Summit runoff starting to peak
Summit County, CO Colorado
SUMMIT COUNTY, Colorado ” A dirty snowpack and warmer-than-average temperatures could be speeding runoff from the local mountains, said water commissioner Scott Hummer.
“I’m already seeing more irrigation ditches running that I usually do in mid-May,” Hummer said.
Local streamflow gauges are reading higher than average for this time of year.
“We’re seeing way above-average flows,” Hummer said.
Just upstream of Dillon Reservoir, the Blue River was flowing at 407 cubic feet per second recently, compared to the 51-year median average of 182 cfs. A gauge on Ten Mile Creek was reading 556 cfs Wednesday morning, compared to the historic average of 299 cfs for the date.
Boulder-based researchers believe some Colorado rivers and streams could see peak runoff 20 to 30 days earlier this year because of the significant amounts of dust in the snow.
Instead of reflecting nearly all the sunlight, the dirty snow absorbs heat and speeds runoff. But temperatures could also be a factor, according to Hummer, who said that local readings climbed above average during the past few days, with a high of around 80 degrees in Dillon on Tuesday.
The dust research only goes back a few years, so it may be hard for researchers to pinpoint exactly how much of the earlier snowmelt can be attributed to the dirty snow.
Snow scientists said a series of storms between December and April may have brought an unusually high concentration of dust to Colorado.
Hummer said the dust is visible locally as discolored snow.
Earlier runoff could mean changes for local ranchers as they plan irrigation for hay crops. There might not be as much water available for diversion later in the summer if the winter’s snowpack melts a month earlier, he said.
Despite only recent research on dust and snowmelt, the effects of the discolored snow are fairly obvious. As the snow starts to melt, the dust layers become more concentrated. As the snow gets darker, the melting accelerates, feeding a self-perpetuating cycle.
Denver Water recently announced it will start to release more water from Dillon Reservoir as it anticipates peak runoff.
Flows below the dam in the Lower Blue reached about 500 cfs Wednesday, according to a press release from Denver Water.
The Aspen Times contributed to this report.
Bob Berwyn can be reached at (970) 331-5996, or at firstname.lastname@example.org.