State of the rivers: Expect full reservoirs and high flows
For the first time in nearly 20 years, all of Colorado is officially free of drought conditions thanks to heavy snowpack and late spring precipitation.
The upper Colorado River basin is at 128 percent of average snowpack for the year, and statewide watersheds are at 134 percent of average for the year, according to federal snowpack analysis from June 1.
“What a difference a year makes,” Zane Kessler of the Colorado River District said at the State of the Rivers meeting in Carbondale Thursday, comparing current snowpack averages to last year.
But as Kessler pointed out, 134 percent of average is only 34 percent better than average, and one good year doesn’t change the rising temperatures or the facts of living in the west, or the southwestern states that rely on Colorado River water are using more and more water.
The high snowpack will translate to fuller rivers and reservoirs, but it won’t solve the larger issues of what happens during the next low-precipitation year.
“One thing we noticed this year … is that our soil moisture was horribly low. So a lot of the moisture that came in the early part of this season, went to restoring those soils, and a lot of the water was sucked up,” Kessler said.
More water is being used up as temperatures rise, and both natural forests and agriculture lands have longer growing seasons.
This year, however, the biggest reservoirs in the region “are all expected to fill,” Alan Martellaro, division engineer with the Department of Water Resources, said at the meeting Thursday.
With the exception of Grandby Reservoir, “the rest are expected to fill and spill. Hopefully, not spill,” Martellaro said.
As the weather warms and more snow melts, there is a risk of flooding on the Crystal River near Carbondale and near the Fryingpan River in Basalt.
The Crystal River “definitely will be above-bank full” at the peak flow for the year, which will likely be weeks later than usual, Martellaro said.
The usual peak occurs by June 7, but this year it will likely be between June 12 and 25, Martellaro said. The peak is also projected to last for weeks instead of days.
While snowpack is well above last year’s average and historical averages, river flows for many rivers only exceeded historical averages this week. The Colorado River just below Glenwood Springs reached 12,700 cubic feet per second Friday, above the historic median peak of 11,200 cfs, according to the USGS.
Lewin pointed to 1995 floods that reached some houses along the river, and noted that a lot of development has occurred since then, and there is a risk of the flooding reaching homes and other buildings.
Another likely flooding area is on the Roaring Fork River just after the confluence with the Fryingpan in Basalt, Lewin said. The park was designed in part to allow the river to overflow there, she said.
Another area of concern, more so during the monsoon season than runoff, is flooding caused by debris buildup from the Lake Christine fire and avalanches.
A dry fall and early foliage growth in the fire’s burn scar may mitigate some of the initial flooding risk during runoff season, Lewin said.
“In a drainage that runs as a tiny trickle, you can get some floes because of the same thing that happens in ice flows,” Lewin said. The flooding risk is magnitudes higher due to the debris, she said.
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