Characterization of Groundwater Dynamics and Their Response Mechanisms to Different Types of Compound Stress in a Typical Hilly Plain Area

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3660649]. We sincerely appreciate the reviewers and editor for their insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Yes

We will give our corresponding response in the point-by-point response letter.

Are all figures and tables clear and well-presented?

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: I would suggest enlarging the legend and the local features (e.g., the dots) in Figure 1 because they can barely be read.

Response 1: Thank you for pointing out that certain elements of Figure 1 were unclear. We have revised the figure accordingly; please see the updated version in the revised manuscript (Line 111). We hope the new image is sufficiently clear.

Comments 2: Do we have any hydrogeological or geological cross-sections for the area to improve our understanding of the subsurface structure of the aquifer system?

Response 2: We are very grateful to the reviewers for their constructive suggestions regarding the inclusion of hydrogeologic/geologic cross-sections. We fully agree that such a visualization will greatly enhance the reader's ability to understand the geometry and structure of the subsurface aquifer in our study area. We have added the hydrogeologic cross section in line 149-152 of the revised manuscript and hope that this addition will effectively address the issues raised by the reviewers and provide a stronger foundation for understanding the aquifer system dynamics discussed in the paper.

Comments 3: Can we add the description of the surface water bodies in Section 3.1? It is important to mutually assess the similarities (if any) between surface and groundwater bodies, because these are strong in the case of surficial or phreatic aquifers and in case of flux exchanges between them (see e.g. Zuecco et al., 2019; Schiavo, 2022).

Response 3: Thank you for your constructive suggestion. Since Section 3.1 is primarily dedicated to describing data sources, we agree that the description of surface water bodies is better suited for the “Study Area Overview” section, where it can provide a more complete spatial context. Accordingly, we have moved the relevant content to that section to enhance the manuscript’s integrity and readability. We hope this adjustment satisfactorily addresses your comment.

Comments 4: About the latter point, I would add a term to equation 9 to take into consideration also the proximity to surface water bodies, as it has been widely proved (see e.g. Zuecco et al., 2019; Schiavo, 2022) that riparian areas are rich in terms of surface-groundwater exchanges, so groundwater features should be strongly influenced by these.

Response 4: Thank you for your valuable suggestion to include a surface water–groundwater exchange term in Equation (9). We fully recognize that riparian zones can exhibit significant surface water–groundwater interactions; however, given the specific characteristics of our study area and the primary focus of our research, we believe that such exchanges would not significantly affect our results. Your Comments 4 and 5 are closely related, and Comment 5 specifically requested an explanation. Therefore, we have addressed this point in our response to Comment 5, where we provide a detailed rationale for why surface water–groundwater exchange was not incorporated into Equation (9). Thank you again for your careful review and professional advice.

Comments 5: If you don’t want to add this term to Eq. 9, please explain why. You may quantify this proximity and then discuss that this doesn’t dramatically affect your results, so it can be considered. But at least you should consider the overall picture.

Response 5: Thank you for your valuable suggestion to include a surface water–groundwater exchange term in Equation (9). We fully acknowledge that riparian zones can exhibit significant surface water–groundwater interactions. However, given the characteristics of our study area and the primary focus of our research, we believe that incorporating this exchange would not substantially affect our results. Specifically, Tangshan City on the North China Plain has a warm‐temperate, semi‐humid continental monsoon climate, where precipitation is the dominant source of groundwater recharge. Major rivers in the region are regulated by upstream reservoirs or controlled by seasonal rainfall, and the average annual contribution from surface water–groundwater exchange is considerably lower than that of precipitation infiltration. Moreover, extensive agricultural activity in the North China Plain has led to intensive groundwater extraction. Our study centers on the geological factors controlling precipitation infiltration and the impact of groundwater withdrawal on dynamic response mechanisms. Therefore, we consider the effect of surface water–groundwater exchange on groundwater dynamics in the study area to be limited and have not included it in the current model. We appreciate your careful review and expert guidance.

Comments 6: How did you fix the weights in table 1, can you explain these values? Shouldn’t it be more appropriate to perform either (i) a Monte Carlo-like analysis by varying these weights or at least (ii) giving these weights a sort of interval of variation? Otherwise they seem completely arbitrary.

Response 6: We thank the reviewer for raising the issue regarding the weighting scheme. The assignment of weights in our manuscript was determined by integrating previous studies, fully considering the characteristics of the study area, and the methods used for the comprehensive evaluation of groundwater dynamics.

Regional groundwater storage is conceptualized as the “reservoir” of groundwater dynamics, with its variations—mediated by geological conditions and human activities—affecting dynamic features such as water level, flow rate, and water quality. In Shandong Province, the changes in groundwater storage are driven by complex human activities. For example, Li et al. developed a predictive model using GRACE/GRACE-FO data and found correlation coefficients of 0.80 for groundwater extraction and 0.71 for farmland irrigation with groundwater storage changes, indicating that groundwater extraction is the dominant driver, followed by farmland irrigation [1]. Similarly, Zhong et al. employed a multi-method temporal analysis framework to investigate the spatiotemporal response of groundwater dynamics to precipitation in the Beijing Plain, revealing that, under the influence of the South-to-North Water Diversion Project, groundwater extraction remains the primary driver of water table fluctuations [2]. Tangshan, located in the northeastern part of the densely populated North China Plain and affected by the South-to-North Water Diversion Project, exhibits groundwater extraction volumes that include water used for agricultural irrigation. Based on the aforementioned studies, we have assigned a relatively high weight to groundwater extraction intensity in our evaluation framework. Moreover, Wang et al. identified key factors influencing groundwater dynamics in the North China Plain using an expert scoring method, highlighting variables such as topography and groundwater depth. Since permeability and soil lithology reflect regional variations in rock types and pore structure, these two factors serve as important reference indices in topographic classification [3]. In addition, Etuk et al. used a multi-factor weighted overlay approach to delineate groundwater potential in geologically complex, densely populated, and water-scarce regions. Applying the Analytic Hierarchy Process (AHP) in conjunction with expert judgment, they assigned weights—for example, the geological influence received the highest weight (25%), soil media 15%, and land-use type only 5%—thereby clearly establishing which factors play more significant roles in governing groundwater dynamics [4]. In conjunction with the above study, we assigned corresponding weights to the parameters in Table 1.

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3660649]. We sincerely appreciate the reviewers and editor for their insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Yes

We will give our corresponding response in the point-by-point response letter.

Are all figures and tables clear and well-presented?

Yes

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The conclusion presented in the abstract is vague. The authors are advised to clarify and supplement the key findings of the study, such as the evaluation results of groundwater dynamics, to enhance the informative value of the abstract.

Response 1: Thank you very much for your constructive comment. We fully agree that the original abstract did not adequately and accurately convey our main research findings. In the revised manuscript, we have supplemented and strengthened the concluding portion of the abstract. The specific changes are highlighted in yellow on Line 24-31 of the marked‐up document. We hope that these clarified and expanded conclusions more clearly reflect the outcomes of our study.

Comments 2: There are instances of redundant expressions and grammatical inaccuracies. For example: L37 contains an incomplete sentence. L38 exhibits awkward sentence structure, which hinders readability.

Response 2: Thank you for pointing out the instances of redundant phrasing and grammatical inaccuracies in the manuscript. We have implemented the following revisions in response to your comments:

On Line 37, the incomplete sentence has been rewritten and completed.

