Catchment-Level Estimation of Snow Depth Using Sentinel-1 and Ground Sensor Validation in the Upper Indus Basin

Previous studies on the cryosphere of the Upper Indus Basin (UIB) have mostly focused on glaciology and have either used remote sensing tools or sparsely deployed ground station networks at the regional or basin scales. This work is instead focused on catchment-level seasonal snowpack monitoring in the little-studied foothills of UIB, using a combination of remote sensing and in-situ measurements. To estimate the snow depth at the catchment level, we have processed Sentinel-1A (C-Band) data and validated our estimates by an indigenously developed ground-based monitoring station. We used differential interferometry for the inversion of spatial snow depth from November 2018 to May 2019. The results indicate a spatial maximum of 350 cm snow depth within the catchment, and a temporal maximum of 216 cm at the validation point. The relative error (RE) with respect to the ground station was estimated to be 90% and an RSME of 3.0 cm. The good performance of TOPS data with spatial-temporal baselines and inexpensive in-situ validation offers significant potential in future applications of snowpack monitoring and water resources management studies in the Upper Indus Basin of Pakistan.