Observed and projected changes on aquifer recharge in a Mediterranean semi-arid area, SE Spain

Groundwater is the major water source in arid and semi-arid regions and its availability under future climatic scenarios is uncertain. In this context, the knowledge of the likely changes in aquifer recharge is very important for sustainable management of groundwater resources in these environments. This work assesses the effect of future potential changes in the climate variables on aquifer recharge in a Mediterranean semi-arid aquifer (Sierra de Las Aguilas (SAG), SE Spain). We used monthly piezometric data to validate the aquifer recharge simulated by HYDROBAL ecohydrological model over the period 2001–2016. This model was then used to simulate the aquifer recharge over the historical period 1971–2000 and over two projected periods (2039–2068 and 2069–2098) using 18 downscaled climate projections. The results show that the percentage of aquifer recharge to precipitation (PAR) decreased significantly over the historical period (− 0.3% year⁻¹, p < 0.05). This decreasing tendency is expected to continue in the same direction with similar reduction rate (− 0.4% year⁻¹, p < 0.001) under the moderate RCP4.5 climate scenario and with a higher rate (− 0.6% year⁻¹, p < 0.001) under the high RCP8.5 scenario. These changes, due principally to the reduction of precipitations, will inverse the recuperation trend observed in the water level. Actually, the current water pumping from the SAG aquifer represents 10% of precipitation below the observed PAR (15.1%). However, in the future, the PAR is expected to decrease below the 10% threshold under the two RCP scenarios for the medium- and long-term periods.