On Line 38, the sentence structure has been reorganized to improve its flow and readability. Specifics are highlighted in line 40-44 of the revised manuscript.

Comments 3: The novelty of the methodology should be further explicitly emphasised in the ‘significance of the study’ section referred to in the introduction.

Response 3: Thank you for your valuable suggestion to further highlight the methodological novelty. In response, we have revised the “Significance of the Study” subsection in the Introduction to provide a clearer overview of our innovative approach. The relevant changes have been highlighted on Line 87 of the revised manuscript. We believe these additions more effectively showcase the novelty of our methods.

Comments 4: L259 discusses possible reasons for the lagged response of groundwater to precipitation. The authors are encouraged to carefully revise the expression and clearly indicate the speculative nature of these interpretations to maintain academic rigor.

Response 4: Thank you for highlighting the need to clarify the speculative nature of the statement on Line 259. We agree that the original wording was unclear. Based on a review of relevant literature, we have revised that sentence to maintain academic rigor. The changes are highlighted on Line 293 of the revised manuscript.

Comments 5: L322, is not taken up with the specific analyses above.

Response 5: Thank you for pointing out that the text at Line 322 did not adequately connect with the preceding analyses. In response to your suggestion, we have added a summary of the earlier discussion on groundwater levels and precipitation dynamics at this location, along with a transitional sentence to improve coherence with the subsequent content. The specific modifications are highlighted on Line 359 of the revised manuscript. We hope this change effectively enhances the quality of the paper.

Comments 6: With regard to the discussion on aquifer thickness, the first part discussed the mechanism by which thickness affected dynamics, followed by an account of spatial distribution and regional variations, which did not logically provide a natural transition between the two parts.

Response 6: Thank you for pointing out that the discussion of aquifer thickness lacked a natural connection between the two sections. We agree that we did not clearly articulate how these two parts relate to each other. To address this, we have inserted a transitional sentence at the appropriate location to better link the mechanistic discussion with the spatial distribution analysis. The specific changes are highlighted on Line 419 of the revised manuscript. We hope this modification significantly improves the logical flow of the section.

Comments 7: While the manuscript mentions the static influence of different land-use types on groundwater dynamics, it lacks a deeper analysis of how land use/land cover (LULC) changes over time may induce spatial and temporal heterogeneity in groundwater response. It is recommended that future research incorporate historical LULC datasets (e.g., from 2000, 2010, and 2020) and groundwater time-series data to assess how land-use transitions—such as the conversion of cropland to built-up areas—dynamically regulate groundwater recharge.

Response 7: Thank you for your valuable suggestion regarding the spatiotemporal heterogeneity of groundwater response to land use/land cover (LULC) dynamics. We acknowledge that the current study focuses primarily on the static effects of different land‐use types and does not explore how historical LULC changes dynamically regulate groundwater recharge and runoff. To address this limitation, we plan to integrate multi‐year remote sensing‐derived LULC datasets with corresponding groundwater level time‐series observations in future. By doing so, we will systematically analyze how transitions from cropland to built‐up areas and other land‐use conversions influence groundwater recharge dynamics, thereby elucidating the spatiotemporal variability of groundwater response to LULC change.

Comments 8: In the conclusion section, the description of the dynamic response types is presented as a long paragraph. It is suggested to restructure this part by summarizing each type concisely and listing them separately.

Response 8: Thank you for pointing out that the description of groundwater dynamic response types in the Conclusions was overly lengthy and could hinder quick comprehension. As you suggested, we have restructured the single, continuous paragraph into four concise bullet points summarizing the key characteristics of groundwater dynamics, thereby improving readability and logical clarity. The specific changes are highlighted on Line 737-744 of the revised manuscript.

Comments 9: L705, there is a lack of sublimation of the potential application value of the research results.

Response 9: Thank you for your valuable comment. We fully agree that the potential application value of our findings should be elevated at Line 705. A statement has been added to the conclusion based on your suggestion, clearly indicating the application of the results of this research in regional water resources planning, ecological protection, and the development of differentiated management strategies under compounded stresses. The specific changes are highlighted on Line 757-761 of the revised manuscript.

Comments 10: Groundwater systems are influenced by a variety of natural and anthropogenic factors, including meteorological, hydrogeological, and socio-economic variables such as population density. Do the authors plan to incorporate additional influencing factors—such as temperature, GDP, etc.—in future studies? Comparative analysis of different regions with similar hydrogeological conditions could help validate the applicability of the proposed evaluation framework and generalize the results.

Response 10: Thank you for your insightful suggestion. We fully agree that groundwater systems are influenced not only by meteorological and hydrogeological factors but also by socio‐economic variables such as population density and GDP. In future work, we plan to incorporate these additional factors into our evaluation framework and perform comparative analyses across multiple regions with similar hydrogeological conditions to validate and generalize the applicability of our multi‐factor weighted assessment approach. We appreciate your valuable recommendation and believe it will significantly strengthen follow‐up studies.

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3660649]. We sincerely appreciate the reviewers and editor for their insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are all figures and tables clear and well-presented?

Must be improved

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The legend given in Fig. 1, is not clearly visible. The font sizes of the figure in the inset also need to be increased for clear visualization. There are some pop-ups linked with brown circles are written in Chinese! Please correct them all.

Response 1: Thank you for pointing out that certain elements in Figure 1 were not sufficiently clear. We agree with your observation and have revised the figure accordingly. The updated version can be seen in the revised manuscript (Line 111).

Comments 2: In the Hydrogeological and Meteorological Characteristics section, mention the soil type, lithology, and aquifer properties.

Response 2: Thank you for your constructive suggestion. Detailed information on aquifer characteristics was already provided in the previous manuscript (highlighted on Line 117 of the revised version). We have now also supplemented the sections on soil types and lithology within the “Hydrogeological and Meteorological Characteristics” to address your comment (see highlighted text on Line 136 of the revised manuscript). We hope these additions enhance the geological and hydrogeological context of the manuscript. Thank you again for your valuable feedback.

Comments 3: In Fig. 1, show the locations of three rain gauge stations used in this study.

Response 3: We have made the appropriate changes in Figure 1 of the revised manuscript.

Comments 4: Why were only 2.5 years of rainfall and groundwater level data chosen for this study? This is a very small dataset to characterize any groundwater dynamics as claimed in the paper title. Why were not more years’ data not used? Why was not the data after August 2020 used for this study? This is a serious drawback of this study.

Response 4: Thank you for highlighting the limitations of our dataset. The groundwater level and rainfall data used in this study were specifically intended to analyze groundwater dynamic types, with an emphasis on intra‐annual fluctuations. Tangshan City experiences distinct seasonal cycles; thus, the 2.5 years of data already encompass the characteristic wet and dry seasons, allowing us to preliminarily reveal the groundwater level’s response patterns to precipitation. We fully acknowledge that a longer time series would provide a more comprehensive characterization of groundwater dynamics. Accordingly, in future work, we will expand the dataset by incorporating additional years of rainfall and groundwater level observations to further validate and refine our conclusions.

Comments 5: “main type of groundwater monitored was submersible, and a pressurized well was selected” – here the meanings of “submersible” and “pressurized well” are not clear.

Response 5: Submersible well in this context refers to wells for monitoring submersible aquifers, and pressurized well monitor a pressurized water aquifer.

Comments 6: Lines 166-167: What information do you obtain from hydrogeology, well drilling, and meteorological stations?

