Climate change impacts on groundwater simulated using the AquiFR modelling platform

Jeantet, Alexis; Vergnes, Jean-Pierre; Munier, Simon; Habets, Florence

doi:10.5194/egusphere-2025-93

Preprints

https://doi.org/10.5194/egusphere-2025-93

Preprints

04 Feb 2025

| 04 Feb 2025

Climate change impacts on groundwater simulated using the AquiFR modelling platform

Alexis Jeantet, Jean-Pierre Vergnes, Simon Munier, and Florence Habets

Abstract. In the context of increasing water stress and climate change, the assessment of changes in groundwater resources is a major challenge for water decision-makers. As part of the EXPLORE2 project, the aim of this study is to estimate changes in groundwater levels over France during the 21^st century. We used the hydrogeological modelling platform AquiFR together with 36 regional climate projections from Eurocordex (CMIP5) from three Representative Concentration Pathways (RCPs), bias-corrected according to a state-of-the-art method: RCP2.6, RCP4.5 and RCP8.5. The future evolution of groundwater is assessed using the standardized piezometric level index, a normalized indicator that provides return periods based on the distribution value over a reference period, here 1976–2004. We found significant scatters between regional climate models and RCPs. Overall, a rise in groundwater levels, affecting most of the study area, is the dominant signal, especially in northern France. This result is in contrast to previous studies in this area. Under RCP8.5 (highest greenhouse gas emissions scenario), the evolution of the occurrence of current 10-year return period events shows a significant increase in the risk of high groundwater levels mostly on the northern part of France, together with an increase in the 10-year low groundwater levels mostly observed in South of France, which highlights a North-South differentiation. The increase in high and low flow events is quite common in surface hydrology, but is less common for groundwater, which has a longer residence time. In order to better reflect the uncertainties, 4 storylines based on the RCP8.5 scenario have been selected to be representative of possible futures that can illustrate the impacts of worst-case scenarios and help decision-makers to adopt sustainable groundwater management policies.

Received: 13 Jan 2025 – Discussion started: 04 Feb 2025

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

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Journal article(s) based on this preprint

20 Oct 2026

Climate change impacts on groundwater simulated using the AquiFR modelling platform

Alexis Jeantet, Jean-Pierre Vergnes, Simon Munier, and Florence Habets

Hydrol. Earth Syst. Sci., 30, 6381–6420, https://doi.org/10.5194/hess-30-6381-2026,https://doi.org/10.5194/hess-30-6381-2026, 2026

Short summary

Alexis Jeantet, Jean-Pierre Vergnes, Simon Munier, and Florence Habets

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-93', Anonymous Referee #1, 02 Mar 2025
The study described in this paper is substantively correct and necessary. Moreover, it surprises with the amount of work put into this study.
However, the issue is that the manuscript is now too extensive. This whole huge work is described in one huge paper, and it is something like 2 in 1, i.e. (i) results obtained for all available climate projections-CP, and (ii) for storylines. As a consequence, it is very difficult to follow, too heavy and not transparent. In addition to the volume, it is influenced by the excessive detail of some descriptions and showing in the main text elements that are not very important. For this reason, the paper is not clear and very difficult to read and understand the main issues.
I believe that the manuscript should be divided into two separate papers. In the paper discussed now, only the most important descriptions, results and discussions of three types of statistical analyses performed for only four storylines should be left. However, storyline No. 4 seems unlikely, so its description and results should be moved to the Supplement Material. Similarly, the RCP2.6 path is rather unlikely, so the description of the study and results for this path can also be moved from the main text to the Supplement Material.

A report of studies based on all the available climate projections (CP) can be successfully published in the second paper, in the discussion of which the obtained results can be related to the results for the storylines. Or vice versa - depending on the authors' decision.

The justification for removing descriptions of tests performed for RCP2.6 from the main text are, among others, section 3.2, Fig. 5 and Table 5. This is all unclear and too far removed from the main thrust of this paper, i.e. spatial projection of climate change on a regional scale. Considering the description in the text, it seems possible to move Table 5 to the Supplement.

Table 1 should rather be in the Supplement because it is additional information and does not directly concern the main research problem solved by this study.

line 113 – it is unclear what "strong seasonal contrast" means in story No. 3 (Purple) – this should be explained.

lines 140-143 - models EROS and HS1D - since these 2 models have not been taken into account in this study, why mention them (it only makes the text harder to follow).

Lines 144 – 160 - models EauDyssee and MARTHE - these descriptions are not necessary in the main text and can be moved to the Supplement. Only the sentence in lines 157-159 is important for the main text.

lines 173 -177 - excessive detail - can be moved to the Supplement.

