Snow surveys key to water supply, runoff info accuracy
Citizen Telegram Editor
SILT – This year’s busy pattern of winter snow storms haven’t necessarily meant Derrick Wyle has been busier than recent years, but he’s pleased to see all the snow nonetheless.
Wyle, a soil conservationist for the Natural Resources Conservation Service office in Glenwood Springs, is one of two snow surveyors in that office. For the first five months of each year, he and his colleague spend a few days at the end of those months taking snowpack readings for the Colorado and Roaring Fork River basins.
Wyle explained his work and what the information he helps gather is used for to around 20 people earlier this month at the Bureau of Land Management’s Colorado River Valley Field Office in Silt. The event was sponsored by the Middle Colorado River Watershed Council. The nonprofit group works to educate people on water quality and other issues along the 84 miles of Colorado River from Glenwood Canyon to DeBeque.
Manual surveys are taken at three sites once a month from January through May: McKenzie Gulch, near Sylvan Lake; Nast Lake, above Ruedi Reservoir; and Shrine Pass, near Vail, Wyle said. At the end of January, those sites had snow depths of 50 to 60 inches, compared to depths in the 20-inch range in recent years.
“So we’re definitely looking better this year,” Wyle added.
Snow surveyors use aluminum snow tubes with steel cutting teeth on one end to break through ice and reach soil, which is important to determine true snow depth, Wyle said. The snow tubes are then weighed on a spring scale, the tube is emptied and weighed again to get the snow water equivalent, Wyle added. For instance, 30 inches of snow might have ten inches of water, he said.
“Accuracy is the key,” Wyle noted. “Small errors in one measurement lead to large errors in snow water forecasts, so we really strive for accuracy and consistency.”
At each manual survey site, ten samples are taken to help ensure accurate readings, he said.
Snowpack forecasting uses historic information and 30-year averages that change each decade, Wyle said. Streamflow forecasting for spring runoff is updated monthly and information gathered from surveys is used to help forecast avalanche danger, he added.
automated sites used frequently
Hundreds of automated Snotel, or snow telemetry, readings from many other locations in the basins are also taken to develop snow depth, water supply forecasts and climate information, Wyle said.
The Snotel system bounces radio signals from each site off the earth’s ionosphere and meteorites the size of sand grains, Wyle explained.
“So there’s no big satellite up there,” he noted.
Each Snotel site requires maintenance about every two years, with trees falling on the equipment or rodents chewing through cables, Wyle said. Solar panels and battery packs supply power to the transmitters, with a “big bladder” filled with a glycol substance that resists freezing providing weight and depth information, he added.
While the Snotel sites get updated information for officials much more frequently, manual surveys take more time, are more labor intensive, have data quality issues if mistakes are made in taking measurements and can be hazardous due to their remote, high elevation locations, Wyle said. However, none are located in avalanche zones, he added.
Snow surveyors undergo training every three to five years, Wyle said, including snow survival training with snow shelters. Each surveyor carries survival backpacks while doing surveys, he added.
“We don’t run into the need to camp out with our three sites,” Wyle said. “But there are other surveyors who have to go 18 miles on snow cats to reach their survey sites on the Flat Tops and they do camp out.”
Federal funding for the manual surveys is assured for only one more year, Wyle said, as part of the federal sequester process in Congress. A seven percent cut in funding is predicted in the coming year, he noted.
“We’ve already had to cut the number of surveyors in Colorado by more than half,” from 40 to 19, Wyle stated. “Hopefully, there will be enough of an outcry from water districts and others to continue the funding. I don’t think $100,000 is a lot of money for something as valuable as this.”
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