Response 6: Thank you for your attention to the data acquisition methods. The original text (Lines 166–167) may have omitted key details and did not accurately convey the data sources. As indicated in the revised manuscript (Line 185-190), we obtained the following data from hydrogeological records, borehole logs, and meteorological stations. The collected data included parameters such as precipitation, groundwater level, hydraulic conductivity, soil media, aquifer thickness, groundwater depth.

Comments 7: It must be mentioned what is the need to use Auto-correlation and Cross-correlation for this study.

Response 7: Thank you for your question regarding the use of auto‐correlation and cross‐correlation in this study. We employed these correlation analyses in order to quantitatively elucidate the temporal relationship between groundwater level fluctuations and precipitation in the study area. Specifically, auto‐correlation analysis allows us to characterize the memory effect and persistence of the groundwater system, while cross‐correlation analysis identifies the lag time of groundwater level responses to precipitation events. By combining these two methods, we can gain a clearer understanding of how precipitation inputs influence groundwater dynamics at different timescales, thereby providing a solid foundation for subsequent groundwater dynamic type classification and mechanism interpretation.

The necessity of using Auto-correlation and Cross-correlation in this study has been modified and is highlighted in revised manuscript L279-282.

Comments 8: In section 3.3, on what basis the function of MFWCESindex was set [formula (9)]? Why does it have linear relations with the independent parameters? Why is it sometimes positively correlated and sometimes negatively correlated with the independent parameters as shown in the formula (9)?

Response 8: Thank you for your inquiry regarding the basis for formulating the MFWCES index (Equation 9) in Section 3.3. The design of this equation is grounded in our analysis of groundwater recharge and discharge processes within the study area. Specifically, we assigned a positive coefficient to factors that enhance recharge and a negative coefficient to the primary pathways of groundwater discharge. We adopted a linear formulation because, at this stage of our research, we assume that each factor’s influence on recharge or discharge accumulates approximately linearly. This allows us to simplify the model into a weighted‐sum format and ensures its practical applicability. In future work, we intend to incorporate more complex non‐linear mechanisms—such as interaction effects—to further optimize the model.

Comments 9: For this equation, how did you quantify soil media (S)?

Response 9: Thank you for raising the question regarding the quantification of soil media (S) in our study. We quantified soil media based on the influence of soil particle size on groundwater recharge. Specifically, we used existing soil texture survey data to classify the soils in the study area into major categories (e.g., sandy, silty, and clayey soils). Each category was then assigned a numerical score reflecting its recharge capacity. Coarse‐textured soils (e.g., sand), which have high porosity and rapid infiltration rates, were given higher recharge scores because they facilitate faster infiltration and thus more readily elevate groundwater levels. In contrast, fine‐textured soils (e.g., silt and clay), which exhibit higher viscosity and lower porosity that inhibit infiltration, were assigned lower recharge scores due to their reduced ability to contribute to groundwater recharge. These scores were subsequently normalized to ensure comparability across soil types and were used as the soil media index within the multi‐factor weighted evaluation framework. We believe this approach effectively captures the mechanistic differences in how soil texture influences groundwater recharge.

Comments 10: Please explain what do you mean by “evaporation from groundwater”? Never heard that groundwater is evaporated!

Response 10: Thank you for raising the concern regarding our terminology. We apologize for using an informal and non‐standard expression in the manuscript. After consulting relevant literature, we have confirmed that the more appropriate and commonly accepted term is “groundwater evaporation”[1-3]. Consequently, we have replaced all instances of the previous expression with “groundwater evaporation” throughout the manuscript. Revision marks have been highlighted in the revised manuscripts.

Comments 11: How the values of all these parameters were obtained?

Response 11: Thank you for your attention to the data sources. We have added detailed explanations in the revised manuscript. Specifically, land‐use data were obtained from the first Landsat‐derived annual land cover product of China (CLCD); groundwater extraction data were calculated based on the Tangshan City Water Use Comprehensive Table; and phreatic evaporation data were sourced from the Tangshan evaporation stations. These additions have been included in the revised manuscript (Line 183-190) and are highlighted for your reference.

Comments 12: In Equations 1-9, several parameters were not defined. It was also not addressed how the values of some of these variables or constants were obtained.

Response 12: Thank you for pointing out that several parameters in Equations 1–9 were not defined. In the revised manuscript, we have provided detailed definitions for all parameters involved in these equations (highlighted on Line 196/206/224).

Comments 13: Why was the Analytic Hierarchy Process (AHP) used among many available methods for assigning weights?

Response 13: Dear reviewer. The hierarchical analysis method (AHP) mentioned in line 209 of the original manuscript is the method used in the cited literature, which was not used in this study.

Comments 14: “greatest influence on groundwater dynamics (25%), while land-use type contribute the least (5%),” – how did you obtain the values 25% and 5%? Nothing was mentioned.

Response 14: Thank you for your inquiry regarding the origin of these two values. Both values are derived from Reference 25, which was cited at the end of the relevant sentence in the original manuscript. You can find the citation indicated on Line 243 of the revised manuscript. The images below reproduce the description of these two values as presented in Reference 25, to clarify their source and context.

Comments 15: As mentioned in Table 1, on what basis, different weights were assigned to different variables?

Response 15: We thank the reviewer for raising the issue regarding the weighting scheme.

Regional groundwater storage is conceptualized as the “reservoir” of groundwater dynamics, with its variations—mediated by geological conditions and human activities—affecting dynamic features such as water level, flow rate, and water quality. In Shandong Province, the changes in groundwater storage are driven by complex human activities. For example, Li et al. developed a predictive model using GRACE/GRACE-FO data and found correlation coefficients of 0.80 for groundwater extraction and 0.71 for farmland irrigation with groundwater storage changes, indicating that groundwater extraction is the dominant driver, followed by farmland irrigation [4]. Similarly, Zhong et al. employed a multi-method temporal analysis framework to investigate the spatiotemporal response of groundwater dynamics to precipitation in the Beijing Plain, revealing that, under the influence of the South-to-North Water Diversion Project, groundwater extraction remains the primary driver of water table fluctuations [5]. Tangshan, located in the northeastern part of the densely populated North China Plain and affected by the South-to-North Water Diversion Project, exhibits groundwater extraction volumes that include water used for agricultural irrigation. Based on the aforementioned studies, we have assigned a relatively high weight to groundwater extraction intensity in our evaluation framework. Moreover, Wang et al. identified key factors influencing groundwater dynamics in the North China Plain using an expert scoring method, highlighting variables such as topography and groundwater depth. Since permeability and soil lithology reflect regional variations in rock types and pore structure, these two factors serve as important reference indices in topographic classification [6]. In addition, Etuk et al. used a multi-factor weighted overlay approach to delineate groundwater potential in geologically complex, densely populated, and water-scarce regions. Applying the Analytic Hierarchy Process (AHP) in conjunction with expert judgment, they assigned weights—for example, the geological influence received the highest weight (25%), soil media 15%, and land-use type only 5%—thereby clearly establishing which factors play more significant roles in governing groundwater dynamics [7]. In conjunction with the above study, we assigned corresponding weights to the parameters in Table 1.

Comments 16: The source of all the information given in Table 2 must be clearly addressed.

Response 16: The sources of all the information in Table 2 have been highlighted on line 183-190 of the revised manuscript.

