Snowmelt Detection from Sentinel-1 Synthetic Aperture Radar in the Lajoie Basin, British Columbia

Snowmelt runoff supplements streamflow and soil moisture during warm summer months in Western North America. As direct snowpack measurements are sparse, many models exist to predict the release of runoff in alpine regions. An increase in spatially distributed observational data of seasonal snow may help to refine and improve these efforts going forward. Synthetic Aperture Radar (SAR) is sensitive to the liquid water content of snow and has been successfully used to map wet snow in alpine regions. We employ SAR and multispectral data to estimate the onset and duration of snowmelt in 2018 in the Lajoie Basin, British Columbia. We collate and process Sentinel-1, Sentinel-2 and Landsat-8 images in Google Earth Engine. A backscatter threshold is used to define the inferred period at which the snowpack is saturated and begins to generate runoff. Multispectral imagery is used to estimate snow-free dates across the basin to define the end of the snowmelt period. These methods are most effective on moderate to low slopes (< 30°) in open areas. This approach has high potential for adaptability to other alpine basins or regions and can be used for future model calibration.