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Snow measurements predict water outcomes in spring, summer

Feb 29, 2016

A group on skis and snowshoes visits a SNOTEL site atop McClure Pass. It gathers snow data used by farmers, ranchers, water managers and others.
Credit Marci Krivonen

Dry February weather melted snow in the high country, but snowpack levels are still substantial. A healthy level of snow up high is important for everyone down low, particularly farmers and ranchers. A crew of snow surveyors and high-tech systems are already sending readings about snowmelt. Marci Krivonen explains.

It’s a calm and sunny February day at 8700 feet above sea level. Snow surveyor Derrick Wyle plunges a long metal tube into deep snow on McClure Pass, south of Carbondale.

"I like to hold it up and let it pendulum itself into straight up and down and then with a swift, but not too hard, plunge, you try to sink it down to the soil surface in one shot," says Wyle.

The tube sinks down nearly 3 feet. Wyle - who’s with the Natural Resources Conservation Service - scribbles the number in a notepad, then puts the tube on a spring balance to weigh the snow.

Derrick Wyle of the Natural Resources Conservation Service weighs a tube containing snow.
Credit Marci Krivonen

"So - this is in one inches, or one ounces - so, 31 is the weight of the tube and the core. Our tube weight is 20.5."

With some quick math, Wyle finds the snow has a 30 percent snow water density.

Wyle isn’t alone up in this snowy aspen grove. About a dozen people on skis and snowshoes are observing the process. The field trip is thanks to the nonprofit Roaring Fork Conservancy.

Sue Edelstein of Carbondale says she’s always been interested in water.

"I was a ranger for the national parks in Yosemite in the 1970s and would sometimes go out on snow measurement expeditions in the Sierra. So, I was curious to see what the change in technology was over the decades," she says.

The snowpack is water storage for industries tightly tied to water.

"We use a lot of water but we basically use whatever comes," says Roy Savage, a rancher near Rifle.

He’s been measuring snow depth for three decades - it’s one way to determine how much water he’ll get for growing hay.

"Our agriculture is completely dependent upon water diversion. If we don’t irrigate, we don’t get a crop.”

His measuring tape readings provide some data, but Savage also depends on field readings from snow surveyor Derrick Wyle. And, data from so-called SNOTEL sites that dot mountaintops across the Western US.

"So this is it. This is what they all sort of look like.”

Wyle stands below a SNOTEL site, not far from where the group took manual snow readings. A green shack shaped like a cylinder holds batteries and plumbing. Nearby instruments measure precipitation, temperature, snow density and depth. Hourly data is transmitted through meteor burst technology that uses the earth’s ionosphere.

"It’s not cell service, it’s not a satellite, it’s using a sort-of 1970s technology to transmit the data back," says Wyle.

The data is used in streamflow forecasts that predict how much water might flow along rivers like the Roaring Fork.

February’s warm and dry conditions lowered snowpack in western Colorado but the National Weather Service predicts March may bring change with a wetter than normal forecast. On Monday, SNOTEL readings in the Roaring Fork Valley were between 75 and 102 percent of average.