Table 3 - can be moved to the Supplement because Figure 3 shows the modelled catchments well.

lines 193-196 - I don't understand how the SPLI values were calculated. Are they based on frequency percentages? The description should be clearer, because that's the basic element of this research.

sections 4.1 and 4.2 - confirm that this manuscript is too burdened with too much information, analysis and discussion. All of these strays too far in different directions from the main topic given in the title. This should be an article about just one specific study - either about the storylines or about the all available CPs , depending on the authors' decision. It is also possible to propose two publications under one common main title, divided into Parts 1 and 2, respectively covering the indicated topics.
Citation: https://doi.org/10.5194/egusphere-2025-93-RC1
- AC2: 'Reply on RC1', Alexis Jeantet, 16 Apr 2025
  
  Please find the reply in the attached file.
  
  Citation: https://doi.org/10.5194/egusphere-2025-93-AC2
RC2:
'Comment on egusphere-2025-93', Anonymous Referee #2, 10 Mar 2025
In their paper, Jeantet et al present a study on the impacts of climate change on groundwater using the modelling plateform AquiFR. 36 combinations of Regional Climate Models and Global Climate Models and 4 storylines for 3 RCPs and different time horizons are used to feed groundwater models over approximatively half of France. The results are mainly analyzed using mapping or temporal evolutions of the Standardized Piezometric Level Index (SPLI). Particular attention is paid to 2.5, 5 or 10 years return period wet/dry events. The paper is overall well structured and organized. The high number of climate scenarios presented makes it quite difficult to present clearly and in a synthetic manner. Moreover, the high level of uncertainties associated with the final results makes the key message of the paper quite unclear. I feel like a lot of effort was put in this work and that it is worth publishing it. But I think the paper should be improved to make it more synthetic and clearer. In the following, you will find my major comments and some minors ones.
Major comments:
The paper focuses on the impact of climate change but do not address – except at the very end of the conclusion – the strong link between water availability and water demand. One could expect agricultural and water drinking demands to change with climate change, potentially strongly impacting groundwater level. I feel like this issue should be mentioned earlier in the paper and discussed a bit more.

The presentation of the results is hard to follow because of the 36 scenarios used and the 4 storylines. I wonder if treating the 4 storylines – that are specifically chosen to illustrate the potential contrasting futures – alone would not be sufficient to give a clear and synthetic message. Especially because the simulated groundwater levels are very uncertain with the 36 scenarios.

I feel like treating the RCP 2.6 in the paper is not relevant. Because the current CO2 emissions trajectories make it very unlikely, and because the results for this specific RCP are so uncertain that no conclusion can be drawn. I would remove it for sake of simplicity.

The way SPLI is computed is not clear enough for me. The way the normal CDFs are transposed in SPLI distribution should be explained.

On all the maps, I would use a very distinct color for the part of France that were not simulated. Figure 3 shows a lot of untreated scenarios. Consequently, the maps for the treated one are very small and hard to read. I don’t know how to improve that but having larger map would be great.

Figure 5 is really dense, and should be looked at together with Table 5 to follow the text. It’s thus quite challenging to catch all the information’s presented in part 3.2. Maybe one more argument to keep only the storylines.

I don’t really get to what extend the results presented in Vergnes et al, 2023 are different from the MARTHE part of the submitted paper. I would appreciate if this could be discussed somewhere in the introduction.

In part 2.2.1, it’s not very clear whether SURFEX or ISBA or both are used for the study. This part is rather confusing and unclear. I think it should be improved.

Multi-model is advocated in the introduction. One could expect that this approach is used throughout the study. It is clearly done for the climate part but not for the groundwater modelling part. If I get it right, most of the time MARTHE and EauDyssé were not applied on the same region. And it’s hard to get where it’s been done, as all the surfaces in Table 3 are different. I think the reasons why only one groundwater model has been applied should be stated somewhere. And Table 3 should be improved so that locations where both models are applied appear clearly.

Minor comments :
First sentence of the introduction is not clear for me. Especially “for both agricultural purposes”. Please rephrase.

Line 83: typo – replace dot by coma

How are the weather regimes defined?

Line 117 : typo (Vergnes et al, …)

Line 128 : typo - to simulate

Line 148: “vertical exchange through aquitards” – not clear for me. Aquitards are not supposed to conduct water.

The way unsaturated zone is treated in MARTHE should be detailed.

Line 228: I don’t get what is meant by ”physical consistency of each storyline is conserved”

Line 304: typo “Figure 6 the maps”. Please rephrase
Citation: https://doi.org/10.5194/egusphere-2025-93-RC2
- AC1: 'Reply on RC2', Alexis Jeantet, 16 Apr 2025
  
  Please find the reply in the attached file.
  
