For the past few winters, CSU professor Dan McGrath and his graduate students have made a bi-weekly trek up Cameron Pass. When they arrive, they split into various tasks designed to measure the snowpack.
Some of the team will strap on snowshoes and start pulling a large sled. The sled holds a ground-penetrating radar system.
鈥淭he radar instrument transmits a pulse of radio energy,鈥� said McGrath. 鈥淎nd we basically measure the time it takes to travel from the instrument down to the ground-snow interface and then back up to the instrument.鈥�
Throughout the season, the researchers see longer and longer delays in the radar travel time as the snowpack builds up. It鈥檚 just the opposite when the snow begins to melt.
In addition to the radar measurements, graduate student Alex Olsen-Mikitowicz flies a drone in a grid. It takes images that he uses to construct a 3D model of the area.
鈥淚t鈥檚 basically like taking your field site home with you. We can fly around in this model just kind of like a video game,鈥� said Olsen-Mikitowicz. 鈥淪o we have these every time we go out, and we can then stack them up on top of each other and basically watch the snow accumulate and melt over time.鈥�
Meanwhile, graduate student Ella Bump digs a snow pit about a meter deep. The team takes measurements of snow temperature and density every 10 centimeters or so. Bump uses a metal tool shaped like a slice of cake to cut out chunks of snow.
鈥淭his is a wedge cutter for measuring density, and it's got a volume of one liter,鈥� she said. 鈥淎nd so, when we take density measurements, we just weigh this and then we can figure out the density from there.鈥�
All of these tasks have the same end goal, according to Dan McGrath 鈥� measuring the snow-water equivalent, or how much total water is stored in the snowpack.
鈥淎t present there鈥檚 no single way of doing that,鈥� he said. 鈥淎nd that鈥檚 why this NASA campaign is occurring, is to test and evaluate these different approaches.鈥�
The CSU research group is one of many across the West working together on NASA鈥檚 SnowEx campaign. U.S. Forest Service hydrologist and SnowEx scientist Kelly Elder said the project came together because the nationwide team wanted to measure snow with a satellite in space.
鈥淭he fantasy was that we could just shoot pictures in some area of the spectrum of Earth鈥檚 surface with snow on it and get answers, he said. 鈥淎fter decades of frustration, we鈥檝e figured out that we really need two other elements to pull it all together.鈥�
The other two necessities are on-site measurements, like the ones on Cameron Pass, and computer models. Without them, images from current satellites can only measure how much area is covered by snow 鈥� not how much water is actually in the snow.
That鈥檚 because of the snow鈥檚 internal properties. One of the main problems is the amount of liquid water in the snowpack. Radar systems send waves of energy through the snow that move at a certain speed depending on the material. Just like a person would move slower running in water than on land, the waves move slower in water than in snow. Without measurements of the amount of liquid water within the snowpack, it鈥檚 difficult to tell if the layer of snow is thick or simply wet.
However, the amount of water in snow is what鈥檚 important for water managers because 70 to 80 percent of the water for Western cities and agriculture comes from snowpack.
鈥淓ven over a basin the size of the Poudre, we have relatively high uncertainty in our predictions of how much water is going to come out on any given year, even with a long record,鈥� said Elder. 鈥淚f you throw climate change in on top of that, we鈥檝e got a real problem.鈥�
Current predictions of snow-water equivalent come from observations of water levels in previous years. Elder said that as global warming changes the environment, that process becomes invalid.
Future satellites, combined with the work on the ground, might address the problem. NASA and the Indian Space Research Organization have partnered to launch one at the beginning of 2023.
But that satellite isn鈥檛 specifically made to measure snow 鈥� it鈥檚 just a bonus. While the data will be useful, McGrath said a perfect solution is probably still years away.
鈥淭he goal of this whole campaign is to be able to measure this snow-water equivalent from space and do it globally all the time, essentially. So, every 10 days or 12 days, we鈥檇 have this image of how much snow is on the ground in these locations,鈥� he said. 鈥淭hat will just hugely inform how agriculture is done and how water is managed, especially in a changing climate.鈥�
The CSU team plans to keep working on different tools to measure snow-water equivalent. Next summer, they鈥檙e headed to Alaska to conduct measurements in an environment with different conditions.
Although measuring the amount of water in snow may not solve the drought problem, McGrath said it will make the West more prepared.
