Early peak runoff for Western Slope rivers
Dust on snow played a role
Rivers in western Colorado have already peaked for the season, creating challenging conditions for reservoir managers and rafting companies.
Fueled by spring windstorms that deposited snow-devouring dust on the mountain snowpack, most streams saw their peak flows between May 19 and 21 for this year, according to data from the Colorado Basin River Forecast Center.
On May 19, the Crystal River near Avalanche Creek hit its high mark for the spring at about 1,870 cubic feet per second. On that day in the southwest part of the state, the San Miguel River at Placerville peaked at 823 cfs; and the Yampa River in Steamboat Springs hit its high mark of 2,915 cfs.
On May 20, the Roaring Fork River just above its confluence with the Colorado River in Glenwood Springs peaked at 4,450 cfs; the Eagle River at Dotsero peaked at about 4,950 cfs.
On May 21, just upstream of major agriculture diversions to the Grand Valley at a location known as Cameo, the Colorado River peaked at about 10,730 cfs. At the Utah state line, streamflows peaked at 16,130 cfs.
The peak streamflow volumes for these locations were within the range of what’s considered normal.
Although there may be a second, smaller peak in coming days as summer temperatures return, forecasters say most of the snow below 11,000 feet has already melted out, meaning not enough is left to fuel a bigger peak than the one that has already happened.
For several locations — the Roaring Fork at Glenwood, the Crystal, the San Miguel and the Colorado at Cameo — the peak came so early that it was outside the window of what’s considered normal. The rest of the locations — the Yampa, the Eagle and the Colorado at the Utah state line — were inside the normal range, although on the earlier side.
These conditions can be partly attributed to dust on snow, which causes the snowpack to melt earlier and faster.
“Dust on snow has played a pretty big role this year,” said Cody Moser, a senior hydrologist with the CBRFC. “It really allows the energy from the sun to get absorbed into the snowpack much more than if you have this white, clean snow surface.”
According to Jeff Derry, executive director of the Silverton-based Center for Snow and Avalanche Studies, a total of 11 dust events occurred in April and May. A total of six or seven occur during a normal year.
This spring has been unusually windy, which has kicked up dust from northern New Mexico and Arizona and deposited it on Colorado’s snow-capped peaks; the San Juan Mountains, in the southwestern part of the state, were the hardest hit. Each year, the center ranks the severity of the dust storms.
“A number of those were really nasty events,” Derry said. “This is the first time since 2013 that we have said it’s a severe dust year.”
Early runoff brings challenges
The early runoff is a challenge for Blazing Adventures, a rafting company based in Aspen and Snowmass that runs trips on the Roaring Fork River. According to owner Vince Nichols, they usually try to run the Roaring Fork through the Fourth of July before heading to other sections of the Arkansas and Colorado rivers that see higher flows later in the summer. This year, it will be closer to mid-June, he said.
“It’s certainly been a strange runoff this year,” Nichols said. “We came out of the ski season with some optimism, but when we mixed in those high winds and dust, it ran off a lot faster than we were anticipating.”
The early runoff could also have implications for reservoir managers, who may have to begin releasing water earlier in the summer to meet downstream calls. A call happens when a senior water right is not receiving its full amount of water and junior upstream water users must cut back in order to send water to the senior user downstream.
This may end up being the situation with Green Mountain Reservoir, which is on the Blue River, is operated by the U.S. Bureau of Reclamation and is affected by the call from the Shoshone hydropower plant in Glenwood Canyon. The call comes on most years in midsummer, but this year, it may be earlier.
“I may have to start making storage releases earlier,” said Victor Lee, an engineer with the Bureau of Reclamation. “That’s pretty typical of dry years, but with this early runoff, the call might come much earlier than what I expected.”
The same may happen at Ruedi Reservoir, on the Fryingpan River. Ruedi is also operated by the Bureau of Reclamation and is affected by the call at Cameo, which comes on most summers.
Although Ruedi had been forecast to fill by the skin of its teeth this year, Bureau of Reclamation hydrologist Tim Miller said he now thinks it will end up 1,000 to 6,000 acre-feet short. He said he will continue releasing the minimum required flow of 110 cfs until downstream calls come on and he has to release more stored water.
“I always like to point out that our snowpack is a natural reservoir and if that reservoir releases its water earlier than what’s normal, you can kind of imagine the disruptions and problems that occur,” Derry said. “It makes reservoir management a little bit more complicated if you have the water coming down earlier than what you expected.”
Aspen Journalism covers water and rivers in collaboration with the Vail Daily and other Swift newspapers. For more, go to AspenJournalism.org.