  Citation: https://doi.org/10.5194/egusphere-2025-93-AC1

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (18 Apr 2025) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (27 May 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (11 Jun 2025) by Heng Dai

RR by Anonymous Referee #1 (20 Jun 2025)

RR by Anonymous Referee #3 (05 Aug 2025)

Suggestions for revision or reasons for rejection

This manuscript presented results from groundwater models forced with a variety of climate scenarios for several regions across France. It is clear that significant effort was put into not only the simulations, but the interpretation of the results. I do think the main points of this work provide significant scientific contributions, but feel the manuscript is still too convoluted and full of extraneous 'stuff' - this makes it hard to follow as a reader.

Although a previous reviewer requested information about the modeling packages be removed, I believe that they are necessary. A key concern of mine is that the comparison of model results across France are not done with one uniform modeling package, so how does the selection of modeling software impact the results? I would like to know what they key differences are and have some discussion about how they may impact the final results. Different modeling approaches will have different uncertainties, structural or otherwise, which will impact results and shouldn't be ignored.

Consistent to previous reviewers, and as indicated above, I do feel that the authors need to spend significant effort focusing this manuscript - a lot of work went into the simulations, but not all of them need to be presented to get to the main contributions of this work. The inclusion of all the simulations and the storylines makes it much harder for the reader to reach the same conclusions. I feel a careful evaluation of what is critical to supporting the conclusions, what is supportive (supplemental), and what is not necessary could help to improve this manuscript. Through this process, I would also encourage the authors to carefully review the grammar, or request assistance as necessary - this would also improve the readability and communication of the work.

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ED: Publish subject to revisions (further review by editor and referees) (06 Aug 2025) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (10 Sep 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (22 Sep 2025) by Heng Dai

RR by Anonymous Referee #3 (20 Oct 2025)

RR by Anonymous Referee #4 (11 Dec 2025)

Suggestions for revision or reasons for rejection

The paper of Jeantet et al. studies the impact of climate change on the groundwater in France. In the paper thirteen groundwater models set up for specific hydrogeological systems in France - grouped in the AquaFR platform - are forced with climate change scenarios making use of 17 GCM/RCM pairs forced by one to tree Radiative Concentration Pathways (RCPs) resulting in 36 model simulations for each hydrogeological model. The analysis is done for climate change scenarios on the short, middle and long-term horizons.

The novelty of the paper lies mainly in the application of the state-of-the-art climate change scenarios for a relatively large area in France, resulting in interesting insights on the expected trends for the groundwater systems in scope. In the analysis of the results, the authors make use of the Standardized Piezometric Level Index allowing to interpret if groundwater levels are above or below the median state.

In the revised version of their paper the authors did a good job in making the paper more concise. Large parts of the text were rewritten, the analysis was focused on the 4 storylines, and many tables and figures were moved to the appendix, which significantly improved the readability of the paper. Some small suggestions are made below to further improve the readability.

However, in my opinion the paper needs some additional revisions on the discussion of the model results. As the other reviewers also mentioned, the rather large spatial variability of the impact of climate change on your groundwater levels makes the key message of the paper unclear. I understand that due to different groundwater systems incorporated in the study there is little room for going in depth on the site characteristics of the different aquifers. The impact of the climate change scenarios on the groundwater seems to have a clear north to south gradient with increasing groundwater levels in the northern catchment and decreasing groundwater levels in the southern catchments, however large spatial differences remain between the different climate change scenarios. As neither the characteristics of the groundwater systems, nor the spatial distribution of the driving forces (groundwater recharge) are described, it is difficult to gain inside of what could be the main reason for this spatial difference in the impact. A revision on the discussion going more in depth regarding potential causes should be included in my opinion (see the first major comment).

Main comments

- In order to increase the understanding of the groundwater system I would like to advise adding some more spatial information. The same type of figure as figure 3 could be used. The following maps could be considered:
o Change in groundwater recharge (maybe even precipitation and evapotranspiration)
o Temporal dynamics of the groundwater in the model domain e.g p10 – p90 for the reference period, as this might be relevant to interpret the SPLI?
o Change in average groundwater level between the scenarios

- Another aspect that is unclear for me is how the climate change scenarios are forced to the hydrogeological models. Please include if groundwater recharge from the SURFEX model is used in the hydrogeological models using a one way coupling or if feedback mechanisms are considered. Are also other boundary conditions of the hydrogeological models are changing (e.g. river water levels, direct evapotranspiration from the groundwater system…)?

