Relative changes in cumulative annual recharge at the end of the century (from 2070 to 2099) compared with the 1976-2005 period, for the four Explore2 study narratives.
- Green: significant warming and increase in precipitation
- Yellow: relatively little change in the future
- Orange: substantial warming and annual dessication
- Violet: substantial warming and sharp seasonal contrasts in precipitation
© Lanini et al., 2024
Periods of drought, severe flooding, etc. – climate change is unquestionably affecting the weather, albeit in different ways in different parts of the world. The impact on river systems is complex on the scale of France. Predicting changes in water resources over the coming decades is all the more difficult given the large number of climate models.
Updating is possible and relevant
In 2021, the French National Agriculture, Food and Environmental Research Institute (INRAE) and the International Office for Water (OiEau) launched the Explore2 project, which involves projecting changes in water resources throughout the 21st century in mainland France. Funded by the Ministry for Ecological Transition and the French Office for Biodiversity, this study follows on from Explore 2070, which between 2010 and 2012 produced initial projections for the period from 2050 to 2070 in mainland France and the French overseas territories. Over the last ten years, climate models have become considerably more refined, making it possible and relevant to update the hydro system projections in France for the period from now until 2100 on the basis of the latest climate scenarios published by the IPCC. Explore2 also aimed to help regional stakeholders understand and use these results to adapt their water resource management strategies.
A number of French research bodies (Météo France, BRGM, ENS-PSL, Sorbonne University, IRD, CNRS and EDF) have joined forces to form a scientific consortium coordinated by INRAE. Each of them focused on a particular issue in a coordinated methodological framework: climate projections, hydrological projections for surface water and groundwater, calculation of uncertainties, scenarios for the occurrence of extreme hydrological events, dissemination and use of the results, etc. “BRGM was called upon in particular to model the groundwater aspects of the water cycle,” explains Jean-Pierre Vergnes. “This mainly relates to changes in groundwater levels, but also groundwater recharge, i.e. the water that seeps underground to potentially replenish aquifers.”
Three emission scenarios
The BRGM researchers used several regional climate models produced by Météo France, themselves based on three greenhouse gas emission scenarios provided by the IPCC. At least 70 hydro-climatic projections have been produced for mainland France, making Explore2 a completely unprecedented project.
