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Can NASA satellites help monitor snowpack across the American Southwest?

Test site on Red Mountain Pass serving as ‘a great natural laboratory’
Crews on the ground check snow depth to compare with the findings of a NASA project that seeks to monitor snowpack by satellite.


Understanding how much snowpack lies in the mountains of the American Southwest is critical for communities in the region, and an unsung project led by NASA may bring the next great technological advancement in the field.

Starting in winter 2016-17, NASA began a five-year experiment throughout North America, which included the San Juan Mountains, hoping to improve the ability to map water and energy components of seasonal snow.

“The goal is to address the most important gaps in our snow remote-sensing knowledge, and thus lay the groundwork for a future snow satellite mission,” NASA wrote on its project page.

In theory, the project’s goal is simple.

Silverton has long been the focal point of groundbreaking snow research, said Jeff Derry, executive director of the Center for Snow and Avalanche Studies.
Since winter 2016-17, researchers have been participating in NASA’s SnowEx program by going into the field and verifying data taken from the air.

Mapping snowpack throughout the entire, vast country is a herculean effort. But what if satellites had equipment to easily measure snowpack as they made the rounds in orbit?

Since the start of the project, NASA each winter has tried different technologies that could potentially fit the need. Then, crews on the ground are tasked with going into the field to measure snow and compare findings.

“Snow is gold in the Mountain West,” said Jeff Derry, executive director of the Center for Snow and Avalanche Studies. “And because snow is so precious, we need to manage it as best as we can.”

Room for improvement

For years, the go-to monitoring method for measuring snowpack in the mountains has been a network of weather stations, known as Snotel sites, that are dispersed throughout the West.

Mostly located in high elevations, the Snotel system gauges data such as snow depth and the amount of water contained in the snow, otherwise known as snow water equivalent.

To measure snow depth, for instance, a downward pointing laser is shot into the snow, which is then reflected back to a sensor. The time it takes the light to travel back gives an idea of the snow depth, but it is prone to error.

And the system has its limitations. There are only about 730 sites across the entire western U.S. and Alaska, and having one monitoring station in one location doesn’t provide a comprehensive picture of the entire basin.

“Snotel sites are the best network we have,” John Lhotak, an operations hydrologist with the Colorado River Basin Forecast Center, said previously. “But there are definitely shortcomings.”

Already, researchers are finding major gaps in the old way of tracking snow.

In 2013, for example, a study of the Rio Grande Basin found forecasts undershot the amount of water that was expected to flow by 50%, according to the Colorado Water Conservation Board.

Every Wednesday through the winter, a team of researchers trek up to the Swamp Angel Study Plot near Red Mountain Pass to measure snow depth.
NASA tries different technologies

Several efforts have been launched in recent years to create a better method to track snowpack.

NASA’s program, called SnowEx, spans six different kinds of climates throughout North America, such as tundra, boreal and maritime forests.

On Red Mountain Pass, between Silverton and Ouray, a site known as the Swamp Angel Study Plot at 11,000 feet in elevation, with years worth of research and data, was an easy selection for the project, Derry said.

“It’s a great natural laboratory,” Derry said. “Silverton has a rich history in snow research.”

Each year, NASA tries out different technologies, attaching the equipment to planes. After flyovers, crews throughout North America go out to measure snowpack to see how accurate the flyovers were.

Lidar, for instance, uses a high-resolution laser pulse to measure snow. It’s extremely accurate for finding out snow depth, but can’t work if it’s cloudy and is not a great tool for anticipating snowmelt.

And radar, which transmits an electromagnetic wavelength that bounces back, is great for monitoring snow water equivalent, but doesn’t work well through tree cover.

“It’s been a process of discovery,” Derry said. “And it’s promising. We’re trying to figure out what technology works best.”

Troubleshooting in the snow

Andy Gleason, a lecturer in the department of geosciences at Fort Lewis College, has been taking a team of his students to the Swamp Angel Study Plot as part of NASA’s SnowEx program since its inception.

Flights start out of Houston, and over more than eight hours, fly over Colorado, Idaho and Montana before returning. Then, crews around those states take to the mountains to collect data on the ground.

For Gleason and his team, that means gearing up the cross-country skis or snowshoes every Wednesday in the winter.

A range of different technologies has been used: radar, Lidar, multispectral imaging. Each has its pros and cons, Gleason said, and no one silver bullet has emerged quite yet.

“We’re starting to narrow down what’s working and what’s not working,” he said.

A separate, but similar, project that uses Lidar attached to planes has proved to be been extremely accurate. But the problem with that method is the extremely high cost of flights and the frequency it requires.

Simply attaching equipment on a satellite in orbit is seen as a cost-effective solution. But the sheer distance of measuring snow in the mountains from space is an issue researchers are trying problem-solve.

“Flyovers with Lidar once a month is so expensive,” Gleason said. “We’re hoping to replace that over time.”

NASA hopes to find a cost-effective way to better map snowpack in North America, which is important for areas like the American West, where the climate is increasingly drying out.
The San Juan Mountains have long drawn the attention of snow scientists because they are home to the headwaters of several major rivers, said Jeff Derry, executive director of the Center for Snow and Avalanche Studies.
Every drop counts

Nearly every drop of water used in Colorado comes from melted snowpack in the high country.

And as the West dries out, predicting how much snowpack is in the mountains, and how much available water there will be in the spring and summer once it melts into rivers and reservoirs, is of ever more importance.

Ken Beck, superintendent of Pine River Irrigation District, which manages releases out of Vallecito Reservoir, said every year is a delicate dance, predicting how much snowfall there is, when it will melt and timing releases.

“It’s a nail-biter,” Beck said.

Beck relies on Snotel sites, as well as the help of forecasters at the Bureau of Reclamation. But another tool in the toolbox, such as the aim of the SnowEx program, would be welcomed.

“Anything we can get to augment is of help to us; it’s just wonderful to have the technology behind that,” Beck said.

Derry, for his part, believes the SnowEx program is getting close.

“I think it is,” he said. “After this project, hopefully NASA will have all the information they need. Then, I think, it is a matter of putting it all together.”