Potentialities of Sentinel-2 images for the study of the fresh water resource in a glacierized mountainous catchment

Water quality and availability are nowadays essential requirements for all those activities that need an exploitation of the water resource: e.g. potable use, hydroelectricity production, agriculture, recreation. Inland water originates from atmospheric events and is stored in solid state as glaciers or snow (e.g. on the mountains) or in natural and artificial lakes at any altitude. The well documented climate warming has, among its multiple effects, the modification of the equilibrium between liquid and solid phase of water, its storage and availability, as well as changes in the precipitation regime, such as the reduction and intensification of rainfall events alternated to long dry periods. All these changes alter water quality and water availability at the catchment level.

We are experimenting the use of earth observation data (Sentinel-2) to track temporal variations of snow cover, water bodies (in terms of size and numbers) and water colour over the last five years in a small high-altitude, glacierized catchment in Italy (Lake Ceresole watershed, Orco Valley, Western Alps). In particular, water colour is chosen here as a proxy of water quality and is considered as mainly driven by the presence of suspended particles, because of the conditions that feature a mountainous environment (e.g.  minimized anthropic pressure and prevailing natural processes). Water colour is then supposed to change following the release of suspended particles from snow/glaciermelting during thaw periods at seasonal timescale, as well as be modified due to the transport of solid particles as river flow or runoff, which can be generated as a consequence of heavy rainfall events.

Satellite derived products on snow cover, lake size/number and water colour are then coupled with meteorological measurements (e.g. precipitation), and information on geo-hydrological events (e.g. floods) in order to find possible linkages between lake water dynamics and both snow/glaciermelting and significant meteorological and geo-hydrological events. Field measurements allow a validation of the satellite data on lake water colour to be performed.

 

With this study, we aim to understand if the high spatial resolution of Sentinel-2 acquisitions, except for the drawbacks of all optical satellite sensors (e.g. cloud cover), can provide useful information on water and sediment dynamics in an alpine glacierized basin, that can allow to follow the on-going modifications that the mountainous environment is facing due to the global warming. The use of Sentinel-2 data for this purpose would be a valuable tool in helping both monitoring and understanding of climate change consequences, and in managing the water resource in places not easily accessible for periodic in-situ measures. In fact, mountains respond promptly to climatic pressures, but are also the water sink of fresh water for downstream valleys.