Comments 17: What are LTX, ACF and ZHF? Full forms are missing throughout the MS. Without them it is not possible to understand the Results and discussion part.

Response 17: We thank the reviewers for their questions about the abbreviations in the manuscript.ACF and CCF refer to auto-correlation and cross-correlation, respectively, which we added in line 192/200 of the revised manuscript.The full names of LTX and ZHS are given in the Appendix.

Comments 18: Figure 3 does not make any sense as the authors again did not mention the meaning of NO.130200210408, NO.130200210419, NO.130229210427, NO.130207210435, ………………..

Response 18: Figure 3 illustrates the schematic of basic groundwater dynamic types, depicting the temporal variations of groundwater levels and precipitation. By analyzing these dynamic characteristics, we can discern the seasonal and interannual variability of groundwater in the study area. This analysis forms the foundation for subsequent investigations into how multiple influencing factors affect groundwater dynamics and serves as the basis for classifying the various groundwater response types. The significance of the content of Figure 3 for subsequent research is mentioned on line 359 of the revised manuscript.

Comments 19: What do you mean by LZS, LNX, LBQ, LNQ and FNQ? ZHS, YTX, FRQ and LZS.?

Response 19: Thank you for raising the question regarding the unexplained abbreviations in the manuscript. The abbreviations “LZS, LNX, LBQ, LNQ, FNQ, ZHS, YTX, and FRQ” correspond to the names of specific counties (or county-level cities) within the study area. Due to limited space in figures and to maintain conciseness during discussion and analysis, we have used these short forms throughout the manuscript. For clarity, we have added the following table in the appendice to indicate the full names associated with each abbreviation.

Comments 20: How did you determine the aquifer thickness?

Response 20: Thank you for your question regarding the derivation of aquifer thickness data. We determined aquifer thickness by combining groundwater depth measurements with borehole data. The procedure is as follows:

Identify the groundwater depth at each observation location and determine the stratigraphic level of the groundwater;

Use borehole logs for that stratigraphic interval to confirm the lithology of the corresponding aquifer;

Obtain the depth to the top of the confining layer (aquitard) at the bottom of the aquifer from the borehole reports;

Calculate aquifer thickness as: AquiferThickness = DepthtoTopofConfiningLayer −GroundwaterDepth.

The borehole data were sourced primarily from the National Geological Borehole Database Service Platform and geotechnical investigation reports.

Comments 21: Units of all variables are missing in Fig. 4.

Response 21: We thank the reviewers for pointing out the omission of units in Fig. 4; we have added units to the figure, and the specific changes can be viewed in the revised manuscript.

Comments 22: Similarly, Fig. 5 is incomplete. What does the legend show? What do all the abbreviations represent? How did you plot the figure?

Response 22: Thank you for your concern about the incomplete information about the images in the manuscript. What is shown in the legend for Figure 5 has been explained in line 580 of the revised manuscript, in the figure title section. All abbreviations in the figure represent study area county names, and the correspondence between county name abbreviations and acronyms is detailed in the Appendix.

Comments 23: Similar questions are applied to figures 6-7. What does the legend show? What do all the abbreviations represent? How did you plot the figure?

Response 23: Thank you for your concern about the incomplete information about the images in the manuscript. What is shown in the legend for figures 6-7 have been explained in line 625/700 of the revised manuscript, in the figure title section. All abbreviations in the figure represent study area county names, and the correspondence between county name abbreviations and acronyms is detailed in the Appendix.

Comments 24: The conclusions do not at all support the paper title.

Response 24: Thank you for your careful review and valuable feedback. With respect to your concern that “the conclusions do not support the paper title,” we have re‐examined the Conclusions section and believe it indeed addresses the topic described in the title. Specifically, our manuscript title is: “Characterization of Groundwater Dynamics and its Response Mechanisms under different Compound Stress in a Typical Hilly Plain Area.” The title emphasizes groundwater dynamic characteristics and their response mechanisms. In the Conclusions, we first summarize the auto-correlation and cross‐correlation features between groundwater levels and precipitation (Line 728); second, we present an analysis of the groundwater dynamic types in the study area (Line 733); and finally, we reveal the mechanisms by which groundwater dynamics respond to precipitation under compound influencing factors (Line 745). Therefore, we are confident that the Conclusions adequately support the research scope and objectives outlined in the title. We hope this explanation resolves your concern.

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3660649]. We sincerely appreciate the reviewers and editor for their insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Yes

We will give our corresponding response in the point-by-point response letter.

Are all figures and tables clear and well-presented?

Yes

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Greetings. I think the manuscript has been significantly improved. I just suggest to include the references I suggested in the reference list. Then the paper is ready for being published for sure. Best regards

Response 1: We have incorporated the references you mentioned into the revised manuscript by highlighting the specific changes on line 98/365. Thank you again for your careful review.

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3660649]. We sincerely appreciate the reviewers and editor for their insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Yes

We will give our corresponding response in the point-by-point response letter.

Are all figures and tables clear and well-presented?

Yes

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Accept in present form

Response 1: Thank you again for your careful review of our manuscript!

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3660649]. We sincerely appreciate the reviewers and editor for their insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are all figures and tables clear and well-presented?

Can be improved

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: In Fig. 1, several things are still hyperlinked in other language. They appear when the cursor is placed upon the representation wells. I could not understand them.The same problem persists with other figures.

Response 1: Thank you very much for your careful review of our manuscript and for pointing out the potential issues of hyperlinks and non-English text in Figure 1. We apologize for not having detected the hyperlinks in other languages in the images earlier due to the differences in PDF readers. After making the necessary revisions, we have checked each image in the PDF editing software (Adobe Acrobat 2024) and found no hyperlinks in other languages. Once again, we are grateful for your meticulous and thorough review of our manuscript.

Comments 2: The same problem persists with other figures.

Response 2: Thank you again for the reviewer's pointing out the issues regarding the figures in the manuscript. All the problems you mentioned have been addressed in the revised manuscript.

Comments 3: In Fig. 1 , the rainfall station does not make any sense. Does it mean rain only falls in these three stations. It is better to replace it with “Rain gauge Station”.

Response 3: Thank you for your comment. Taking your comment into account, we think it would be more appropriate to change the name to “Precipitation gauge station”. We have modified the picture according to your comment.

Comments 4: “Tangshan City experiences distinct seasonal cycles; thus, the 2.5 years of data already encompass the characteristic wet and dry seasons,” – meaning not clear. Why does Tangshan City experience distinct seasonal cycles? Do you mean it changes after every 2.5 years!!!! This statement should be given in the manuscript.

Response 4: We apologize for the unclear expression that led to your doubts about our reply. Therefore, we are responding to the above questions. What we mean here is that Tangshan City has a warm temperate semi-humid continental monsoon climate. There are obvious alternations between rainy and dry seasons throughout the year: in summer, it is hot and humid with concentrated precipitation; in winter, it is cold and dry with scarce precipitation. Since the groundwater level and rainfall data used in this study are for analyzing the types of groundwater dynamics, and the analysis direction focuses more on the annual changes of groundwater dynamics. The 2.5-year groundwater level and rainfall data cover at least two complete rain-dry season cycles, which can support and initially reveal the response pattern of groundwater level to rainfall. We have detailedly described the climate characteristics of the study area in Section 2.2 of the manuscript and highlighted the 152th line of the revised manuscript. We hope our reply can answer your doubts. Once again, we appreciate your meticulous review and constructive suggestions.

