Western states map snow by air to refine water forecasts
GUNNISON, Colo. — At a tiny airport surrounded by mountains, a three-person crew takes off for the inaugural flight above the headwaters of the Colorado River to measure the region’s snow by air.
Under the plane is a device that uses lasers, cameras and sensors to map snow and help drought-prone communities improve forecasts of how much water will later fill reservoirs.
The method, developed nearly a decade ago at NASA’S Jet Propulsion Laboratory, “is the gold standard of snow measurement,” said Emily Carbone of the Northern Colorado Water Conservancy District, one of Colorado’s largest water providers and the flight’s primary funder.
For decades, Western U.S. states have been measuring snow through hundreds of remote sensing sites known as SNOTEL stations, which are operated by the federal Natural Resources Conservation Service. But as climate change causes rising temperatures, snow at those sites — at around 9,000 feet above sea level — is melting earlier than normal and pushing water managers to look for other ways to fine-tune forecasting methods.
Among the options is a method of aerial snow mapping that gives precise snow measurements across an entire basin.
The flight by Airborne Snow Observatories in mid-april measured the area around the headwaters of the Colorado River. But the hope is to expand the work along the stressed river, said Jeffrey Deems, co-founder of the company.
Paul Miller, a hydrologist at the Colorado Basin River Forecast Center, said “removing uncertainty in one of the data points” can be critical in a waterstressed region.
But Miller noted the limitations of even aerial snow mapping, which can cost tens of thousands of dollars or more per flight and only provide measurements for the day flown. The technology also doesn’t account for variables such as air temperature and late-season storms that can affect water supplies.
Others are working on ways to improve snow measurements too. The U.S. Geological Survey is on the ground researching an option that could be more affordable, even if it’s not as precise. The agency installed its own remote sensing stations above and below the typical elevation of SNOTEL sites and its laser-equipped drones measured the surrounding area.
Those results could take a couple of months to process since they’re still in the testing phase, said Suzanne Paschke, who is managing the project for USGS.
Meanwhile, SNOTEL sites are also undergoing upgrades that could result in more accurate modeling, said Karl Wetlaufer, who helps run the program. In coming years, the federal agency plans to expand the number of sites that include sensors for solar radiation, wind and soil moisture. But the stations still can’t be moved to higher elevations, where wind can whip snow around and make it hard to measure, Wetlaufer said.
The newer methods help fill in those data gaps at high elevations.