Jeantet et al. (2026) Climate change impacts on groundwater simulated using the AquiFR modelling platform

Identification

• Journal: Hydrology and earth system sciences
• Year: 2026
• Date: 2026-10-20
• Authors: Alexis Jeantet, Jean‐Pierre Vergnes, Simon Munier, Florence Habets L
• DOI: 10.5194/hess-30-6381-2026

Research Groups

• Laboratoire de Géologie, CNRS UMR 8538, École Normale Supérieure, PSL University, IPSL, Paris, France
• Water, Environment, Processes and Analyses Division, BRGM – French Geological Survey, Orléans, France
• CNRM, Université de Toulouse, Météo-France, CNRS UMR 3589, Toulouse, France

Short Summary

This study assesses climate change impacts on groundwater levels in French aquifers during the 21st century using the AquiFR hydrogeological platform forced by 36 regional climate projections. It reveals significant variability, but a predominant signal of increasing groundwater levels in northern France and increasing low groundwater levels in southern France under the RCP8.5 scenario, highlighting a discernible North-South distinction.

Objective

• To estimate changes in groundwater levels on French aquifers during the 21st century under various climate change scenarios using the AquiFR modelling platform.

Study Configuration

• Spatial Scale: French aquifers covered by the AquiFR platform, including Nord Pas-de-Calais, Basse-Normandie, Parisian Basin, Loire, Poitou-Charentes, Alsace, and Tarn-et-Garonne. The AquiFR domain comprises 13 models with surface areas ranging from approximately 1100 km² to 66000 km². Climate projections are provided on an 8 km × 8 km regular grid, and AquiFR results are on an irregular grid with 100 m to 2000 m resolution.
• Temporal Scale: Simulations cover the period from 1975 to 2099. A historical reference period of 1975–2004 is used for the Standardized Piezometric Level Index (SPLI). Future projections are analyzed over three horizons: short-term (2021–2050), intermediate-term (2041–2070), and long-term (2071–2099). Climate variables are at an hourly time step, and AquiFR outputs are monthly.

Methodology and Data

• Models used:
  • Hydrogeological modelling platform: AquiFR, integrating two physically-based hydrogeological software packages: EauDyssée (for 2D horizontal groundwater flows and vertical exchange) and MARTHE (for 3D finite volume groundwater flows and river flows).
  • Land surface model: SURFEX, using the ISBA (Interactions Sol – Biosphère – Atmosphère) land surface scheme to simulate water and energy balances and provide groundwater recharge terms (surface runoff and drainage).
  • Climate models: 6 General Circulation Models (GCMs) coupled with 9 Regional Climate Models (RCMs) from the Euro-CORDEX project (CMIP5).
  • Downscaling and bias correction method: ADAMONT (ADjustment to MOuNTain regions), which combines weather regime computation and quantile mapping.
• Data sources:
  • Climate projections: EXPLORE2-Climat 2022 database, a subset of Euro-CORDEX (CMIP5) projections, providing 36 GCM/RCM combinations forced by three Representative Concentration Pathways (RCPs): RCP2.6, RCP4.5, and RCP8.5. Four contrasting storylines based on RCP8.5 are also used.
  • Historical meteorological reference for bias correction: SAFRAN reanalysis (Système d'Analyse Fournissant des Renseignements Adaptés à la Nivologie).
  • Groundwater abstraction: Monthly climatology-based historical data, held constant for future projections.
  • Hydrological indicator: Standardized Piezometric Level Index (SPLI), a normalized indicator of monthly groundwater level.

Main Results

• Overall Variability: Projections show significant variability between GCM/RCM couples, limiting the identification of a single clear trend, especially for RCP2.6 and RCP4.5 on short- and intermediate-term horizons.
• North-South Divide (RCP8.5): A discernible North-South distinction is observed.
  • Northern France: A predominant signal of increasing groundwater levels, reaching 5-year to 10-year wet events on the long-term horizon, supported by 3 out of 4 storylines. This contrasts with previous studies.
  • Southern France (e.g., Tarn-et-Garonne, Alsace): Groundwater levels tend to remain stable or decrease, reaching 5-year dry events in the long-term horizon.
• Extreme Events (RCP8.5):
  • Extreme Wet Events (≥ 10-year return period): The surface area affected by extreme wet events is projected to increase by a factor of 4.5 on the long-term horizon (ensemble median), with 3 out of 4 storylines supporting this trend.
  • Extreme Dry Events (≥ 10-year return period): The surface area affected by extreme dry events is also projected to increase, but with a less pronounced trend (at most 10.0% of the AquiFR domain for the ensemble median). The "orange storyline" (driest) projects a 25-fold increase in extreme dry events across almost the entire domain.
• Seasonal Dynamics: No significant modification in the seasonal regime of groundwater levels is observed, attributed to the slow temporal dynamics of the aquifers in the study area.
• RCP2.6 and RCP4.5 (Long-term): While divergent on shorter horizons, long-term projections show a more convergent signal of increasing groundwater levels, particularly in the northern AquiFR domain, with RCP4.5 indicating extreme wet events.

Contributions

• Utilisation of a large ensemble of 36 climate projections (GCM/RCM pairs) to robustly assess uncertainties associated with internal climate variability, a dimension poorly explored in groundwater literature.
• Application of four contrasting storylines to explore the range of climate change impacts on groundwater, an approach rarely adopted in existing groundwater studies.
• Integration of heterogeneous aquifer systems across France using the AquiFR platform, enhancing the realism of hydrogeological modelling.
• Provision of spatially explicit analyses of future groundwater level trends using the Standardized Piezometric Level Index (SPLI).
• Updates previous national assessments (e.g., EXPLORE 2070) with more recent CMIP5 climate projections, revealing a more nuanced picture of groundwater evolution, particularly the increase in northern France.

Funding

• Office Français de la Biodiversité
• Ministère de l'Écologie, du Développement Durable et de l'Énergie (EXPLORE2 project)

Citation

@article{Jeantet2026Climate,
  author = {Jeantet, Alexis and Vergnes, Jean‐Pierre and Munier, Simon and L, Florence Habets},
  title = {Climate change impacts on groundwater simulated using the AquiFR modelling platform},
  journal = {Hydrology and earth system sciences},
  year = {2026},
  doi = {10.5194/hess-30-6381-2026},
  url = {https://doi.org/10.5194/hess-30-6381-2026}
}