How agencies in Colorado measure snow

Snowpack this year average so far

MONTE VISTA — Research Associate Blake Osborn with the Colorado Water Center/CSU Extension Service explained the various methods used to measure snowfall in Colorado and how they function at the annual Agriculture Conference at Ski-Hi in Monte Vista Feb. 4.
Osborn was introduced by Extension Agent and Director Marvin Reynolds. He began by noting that currently the state is doing experimental work in the Rio Grande Watershed and the San Juans. Snow comes through the Valley when the jet stream pulls moisture in from the Pacific Ocean, bringing cool temperatures with slow release.
The mountains are just “a big water reservoir” he said. Federal agencies, including the National Aeronautics and Space Association (NASA), the National Conservation Service and the National Oceanic and Atmospheric Administration (NOAA) measure snow primarily from December through the following March.
Snow is collected manually with SNOTEL (Snowpack Telemetry) and by remote sensing with other systems. A two person team measures snow depth, density and weight in certain locations. “SNOTEL can go back decades in data records,” Osborn commented.
• SNOTEL is an automated snow measuring system in a permanent location, based on point sampling and interpolation. Osborn calls it “a very robust system.”
• LIDAR (Light Detection and Ranging) uses a high-resolution laser pulse that is extremely precise to measure snow. LIDAR provides greater spatial coverage but can be very expensive, Osborn said. Because of its high resolution it can measure down to centimeter scale. It is best used in April when snow is monitored in different stages.
• SNODAS (Snow Data Assessment System) uses satellite imagery to measure snow and is computationally intensive. Using satellite, it can look at the entire watershed and download measurements to a computer. But it provides only a snapshot of snow conditions and only a few agencies use it, Osborn pointed out.
This time of year the snowpack is still developing, Osborn explained. January estimates show the measurements at about average. Stream flows are running 90-110 percent of average according to early reports. From January through April it might be 1,000 CFS or lower.


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