Minor comments

- The background image in e.g. figure 3 has similar colors as the color used for the SPLI change. Can this be improved? Maybe even a polygon around the model area could help.
- Try to limit the use of terminology specific for the region (eg. EXPLORE2 project, EXPLORE 2070 project, SURFEX, MODCOU..), this terminology makes reading difficult for people who do not know these projects or models.
- If I am correct, you only discuss T10 of figure 4. You could move T5 and T2.5 to the appendix. It might be interesting to include the T10 of figure C1 in figure 4 as you also discuss this figure in the text.
- Line 361: remove one ‘evaluation’
- On page 17 your mention that Habets et al. (2013) obtained similar results using different methods with the same climate change scenarios. Other studies, however, have obtained significantly different results with different models. I would just mention that you did not investigated the impact of uncertainty resulting from the hydrogeological model.
- The part on the different CDF’s for the different CP’s (paragraph from line 379) is difficult for me to understand. Please include why this is relevant for the comparison of the SPLI’s.
- Some of the figures that were not included in the paper, but that are mentioned in the text (e.g. figure 6 for different months) could be included as supplementary information.

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ED: Publish subject to revisions (further review by editor and referees) (24 Dec 2025) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (29 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (19 Feb 2026) by Heng Dai

RR by Anonymous Referee #5 (20 May 2026)

Suggestions for revision or reasons for rejection

This manuscript addresses an important and timely topic by investigating groundwater level responses under different future climate scenarios. Given the substantial computational cost in large-scale groundwater modeling, the application of multiple scenarios and model combinations, even within a regional focus on France, represents a significant technical effort. The use of the SPLI indicator to characterize future groundwater trends also provides an innovative perspective for assessment on groundwater level change variability. However, despite the scientific relevance and technical scope, the manuscript requires substantial revisions to improve clarity and interpretability of the results. The main concerns are outlined below.

Major comments:
#1 The manuscript currently spends considerable space to describe the comprehensive modeling systems, but the relationships among the different components are not clear. The context includes extensive jargon and acronyms, making it difficult to identify which model components are central to the study. For example, in Section 2.2.2, AquiFR is described as using two groundwater models, EauDyssée and MODCOU. However, their conceptual and structural differences are not clearly articulated. It also remains unclear why two groundwater models are required for different aquifers rather than a unified modeling framework. I fully understand this is a community effort and credit should be fully acknowledged, but to make the manuscript's message clear and scientifically meaningful, I suggest the authors to pick up the most relevant components for description.

#2 An important element is missing from the current study: the model simulation during the historical period should be validated against observations. Such validation is essential to demonstrate confidence in the models’ ability to represent groundwater dynamics before applying it to future climate projections.

#3 In the result part, the manuscript mainly presents groundwater level projections without sufficiently analyzing the processes driving those changes. The forcings that drive groundwater variability, such as precipitation, evapotranspiration, recharge, and river-aquifer interaction regimes, and topographic and hydrogeologic factors that shape groundwater heteorogeneity, are not systematically presented or discussed. Without such process-based analysis, it is difficult to assess whether differences arise from climate forcing, hydrological parameterization, or structural model differences. I strongly encourage the authors to include analyses on the components below in their result presentation:
• Changes in precipitation and recharge across scenarios;
• Changes in river discharge or surface water interactions where relevant;
• A structured discussion linking climate forcing --> recharge --> groundwater level response.

#4 Potentially related to the previous point, the study employs six GCMs to generate climate forcing. However, there is little discussion of how these GCMs differ in terms of their physical representations (e.g., precipitation bias structure, evapotranspiration sensitivity, circulation patterns), which directly influence recharge and groundwater dynamics. Including a concise description of key structural differences among the selected GCMs would help readers interpret why groundwater responses differ under different climate forcings. At minimum, a short summary of known characteristics (e.g., wetter/drier bias tendencies, seasonal precipitation shifts, etc.) would strengthen the interpretation of ensemble spread.

Minor comments:
Line 4: “CMIP5”: Since there are updated results from CMIP6, why not use the latest one but CMIP5? At least the author should explain the reason.
Line 16: “high and low flow events”: In terms of groundwater, groundwater levels high or low are not necessarily related to high/low groundwater flow. The authors might want to rephrase the wording here.
Line 57: “two distributed hydrogeological modellling …” Please specify which two
Line 111: what is quantile mapping and why it should be quantile-based, not the original value based?
Line 119: “gaz”, typo, should be “gas”
Line 159: This is interesting. The authors may need to explain more about why groundwater contribution is this low. Is it because groundwater level is generally deep in France?
Line 182: “homogeneous format”, what does it mean? What format?
Line 194-195: Why to use different models for different aquifers? The authors need to clearly explain their motivation (pros and cons of each model)
Line 228, Table2: What’s the criteria to determine the thresholds for each category?
Line 312, Figure 3: Why there are missing panels? Is it because no GCM data available? The authors need to indicate this in caption.

