NRCS samplers measure snowpack
It’s a simple law of physics – what is up must come down.
Since snow began to fall in the mountains above us last winter, many experts have been looking “up there” to try and predict how much water will come “down here” out of that snow this spring. Will there be enough? Will it flood?
One of the most important tools used in forecasting the spring runoff is the snow telemetry (SNOTEL) measurement data taken in late winter and early spring each year – typically, when the most snow falls.
Monday, two experienced SNOTEL samplers, Vada Hubbard, 46, and Ed Blake, 47, of the Natural Resources Conservation Service, trekked uphill through the snow for the third time this year to take readings at two sites on the east side drainage areas of the Sierra – Spooner and Glenbrook.
“Congress charges us to do this snow survey program, and it is really only about 10 percent of our job,” said Hubbard, who is an engineering technician for NRCS. “I like to do these manual sites because I’m not too crazy about going up in the helicopters for the other sites.”
n So many sites to sample. There are 39 SNOTEL sites throughout the Sierra – 24 that are remote and automated, requiring no regular visits by technicians, and 15 manual “snow courses,” which must be read by NRCS personnel the first part of February, March and April.
Of these 15 SNOTEL sites, 10 are isolated enough to require helicopter access and the other five can be reached on foot.
Blake, a soil scientist who also goes out to the more isolated fly-in sites, said the reason all the locations aren’t automated is simple economics.
“Every year our money goes down,” he said. “There are always budget constraints at play.”
Monday, at the same time Blake and Hubbard were testing their sites on foot, helicopter crews were out sampling other sites from Twin Lakes to Squaw Valley, Blake said.
n In our back yard. At Spooner, the 1-mile hike takes the scientists to a marker which is used year after year. Depending on the weather and snowpack, they will either walk, snowshoe or ski in.
“It’s nice to go in when the weather’s nice, but even when it’s bad, we still have to get the readings,” Hubbard said.
SNOTEL technicians always go out in pairs for safety, Hubbard said.
At each station, the pair assembles a hollow aluminum tube as long as they estimate the snow is deep. The pipe is then pushed down into the snow until it hits bottom.
The deepest core Blake could recall pulling out of the ground was 260 feet – requiring nine 30-foot sections of pipe – at Lake Lucille, a fly-in site in the Desolation Wilderness.
“That’s not fun to pull out,” he said. “Typically, you’ll go through layers of ice and it’s hard to work with.”
Monday, Blake measured the snow depth at around 60 inches- give or take – at each of the eight Spooner stations.
After pulling out the core sample, the pipe is weighed and calibrated to calculate the actual water content of the snow, or snow water equivalent.
Hubbard said that wildlife encounters by samplers have thus far been limited to hearing birds and seeing deer and bear tracks.
“Fortunately, the bears aren’t usually up and around when we’re coming in,” Blake said. “We’ve only seen tracks.”
n How much is in there? Dry snow can have as little as 10 percent water and be very light. Wet snow, typically found toward the end of the winter season, can come in as high as 50 percent water, which is considered saturated. This means that if 10 feet of snow melted, it would yield 5 feet of water.
Monday’s average water content at Spooner was around 38 percent, which both Blake and Hubbard said was right on par with what they had expected.
“As of today, we are at 100 percent of average for the Walker and Carson areas,” Blake said, adding that the Truckee drainage area is slightly higher than 100 percent.
Given a spring without excessive rains or sudden high mountain temperatures, the runoff should be good, but not threatening, although both technicians were reluctant to exclude the possibility of flooding.
Prior to the 1997 New Year’s flood, data from the SNOTEL sites actually served to help predict the high runoff, Blake said.
As experts began to notice an increase in snow buildup and then melting, the automated gauges were programmed to send hourly readings, giving experts up-to-date numbers to work with.
n UNR professor was pioneer. The Snow Survey Program was actually started by a University of Nevada professor, Dr. James Church. In 1906, he laid out what is considered to be the first Western snow course on Mount Rose ,used to predict the seasonal fluctuations at Lake Tahoe.
At first, all that was measured was snow depth. In the Eastern U.S., snow samples were melted to determine water content.
Later, Church pioneered the Mount Rose Sampler, a simpler weighing technique, which, with some refinements, is still used today.
Snow survey information is presently collected from a network of about 1,600 sites in 10 Western states including Alaska.
The information is forwarded to, and used by, thousands of experts and forecasters in the West.
“We still sample the original Mount Rose course, so we have almost 100 years of data,” Blake said.
n Information you can access. All the data collected by Hubbard and Blake will go into the computer and factor into graphs and data patterns in a computer model that adjusts every year.
The automated sites have both a precipitation container that measures depth and a pillow device which actually figures the moisture content of the snow.
That information is sent out from the remote sites, actually bounces off a meteor trail, and then bounces back to master stations in Utah and/or Idaho.
This data can be found on the Internet address: ftp://ftp.wcc.nrcs. usda.gov/data/snow/update/ca.txt