Hydrological drought extents in a warming world in large Alpine river basins

Climate change affects different hydrological drought characteristics, including their spatial extent. This drought property is crucial for water management, as drought size can limit the effectiveness of drought mitigation strategies such as water transfers. As droughts propagate through the hydrological cycle, hydrological drought extent is influenced by meteorological factors such as precipitation and land-surface conditions such as soil moisture and snow cover. Each of these components responds differently to climate change and it remains unclear how their combined changes influence hydrological drought extent in the future. 

Here, we study the influence of climate change on spatial extent in droughts around the European Alps. We use climate projections from a single-model initial-condition large ensemble (SMILE) to run the PCR-GLOBWB model (at 1km resolution) over 4 major Alpine river basins (Danube, Rhine, Rhone, and Po rivers) until 2100. Using the resulting simulations, we study trends in drought extent, specifically focusing on the different components of the hydrological system such as meteorological, soil moisture and hydrological droughts.  

Our results indicate that trends in drought extent vary depending on the hydro-climatological characteristics of the Alpine basins considered. Furthermore, we highlight that trends in meteorological drought extent do not translate directly to trends in the extent of other hydrological components due to land surface processes. These findings can contribute to a better understanding of drought extent evolution, which can inform future water management decisions and lead to more robust drought mitigation strategies.