Remotely Monitoring Snow Water Equivalent Using Basic Photogrammetry

Accurately monitoring the snow water equivalent (SWE) in watersheds and water supply areas is increasingly important in a changing climate as average temperatures are predicted to rise, resulting in diminishing mountain snowpacks. Recent research has shown that it is possible to accurately convert snow depth measurements to snow water equivalent using estimated bulk snow density; multiplying snow depth by the average density of the entire snowpack. Measuring snow depth is relatively simple and cost-effective in comparison to SWE measurements. This study describes a local-scale application of a snow density model with snow depth measurements taken using basic photogrammetry. The study site was situated at 1325 m on a sub-alpine ridge in the Capilano Watershed in British Columbia. Snow depth is estimated from images of a graduated snow depth pole, which is then converted to SWE. For this study, bulk snow density was calculated from historical (c. 1936) average monthly snowpack density at five nearby snow course sites. Calculated SWE values using this snow density model averaged 95% of the periodic manual validations, and proved to be more accurate and reliable than measurements from nearby automated SWE sensors. This technology can be used to fill data gaps and provide additional valuable information to water supply managers at a relatively low cost. (KEYWORDS: snow water equivalent, snow depth, snow density, photogrammetry, hydrology)