Recent Trends in Snow Water Equivalent and Evapotranspiration in the Western Italian Alps: Emerging Signals of Climate Warming

European Alps are essential sources of water sustaining downstream ecosystems and human activities. In this regard, they are referred to ‘the water towers of Europe’. However, these regions are also among the most sensitive to climate change. Indeed, the high rate of temperature increase, altered precipitation regimes, and “snow droughts”, i.e., a lack of snow accumulation in winter, are significantly impacting the hydrological processes in snow-dominated areas.

In this context, Snow Water Equivalent (SWE) and Actual EvapoTranspiration (AET) are two key variables for understanding the mountain water cycle. Investigating SWE and AET changes is essential to detect whether the hydrological cycle is accelerating in response to climate warming.

Gridded datasets, such as those derived from reanalysis products or satellite-based observations, have significantly enhanced the spatial representation of climatic and environmental variables in topographically complex regions, where the availability of ground-based observational data is often sparse or unevenly distributed due to logistical and environmental constraints.

This study examines the dynamics of SWE and AET over recent years across catchments of varying spatial scales in the Western Italian Alps, based on SWE data from the IT-SNOW dataset and AET data from MODIS. The analysis also includes a comparison between gridded data and in-situ measurements. The main aims are:

• evaluate the ability of gridded datasets to capture key hydrological processes at multiple spatial scales;
• identify shifts in snow regimes and evapotranspiration patterns potentially driven by climate warming;
• assess the reliability of gridded data for local-scale hydrological applications through comparison with ground-based observations.

This publication is part of the project NODES which has received funding from the MUR – M4C2 1.5 of PNRR funded by the European Union - NextGenerationEU (Grant agreement no. ECS00000036). This work was supported  by the PRIN 2022 202295PFKP SUNSET Project and by Funding 2023-2025 Fondazione CRT.