Climate change could cut water flow in some of the American West’s biggest river basins – including the Rio Grande and the Colorado – by up to 20 per cent this century, the Interior Department reported April 25.
This steep drop in stream flow is projected for parts of the U.S. West that have seen marked increases in population and droughts over recent decades, Interior Secretary Ken Salazar said in a telephone briefing.
“These changes will directly affect the West’s water supplies, which are already stretched in meeting demands for drinking, irrigating crops, generating electricity and filling our lakes and aquifers for activities like fishing, boating and to power our economy,” he said.
A new Interior Department report outlines increased risks to water resources in the U.S. West for the 21st century, including:
A temperature increase of 2.77 to 3.88 C;
More precipitation where it’s already wet (northwestern and north-central parts of the American West) and less where it’s already too dry (southwestern and south-central parts);
A decrease in April 1 snow-pack, a standard benchmark measurement used to project river basin run-off;
An eight to 20 per cent decrease in average annual stream flow in several river basins, including the Colorado, the Rio Grande, and the San Joaquin.
“Climate change will add to the challenges we face, which will be felt first in the Western United States,” said Anne Castle, the Interior Department’s assistant secretary for science and water. She noted that some of the fastest population growth has occurred in the driest areas, including parts of Nevada, Arizona, Utah, Idaho and Texas.
Water managers in the U.S. West are already emphasizing water conservation and efficiency, Castle said, adding that they are increasingly focusing on “the energy-water nexus.”
“People are paying greater attention to the water demands of energy development and recognizing that conservation of energy can mean conservation of water as well,” she said.
Salazar said “alarm bells” about the West’s water supplies were sounding across the U.S. political spectrum, and that he himself felt the need for an “urgency of planning” to deal with the issue.
The full report and other related documents are available online at http://www.usbr.gov/climate/.