Spring runoff to be fast and furious
The Aspen Times
Aspen, CO Colorado
ALL |
CARBONDALE ” The Crystal River inched toward flood level near Redstone Monday in a spring runoff season that scientists say is being altered by layers of grime.
Colorado’s rivers and streams could reach their peak runoff 20 to 30 days earlier than average this year because of the dust that coated the mountains, according to Andy Barrett, a hydrologist with the National Snow and Ice Data Center in Boulder. The dirt was deposited in 12 dust storms between mid-December and early April.
“This year appears to be a very heavy dust year,” he said.
Three of the storms that blew in from the Colorado Plateau farther to the west were particularly intense, according to Chris Landry, director of the Center for Snow and Avalanche Studies in Silverton. Landry, a former resident of the Crystal River Valley, began studying the dust’s impacts on the snowpack with Tom Painter of the University of Utah in the winter of 2003-04. They found that a particularly intense dust storm in February 2006 accelerated the melting of the snowpack by about 30 days that spring. The three dust storms that hit March 22, March 29 and April 3 this season equaled the 2006 event in intensity.
Snow typically reflects 90 to 100 percent of the sunlight. That high level of reflectiveness is known as the “albedo effect,” Landry said. When a high level of dirt mixes with the snowpack, only about 50 percent of the sunlight is reflected. When more of the sun is absorbed, the snowpack melts faster.
Landry said as the air temperature warms, it melts upper snow layers off high peaks, exposing dust layers underneath. Once that dirt is exposed, the melting accelerates. That process has been evident on Mount Sopris and other peaks surrounding the Roaring Fork Valley in recent days. The snow on Sopris looked clean from slightly above tree line to the summit last week. As temperatures warmed last weekend, Sopris got grungy. The pure white snow is now stained brown up to the summit.
Tom Turnbull, who has ranched at the base of Mount Sopris for 40 years, said he has seen dust on the mountains before but probably never to the current degree. And the uniformity of the dust sticks out this season, he said.
Landry said the dust layers laid by the different storms are consolidating as the snow melts.
“That dirt layer stays at the surface. It doesn’t wash away with the snowmelt,” he said. “It just keeps churning its way downward.”
Landry worked at nine monitoring stations from Rabbit Ears Pass in the north, McClure Pass in the central mountains and Red Mountain Pass in the southwest. Whenever he squeezed a handful of the snow-dirt mix, muddy water would drain out.
“It’s hideous skiing,” Landry said.
Backcountry skiers in the Aspen area have found decent conditions as long as they are descending early in the day, according to Aspenite Al Beyer. Later in the afternoon, it’s like skiing “chocolate milk,” he said.
Barrett said computer models of conditions similar to this year indicate peak runoff in Colorado’s rivers and streams will come 20 to 30 days earlier than average. Peak runoff in the Roaring Fork Valley is typically in the third week of June, but the Crystal and Roaring Fork rivers were flowing much higher than usual Monday for May 18.
The Crystal River near Redstone was flowing at 1,580 cubic feet per second, according to a gauging station maintained by the U.S. Geological Survey. The median flow for that date is 809 cfs, and the previous peak for that date in the past 53 years was 1,450 cfs in 1966. The National Weather Service on Monday issued a flood advisory for low-lying areas of the Crystal River upstream from Redstone. The advisory will continue until Thursday afternoon. No problems from flooding were reported to the Pitkin County Sheriff’s Office on Monday.
The Roaring Fork River also is flowing well above average. The river near Emma was at 2,400 cfs Monday afternoon. It’s median for May 18 is 842 cfs. Its prior high flow was 1,320 cfs in 2007.
Mike Gillespie, snow survey supervisor for the U.S. Department of Agriculture’s Natural Resources Conservation Service, said the impact of the dust will be a condensed runoff season. High flows will come earlier, and the duration of high water will be shorter.
That also means that flows will recede sooner this summer in rivers and streams.
“That’s good news if you’re a fly fisherman and you want to get out there sooner,” Gillespie said. It’s not such great news for the rafting industry or water users.
River conditions usually experienced in July might appear in June, Gillespie said. That could mean less water will be available for irrigation systems tied to rivers and streams. Landry said water for crops will be plentiful before farmers need it in large amounts. Less water might be available in July when farmers depend on it.
The result is a mixed bag for managers of reservoirs. “We’re not looking at the quantity decreasing that much from this dust scenario,” Gillespie said. The same amount of water will flow into the reservoirs; it will just come sooner.
Landry said that could produce challenges for water managers. They will have a shorter time to prepare reservoirs for inflow.
Warm temperatures and the dust have combined to consume the Roaring Fork River basin’s snowpack. It was at just 43 percent of average Monday afternoon.
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