“Lidar technology more accurately measures snow depth” — The Durango Herald #snowpack

This map shows the snowpack depth of the Maroon Bells in spring 2019. The map was created with information from NASA’s Airborne Snow Observatory, which will help water managers make more accurate streamflow predictions. Jeffrey Deems/ASO, National Snow and Ice Data Center

From The Durango Herald (Jonathan Romeo):

At a time when monitoring mountain snowpack is crucial for communities throughout the American West, has the next generation of measuring snow depth arrived?

Some top researchers seem to think so.

“We really feel we have the next evolution for water management,” said Jeffery Deems, a research scientist for the National Snow and Ice Data Center.

For years, the go-to monitoring method for measuring snowpack in the mountains has been a network of weather stations, known as Snotel sites, which are dispersed throughout the West to gauge snow depth and the amount of water contained in the snow.

But the system has its limitations: There are only about 730 sites across the entire western U.S. and Alaska, which is a small sample pool and doesn’t provide a comprehensive picture of entire basins. And, the technology for Snotels hasn’t been seriously updated since being installed in the late 1970s and early 1980s…

Combined lidar and aerial mapping

A better way?
In the early 2010s, NASA’s Jet Propulsion Laboratory teamed with the California Department of Water Resources to create the Airborne Snow Observatory to develop a new way of tracking snowpack in the mountains, looking to Light Detection and Ranging (lidar), a 3D scanning system, as a possible answer.

Lidar is not new technology. For years, it has been outfitted on planes to send beams down to earth to map elevations on the landscape, evaluate flood plains and even find the remnants of archaeological ruins underneath the ground.

But researchers started wondering if it could be applied to measuring snowpack.

The first flights were conducted in California in fall 2012 to create a baseline model of the mountains without snow, flying about 20,000 feet off the ground for five to six hours in a back-and-forth pattern.

Then, after a few storms, planes took flight again, and researchers were able to subtract elevation amounts to determine precise snow depths through high-resolution maps.

“We see it as moving from a sparse-point base network (with Snotel) to a system that can map the entire snowpack in a river basin,” Deems said. “It is really an enabling technology.”

[…]

This map shows the snowpack depth of Castle and Maroon valleys in spring 2019. The map was created with information from NASA’s Airborne Snow Observatory, which will help water managers make more accurate streamflow predictions. Jeffrey Deems/ASO, National Snow and Ice Data Center

Flying isn’t free
While those in the water world are excited about the potential of lidar, there is less enthusiasm for bringing out the check book.

Frank Kugel, the new director of the Southwestern Water Conservation District, said he saw the benefits firsthand when he was working in Gunnison, a time when many of the flights were in the experimental stage…

But Kugel said it could cost somewhere around $400,000 a year to fly the entire boundaries of the southwest district and convert that data to maps and usable information…

The Colorado Water Conservation Board is investing $250,000 in 2021 to conduct flights in the Gunnison basin, but Skeie said he hopes the project expands to other parts of Colorado in the coming years. But how that will look is yet to be determined.

In California, for example, lidar planes fly about 10 times a year, starting in January. When snowmelt begins around April, those flights ramp up.

Deems said the needs of each basin in Colorado, and how often water managers want flights, will vary, and the project can be tailored to those needs.

Note: I caught up with Jeff Deems last summer at the Colorado Water Congress Annual Summer Convention to ask about measuring density, which LIDAR and current aerial technology cannot do. He told me that we still need the SNOTEL sites and, in fact, we need more.

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