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RR by Anonymous Referee #6 (07 Jun 2026)

Suggestions for revision or reasons for rejection

The work is technically substantial and relevant for groundwater resource planning under climate change. However, the manuscript would benefit from minor but important revisions before publication. Most importantly, the authors should carefully correct remaining grammatical, typographical, and formatting issues.
(1) The novelty of the work is still not articulated clearly enough. I encourage the authors to refine the framing of the manuscript and to state more explicitly where the scientific contribution lies. In particular, the contribution appears to lie in the integrated use of a large regional climate-projection ensemble, a physically based multi-aquifer hydrogeological platform, SPLI-based comparison across heterogeneous aquifer systems, and storyline-based interpretation for risk communication. The authors should also better explain the relevance of this framework beyond the French context, especially for regions where groundwater projections are strongly affected by climate-model uncertainty and spatially heterogeneous recharge responses. Clarifying this broader relevance would strengthen the contribution of the manuscript.
(2) The description of the SURFEX–AquiFR coupling has been improved, but the modelling assumptions regarding boundary conditions remain insufficiently explicit. The authors should clearly state whether future groundwater changes are driven only by climate-induced changes in SURFEX-derived drainage and runoff, or whether other factors such as river boundary conditions, river stages, groundwater abstraction, land use, and direct groundwater evapotranspiration are also modified. A short clarification in the methods section would help readers understand whether the study isolates the climate-change signal or represents combined climate and anthropogenic influences.
(3) The use of SPLI is appropriate because it enables comparison of groundwater-level anomalies across heterogeneous aquifer systems. However, the manuscript should avoid overstating the novelty of the index itself, as SPLI is conceptually close to other standardized groundwater-level or groundwater-drought indicators. The authors should emphasize that the main contribution lies in applying SPLI within a large climate-projection ensemble and the AquiFR multi-aquifer modelling framework.
(4) The manuscript still contains a number of grammatical, spelling and formatting issues. These are minor issues, but they affect the readability and polish of the manuscript, and I recommend a careful final proofreading.
Line 14, “This accompanied by”should be “This is accompanied by”;
Line 16,“high and low flow events”is not fully appropriate for groundwater and could be replaced by “high and low groundwater-level events”;
Lines 70–74,“an multi-model ensemble approach” should be corrected to “a multi-model ensemble approach”and “The large number of used projections” should be corrected to “The large ensemble of projections used here”;
Line 135,“french rivers” should be revised to “French rivers”;
Line 158, there is an extra opening parenthesis in “2% ((Decharme et al., 2019)”;
Lines 204–214, “groundwater levels is”, “wheareas”, and “Thrid” should be corrected;
Lines 327–328, “more %50 of the time” should be revised to “more than 50% of the time”.

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ED: Publish subject to minor revisions (review by editor) (17 Jun 2026) by Heng Dai

ED: Publish subject to revisions (further review by editor and referees) (22 Jun 2026) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (20 Jul 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (01 Aug 2026) by Heng Dai

RR by Anonymous Referee #6 (10 Aug 2026)

