View Letter  观览信

Manuscript Number: GEOT-D-25-00386
手稿编号：GEOT-D-25-00386  

The Heat Accumulation Effect Enhanced by Groundwater Convection in Karst Geothermal Systems: A Case Study of the Jizhong Depression, Bohai Bay Basin, North China
喀斯特地热系统中地下水对热积聚效应的增强作用：中国渤海湾盆地冀中坳陷的案例研究

Dear Dr. Rao,  尊敬的 Rao 博士，

Thank you for submitting your manuscript to Geothermics.
感谢您向《地热学》提交您的手稿。

I have completed my evaluation of your manuscript. The reviewers recommend reconsideration of your manuscript following major revision. I invite you to resubmit your manuscript after addressing the comments below. Please resubmit your revised manuscript by Jul 31, 2025.
我已经完成了对手稿的评估。审稿人建议在重大修改后重新考虑您的手稿。我邀请您在下面的评论中进行修改后重新提交您的手稿。请在 2025 年 7 月 31 日前重新提交修订后的手稿。

When revising your manuscript, please consider all issues mentioned in the reviewers' comments carefully: please outline every change made in response to their comments and provide suitable rebuttals for any comments not addressed. Please note that your revised submission may need to be re-reviewed. 
在修订您的手稿时，请仔细考虑审稿人提出的所有问题：请列出对审稿人意见所做的一切修改，并为未予回应的任何意见提供合适的反驳。请注意，您的修订提交可能需要重新审阅。

To submit your revised manuscript, please log in as an author at https://www.editorialmanager.com/geot/, and navigate to the "Submissions Needing Revision" folder.  
请登录 https://www.editorialmanager.com/geot/ 作为作者，然后导航到“需修订的提交”文件夹，以提交您的修订手稿。

Research Elements (optional)
研究元素（可选）
This journal encourages you to share research objects - including your raw data, methods, protocols, software, hardware and more – which support your original research article in a Research Elements journal. Research Elements are open access, multidisciplinary, peer-reviewed journals which make the objects associated with your research more discoverable, trustworthy and promote replicability and reproducibility. As open access journals, there may be an Article Publishing Charge if your paper is accepted for publication. Find out more about the Research Elements journals at https://www.elsevier.com/authors/tools-and-resources/research-elements-journals?dgcid=ec_em_research_elements_email.
本期刊鼓励您分享支持您原始研究文章的研究对象——包括您的原始数据、方法、协议、软件、硬件等。研究元素是开放获取、跨学科、同行评审的期刊，使与您的研究相关的对象更加可发现、可信赖，并促进可重复性和可再现性。作为开放获取期刊，如果您的论文被接受发表，可能会收取文章出版费。有关研究元素期刊的更多信息，请访问 https://www.elsevier.com/authors/tools-and-resources/research-elements-journals?dgcid=ec_em_research_elements_email。


Geothermics values your contribution and I look forward to receiving your revised manuscript.
地热学值您的贡献，并期待收到您的修订手稿。

Kind regards,    此致，
Sadiq Zarrouk, BE PGDipGeothermTech ME PhD  
Sadiq Zarrouk，学士，研究生证书，地热技术，工学硕士，哲学博士
Editor in Chief    主编

Geothermics  地热学

Editor and Reviewer comments:
编辑和审稿人意见：



Reviewer's Responses to Questions
审稿人对问题的回应

Note: In order to effectively convey your recommendations for improvement to the author(s), and help editors make well-informed and efficient decisions, we ask you to answer the following specific questions about the manuscript and provide additional suggestions where appropriate.
为了有效地向作者（们）提出改进建议，并帮助编辑做出知情且高效的决策，我们要求您回答以下具体问题，并在适当的情况下提供额外的建议。

1. Are the objectives and the rationale of the study clearly stated?
1. 研究的目标和研究动机是否表述清晰？

Please provide suggestions to the author(s) on how to improve the clarity of the objectives and rationale of the study. Please number each suggestion so that author(s) can more easily respond.
请向作者提供改进建议，以提高研究目标和动机的清晰度。请按序号编号，以便作者更易于回复。

Reviewer #1: The objectives and the rationale of the study are clearly stated.
审稿人 #1：研究的目标和研究动机表述清晰。

