Water Balance in Alpine Catchments by Sentinel Data

A comprehensive and reliable water balance of snow-dominated alpine catchments is required for a holistic analysis of the hydrological and hydrogeological processes. A major limitation to the elaboration of this balance in alpine terrain is the difficulty of data acquisition as well as the limited presence of meteorological stations. Remotely sensed data can provide valuable information for the water balance assessment on a regional scale. We exploited Sentinel-satellite data to estimate the groundwater storage for one hydrologic year in an extensive Alpine catchment located in northern Italy by means of the residual water balance approach. In particular, Evapotranspiration (ET) and Snow Water Equivalent were estimated with the combined use of Sentinel data, at a spatial resolution of 20 and 30 m, respectively. The results show that the adopted satellite-based methods allow obtaining consistent and physically realistic values to describe the groundwater storage dynamics. In the period 2018–2020, a positive storage occurred only during the snowmelt period and the overall storage was negative, leading to a net lowering of the groundwater level in the floodplain. In addition, the influence of physiographic parameters (altitude, slope, and aspect) and seasonality on the estimates of ET and snow-depth were investigated.