Suggestions for revision or reasons for rejection

The manuscript has been substantially improved through the successive rounds of revision. In the current version, the modelling chain, the SURFEX–AquiFR coupling, the assumptions related to anthropogenic factors, and the link between climate forcing, groundwater recharge, and groundwater-level response are described more clearly. The additional water-balance results provided in the Supplementary Material also help strengthen the process-based interpretation of the projected groundwater responses. Overall, the main research framework and the presentation of the results are now reasonably complete. However, after carefully reading the latest version, I believe that several issues still require further clarification or verification. Some concern the interpretation of uncertainty sources and the implementation of the statistical analyses, which may affect the robustness of the corresponding conclusions. Others relate to the definition of the modelling framework, the SPLI analysis, and the consistency of quantitative information between the main text and the Supplementary Material. I therefore recommend that the authors carefully address the following issues before the manuscript is finalized.
1. The manuscript acknowledges that a proper evaluation of the contribution from the hydrogeological component would require a multi-model approach, which is not available for most of the AquiFR domain. However, it subsequently concludes that the contribution of the hydrogeological components to the total uncertainty remains negligible compared with that from the climate components. I may suggest authors stating more explicitly that hydrogeological-model uncertainty is not explicitly quantified in this study and moderating the corresponding conclusion. In addition, the subsequent comparison of the CDFs mainly evaluates the influence of the climate projections on the historical reference distributions used to construct the SPLI, rather than directly evaluating uncertainty arising from the hydrogeological models. The scope of this analysis should therefore be clarified accordingly.
2. In Section 2.3.2, the Mann–Kendall test is currently cited as Mann and Whitney (1947), which might be a wrong citation. Please check it. More importantly, detailed information is needed to verify which statistical test was actually implemented in the analysis and clearly specify the input time series and temporal resolution used for both tests, whether the tests were applied to the original time series or to the 5-year running median. If necessary, the significance results reported in Appendix C should be reassessed accordingly.
3. The Introduction states that AquiFR “is not based on a multi-model approach” because each hydrogeological modelling software package is generally applied to a specific catchment and very few simulated areas overlap spatially. In contrast, Section 2.2 describes AquiFR as “a hydro-meteorological modelling platform based on a multi-model approach.” It is recommended to clearly distinguish between a platform that integrates several regional hydrogeological model configurations and a hydrogeological multi-model ensemble that can be used to assess structural model uncertainty, and then use the terminology consistently throughout the manuscript.
4. A systematic cross-check of the quantitative information in the main text and Supplementary Material is recommended. For example, the model-area range reported in Section 2.2.3 is inconsistent with the values in Table A2; the spatial resolutions of the GCMs and RCMs are expressed in km² rather than km; and the third future horizon in Tables C1–C3 appears to contain an incorrect time-period label. In addition, the origin of the “6.3%” value reported for the green storyline in Section 3.2 should be checked against Table C1, and the statement that extreme wet events increase “by a factor of 7” in Section 4.3 does not appear to follow directly from the values reported in Table C3. I therefore recommend checking the relevant values, units, time periods, and calculations throughout the manuscript and Supplementary Material.
5. Section 2.3.1 explains that monthly CDFs are fitted using a non-parametric Kernel Density Estimation with the scikit-learn package. However, the main KDE settings, particularly the kernel, bandwidth, and bandwidth-selection procedure, are not specified. These details should be briefly provided to improve reproducibility. In addition, it is recommended to use precise terminology in the Results and Conclusions instead of repeatedly referring simply to “10-year wet events” or “10-year dry events”, as was done in the "Methods" section, where the SPLI values were correctly related to the return period of the equivalent event in the historical reference period.
6. Please clarify whether Figure 4 and Appendix C represent mutually exclusive SPLI categories or cumulative exceedance thresholds. Table 2 defines separate categories such as “between 2.5-year wet and 5-year wet,” “between 5-year wet and 10-year wet,” and “>10-year wet.” In contrast, Tables C1–C3 use expressions such as “≥2.5-year wet,” “≥5-year wet,” and “≥10-year wet,” which appear to represent cumulative exceedance thresholds. The authors should ensure that the definitions and terminology are consistent among Table 2, the Methods, the Results, figure captions, and Appendix C.
7. The Discussion appropriately acknowledges that the limited representation of southern France in the AquiFR platform prevents the existence of a France-wide North-South divide from being established with certainty. However, the Abstract still refers more broadly to groundwater changes “over France,” “South of France,” and a “discernible North-South distinction.” It is recommended to make the Abstract, Results, and Conclusions consistent with the more cautious interpretation in the Discussion, for example by referring to the AquiFR domain or to the French aquifer systems represented by AquiFR.
8. The Introduction currently states that the use of the selected projections as storylines to illustrate climate-change impacts on groundwater is an approach that, “to the best of our knowledge, has not yet been carried out in the literature.” Unless this statement can be supported by a sufficiently comprehensive literature assessment, I suggest avoiding such an absolute claim.

Referee Report: PDF

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RR by Anonymous Referee #5 (27 Aug 2026)

ED: Publish subject to minor revisions (review by editor) (30 Aug 2026) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (07 Sep 2026) Author's response Author's tracked changes Manuscript

ED: Publish as is (22 Sep 2026) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (01 Oct 2026) Author's response Manuscript

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-93', Anonymous Referee #1, 02 Mar 2025
The study described in this paper is substantively correct and necessary. Moreover, it surprises with the amount of work put into this study.
However, the issue is that the manuscript is now too extensive. This whole huge work is described in one huge paper, and it is something like 2 in 1, i.e. (i) results obtained for all available climate projections-CP, and (ii) for storylines. As a consequence, it is very difficult to follow, too heavy and not transparent. In addition to the volume, it is influenced by the excessive detail of some descriptions and showing in the main text elements that are not very important. For this reason, the paper is not clear and very difficult to read and understand the main issues.
I believe that the manuscript should be divided into two separate papers. In the paper discussed now, only the most important descriptions, results and discussions of three types of statistical analyses performed for only four storylines should be left. However, storyline No. 4 seems unlikely, so its description and results should be moved to the Supplement Material. Similarly, the RCP2.6 path is rather unlikely, so the description of the study and results for this path can also be moved from the main text to the Supplement Material.