Reviewer #2: The objectives are clear, but framing them as testable hypotheses or explicit research questions would enhance focus. This could help readers better understand the novelty of your contribution and its relevance in the broader context of karst geothermal system studies.
审稿人 #2：研究目标表述清晰，但将其作为可测试的假设或明确的研究问题来表述，可以增强其聚焦性。这将有助于读者更好地理解您的贡献的新颖性及其在喀斯特地热系统研究中的相关性。

1. Strengthen the rationale by linking your findings to broader geothermal system development challenges and resource management implications (e.g., how the results could inform well placement or reinjection strategies in similar karst systems).
1. 加强论据，将你的发现与更广泛的地热系统开发挑战和资源管理影响联系起来（例如，结果如何可以指导类似喀斯特系统中的井位或再注入策略）。

2. Clarify how your work builds upon and advances beyond prior models (Szijártó et al., 2021; Kang et al., 2023).
2. 明确您的工作是如何建立在并超越了先前模型（Szijártó等，2021；康等，2023）的基础上的。

2. If applicable, is the method/study reported in sufficient detail to allow for its replicability and/or reproducibility?
2. 如果适用，该方法/研究是否报告得足够详细，以使其具有可复制性和/或可再现性？

Please provide suggestions to the author(s) on how to improve the replicability/reproducibility of their study. Please number each suggestion so that the author(s) can more easily respond.
请向作者提供关于如何提高其研究的可复制性/再现性的建议。请按序号列出每条建议，以便作者能够更容易地回应。

Reviewer #1: Mark as appropriate with an X:
审稿人 #1: 适当请标记为 X:
Yes [X] No [] N/A []
是 [X] 否 [] 无法确定 []
Provide further comments here:
在此提供进一步评论：

Reviewer #2: Mark as appropriate with an X:
审稿人 #2: 适当请标记为 X:
Yes [] No [X] N/A []
译文： 是 [] 否 [X] 无 []
Provide further comments here:
在此提供进一步评论：
While the methods are described in detail, a few aspects could be improved to ensure reproducibility and transparency:
虽然方法描述详细，但仍有一些方面可以改进以确保可重复性和透明度：

1. Permeability values (10–100 mD): Clarify whether these are based on field measurements or literature estimates. If assumptions were made, explicitly discuss potential uncertainties and their implications for model outcomes.
1. 渗透率值（10–100 mD）：明确这些值是基于现场测量还是文献估计。如果做出了假设，应明确讨论潜在的不确定性及其对模型结果的影响。

2. 2D porous medium simplification: The decision to model the karst reservoir as an equivalent porous medium oversimplifies the flow dynamics typical in karst systems. Consider discussing this limitation and how it may influence results.
2. 二维多孔介质简化：将喀斯特储层等效为多孔介质进行建模会过度简化喀斯特系统中典型的流动动力学。建议讨论这一局限性及其可能对结果的影响。

3. Diving surface approximation: The approximation of the diving surface in Model 2 deserves sensitivity testing to confirm the robustness of the results.
3. 潜水面近似：在模型 2 中对潜水面的近似需要进行敏感性测试，以确认结果的稳健性。

4. Mesh sensitivity and convergence: Provide details on mesh refinement and convergence criteria in the numerical simulations to strengthen reproducibility.
4. 网格敏感性和收敛性：提供数值模拟中网格细化和收敛标准的详细信息，以增强可重复性。

5. Geological calibration: The model would benefit from stronger integration of geological and hydrogeological field data for validation. Suggestions:
5. 地质校准：模型可以从更紧密地整合地质和水文地质实地数据中受益，以进行验证。建议：

6. Include borehole temperature profiles, permeability/porosity data, tracer test results, or production test data (if available).
6. 包括孔隙温度剖面、渗透率/孔隙度数据、示踪剂测试结果或生产测试数据（如果可用）。
a. Use these datasets to cross-check model outputs and refine parameterization of karst heterogeneity.
a. 使用这些数据集对模型输出进行交叉验证，并细化喀斯特不均匀性的参数化。
b. If direct field data are unavailable, clearly acknowledge this and discuss the implications for model reliability.
b. 如果没有直接的现场数据，请明确承认这一点，并讨论这对模型可靠性的影响。

3. If applicable, are statistical analyses, controls, sampling mechanism, and statistical reporting (e.g., P-values, CIs, effect sizes) appropriate and well described?

Please clearly indicate if the manuscript requires additional peer review by a statistician. Kindly provide suggestions to the author(s) on how to improve the statistical analyses, controls, sampling mechanism, or statistical reporting. Please number each suggestion so that the author(s) can more easily respond.

