling into the streams that feed the Colorado River.

The scientists found the link by measuring the relationship between the amount of water in the snow, the amount of the sun's incoming radiation and how much of that was reflected back by the snowpack's albedo, showing that, as the snowpack dwindled, the river's flow declined.

Brad Udall, a climate scientist with the Colorado River Research Group,  said the study "adds another brick in the wall of evidence that it's very likely we're going to see significant declines in Colorado River flows.