Colorado snowpack thin in south; Colorado River basin at 86 percent

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Brent Gardner-Smith/Aspen Journalism

A peak in the San Juan Mountain near Molas Pass on April 12, 2018.

ALAMOSA – The members of the Rio Grande Basin Roundtable got a disheartening report this week about this year’s snowpack and likely runoff in the Rio Grande River basin, as well as an update on a 30-year warming and drying trend.

“We’re going to have low stream flows,” Craig Cotten, the division engineer for the Colorado Division of Water Resources in the Rio Grande River basin, told the roundtable Tuesday at its monthly meeting in Alamosa, just a few blocks from the Rio Grande River. “I’m sure we’re going to dry up the Conejos [River] and maybe the Rio Grande, in some spots.”

To put the Rio Grande’s situation in context, Cotten shared snowpack data taken from snow telemetry, or SNOTEL sites, around Colorado, which measure the amount, and weight, of the snowpack at specific locations around the state.

The data from the federal Natural Resources Conservation Service on April 11 showed a decline in snowpack as one travels from north to south in Colorado.

The North Platte River basin, to the northeast of Steamboat Springs, was at 102 percent of the median level for that date.

The South Platte River basin, which includes Denver, was at 93 percent.

The Yampa and White river basins, north of I-70, were at 89 percent.

The Colorado River basin, which includes Glenwood Springs and Aspen, was at 86 percent.

The Gunnison River basin, further south, was at 60 percent.

The Rio Grande River basin was at 40 percent.

And the San Miguel, Dolores, Animas and San Juan river basin, in the southwest corner of the state, was at 39 percent.

The Rio Grande and San Juan river basins are fed by snow from the San Juan Mountains.

So while water managers and river users in the northern and eastern part of the state may have more water than their southern counterparts, it’s a bit like passengers in a lifeboat having more drinking water in their end of the boat than the passengers in the other end — it’s nothing to gloat about.

Center for Snow and Avalanche Studies

A graphic showing the snow water equivalent, or SWE, in Colorado’s snowpack from 1938 to 2018, taken from the average of 81 snow course measurement sites in the state on April 1. The graphic was prepared by Jeff Derry, executive director of the Center for Snow and Avalanche Studies in Silverton. The state is faring only slightly better, as of April 1, than in the very dry years of 1977 and 2002.

Of course

Also presenting to the Rio Grande Basin Roundtable on Tuesday was Jeff Derry, the executive director of the Center for Snow and Avalanche Studies in Silverton, which studies the “dust on snow” phenomenon and how it affects the state’s snowpack.

Derry focuses on information from “snow course” sites, in addition to SNOTEL sites, as the snow course sites measure the snow water equivalent, or moisture levels in the snow, across broader landscape areas and have often done so over longer periods of time than SNOTEL sites.

He showed the roundtable members graphs that indicate the snowpack in the southern part of the state, as of April 1, was tracking right at the same level as the very dry years of 1977 and 2002, while the whole of the state, on average, was tracking just above those drastically low years.

“This low snow season is hitting southern Colorado the hardest,” Derry wrote in an April 3 report on the Center’s website. “Water-year 2018 conditions are very similar to 1977 and 2002, and are slightly less than 1946, 1971, 1972, and 1999 snow water equivalent values.”

The website also shows a graph taking the average of 81 snow course sites across Colorado.

“Water year 2018 is comparable to 1966, 1981, 1999, 2004, (and) 2012,” Derry wrote. “We are faring just very slightly better than 1977 and 2002.”

Center for Snow and Avalanche Studies

A graphic showing the snow water equivalent, or SWE, in the snowpack of the San Juan Mountains from 1938 to 2018, as of April 1. The graphic was prepared by Jeff Derry, executive director of the Center for Snow and Avalanche Studies in Silverton. As of Apirl 1, the San Juan snowpack is tracking nearly exactly with the very dry years of 1977 and 2002.

Brent Gardner-Smith/Aspen Journalism

Peaks in the San Juan Mountains near Molas Pass on April 12, 2018.

Warmer, drier

Derry’s graphs also included long-term trend lines dating back 30 to 80 years, which clearly indicate Colorado’s snowpack has been shrinking and temperatures have been rising, especially on the colder end of the spectrum, meaning the lowest temperatures in winter are not as low as they used to be, especially over the last 30 years.

“It’s getting warmer and we’re seeing less precipitation in the wintertime,” Derry told the roundtable members.

And focusing on the runoff from the San Juan Mountains, Derry showed graphics that indicate that seasonal runoff, when snow turns to water and rushes downstream, is happening about a month earlier than it used to.

The peak snow water equivalent date used to be April 10, but now that benchmark is coming during the last week of March in the San Juan and Rio Grande basins.

“Snow is leaving the landscape earlier,” Derry said.

This year in the Rio Grande River basin looks especially stark in terms of snowpack, especially at lower elevations.

For example, Le Veta Pass, between Walsenburg and Alamosa at 9,426 feet, had the lowest April 1 snow water equivalent levels since 1960, Derry said.

Editor’s note: Aspen Journalism is covering rivers and water in collaboration with The Aspen Times, the Glenwood Springs Post Independent, the Vail Daily and the Summit Daily News. The Times published a version of this story on April 12, 2018, as did the Glenwood Springs Post Independent and the Summit Daily News.

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