Projected Changes in the Euro-Mediterranean Hydrological Extremes

Recent extreme hydrological events in the Euro-Mediterranean region have highlighted the urgent need for improved understanding and prediction of floods and droughts. Catastrophic floods, such as those in Austria, the Czech Republic, Poland, Romania, and Slovakia, have resulted in significant socioeconomic losses. More recently, unprecedented flooding in Valencia on October 29th underscores the increasing unpredictability and intensity of such events. Concurrently, Northern Africa has experienced severe, prolonged droughts over the past six years, with southern and eastern Europe facing similar challenges marked by persistent drought conditions and critical water shortages, leading to exacerbated soil moisture deficits and stressed vegetation. While the focus has largely remained on short-term meteorological drought forecasting, many significant impacts—ranging from public water supply to hydropower production—are closely tied to hydrological droughts. Understanding future variations in both flood and drought conditions is then essential for developing robust defence strategies and ensuring resilient infrastructure across the region.

This study investigates the impact of climate change on future hydrological extremes over the Med-CORDEX region. We utilized the ENEA-REG regional coupled model, which downscales historical and CMIP6 scenario simulations (SSP1-2.6, SSP2-4.5, and SSP5-8.5) from the MPI-ESM1-2-HR global model, to drive the CaMa-Flood River Hydrodynamics model for streamflow and river flood simulations. ENEA-REG integrates a coupled atmosphere (WRF) and ocean (MITgcm) components, which enhance our ability to capture complex interactions between sea surface temperatures and extreme hydrological events. Preliminary results indicate notable spatial variability in future flood and drought hazards. Considering floods, changes in their extent, duration, and high-flow frequencies (20-year and 50-year events) suggest a decrease in magnitude in eastern Mediterranean basins under SSP5-8.5, while Spanish northern (Ebro, Duero, Tajo) and southern (Guadalquivir and Andalusian) hydrographic basins, the Po River basin, together with UK and the north of Europe show increases. For droughts, the analysis focuses on changes in magnitude, duration, and trends in streamflow and streamflow drought index, highlighting critical vulnerabilities across the region. These findings emphasize the need for targeted adaptation strategies in response to evolving hydrological extremes.