Roaring Fork River threatens to flood
The Roaring Fork River could possibly reach flood stage over the weekend, depending on the weather.
“We’re getting close,” said Valerie MacDonald, the Pitkin County emergency manager, at about 5:30 p.m. Friday. “It depends on temperatures, snowmelt and precipitation.”
MacDonald participated in an interagency conference call Friday afternoon that included a discussion with weather forecasters.
“They are expecting moisture through the weekend and for the rivers to rise,” MacDonald said.
Today’s forecast for Aspen from the National Weather Service showed temperatures in the mid-70s and a 40 percent chance of showers and thunderstorms.
A flood advisory issued by Pitkin County remains in effect for the Roaring Fork River near Aspen through Monday.
“Water levels along the Roaring Fork near Aspen will remain near bankfull through the next few days due to recent rainfall and snow melt,” a Friday evening update of the flood advisory said. “Minor flooding of low lying areas near the river is possible.”
The river was expected to keep rising until at least midnight tonight, when it is expected to reach 4.6 feet as measured on a gauge near Aspen. Flood stage is considered 5 feet on the same gauge, according to the county’s flood advisory.
Brenda Alcorn, a senior hydrologist with the Colorado River Basin Forecast Center in Salt Lake City, said future peaks on the river will likely be driven by precipitation levels.
“I don’t believe flows will go higher due to snowmelt alone, but there is a chance for additional precipitation the next couple of days,” Alcorn said. “If the Roaring Fork Basin gets additional thunderstorms, then flows could go higher again.”
Diversions off, on and off again
It’s been an unusual 10 days for the upper Roaring Fork River.
On the morning of June 3, the gauge on the Roaring Fork River at Difficult Campground at the bottom of Independence Pass showed the river tamely flowing at about 100 cubic feet per second.
At the same time, about 500 cfs of water was flowing through the Twin Lakes Reservoir and Canal Company Tunnel Number One, which runs from Grizzly Reservoir to the North Fork of Lake Creek on the other side of Independence Pass.
But because of concerns about flooding in the Arkansas River Basin on the east side of the Continental Divide, managers at Colorado Springs Utilities, which controls the Twin Lakes diversion tunnel, shut down the diversions the evening of June 3 to a base flow of 3 to 4 cfs.
By midnight June 5, the Difficult gauge was showing that 900 cfs was now rushing down the upper Roaring Fork because of a combination of the river not being diverted, rain and snowmelt runoff.
After a week of high water, the gauge at Difficult on Friday showed the river holding steady at 1,100 cfs.
The Devil’s Punchbowl was a swirling maelstrom, the Grottos was a rage of cascading water and the meadow at North Star was nearly covered in water for the first time since the 1990s.
Also on Friday, the Roaring Fork River below Maroon Creek was flowing at about 2,400 cfs, and at its confluence with the Colorado River in Glenwood Springs, the Roaring Fork was flowing at 6,000 cfs. The historic peak flow at this point is 11,800 cfs, which was recorded July 13, 1995.
After seeing Thursday that the Roaring Fork was heading toward flood levels, managers of the Twin Lakes diversion tunnel began diverting water again — about 200 cfs — in a cooperative effort to help “shave off the peak flow” in the upper Roaring Fork.
But after the Friday afternoon conference call, the Twin Lakes managers decided to shut the diversions back down again after only a day because of ongoing concerns about flooding on the east slope, especially as Twin Lakes Reservoir is 90 percent full.
“We’re hoping to cause the least amount of damage on either side,” said Kevin Lusk, a senior engineer with Colorado Springs Utilities. “But we’re pretty much out of options.”
MacDonald said Friday evening that only one report of property damage had come to the county so far, and that was for an old cabin that sits right on the Fork in the Stillwater section east of Aspen.
“Some of the older houses along the river flood when the river floods,” MacDonald said, noting that emergency responders would be on alert this weekend for flooding throughout the watershed. She also urged caution for boaters and anyone else taking part in recreational activities near the river this weekend.
Aspen Journalism is collaborating with The Aspen Times and the Glenwood Springs Post Independent on coverage of rivers and water. More at http://www.aspenjournalism.org.