Assessing Water Availability and Drought Dynamics in the Po River District Using the GEOframe Modelling System - the Sesia River basin case

The Po River Basin represents one of the most socio-economically and environmentally critical regions in Europe, supporting agriculture, hydropower production, ecosystems, and urban water supply. Its hydrological regime is strongly influenced by climate variability and change, particularly through alterations in snow accumulation and melt processes in Alpine headwaters. In this context, improving the quantification and forecasting of water availability is essential to support adaptive water management strategies.

For this reason, since 2021, a collaboration between the Po River Basin District Authority and the University of Trento has focused on the application of the GEOframe modelling system to the entire Po River District. The primary objective is to provide a spatially and temporally consistent assessment of water availability across the basin, supporting planning and decision-making activities of the Basin Authority under current and future climate conditions.

GEOframe is a fully open-source, semi-distributed, conceptual hydrological modelling system capable of simulating the complete water balance, including snow accumulation and melt, evapotranspiration, soil water dynamics, and river discharge. The model was implemented at daily temporal resolution and fine spatial scale across the Po River District, accounting for the region’s complex topography and pronounced climatic gradients. Model calibration was performed using an extensive set of hydrometeorological observations collected by regional and local authorities, primarily through the ARPA monitoring networks, enabling the integration of heterogeneous datasets and the representation of spatial variability across sub-catchments.

Following calibration, the modelling framework was applied to analyse drought periods during the 2010–2020 decade, focusing on the Sesia River catchment as a representative and particularly complex study area within the Po River District. The Sesia basin is indeed characterised by a strong altitudinal gradient, significant Alpine headwaters with glacierised areas, and highly anthropised lowland sectors, making it especially sensitive to both climatic variability and human water use pressures. This complexity provides a robust test case for evaluating model performance across contrasting hydrological regimes.

The analysis focused on the response of the main hydrological components during drought conditions, with particular emphasis on snow-related processes, given their critical role in regulating seasonal water availability. Simulated snow water equivalent (SWE) data were compared against the SWE dataset by Dall’Amico et al., enabling a more precise evaluation of the snow component in the water balance.

Results highlight the strong influence of reduced snow accumulation and earlier snowmelt on water availability during drought conditions, particularly in Alpine subcatchments, with cascading effects on downstream flows in more heavily anthropized areas. The comparison with the reference SWE dataset confirms the ability of GEOframe to reproduce both interannual variability and spatial patterns of snow storage, while also revealing key sensitivities relevant for drought monitoring and seasonal forecasting.

Overall, this study demonstrates the suitability of the open-source GEOframe modelling system not only for detailed basin-scale analyses, but also for consistent, large-scale applications across the entire Po River District. The results provide actionable insights for water management authorities, supporting improved drought preparedness, strategic planning, and adaptive water management under current and future climate variability.