A report of studies based on all the available climate projections (CP) can be successfully published in the second paper, in the discussion of which the obtained results can be related to the results for the storylines. Or vice versa - depending on the authors' decision.

The justification for removing descriptions of tests performed for RCP2.6 from the main text are, among others, section 3.2, Fig. 5 and Table 5. This is all unclear and too far removed from the main thrust of this paper, i.e. spatial projection of climate change on a regional scale. Considering the description in the text, it seems possible to move Table 5 to the Supplement.

Table 1 should rather be in the Supplement because it is additional information and does not directly concern the main research problem solved by this study.

line 113 – it is unclear what "strong seasonal contrast" means in story No. 3 (Purple) – this should be explained.

lines 140-143 - models EROS and HS1D - since these 2 models have not been taken into account in this study, why mention them (it only makes the text harder to follow).

Lines 144 – 160 - models EauDyssee and MARTHE - these descriptions are not necessary in the main text and can be moved to the Supplement. Only the sentence in lines 157-159 is important for the main text.

lines 173 -177 - excessive detail - can be moved to the Supplement.

Table 3 - can be moved to the Supplement because Figure 3 shows the modelled catchments well.

lines 193-196 - I don't understand how the SPLI values were calculated. Are they based on frequency percentages? The description should be clearer, because that's the basic element of this research.

sections 4.1 and 4.2 - confirm that this manuscript is too burdened with too much information, analysis and discussion. All of these strays too far in different directions from the main topic given in the title. This should be an article about just one specific study - either about the storylines or about the all available CPs , depending on the authors' decision. It is also possible to propose two publications under one common main title, divided into Parts 1 and 2, respectively covering the indicated topics.
Citation: https://doi.org/10.5194/egusphere-2025-93-RC1
- AC2: 'Reply on RC1', Alexis Jeantet, 16 Apr 2025
  
  Please find the reply in the attached file.
  
  Citation: https://doi.org/10.5194/egusphere-2025-93-AC2
RC2:
'Comment on egusphere-2025-93', Anonymous Referee #2, 10 Mar 2025
In their paper, Jeantet et al present a study on the impacts of climate change on groundwater using the modelling plateform AquiFR. 36 combinations of Regional Climate Models and Global Climate Models and 4 storylines for 3 RCPs and different time horizons are used to feed groundwater models over approximatively half of France. The results are mainly analyzed using mapping or temporal evolutions of the Standardized Piezometric Level Index (SPLI). Particular attention is paid to 2.5, 5 or 10 years return period wet/dry events. The paper is overall well structured and organized. The high number of climate scenarios presented makes it quite difficult to present clearly and in a synthetic manner. Moreover, the high level of uncertainties associated with the final results makes the key message of the paper quite unclear. I feel like a lot of effort was put in this work and that it is worth publishing it. But I think the paper should be improved to make it more synthetic and clearer. In the following, you will find my major comments and some minors ones.
Major comments:
The paper focuses on the impact of climate change but do not address – except at the very end of the conclusion – the strong link between water availability and water demand. One could expect agricultural and water drinking demands to change with climate change, potentially strongly impacting groundwater level. I feel like this issue should be mentioned earlier in the paper and discussed a bit more.

The presentation of the results is hard to follow because of the 36 scenarios used and the 4 storylines. I wonder if treating the 4 storylines – that are specifically chosen to illustrate the potential contrasting futures – alone would not be sufficient to give a clear and synthetic message. Especially because the simulated groundwater levels are very uncertain with the 36 scenarios.

I feel like treating the RCP 2.6 in the paper is not relevant. Because the current CO2 emissions trajectories make it very unlikely, and because the results for this specific RCP are so uncertain that no conclusion can be drawn. I would remove it for sake of simplicity.

The way SPLI is computed is not clear enough for me. The way the normal CDFs are transposed in SPLI distribution should be explained.

On all the maps, I would use a very distinct color for the part of France that were not simulated. Figure 3 shows a lot of untreated scenarios. Consequently, the maps for the treated one are very small and hard to read. I don’t know how to improve that but having larger map would be great.

Figure 5 is really dense, and should be looked at together with Table 5 to follow the text. It’s thus quite challenging to catch all the information’s presented in part 3.2. Maybe one more argument to keep only the storylines.

I don’t really get to what extend the results presented in Vergnes et al, 2023 are different from the MARTHE part of the submitted paper. I would appreciate if this could be discussed somewhere in the introduction.

