Modeling Climate Change and Human Pressure in Karst Systems: Insights from Mediterranean Springs in France and Morocco

The Mediterranean basin is particularly vulnerable to climate change. These changes are potentially impacting groundwater resources and aquifer recharge. In this context, reducing vulnerability to hydrological extremes (drought and flooding) and preserving both the quantity and quality of the resource are two key priorities for public authorities. Hydrogeological simulations are conducted based on different climate scenarios to provide information on how the resource may evolve in various scenarios. The hydrographic basin of the Lez spring is located in southern France. It is a basin composed of Upper Cretaceous and Lower Jurassic rocks, which are highly karstified. The spring of this basin is used to supply drinking water to the Montpellier metropolitan area (approximately 400,000 residents), generating strong pressure on this resource. The hydrogeological catchment of the Asserdoune karst spring, located in northern Morocco, is actively used to supply Beni Mellal (280,000 residents) with drinking water. The two main objectives of this study are (i) to assess long-term trends in climatic (rainfall, temperature, potential evapotranspiration) and hydrological variables (spring and river discharges) and (ii) to develop hydrological projections based on CMIP6 climate projections under the SSP2-4.5 and SSP5-8.5. For the Lez spring, these climate projections are coupled with anthropogenic withdrawal projections, developed in collaboration with water managers. The trend analysis results indicated a strong increase in temperature and evapotranspiration, but contrasting trends in precipitation between France and Morocco. The modeling of groundwater recharge and availability under different climatic and anthropogenic scenarios could provide a better understanding of the evolution of the resource at different time horizons, and support the decisions taken by water resource managers.