Average peak runoff forecast for Aspen’s Roaring Fork River
May 19, 2017
Winter's last gasp this week temporarily replenished a snowpack that was disappearing fast and increased chances for higher streamflows further into the summer, according to experts.
The storm that blew in Wednesday night dumped 8 inches of snow at the top of Aspen Mountain and was forecast to deposit well over a foot of wet snow at higher elevations before it rolls out sometime today.
"We're basically putting the pause button on snowmelt," Liza Mitchell, education and outreach coordinator for the Roaring Fork Conservancy, said Thursday.
She noted the snowpack at the headwaters of the Roaring Fork River had lost slightly more than 50 percent of its snow-water equivalent — the amount of water when the snow is melted — in the prior week.
“Based on all the indicators I use, we’re looking at a normal year
— and that’s great.”
— Jim Ingram, Aspen Whitewater Rafting
There is a "hard line at 10,000 feet" in elevation, Mitchell noted. Below that point, the snowpack generally has melted out because of warm spring temperatures and sunny days. But above that point, the snowpack is above average at many places, such as Schofield Pass at the head of the Crystal River and Ivanhoe at the head of the Fryingpan River.
"There's still a lot of snow up there," Mitchell said.
The Colorado Basin River Forecast Center forecasted in its May 1 report that the Roaring Fork River will experience average runoff this year. A peak flow of about 5,700 cubic feet per second is expected on the river's gauge at Glenwood Springs. The average peak is 5,920. Last year, the Roaring Fork peaked at 6,200 cfs in Glenwood Springs on June 12, according to the river forecast center.
Whitewater enthusiasts are pleased by what they see.
"Based on all the indicators I use, we're looking at a normal year," said Jim Ingram, owner of Aspen Whitewater Rafting, "and that's great."
He said long-range forecasts are not showing temperatures rising to the 80-degree range prior to Memorial Day, so that means a slow, steady melting of the upper snowpack. Cloudy skies and cooler temperatures before Wednesday night's storm already were having an impact on streamflows.
"You can see it on the Fork," Ingram said Wednesday. "It's dropped down the last couple of days."
A slower rate of snowmelt means the Upper Roaring Fork could be run through the Fourth of July, he said. That's important because the rafting season ramps up starting in mid-June. Customers already are responding to what appears to be a solid whitewater season.
"Our reservations are way up," Ingram said.
The river forecast center can predict the water volume, but they cannot predict the timing of peak runoff. The center said the Roaring Fork normally peaks between May 29 and June 23.
"Runoff is not simple because it's all temperature driven," said Eric Kuhn, general manager of the Colorado River District in Glenwood Springs. The organization advocates for Western Slope water causes.
Western Slope rivers and streams usually have a number of different peaks, depending on how weather warms up and cools down, he said.
The snowpack from Steamboat Springs to Aspen was about average this year, so that's fueling forecasts of average runoff, Kuhn said. This will be the fourth consecutive year of "decent" runoff, so reservoir storage won't be an issue, he said.
Reservoirs such as Ruedi, 13 miles east of Basalt, are expected to fill with no problem. The outlook also is favorable for rafters, kayakers and paddle boarders.
"For recreation, I think it's going to be a good year," Kuhn said.
Ingram said the peak on the Upper Roaring Fork typically occurs during the first week of June. Old-timers taught him that peak runoff hits when the snow melts off the top of Bell Mountain.
"But that's just an old kayakers' tale," he said.