Reviewer #1: Mark as appropriate with an X:
Yes [] No [] N/A [X]
Provide further comments here:

Reviewer #2: Mark as appropriate with an X:
Yes [] No [] N/A [X]
Provide further comments here:
The manuscript does not involve traditional statistical analyses. However, to strengthen rigor, consider:

1. Providing a brief explanation of model calibration and validation strategies.
2. Including uncertainty bounds or sensitivity analyses for key parameters (e.g., permeability, fault conductivity) to give readers a sense of result robustness.

4. Could the manuscript benefit from additional tables or figures, or from improving or removing (some of the) existing ones?

Please provide specific suggestions for improvements, removals, or additions of figures or tables. Please number each suggestion so that author(s) can more easily respond.

Reviewer #1: 1. Fig. 1, what is the blue color stratum in the profile?
2. Fig. 3, label the stratum character in the profile.
3. Table 1, a unified value of k is assigned to the faults. Are all the faults conductive? Add a new table to display the characteristic geologic parameters and hydraulic property of each fault in the study area.
4. Change the unit of the k to a common unit, i.e. m/d.
5. Intuitively display the difference of temperature, Darcy flux and hydraulic head distribution in the model area between Model I and Model II by means of subtraction. And analyze the reasons for the differences from the perspectives of groundwater flow system.
6. Fig.5 and other Figures, which one is the karst geothermal reservoir in the figure? Gaoyang High or Xianxian High?
7. Add some analyses regarding the fluctuation of the simulated Darcy flux with Time in Fig.5.

Reviewer #2: The manuscript would benefit from clearer figures and additional supporting tables:

Figures:

Improve resolution and ensure consistent font sizes and color contrasts (especially in Figs. 4–6).

Annotate recharge/discharge areas and major faults for easier interpretation.

Tables:

Include a comprehensive table summarizing field-based geological parameters (e.g., lithologies, karstification features, fault characteristics).

Add a table describing the geological setting and model structure (stratigraphic units, boundary conditions, parameter ranges).

5. If applicable, are the interpretation of results and study conclusions supported by the data?

Please provide suggestions (if needed) to the author(s) on how to improve, tone down, or expand the study interpretations/conclusions. Please number each suggestion so that the author(s) can more easily respond.

Reviewer #1: Mark as appropriate with an X:
Yes [X] No [] N/A []
Provide further comments here:

Reviewer #2: Mark as appropriate with an X:
Yes [X] No [] N/A []
Provide further comments here:
The interpretations are broadly supported, but a few refinements could strengthen confidence in the conclusions:

1. Avoid overgeneralizing results, especially given the simplifications in model geometry (the use of an equivalent porous medium for karst systems).

2. Discuss how better geological calibration (e.g., integrating hydrogeological field data such as borehole temperature logs, permeability measurements, or tracer studies) could refine and validate the conclusions.

3. Emphasize the contexts in which the current findings are robust and identify where additional data could further support them.

6. Have the authors clearly emphasized the strengths of their study/methods?

Please provide suggestions to the author(s) on how to better emphasize the strengths of their study. Please number each suggestion so that the author(s) can more easily respond.

Reviewer #1: The strengths of their study/methods should be made more efforts to be improved. The author should further summarize the current status of relevant research, and propose a proper scientific issue.

Reviewer #2: Partially.
The study has several strengths that could be highlighted more explicitly to showcase its novelty:

1. Highlight the integration of free and forced convection effects in karst geothermal systems as a novel approach.

2. Emphasize the relevance of applying coupled numerical simulations to understand basin-scale thermal anomalies.

3. Stress how the model aligns with observed geothermal gradients and explain how this strengthens the conclusions.

4. Point out the value of the sensitivity analysis on reservoir thickness, permeability, and fault zone width in illustrating key system controls.

7. Have the authors clearly stated the limitations of their study/methods?

Please list the limitations that the author(s) need to add or emphasize. Please number each limitation so that author(s) can more easily respond.

Reviewer #1: The authors have clearly stated the limitations of their study/methods.

Reviewer #2: Expand on the limitations of assuming isotropy and homogeneity in karst reservoirs, which are typically highly heterogeneous.

1. Acknowledge uncertainties in boundary conditions (assumed diving surface geometry) and parameter estimates (fault permeability, recharge rates).

