DENVER (AP) — Snowpack in the mountains and valleys where the Colorado River originates has been shrinking since the beginning of March, a federal water expert said Tuesday.
The snow ranged between 89 and 91 percent of the long-term average, depending on which measurement is used.
The Colorado River is under especially close scrutiny because it helps supply California, which is in the midst of a historic drought. The most recent assessment available showed 40 percent of California was in an exceptional drought, the driest of five categories used by the federal government’s U.S. Drought Monitor. Nearly 28 percent was in an extreme drought, the second-driest category.
“We dried out relatively significantly here since the beginning of March,” said Brian Domonkos, supervisor of the Colorado Snow Survey for the U.S. Agriculture Department.
Figures for the early March snow levels weren’t immediately available.
Domonkos told the state task force on water availability that recent warm weather had begun to melt the snow at lower elevations in parts of the Colorado River basin.
Colorado’s snowpack is closely watched because it provides water for four major river systems that originate in the state: the Platte, the Arkansas and the Rio Grande as well as the Colorado.
In addition to the Colorado River basin, three other river basins in the western part of the state feed into the Colorado River downstream. In those basins, the snowpack was 72 to 79 percent of average Tuesday.
East of the Continental Divide, snowpack in the basin that feeds the South Platte was average, while the North Platte River basin was at 85 percent. The North Platte flows north into Wyoming before turning east into Nebraska, where it joins the South Platte to form the Platte River.
The Arkansas River basin had 96 percent of average snowpack, and the Upper Rio Grande basin had 77 percent.
Early indications are that the risk of flooding in Colorado will be lower this year than last but still higher than average, said Klaus Wolter, a climate scientist with the Cooperative Institute for Research in Environmental Sciences in Boulder.
Wolter said little dust appears to have accumulated on Colorado’s snow this year. Because of its darker color, dust can absorb more heat than snow and hasten melting and the spring runoff.
Rain or extended warm spells in springtime can speed up the runoff and trigger floods by putting more snowmelt into Colorado’s rivers and streams than they can handle.