On the River: Summit rivers peaking | AspenTimes.com

On the River: Summit rivers peaking

Summit Daily News Staff

While some parts of the state are still concerned about river flooding, flows in Summit County have already peaked for the year or will have done so by this weekend, says Scott Hummer, the Silverthorne-based water watcher for the State Engineer’s office.

With most of the low- and mid-elevation snowpack already gone, Hummer doesn’t anticipate any serious flood danger locally, unless runoff combines with an unusually heavy rainstorm.

“Ten Mile Creek is carrying the best right now [596 cubic feet per second], no surprise, since it had the best snowpack,” Hummer said. That’s well above the 391 cfs historic mean flow on this date, based on 47 years of data.

By comparison, the Snake River reached a seasonal high flow of about 350 cfs on May 24. The Blue River just above Dillon Reservoir is flowing at about 350 cfs, compared to a historic mean of 270 cfs.

The weather in May has been exceptionally dry and warm so far, and a string of days with record high temperatures (in the mid-70s in Breckenridge) rapidly melted the snowpack, with eye-popping drops in moisture content, according to Hummer.

Monitoring the automated sites from his computer, Hummer said within the past week snowpack at the Copper Mountain site dropped from 102 percent down to 8 percent on Thursday. The water equivalent in the snowpack dropped from 4.5 inches May 23 to 0.8 inches as of Thursday. The Grizzly Peak site went from 67 percent to zero, while the snowpack at Hoosier Pass was halved, from about 100 percent down to 50 percent.

Earlier this week, flows into Dillon Reservoir reached a high for the season so far, with 1,163 cfs streaming into the impoundment from the Snake, Blue and Ten Mile drainages.