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Measuring Snow Properties with Laser Scanning and Radar


Researchers: R. W. Webb, K. S. Jennings, and N. P. Molotch, University of Colorado, Boulder; and M. Fend, UNAVCO.

Written by Linda Rowan
26 March 2020


Summary

A novel combination of ground penetrating radar and terrestrial lidar scanning provides details about the state of seasonal snowpack in Colorado without destroying the snow layers. Testing shows high variability in volumetric liquid water contents. The rapid changes in the amount of liquid water occurred in small areas over short time periods. Understanding the state of a snowpack is important for managing water resources.


Observations

Ground penetrating radar systems (GPR) send radar pulses into the ground and return strong to weak reflections where the density and other properties of the material changes. For measuring snowpack, the instrument is pulled on a sled along a transect and measures the time it takes for reflections from the ground-snow interface to return. A faster return is associated with a dry snowpack whereas a slow return is a result of higher amounts of liquid water from snowmelt.

Terrestrial lidar (light ranging and detection) scanners (TLS) are instruments placed on a tripod. They can measure the surface elevation of bare ground or snowpack. By measuring the bare ground and then the snowpack, the ground elevation can be subtracted from the snow elevation to determine the snow depth.

Here the authors use two well-studied locations at the Niwot Ridge Long Term Ecological Research area in the Colorado Rocky Mountains to test the combination of GPR and TLS to determine the state of the snowpack. One location is near the tree line in an open meadow and the other location is above the tree line on a leeward hillslope. The snowpack was surveyed with both methods on a daily and sub daily timescale and over short transects of less than one kilometer. The results were compared to observations in nearby snow pits.


Results

The combination of GPR and TLS successfully deciphered the state of the melting snowpacks on sub daily to daily timescales from the meter to hundreds of meters scale. The melting snowpacks showed large variability in liquid water over short distances and short times. More liquid water was measured at the bottom of hillslopes. This new, non-destructive technique will help to better understand how liquid water is stored or diverted in a snowpack, helping to manage water resources.

Related Links


Related Data Links

  • UNAVCO Terrestrial Laser Scanning (TLS) Project Support
  • Lidar data for this study

  • References

    Webb, R. W., Jennings, K. S., Fend, M., & Molotch, N. P. (2018). Combining ground-penetrating radar with terrestrial LiDAR scanning to estimate the spatial distribution of liquid water content in seasonal snowpacks. Water Resources Research, 54, doi:10.1029/2018WR022680.

    Keywords

    liquid water content, snowpack, ground penetrating radar, light detection and ranging


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Last modified: 2020-03-30  14:14:57  America/Denver