Résumé
Explore 2 is a multi-partner project supported by the French Ministry of the Environment aimed at assessing the impact of climate change on water resources by 2100 in France. The present study focuses on estimating this impact on groundwater resources. The climate change projections correspond to a selection of regional climate projections based on the EURO-CORDEX database and made available by Météo France on the DRIAS website (https://www.drias-climat.fr/). These regional climate projections were corrected biases in relation to the SAFRAN historical meteorological dataset using the adjustment method ADAMONT (Verfaillie et al., 2017). They rely on the three greenhouse emission scenarios RCP 2.6, RCP4.5 and RCP8.5 according to the CMIP5 exercise. Several modelling tools covering all or part of France provide hydrogeological projections according to those climate projections. A calculation method based on the soil water balance (Caballero et al., 2021) estimates variations in recharge across France. The AquiFR modelling platform (Vergnes et al. 2020) provides access to variations in piezometric levels over part of the sedimentary basins, including the Paris basin. The North-Aquitanian model (Satlel et al., 2019) provide changes in the deep aquifers in the Aquitanian region. Finally, a lumped-parameter hydrological model developed with the EROS computer code (Thiéry 2018) yields groundwater levels at a selection of piezometers across Brittany. Preliminary results based on the RCP8.5 scenario show that France will be wetter at the end of the century in the northern half of the country regarding the groundwater resources evolution, and drier in the southern half. However, a large dispersion characterizes the ensemble of hydrogeological projections. This dispersion involves contrasting evolution in seasonal trends and extreme events occurrence between the models. It reflects uncertainties in the regional climate projections and in the hydrogeological model structures.