Assessing climate change impact on French groundwater resources using a spatially distributed hydrogeological model

Today, large-scale modelling tools are needed for anticipating the expected impacts of climate change on hydrosystems and for planning mitigation measures. We developed a spatially-distributed model for the MARTHE (Modélisation d'Aquifères avec un maillage Rectangulaire, Transport et HydrodynamiquE; Modelling Aquifers with Rectangular cells, Transport and Hydrodynamics) hydrogeological modelling computer code as a preliminary tool for France, and carried out a first evaluation over a 10-year period, comparing observed and modelled time series of groundwater levels and river flows. Then, prospective hydrological simulations were undertaken using five regionalized climate simulations. The evaluation results show varying performance depending upon the regions and variables considered, but they provide encouraging perspectives. Future hydrological projections anticipate increased recharge by +15% on average over France, accompanied by increases in wetter/drier groundwater extreme events in the north/south by the 2070–2099 period compared to the 1976–2005 reference period. Based on these results, the MARTHE model can be considered a promising template for the construction of a nation-wide hydrological model.