In part 2.2.1, it’s not very clear whether SURFEX or ISBA or both are used for the study. This part is rather confusing and unclear. I think it should be improved.

Multi-model is advocated in the introduction. One could expect that this approach is used throughout the study. It is clearly done for the climate part but not for the groundwater modelling part. If I get it right, most of the time MARTHE and EauDyssé were not applied on the same region. And it’s hard to get where it’s been done, as all the surfaces in Table 3 are different. I think the reasons why only one groundwater model has been applied should be stated somewhere. And Table 3 should be improved so that locations where both models are applied appear clearly.

Minor comments :
First sentence of the introduction is not clear for me. Especially “for both agricultural purposes”. Please rephrase.

Line 83: typo – replace dot by coma

How are the weather regimes defined?

Line 117 : typo (Vergnes et al, …)

Line 128 : typo - to simulate

Line 148: “vertical exchange through aquitards” – not clear for me. Aquitards are not supposed to conduct water.

The way unsaturated zone is treated in MARTHE should be detailed.

Line 228: I don’t get what is meant by ”physical consistency of each storyline is conserved”

Line 304: typo “Figure 6 the maps”. Please rephrase
Citation: https://doi.org/10.5194/egusphere-2025-93-RC2
- AC1: 'Reply on RC2', Alexis Jeantet, 16 Apr 2025
  
  Please find the reply in the attached file.
  
  Citation: https://doi.org/10.5194/egusphere-2025-93-AC1

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (18 Apr 2025) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (27 May 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (11 Jun 2025) by Heng Dai

RR by Anonymous Referee #1 (20 Jun 2025)

RR by Anonymous Referee #3 (05 Aug 2025)

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ED: Publish subject to revisions (further review by editor and referees) (06 Aug 2025) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (10 Sep 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (22 Sep 2025) by Heng Dai

RR by Anonymous Referee #3 (20 Oct 2025)

RR by Anonymous Referee #4 (11 Dec 2025)

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ED: Publish subject to revisions (further review by editor and referees) (24 Dec 2025) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (29 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (19 Feb 2026) by Heng Dai

RR by Anonymous Referee #5 (20 May 2026)

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RR by Anonymous Referee #6 (07 Jun 2026)

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ED: Publish subject to minor revisions (review by editor) (17 Jun 2026) by Heng Dai

ED: Publish subject to revisions (further review by editor and referees) (22 Jun 2026) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (20 Jul 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (01 Aug 2026) by Heng Dai

RR by Anonymous Referee #6 (10 Aug 2026)

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RR by Anonymous Referee #5 (27 Aug 2026)

ED: Publish subject to minor revisions (review by editor) (30 Aug 2026) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (07 Sep 2026) Author's response Author's tracked changes Manuscript

ED: Publish as is (22 Sep 2026) by Heng Dai

AR by Alexis Jeantet on behalf of the Authors (01 Oct 2026) Author's response Manuscript

Journal article(s) based on this preprint

20 Oct 2026

Climate change impacts on groundwater simulated using the AquiFR modelling platform

Alexis Jeantet, Jean-Pierre Vergnes, Simon Munier, and Florence Habets

Hydrol. Earth Syst. Sci., 30, 6381–6420, https://doi.org/10.5194/hess-30-6381-2026,https://doi.org/10.5194/hess-30-6381-2026, 2026

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Alexis Jeantet, Jean-Pierre Vergnes, Simon Munier, and Florence Habets

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Feb 2025	466	106	15	587
Mar 2025	382	144	20	546
Apr 2025	171	134	25	330
May 2025	200	155	10	365
Jun 2025	224	130	30	384
Jul 2025	145	70	10	225
Aug 2025	689	35	18	742
Sep 2025	2,657	119	9	2,785
Oct 2025	165	50	5	220
Nov 2025	239	161	10	410
Dec 2025	219	110	10	339
Jan 2026	227	180	25	432
Feb 2026	162	139	19	320
Mar 2026	269	183	31	483
Apr 2026	39	30	3	72
May 2026	21	22	0	43
Jun 2026	10	3	0	13
Jul 2026	15	15	2	32
Aug 2026	16	16	8	40
Sep 2026	28	28	6	62
Oct 2026	50	41	6	97
Nov 2026	45	5	1	51

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Short summary

The AquiFR hydrogeological modelling plateform is forced by 36 climate projections in order to simulate future groundwater levels over France. The results show significant scatters between regional climate models and RCPs. Overall, a rise in groundwater levels, affecting most of the study area, is the dominant signal. Four storylines have been selected to to illustrate the impacts of worst-case scenarios and help decision-makers to adopt sustainable groundwater management policies.


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Climate change impacts on groundwater simulated using the AquiFR modelling platform

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