Comments 5: Now the meaning of “submersible aquifers” is not clear. Never heard of this term. Can any aquifer be of submersible type!!!

Response 5: Thank you for highlighting the ambiguity in our terminology. We apologize for using a non‐standard and informal expression in the manuscript. In the previous draft, we used the term “submersible aquifers” to describe the type of monitoring well. After careful revision, we agree that the correct term is “unconfined‐aquifer well.”

Below is the updated wording in the revised manuscript:

Since the main objective of this study is to analyze the relationship between

groundwater dynamics in response to precipitation, unconfined‐aquifer well that directly receive recharge from precipitation were selected as the study object, and the main type of groundwater monitored was unconfined aquifer, and an confined‐aquifer well was selected as the study object in the Xiaobeihai Area, where there are no unconfined‐aquifer well.

The above changes are highlighted in line 171 of the revised manuscript.

Comments 6: The difference between Submersible well and pressurized well needs to be clearly addressed.

“we assume that each factor’s influence on recharge or discharge accumulates approximately linearly. This allows us to simplify the model into a weighted-sum format and ensures its practical applicability” – these are vague statements. None can assume anything arbitrarily that too for technical analysis. How could the authors claim that their baseless assumption has any practical applicability!!!

Response 6: We thank the reviewers reviewers for their queries. We refer to the evaluation system for evaluating the vulnerability of groundwater contamination: the DRASTIC [1, 2] model, on the basis of which the evaluation system in the manuscript was developed.The DRASTIC model consists of various hydrogeological parameters, and each indicator in the model is divided into several zones, with each zone assigned a score. Then each indicator is assigned a corresponding weight according to the magnitude of its impact on vulnerability, and finally a composite groundwater vulnerability index is obtained by weighted summation. The groundwater dynamics evaluation system (i.e., Equation 9) in the manuscript is based on the following two aspects. Firstly, the two factors (natural and anthropogenic factors) that influence groundwater dynamics, and secondly, the characteristics of groundwater recharge and discharge processes. After clarifying what influencing factors are in the evaluation system, weights are assigned to each indicator according to the magnitude of its influence on groundwater dynamics, and finally the comprehensive evaluation value of groundwater dynamics is obtained by weighted summation. We hope our reply can solve your questions.

Comments 7: Reply to my Comment 9: “For this equation, how did you quantify soil media (S)?” must be reflected in the revised manuscript. Otherwise, the same question will come to the mind of every reader.

Response 7: We thank the reviewers for pointing out in detail what should be added to the manuscript. We have added the relevant part of “For this equation, how did you quantify soil media (S)?” to the manuscript, which is highlighted in line 408 of the revised manuscript.

Comments 8: How did you obtain Eq. 4? Still, nothing was mentioned.

Response 8: Thank you for drawing attention to the formula in our manuscript. Equation 4 is derived from Bartlett’s variance formula, and Qing et al. [3] also employed this empirical estimate when investigating the time‐lag characteristics of precipitation. Specifically, Manuela et al [4]., through theoretical derivation, obtained a 95% confidence interval of . Under the white‐noise assumption (v0=1) , this simplifies to . For the sake of quick assessment, the value is conventionally rounded to , which is the empirical value we have adopted in this study. Because the derivation of this equation is not the primary focus of our research, we have supplemented the revised manuscript with the relevant references (line 198) .

Comments 9: Authors need to address my Comment 15: “As mentioned in Table 1, on what basis, different weights were assigned to different variables?” on the revised manuscript. This is an important issue.

Response 9: We thank the reviewer for raising the issue regarding the weighting scheme. Tangshan is situated on the North China Plain; consequently, the weighting scheme adopted in this study draws on research carried out for that region.

l  Wang et al., in their investigation of groundwater dynamic patterns, identified three principal controlling factors for the North China Plain: topography and landforms, depth of groundwater, and exploitation degree. Using an expert scoring approach, they assigned identical weights to these three factors [5]. Because topography and geomorphology regulate the permeability of near-surface materials through weathering, erosion, and depositional processes, our evaluation framework employs hydraulic conductivity to represent their influence on groundwater dynamics. On this basis, both hydraulic conductivity and groundwater depth are given the highest weights in our assessment system.

l  Li et al. developed a predictive model using GRACE/GRACE-FO data and found correlation coefficients of 0.80 for groundwater extraction and 0.71 for farmland irrigation with groundwater storage changes, indicating that groundwater extraction is the dominant driver, followed by farmland irrigation [6]. Similarly, Zhong et al. employed a multi-method temporal analysis framework to investigate the spatiotemporal response of groundwater dynamics to precipitation in the Beijing Plain, revealing that, under the influence of the South-to-North Water Diversion Project, groundwater extraction remains the primary driver of water table fluctuations [7]. Tangshan, located in the northeastern part of the densely populated North China Plain and affected by the South-to-North Water Diversion Project. Therefore, the weight of groundwater extraction intensity in the evaluation system is second only to geological factors (hydraulic conductivity and depth of groundwater).

l  Secondly, the weights of soil media and land use type are determined on the basis of the following discussion. Etuk et al. used a multi-factor weighted overlay approach to delineate groundwater potential in geologically complex, densely populated, and water-scarce regions. Applying the Analytic Hierarchy Process (AHP) in conjunction with expert judgment, they assigned weights—for example, the geological influence received the highest weight, soil media 15%, and land-use type only 5%—thereby clearly establishing which factors play more significant roles in governing groundwater dynamics [8].

l  Finally, since the depth of groundwater in most areas of Tangshan exceeds the general evaporation limit depth (5m), it is given less weight in the overall evaluation system.

We hope that the above response answers your questions, and thank you again for your careful review.

Comments 10: My previous comment 18: The meaning of “NO.130200210408, NO.130200210419, NO.130229210427, NO.130207210435, ………………..” should be addressed in the revised manuscript.

Response 10: Thank you again to the reviewers for their constructive comments. We have followed your suggestions and added relevant content, as highlighted in line 357 of the revised manuscript.

Comments 11: My previous comment 19: The meaning of “LZS, LNX, LBQ, LNQ and FNQ? ZHS, YTX, FRQ and LZS” should be addressed in the revised manuscript.

Response 11: We thank the reviewers for their comments. In the first round of review responses, we have added a description of the above mentioned abbreviations in the appendix. In the new round of review responses, we have added the description of the above abbreviations in the revised manuscript according to your suggestion. The details are highlighted in line 781 of the revised manuscript.

Comments 12: “Obtain the depth to the top of the confining layer (aquitard) at the bottom of the aquifer from the borehole reports” - - this is not correct. This depth varies with respect to time. Therefore, is there any aquifer whose depth varies at a particular point!!!!

Response 12: Thank you for your feedback on our previous response. We apologize for any confusion caused by our wording. We fully agree that groundwater levels vary over time—this is a fundamental hydrogeological characteristic. When determining the depth of the aquifer floor from borehole data, it is important to clarify that the “aquifer floor” also corresponds to the top of the underlying aquitard. Therefore, aquifer thickness is calculated as:AquiferThickness = Depth to top of underlying aquitard − Groundwater depth.

We hope our response addresses your concern.

Comments 13: In the Legend of Fig. 6, what do you mean by “Value” ?

