When kids dream of growing up to work for NASA, they generally imagine themselves piloting rocketships or exploring Mars, not tromping around in the snow. But for three weeks this winter, you could find a bunch of NASA-funded scientists digging snow caves and measuring snowpack density on a frosty plateau in western Colorado. Although NASA may be best known for studying other worlds, its exploration of the universe begins with our home planet,1 and NASA’s satellites and other space-age technologies have proved vital to understanding Earth.
Launched this year with a $4.5 million budget funded by NASA’s Terrestrial Hydrology Program, the SnowEx project involves nearly 100 scientists from two dozen organizations and aims to answer a basic question: How much water is stored in Earth’s snow cover?
The answer has important economic implications. Water is the lifeblood of the West, and managing it requires tracking and understanding snowpack dynamics because more than half of the water supply in the western U.S. comes from mountain snowmelt. Snowpack at high elevations provides a natural reservoir that holds water in reserve and then gradually (or sometimes not so gradually) releases it in the spring and summer. The western U.S. gets most of its drinking water, agricultural water and hydropower from the snowpack, and “if we can do a little bit better in forecasting how much [snowmelt] is coming out of the mountains and when it’s going to come out, it’s worth millions to billions of dollars in terms of commerce,” said Kelly Elder, a research hydrologist at the U.S. Forest Service and a leader of the fieldwork that took place in February on the Grand Mesa in western Colorado. The dollars he refers to represent the money that can be saved or lost through decisions regarding water allocation for agriculture, domestic use and flood management, among other things.
The system currently used to forecast runoff relies on statistical models based on historical averages, but warmer winters have meant that snow melts earlier and more precipitation falls as rain instead of snow. “We have a changing average in the snowpack,” Elder said, “and that makes statistical models more difficult to use.” These models aren’t just formulas in some scientific journal, they’re tools that water managers rely on to make decisions about things like how much water to discharge from dams and how to allocate precious water supplies.
By the end of the five-year project, SnowEx researchers hope to have developed a package of remote sensing tools that can be deployed on a new satellite to take continuous measurements in real time across the globe. During this winter’s field campaign, researchers flew over the Grand Mesa on military planes equipped with measuring instruments including radar, a laser altimeter and microwave sensors for calculating snow depth, a thermometer for reading snow surface temperature, a thermal infrared camera, and an imaging spectrometer for measuring the amount of light reflected by the snow. These airborne measurements will be compared and combined with data from the ground.
“We still do lots of digging. Skis, shovels and probes are our fundamental long-term tools,” said Chris Hiemstra, an Alaska-based scientist with the U.S. Army Corps of Engineers. “You can’t lose the focus of what’s happening in the field.”
What scientists measure on the ground will be integrated with what’s captured on the airborne instruments to create models that link the two, Elder said. “It’s an initially expensive venture, but it will pay for itself very quickly if we’re successful.”
It’s not enough to simply measure snow depth, because snow density varies even within a single snowpack. “The holy grail here is to measure snow water equivalent — the amount of water you’d have if you instantly melted the snow,” Hiemstra said. To measure that, you need to know the snow’s density as well as its depth. Currently, snow water equivalent is measured every day, every hour, at about 800 field sites across the West, but these stations can capture only what’s happening at their exact spot. “The snowpack varies over really short distances — like over the scale of a football field — so we’re not able to take those sites and estimate what’s going on in between them very accurately,” said H.P. Marshall, a geophysicist at Boise State University who is involved in the project. “The big advantage of doing this remotely from an aircraft or a satellite is the large spatial coverage.”
Grand Mesa was chosen for the SnowEx study partly because as the world’s largest flat-topped mountain, its topography is relatively uncomplicated, but it contains a wide variety of vegetation. The 100 study sections set up along the top of the mesa vary from completely open meadows to areas of scattered trees and dense spruce forest. Many of the remote sensing technologies now used to measure snow are thwarted by trees and other plants that capture snow in their canopy. “Very little is known about how trees and snow and wind and sun interact to influence the snowpack over time, so a lot of these data sets we’re collecting will help us improve how models physically account for tree interception,” Hiemstra said. “This has global implications, because the boreal forest is the largest terrestrial land cover type, and snow is a really important part of the water cycle there.”
SnowEx researchers have installed more than 100 red poles across the Grand Mesa to measure snow. “I think it’s become a game for people to try and find them,” Hiemstra said. “We’ve had a lot of really great local support. People have been really curious, and they’re very respectful of our sites.”
The Trump administration seems to be less enthusiastic about NASA’s Earth sciences programs. The $1.8 billion President Trump’s fiscal year 2018 budget proposal would set aside for Earth science programs is about 13 percent less than the amount requested in President Barack Obama’s 2017 budget (Congress granted less than Obama asked for and will have the final word on Trump’s request, too). The SnowEx project budget has already been allocated and spent, but Trump’s proposed 2018 budget request “terminates” four Earth science missions and reduces funding for Earth science research grants, which could affect other projects with similar goals. Trump’s budget is more a statement of priorities than a roadmap of future funding, but cuts to this programming could have repercussions for those who use and are affected by climate data.
SnowEx is a basic science project, but its results will have wide-ranging applications. Current runoff forecasts contain a lot of uncertainty, and that has economic implications downhill. “If we know how much water we have stored in the mountains in a given year, we can change when we plant crops; we can do reservoir management for agriculture and plan when we’re going to use hydropower,” Elder said. NASA’s planetary science programs will probably always garner the most oohs and ahs, but the agency’s work here on Earth has far-reaching consequences for many people’s lives.