Climate change could wreak havoc on local rivers in Colorado

Aspen Daily News: Global warming could mean both more droughts and more flooding to the Roaring Fork and other Western rivers, and in just decades it could bring dramatic consequences to local farmers, anglers and fish, a University of Colorado climate researcher said.

….Strzepek discussed the predictions at the Given Institute on Thursday in a presentation organized by the Roaring Fork Conservancy. He dubbed the presentation a “sequel” to one he delivered in Aspen 15 years earlier. Since then, he said, scientists’ models on the impact on the world’s water systems have improved greatly.

Arid climates are expected to become even drier, Strzepek said, and areas that flood may see worse flooding, sometimes with devastating consequences, particularly in the developing world. “The poor will suffer the most, who have the least capability of adapting and dealing with that,” he said.

…Similar heavy flooding is likely for the Roaring Fork, he said, and bridges aren’t built to handle it. It’s not clear how warming temperatures will affect Colorado precipitation, Strzepek said. The Southwestern United States is expected to become drier, meaning more demands on the Colorado River. But northern states could see more precipitation, and Colorado is caught in the middle. But models show snowmelt coming sooner, runoff peaking earlier and river levels dropping faster.

That’s bad for trout, which could see dangerously low water levels and temperatures reaching fatal levels, Strzepek said. It’s also bad for rafting companies that could see shorter seasons, and for ranchers who will likely need more irrigation water. By 2070, he said, runoff could peak a month early, putting water levels out of synch with growing seasons. That could leave even some senior water rights holders out of luck if their rights are timed, he said.

Low water levels could also affect ski areas’ ability to use water for snowmaking, he said. Prior to his presentation, Strzepek said, he went on a Roaring Fork “field trip,” catching an 18-inch trout in its famous waters, but he worried about the impact on river habitat under global warming. “What I want to be able to do is have my grandkids catch a fish like that,” he said.