2. Suggest future directions for incorporating 3D heterogeneity and dynamic fault activity into the modeling approach.

3. Explicitly state the lack of direct geological calibration data (e.g., fault transmissivity measurements, tracer studies) as a key limitation and discuss its potential impacts on model results.

8. Does the manuscript structure, flow or writing need improving (e.g., the addition of subheadings, shortening of text, reorganization of sections, or moving details from one section to another)?

Please provide suggestions to the author(s) on how to improve the manuscript structure and flow. Please number each suggestion so that author(s) can more easily respond.

Reviewer #1: The manuscript structure is fine.

Reviewer #2: Simplify complex sentences and ensure logical flow between sections, especially in the Results and Discussion.

Add subheadings within the Results and Discussion to improve navigation and focus for the reader.

9. Could the manuscript benefit from language editing?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #1: This paper study the heat accumulation effect in karst geothermal systems by means of numerical simulation. Results can help understand the formation mechanism of the geothermal systems. To improve the quality of the paper, some suggestions are listed below:
1. According to the paper title, the hypothesis in this paper is the heat accumulation effect is enhanced by groundwater convection. But the enhancing way and characteristics by groundwater convection, i.e. the groundwater flow and heat convection pattern driven by topography and buoyancy, need to be further present and analyzed in the paper.
2. Line 115-118, lacking quantitative investigations of the study area is not an advisable scientific issue (as mentioned earlier, some studies have been carried out in this area). The author should further summarize the current status of relevant research, and propose a proper scientific issue.
3. Fig. 1, what is the blue color stratum in the profile?
4. Line 229, why using "0.1MPa" to assign the constant pressure boundary condition? What's the meaning of this value?
5. Fig. 3, label the stratum character in the profile.
6. Table 1, a unified value of k is assigned to the faults. Are all the faults conductive? Add a new table to display the characteristic geologic parameters and hydraulic property of each fault in the study area.
7. Change the unit of the k to a common unit, i.e. m/d.
8. Intuitively display the difference of temperature, Darcy flux and hydraulic head distribution in the model area between Model I and Model II by means of subtraction. And analyze the reasons for the differences from the perspectives of groundwater flow system.
9. Fig.5 and other Figures, which one is the karst geothermal reservoir in the figure? Gaoyang High or Xianxian High?
10. Add some analyses regarding the fluctuation of the simulated Darcy flux with Time in Fig.5.
11. Line 666, the karst cavity-fracture system is not generalized and modeled in the simulation, so it's not proper to mention this matter in the conclusion.
12. The conclusion need more efforts to be revised and improved. What's the new findings and insights, as well as the innovation points of this paper should be included in the conclusion.


Reviewer #2: Consider adding more field data (temperature logs, permeability, tracer tests) to strengthen model calibration and validation.

It may be helpful to discuss the potential limitations of using an equivalent porous medium to represent karst heterogeneity.

Enhancing figure resolution and adding clear annotations could improve readability.

Highlighting practical implications for geothermal development (well placement) would add value.




More information and support 

FAQ: How do I revise my submission in Editorial Manager?
https://service.elsevier.com/app/answers/detail/a_id/28463/supporthub/publishing/

FAQ: How can I reset a forgotten password?
https://service.elsevier.com/app/answers/detail/a_id/28452/supporthub/publishing/
For further assistance, please visit our customer service site: https://service.elsevier.com/app/home/supporthub/publishing/
Here you can search for solutions on a range of topics, find answers to frequently asked questions, and learn more about Editorial Manager via interactive tutorials. You can also talk 24/7 to our customer support team by phone and 24/7 by live chat and email

At Elsevier, we want to help all our authors to stay safe when publishing. Please be aware of fraudulent messages requesting money in return for the publication of your paper. If you are publishing open access with Elsevier, bear in mind that we will never request payment before the paper has been accepted. We have prepared some guidelines (https://www.elsevier.com/connect/authors-update/seven-top-tips-on-stopping-apc-scams ) that you may find helpful, including a short video on Identifying fake acceptance letters (https://www.youtube.com/watch?v=o5l8thD9XtE ). Please remember that you can contact Elsevier s Researcher Support team (https://service.elsevier.com/app/home/supporthub/publishing/) at any time if you have questions about your manuscript, and you can log into Editorial Manager to check the status of your manuscript (https://service.elsevier.com/app/answers/detail/a_id/29155/c/10530/supporthub/publishing/kw/status/).

#AU_GEOT#

To ensure this email reaches the intended recipient, please do not delete the above code