NASA to test [snowpack] data technique in upper Rio Grande Basin — The Santa Fe New Mexican

Combined lidar and aerial mapping
Combined lidar and aerial mapping

From the Associated Press (Dan Elliott) via the Santa Fe New Mexican:

NASA is providing drought-stricken California with valuable data about how much water is locked up in the scant Sierra Nevada snow, and now Colorado is trying the technique in the mountains where the Rio Grande begins its journey to New Mexico and Texas.

An airplane called the Airborne Snow Observatory flies over California’s Tuolumne River Basin east of San Francisco during peak snow months, using scanners to collect data on how deep the snow is and how much of the sun’s warming rays are bouncing off. That helps project when the snow will melt and how much water it will release into rivers for cities, farms and wildlife…

“Once the water managers get a look at the data, they say, ‘I like that,’ ” said Frank Gehrke, chief of the California Cooperative Snow Surveys Program. NASA has been providing California with snow data from the Tuolumne Basin since 2013, and flights will resume there next spring.

Colorado signed up for three flights over the Rio Grande Basin in the south-central part of the state. The first were in March and September of this year. The third will be next spring…

Estimating how much Colorado snow will melt into the Rio Grande is difficult. The mountains block weather radars that could help gauge how much precipitation is falling, said Joe Busto of the Colorado Water Conservation Board.

Colorado will use the NASA data to improve computer modeling for runoff forecasts…

The Airborne Snow Observatory, a propeller-driven plane, sweeps back and forth over mountain snowfields scanning with lidar — the term combines “light” and “radar” — and an imaging spectrometer.

Lidar measures snow depth by bouncing a laser off the surface and comparing that to an aerial survey done without snow. Coupled with snow density data from ground sites and computer modeling, researchers can project how much water is in the snow.

The spectrometer measures how much sunlight the snow is reflecting and absorbing. That allows researchers to project when it will melt.

The ground sites, scattered across the West, are the primary source of data for most snowmelt projections. U.S. Department of Agriculture employees trek to some sites to measure and weigh the snow. Other sites are automated.

Painter said the airborne survey won’t eliminate ground sites, but he foresees a day when aerial surveys become the standard. Satellites might also play a role, but airplanes can provide a level of detail and frequency that spacecraft cannot, Painter said.

“At least not yet. Maybe in 50 years,” he said.


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