Response 13: We thank the reviewer for pointing out the lack of clarity in some parts of the figure legend. In Figure 6, ‘Value’ means comprehensive evaluation value of groundwater dynamics, and We are sorry that the original manuscript did not specify this in the legend. The revised manuscript has provided additional explanations in the legend, and we hope that the revised manuscript will solve your doubts.

Comments 14: In Fig. 7, “the phrase “Map of … hydraulic engineering” does not make any sense and therefore it should be removed.

Response 14: Thank you for the comment raised by the reviewer. "Map of major watersheds and hydraulic engineering" is the title of Figure 7, and "Bold blue... groundwater levels" is a brief description of the detailed content of Figure 7. Each figure should have a clear title and a brief description of the image. Therefore, regarding your suggestion that the figure name of figure 7 doesn't make any sense, we don't understand exactly what it means.

Comments 15: In Fig. 7, “circles denote the standard deviation”, units of the values of standard deviation given in the legend should be mentioned.

Response 15: We are very grateful to the reviewer for raising the issue of missing units. We have made the corresponding additions in Figure 7 of the revised manuscript.

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking your time to review manuscript [3491829]. We sincerely appreciate the reviewers' insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions/corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Yes

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Yes

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Can be improved

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Can be improved

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Furnish further background on the particular hydrogeological attributes of Tangshan for enhanced comprehension.

Response 1: We agree with this comment. The addition of a description of the special hydrogeology of Tangshan City is necessary to further the understanding of the study area profile. Therefore, we have added the following relevant descriptions. In the hilly and plain regions of Tangshan, fault structures are densely distributed; these fault zones not only act as barriers to water flow but also serve as preferential conduits, resulting in a highly heterogeneous groundwater system. Furthermore, Tangshan is located within the North China Plain, where long-term agricultural irrigation and industrial water demands have led to significant groundwater over-extraction and land subsidence, causing pronounced hydrogeological disturbances. The above addition can be found in L127-130 of the revised manuscript.

Comments 2: Incorporate a comparative analysis with like places to emphasize distinctive groundwater processes.

Response 2: We thank the reviewers for their valuable comments, and the comparison can better highlight the uniqueness of the groundwater system in Tangshan. We have added the following as an analytical comparison. The central part of the North China Plain has a flat topography with good stratigraphic continuity and a relatively homogeneous groundwater system, whereas Tangshan has a complex groundwater runoff due to the presence of fracture zones, and earthquakes occurred several times in history. In the southern coastal plain, there may be seawater intrusion into the freshwater areas of the aquifer. As an additional analysis can be found in L133-138 of the revised manuscript.

Comments 3: Incorporate a section addressing future monitoring and the long-term sustainability of groundwater supplies.

Response 3: We agree with this comment that the future monitoring of groundwater and its long-term sustainability is particularly important in the context of global climate change. The following discussions were therefore held. Sustainable management of groundwater resources is of paramount importance; however, current management measures may significantly lag behind the rate of aquifer depletion, especially in the severely over-exploited North China Plain. The MFWCES model developed in this study does not incorporate key factors such as meteorological variables and drainage line density, indicating that the evaluation framework requires further refinement. In addressing complex nonlinear groundwater dynamics, machine learning techniques—particularly ensemble methods like random forest—show substantial potential. An integrated approach that combines the evaluation framework, machine learning-based hydrological models, and both in-situ and remote sensing data can estimate parameters that are otherwise difficult to measure directly, thereby providing reliable information for sustainable economic and hydrological management. Currently, methodologies for studying changes in groundwater storage are constrained by limitations in data resolution, temporal span, and model uncertainty; as a result, the overall complexity, local precision, and long-term applicability of the conclusions require further verification. Future research should integrate higher-resolution remote sensing data, field monitoring, and policy analysis to support the development of more precise sustainable management strategies. The additional section can be seen on L646-663 of the revised manuscript.

Comments 4: In what ways does the interplay between precipitation and human activity fluctuate throughout several seasons?

Response 4: We appreciate the reviewer’s inquiry. Tangshan experiences a warm temperate, semi-humid continental monsoon climate characterized by distinct seasons, with both temperature and precipitation exhibiting pronounced seasonal variability. In summer, monsoonal influences lead to concentrated and intense rainfall, which partly alleviates the extraction pressures on groundwater from industrial, agricultural, and urban water use. However, high temperatures and urban heat island effects may alter local precipitation distributions, exacerbating conflicts in water resource utilization. In winter, precipitation is scarce and overall recharge capacity is weak; despite a relatively lower water demand, the insufficient recharge often hinders groundwater recovery, thereby amplifying the impact of human activities on the groundwater system. During the transitional spring and autumn seasons, both precipitation and water demand are moderate, resulting in a more balanced interaction between rainfall and human activities, although localized variations may occur due to changes in land use.

Comments 5: What particular actions are being implemented to mitigate groundwater over-extraction in regions of high intensity?

Response 5: Thank you to the reviewers for raising the issue of how to mitigate areas of high-intensity groundwater extraction. In regions suffering from groundwater overexploitation, water stress is primarily mitigated through strategies such as zoned management, water source substitution projects, agricultural water conservation, and land subsidence monitoring. In industrial clusters and coal-mining subsidence zones (e.g., the FNQ and GZQ), groundwater extraction is regulated by designating prohibition and restriction zones, thereby banning or limiting the installation of new extraction wells. In agricultural irrigation areas, the promotion of canal-based water diversion facilitates the partial replacement of groundwater with surface water. Moreover, in agricultural regions like YTX, the implementation of high-efficiency drip irrigation systems is encouraged to further conserve water resources. The revision can be found on L464-473 of the revised manuscript.

Comments 6: In what ways may the technique be modified for use in locations characterized by distinct geological features or varying degrees of human activity?

Response 6: We thank the reviewer for the sixth suggestion. We agree that the technology should indeed consider universality. The multi-factor composite evaluation system should not be limited solely to the hilly and plain areas of Tangshan but must also be transferable to similar study regions. This transferability is essential for providing novel insights into groundwater management in other regions. From a geographic perspective, a Geographic Information System (GIS) efficiently captures, stores, displays, and analyzes data related to Earth's surface locations. Its core functionality lies in linking and integrating spatial and attribute data to construct a digital geographic space model. In our evaluation framework, we have leveraged this capability of GIS to visualize regional hydrogeological conditions and characteristics. For study areas with distinct geological features, it is imperative to obtain relevant hydrogeological parameters (e.g., soil lithology, aquifer thickness, and permeability), as these parameters form the core of the evaluation system. Storing these data as separate GIS layers ensures that local hydrogeological characteristics are accurately reflected. Furthermore, human activities exert complex and diverse influences on regional groundwater dynamics. Variations in the intensity, type, and duration of these activities can induce changes in groundwater levels as well as recharge and discharge processes. For instance, high-intensity agricultural activities—such as greenhouse cultivation—can reduce infiltration rates, while urbanization leads to impermeable surfaces that hinder natural recharge and exacerbate water scarcity. Excessive groundwater extraction to meet industrial demands may even trigger regional groundwater cones of depression. Since human activities indirectly alter groundwater dynamics by affecting hydrogeological conditions—and given that the relative importance of these parameters varies by region—the technology can be adapted to areas with different levels of human impact by adjusting the weights of the influencing factors or by incorporating additional factors. In summary, by employing the methods described above, the applicability of the technology can be enhanced to accommodate regions with varying geological features and differing intensities of human activity, thereby providing a more robust and universal approach to groundwater management.

