Domestic water supply under stress due to future climatic and socio-economic changes: A European-scale analysis

Groundwater resources are essential for human water supply and ecosystem functioning. Against the background of climate change, groundwater use becomes increasingly important, as it serves as a buffer during dry periods and is often less polluted than surface water. However, changing socio-economic factors influence groundwater use patterns (e.g. demographic transition, economic development and efficiency gains) and can lead to high demands during (dry summer) periods of low availability. In addition, there are climate change-related changes in groundwater recharge due to altered precipitation patterns and increased potential evapotranspiration. Therefore, it is necessary to consider scenarios of future groundwater availability and use to support sustainable groundwater management in Europe. We combine groundwater recharge and societal water demand in Europe to identify spatial patterns of groundwater availability and demand mismatches. For the current situation, we use data from the global hydrological model WaterGAP to quantify, with a spatial resolution of 0.5°, groundwater stress across Europe as the ratio of total groundwater abstractions to groundwater recharge. For future recharge estimation, we compile a multi-model ensemble with data from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) that includes four global climate and eight global hydrological models to assess the uncertainties that are inevitable in analyzing the future impacts of climate change. We quantify scenarios of future domestic water demand using water use data, population scenarios and climate variables on a national and sub-national scale. By combining current groundwater stress with trends in future groundwater recharge and domestic water demand, we identify hotspots of future stress on domestic water supply. Our approach contributes to the understanding of human-water interactions and highlights the importance of combining physical conditions and human influences. The methodology can be easily adapted to other regions of the world (if data on water use and population are available) to support sustainable groundwater management.