Rainfall and groundwater isotopes to investigate aquifer recharge mechanisms and seasonality in the Mediterranean region. Implications for long-term groundwater sustainability in the climate change context

Abstract

The Western Mediterranean Region with a focus on Corsica Island. Groundwater recharge, a complex component of the water cycle, highly sensitive to climate change and controlled by other several factors. Based on long-term records of precipitation stable isotopes and groundwater through different sites, this paper aims to analyze the groundwater response to rainfall input and thus to define the different recharge mechanisms in various geomorphological and geological settings. Results show various patterns of groundwater recharge in alluvium, limestone and basement with greatest variability in rainwater infiltration in alluvial systems. Groundwater recharge ratios in coastal areas are similar in winter and summer periods while in inland areas the summer recharge is negligible. An assessment of the rainwater signal damping was conducted and revealed a limited influence of plants while the direct control of climatic regime through snowpack, precipitation intensity and evaporation is highlighted. The evaporation mechanism in groundwater, investigated using deuterium-excess and line-conditioned excess, is mainly related to a connection between rivers and aquifers. This work provides a clear understanding of aquifer response to meteorological conditions in the Mediterranean region. Groundwater is not just a weighted mean of rainfall events but rather reflects a complex eco-hydro-meteorological system. These results are beneficial for the development of sustainable water management practices according to the climate scenarios. • Summer and winter groundwater recharge ratios are similar in coastal areas. • Land cover does not impact the rainwater isotopic signal during infiltration. • Evaporation affects groundwater independently of the hydrogeological context. • Groundwater reflects a control of climate and landscape on isotope signature.