Comments 7: What is the significance of land use change in groundwater dynamics, and how is it included into the assessment?

Response 7: We thank the reviewer for this constructive comment. We are currently considering incorporating this new parameter into our evaluation framework. In China, a highly urbanized country, the extent of urban built-up areas and agricultural lands has largely stabilized, so land use changes may not exert a markedly significant influence on groundwater dynamics, with the most substantial effects observed during the rapid urbanization period from approximately 1980 to 2010. Nonetheless, different land-use types produce regional fluctuations in groundwater dynamics.

Groundwater recharge is regulated by the synergistic effects of climate change and human activities, with land-use type serving as critical factors within the hydrological cycle. Different types of land-use type influence groundwater dynamics by altering key processes such as interception, infiltration, evapotranspiration, and surface runoff. There are detailed additions to the article about this section, which can be found in L422-446 of the revised manuscript.

Comments 8: Are there plans to integrate supplementary data sources for groundwater studies in Tangshan?

Response 8: We appreciate the reviewer’s constructive suggestions. We plan to integrate and supplement new data sources in our Tangshan groundwater study. In addition to the land use changes mentioned in comment seven, we propose incorporating two additional variables: terrain slope and unsaturated zone media. The terrain slope influences the surface retention time of precipitation, thereby affecting infiltration rates. On steep slopes, gravitational forces accelerate runoff, reducing the retention time and limiting infiltration, which can lead to insufficient groundwater recharge—especially during dry seasons when declines in the water table become pronounced. Conversely, on gentle slopes, slower water flow allows precipitation more time to infiltrate and recharge groundwater. Furthermore, the vadose zone media acts as a filter in the process of converting precipitation into groundwater recharge. Its permeability and water-holding capacity directly govern the rate, pathways, and distribution of infiltration. For future investigations, we also plan to explore the integration of remote sensing techniques to include additional meteorological factors, which may further enhance our understanding of groundwater dynamics.

Comments 9: The correlation between precipitation and human activity warrants additional investigation, particularly in metropolitan regions.

Response 9: We appreciate the reviewer’s insightful comment. In metropolitan regions, the relationship between precipitation and human activities is characterized by complex interactions. Anthropogenic influences—such as the urban heat island effect, excessive pollutant emissions, and localized climatic modifications—disrupt the spatiotemporal distribution of precipitation. In turn, these precipitation changes exert feedback on urban environments; for example, the proliferation of impervious surfaces can hinder groundwater recharge. In the future, it will be essential for metropolitan areas to break this vicious cycle through integrated infrastructure planning and cross-scale climate adaptation strategies, thereby gradually restoring natural groundwater balance.

4. Response to Comments on the Quality of English Language

Point 1: The English is fine and does not require any improvement.

Response 1: We appreciate the reviewer's positive feedback on the language quality of our manuscript. Your comment that "The English is fine and does not require any improvement" is very encouraging, and we have polished our manuscript for well read, and also we will continue to maintain high standards of clarity and precision in our writing. Thank you for your supportive remark.

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review manuscript [3491829]. We sincerely appreciate the reviewers' insightful comments and suggestions, which have significantly improved the quality of our manuscript. We have carefully addressed all the points raised and provided detailed responses below. Please find the detailed responses below and the corresponding revisions and corrections highlighted in the re-submitted files.

2. Questions for General Evaluation

Reviewer’s Evaluation

Response and Revisions

Does the introduction provide sufficient background and include all relevant references?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Is the research design appropriate?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are the methods adequately described?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are the results clearly presented?

Must be improved

We will give our corresponding response in the point-by-point response letter.

Are the conclusions supported by the results?

Must be improved

We will give our corresponding response in the point-by-point response letter.

3. Point-by-point response to Comments and Suggestions for Authors

Comments 1: Remove Lines 128-130, “This section may be divided by subheadings…conclusions that can be drawn.” These are copied form the instructions.

Response 1: We thank the reviewer for pointing out this oversight. We sincerely apologize for the inadvertent inclusion of the template text in Lines 128-130, which resulted from a copying error during manuscript preparation. We have already removed these lines in the revised version. Changes are labelled in L145 of the revised manuscript. We appreciate your careful review and helpful guidance.

Comments 2: The authors should highlight in a Table where did they get the data (groundwater level, precipitation) that has been used in their research.  I do not have any clue what is the study period.

Response 2: We appreciate the reviewer’s comment and will include additional details in the manuscript. Precipitation data were primarily obtained from three rain gauge stations located in Zunhua, Tangshan, and Leting, while groundwater level data were sourced from the monitoring wells indicated in Figure 1. The study period spans from January 2018 to August 2020. Changes are labelled in L148-150, 156 of the revised manuscript.

Comments 3: I am not sure how the allocation of weights to the MFWCES as described in Table 1 was done. The authors mention, “Based on the "Guidelines for Ground- 183 water Dynamics Analysis and Evaluation" published by the Hydrology Society in 2023 [21], and drawing on field surveys, practical experience, and the impact of each influencing factor on groundwater dynamics” in L183-186, however there is a lot of subjectivity in these weights. More clarification/references from previous studies should be carried out.

Response 3: We thank the reviewer for raising the issue regarding the weighting scheme.

Regional groundwater storage is conceptualized as the “reservoir” of groundwater dynamics, with its variations—mediated by geological conditions and human activities—affecting dynamic features such as water level, flow rate, and water quality. In Shandong Province, the changes in groundwater storage are driven by complex human activities. For example, Li et al. developed a predictive model using GRACE/GRACE-FO data and found correlation coefficients of 0.80 for groundwater extraction and 0.71 for farmland irrigation with groundwater storage changes, indicating that groundwater extraction is the dominant driver, followed by farmland irrigation [1]. Similarly, Zhong et al. employed a multi-method temporal analysis framework to investigate the spatiotemporal response of groundwater dynamics to precipitation in the Beijing Plain, revealing that, under the influence of the South-to-North Water Diversion Project, groundwater extraction remains the primary driver of water table fluctuations [2]. Tangshan, located in the northeastern part of the densely populated North China Plain and affected by the South-to-North Water Diversion Project, exhibits groundwater extraction volumes that include water used for agricultural irrigation. Based on the aforementioned studies, we have assigned a relatively high weight to groundwater extraction intensity in our evaluation framework. Moreover, Wang et al. identified key factors influencing groundwater dynamics in the North China Plain using an expert scoring method, highlighting variables such as topography and groundwater depth. Since permeability and soil lithology reflect regional variations in rock types and pore structure, these two factors serve as important reference indices in topographic classification [3]. In addition, Etuk et al. used a multi-factor weighted overlay approach to delineate groundwater potential in geologically complex, densely populated, and water-scarce regions. Applying the Analytic Hierarchy Process (AHP) in conjunction with expert judgment, they assigned weights—for example, the geological influence received the highest weight (25%), soil media 15%, and land-use type only 5%—thereby clearly establishing which factors play more significant roles in governing groundwater dynamics [4].

In our manuscript, the weight assignment for the MFWCES follows these studies. We apologize for the oversight in our initial submission regarding the omission of the relevant references. The revised manuscript now includes the appropriate textual description and citations, as noted in L201-221.

1.            Li, W., et al., The analysis on groundwater storage variations from GRACE/GRACE-FO in recent 20 years driven by influencing factors and prediction in Shandong Province, China. Scientific Reports, 2024. 14(1): p. 5819.

