Runoff could be dud for the Fork
The spring runoff in the Roaring Fork River between April and July is expected to be the fourth or fifth lowest level since 1938, according to federal officials monitoring the stream flows.
The total stream flow is forecast to be about 57 percent of normal for the entire runoff season, according to Tom Pagano, water supply forecaster with the Natural Resources Conservation Service.
Stream flow in the Roaring Fork basin has been 84 percent of normal during April and May. But it is expected to drop to only 50 percent of normal during June and July, Pagano said.
The only silver lining is conditions aren’t nearly as dry as spring 2002 or 1977, when only about a quarter of the normal runoff water flowed through the river, he said.
Gauging stations maintained by the U.S. Geologic Survey show that the Roaring Fork River slipped well below the median daily stream flow starting May 23. A measuring station just east of Aspen showed there was a surge of higher-than-average flow from May 6 through May 14. Stream flows were also higher than average on May 20-22 before falling drastically.
By yesterday the flow had dropped to 132 cubic feet per second at a time when it should have hovered around 300 cfs, according to USGS data.
The water flowing into Ruedi Reservoir from the upper Fryingpan River is also significantly lower than usual. It was at 109 cfs compared to a mean level on that date of about 340 cfs.
A gauging station on the Crystal River near Avalanche Creek is considered one of the truest measurements in the basin because the river isn’t diverted above that point. The 48-year mean for June 1 was about 1,100 cfs. Yesterday the flow was about half that amount.
People waiting for peak runoff might have already missed it. May 20-21 could have set the high water marks for the season. There is going to be another surge next week when temperatures throughout the Colorado Basin climb as much as 15 degrees higher than average, according to Pagano. That will make the rivers rise and fall again, but it is “unlikely” the flows will creep higher than last month, he said.
But Pagano noted that forecasting stream flows is an inexact science. Most of the computerized snow measuring stations maintained by the conservation service are below 10,500 feet. About 40 percent of the snow is typically above 10,000 feet. So the unknown, Pagano said, is how much snow remains above that level.
“You’re actually asking a pretty tough question” about the peak, Pagano said. “That’s a topic of hot debate – whether things have peaked or not.”
Peak and total runoffs are difficult to gauge this year because the weather was so strange, he added. Temperatures were way above average in most parts of Colorado in March. Storms in early April restored some of the snowpack but the Roaring Fork Valley didn’t benefit as much as other parts of the state, according to the conservation service’s Web site.
Alan Martellaro, Colorado Division of Water Resources engineer for the Colorado River basin, said he believes there is still a decent snowpack up high. He said he drove over Independence Pass during Memorial Day weekend and saw a lot of snow still on the higher peaks.
It’s possible that 80-degree daytime highs combined with nighttime low temperatures above freezing could produce peak runoff in the Roaring Fork River, he said.
Pagano didn’t rule out that the peak is yet to come. If it happens, it will probably happen within the next week or so, he said.
Scott Condon’s e-mail address is email@example.com
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