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September 16, 2019

Improving the Measurement of Snowpack

Photo credit: Heather Sackett, Aspen Journalism

The National Snow and Ice Center’s Jeffrey Deems is heading up a project, in California and Colorado, aimed at improving the measurement of snowpack to help water providers and irrigators better estimate and manage runoff. Much of the western U.S. depends on annual snow accumulations in the mountains for their water supply. Deems' technique uses flyovers from aircraft equipped with LIDAR.

LIDAR, which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth.

The scientists fly over an area before snow starts falling in the Fall and then again over the winter. They are able calculate snow depth very accurately. Here’s a graphic depiction of snow depth on the Maroon Bells near Aspen, Colorado during Spring of 2019.

Graphic credit: Jeffrey Deems, National Snow and Ice Center

One interesting result this season was the measurement of snow at the bottom of avalanche chutes which were below the level of SNOTEL measurement stations. Normally that accumulation would not be included in estimates.

Deems’ methods helped Denver Water’s operations more accurately gauge runoff into their Dillon Reservoir. Nathan Elder told a recent gathering in Steamboat Springs, Colorado, that the utility changed operations and released more water from the reservoir during Spring and avoided large releases that may have flooded downstream locations once runoff started up in earnest.

Here’s a link to an article about the technique from Aspen Journalism.

CRWUA caught up with Jeffrey Deems at the conference. Snow depth is one component of snow water equivalent but density is also very important. Dr. Deems told us that they use SNOTEL data to estimate density and that many more SNOTEL installations are necessary to use in combination with the LIDAR equipped aircraft. Below is a photo of a SNOTEL station. You can see the outline of the snow pillow in the bottom center of the photograph. The snow pillows measure the weight of the snow sitting on it and density can be calculated by knowing the depth.

Photo credit: Natural Resources Conservation Service

Most SNOTEL snow courses are automated nowadays but the Natural Resources Conservation Service, the State of California, along with many utilities still measure snow courses to “truth check” the automated equipment. Below is a photo from Aspen Journalism during a manual measurement operation.

Liza Mitchell, education and outreach coordinator with the Roaring Fork Conservancy, left, and a participant in the Water Education Colorado SNOTEL workshop measure the snow-water equivalent of different layers of the snowpack. The liquid content of snow from this site measured roughly 21 percent, March 2018.

Deems project and the time-honored snow course measurement techniques have the potential to revolutionize the accuracy of snowpack measurement.