2.            Zhong, X., et al., Study on the evolution of shallow groundwater levels and its spatiotemporal response to precipitation in the Beijing Plain of China based on variation points. Ecological Indicators, 2024. 166: p. 112466.

3.            Wang, S., et al., Shallow groundwater dynamics in North China Plain. Journal of Geographical Sciences, 2009. 19(2): p. 175-188.

4.            Etuk, M.N., O. Igwe, and J.C. Egbueri, An integrated geoinformatics and hydrogeological approach to delineating groundwater potential zones in the complex geological terrain of Abuja, Nigeria. Modeling Earth Systems and Environment, 2023. 9(1): p. 285-311.

Comments 4: The authors can also look at some recent studies which have looked into the modeling groundwater level using multiple meteorological factors.

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=5105509

https://www.sciencedirect.com/science/article/pii/S0048969722082419

Response 4: We thank the reviewer for providing these valuable references. After a thorough review, we have summarized four key points:

1. The integration of multi-source data (including remote sensing, in situ measurements, and meteorological variables) enables a more comprehensive understanding of both the direct and indirect impacts of precipitation on groundwater recharge, serving as a strong example for data integration in precipitation–groundwater dynamics studies. 

2. The contributions of different factors to groundwater dynamics vary significantly across regions, highlighting the need to fully consider regional characteristics and local hydrological processes when investigating groundwater responses. 

3. Our current model has limitations in temporal extrapolation and forecasting future groundwater dynamics. Future work could benefit from incorporating deep learning or hybrid mechanistic models to better capture the nonlinear and complex relationships between precipitation and groundwater, especially under climate change scenarios. 

4. A multi-dimensional validation approach is highly valuable for assessing the accuracy of precipitation event responses in groundwater systems.

We will integrate these insights into our revised manuscript and future research directions. Specific changes can be found in L649-663. Thank you again for your constructive feedback.

Comments 5: I am equally unsure about the Factors in the MFWCES and their assessment levels as reflected in Table. How did the authors come up with an assessment level.

Response 5: We appreciate the reviewer’s inquiry and take this matter very seriously. Tangshan is characterized by a warm temperate, semi-humid continental monsoon climate, with distinct seasonal variations in both temperature and precipitation. Drawing on objective experience from previous projects and analysis of precipitation–groundwater relationships, we found that the groundwater response to precipitation in the study area exhibits different dynamic patterns due to factors such as agricultural irrigation, industrial water use, and the construction of water conservancy projects.

Comments 6: In L219, why have the authors chosen 0.2 as the lower limit of correlation?

Response 6: We appreciate the reviewer’s thoughtful comments and suggestions.

https://www.mdpi.com/2073-4441/8/5/171

In this study on groundwater dynamics, the author quantify the inertia of different hydrological systems by comparing the time lag k at which the autocorrelation function decays to r(k) = 0.2 . Specifically, to compare the response speed of groundwater levels in different administrative regions to historical events, we employed the time lag corresponding to r(k) = 0.2 as a comparative metric. The rationale behind choosing a threshold of 0.2 is that, at this level, the data still exhibit a weak correlation (approximately 20%), yet the correlation has decreased significantly from its initial value, making it a robust and representative standard for comparison. I have described and added this reference in the revised manuscript, specifically in L254 of the text.

Comments 7: In Figure 2, what is LTX and ZHS?

Response 7: We appreciate the reviewer’s concerns regarding the two annotations. LTX and ZHS denote the abbreviations for Laoting Xian and Zunhua Shi, two administrative regions in Tangshan City. Due to figure size limitations and to enhance clarity, abbreviations are consistently used throughout the manuscript. The correspondence between the abbreviations and the full administrative names is provided in the supplementary table. We sincerely apologize for the oversight and have proactively corrected these issues in the revised manuscript.

Table 1. Abbreviation and full name of administrative region.

Comments 8: L229 is weirdly written

Response 8: We sincerely appreciate your thorough review and constructive feedback. We deeply regret that some of the original phrasing appeared awkward due to insufficient linguistic refinement and poor readability. To address this issue, we have thoroughly revised the problematic sentences to enhance clarity. The revised content is as follows: The cross-correlation functions between groundwater levels and precipitation are displayed in Figures 2-c, 2-d. Negative correlations peak at lag times of 0–2 months, with the correlation approaching zero around 3–4 months after precipitation. In contrast, positive correlations reach a maximum at a lag of 5–6 months, indicating a significant manifestation of precipitation-induced groundwater recharge. The revision can be found in the L264-268 of the revised manuscript.

Comments 9: L241-247 should be better worded for clear understanding as I fail to comprehend the meaning of the paragraph.

Response 9: Thank you for your insightful feedback and for pointing out the wording issue in line L241-247. We sincerely apologize for the confusion caused by the original phrasing. After careful reconsideration, we have implemented the following improvements: Based on the selection and data processing from monitoring wells and rainfall stations, monthly average values of groundwater levels and precipitation were obtained from January 2018 to August 2020. Groundwater dynamic curves were plotted and classified according to fundamental theories of groundwater dynamics and the aforementioned correlation analysis results. According to the analysis of the curve characteristics, the main types of groundwater dynamics in the study area can be categorized as follows. The revision can be found in the L279-285 of the revised manuscript.

Comments 10: L280-282: It is not clear to me how the authors reach a conclusion “Based on the analysis of natural groundwater dynamics, it is evident that the groundwater dynamics in the study area, as a typical coastal region, are subject to the combined stress of hydrological conditions, geological factors, and human activities.” The earlier results do not prove it conclusively.

Response 10: We thank the reviewer for his query, about which I refer to the following two papers for a summary in order to respond.

https://www.sciencedirect.com/science/article/abs/pii/S2213343721018509

https://www.nature.com/articles/s43017-023-00500-2

The significant diversity of landscapes, geological and atmospheric conditions, and human activities renders each coastal aquifer unique. For example, Chala et al. developed a saltwater intrusion model for unconfined coastal aquifers using a multi-factor coupling analysis that incorporated hydrological conditions, geological structures, natural factors, and anthropogenic influences. Similarly, Richardson et al. integrated hydrogeological parameters with geochemical processes to investigate the synergistic or counteracting effects of various climate drivers on coastal groundwater. Their findings indicate that the combined impacts of climate change and human activities are actively reshaping coastal groundwater systems. Based on these studies, we conclude that: “Based on the analysis of natural groundwater dynamics, it is evident that the groundwater dynamics in the study area, as a typical coastal region, are subject to the combined stress of hydrological conditions, geological factors, and human activities.” The revision can be found in the L322-323 of the revised manuscript.

Comments 11: All the figure and table should have better concise, but clear explanations about the figure.

Response 11: We appreciate the reviewer’s valuable comment regarding the need for concise yet clear explanations for all figures and tables. In response, we have revised the captions and annotations to ensure they are succinct while providing sufficient clarity to the reader. We believe these improvements enhance the overall presentation of our results. Thank you for your constructive suggestion. Changes have been highlighted in the revised manuscripts.

4. Response to Comments on the Quality of English Language

Point 1: The authors write several paragraphs and lines where the intended meaning is not clear. The authors should consult a native English speaker for better written English in their manuscript. 

Response 1: We are grateful to the reviewers for raising questions about language，and we have already polished the languages for making it better in the manuscript. We will continue to maintain high standards of clarity and precision in our writing.