the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Oct 2025
Using Cave Drip Loggers to Characterize Groundwater Infiltration and Examine Hydrological Response in Cretaceous Karst Formation
Abstract. In Texas, groundwater from karst aquifers represents a significant percentage of the State's water supply. Karst regions are vital groundwater resources, and caves offer natural access points for observing long-term vadose zone water storage and fluxes, offering a better understanding of groundwater flow paths. Natural Bridge Caverns (NBC), which is situated within the recharge zone of the Cretaceous age Edwards (Balcones Fault Zone) aquifer and also recharges the Trinity aquifer below the Edwards, was monitored with a high resolution, spatially dense cave drip rate network during one hydrological year to characterize water infiltration within this karst system. Precipitation, soil water content (SWC), and evapotranspiration (ET) data were obtained for the location and used to evaluate the infiltration-discharge relationship for 20 drip loggers. All drip sites remained active throughout the monitoring period and generally exhibited low discharge rates during dry periods and high discharge rates in response to rainfall events. Discharge at the drip sites varied substantially, and analysis revealed a spatial relationship emerging from the dataset. Using Multidimensional Scaling (MDS) and agglomerative hierarchical clustering (AHC) we were able to classify similar drip types to obtain four unique drip regimes. A lithological assessment suggests that secondary porosity is influencing water movement rather than overburden thickness. Despite the relatively short time frame of this study, we find that the results shed valuable insights into the heterogeneity of hydrological flow within the vadose zone at NBC. It also emphasizes the importance of advancing our understanding and characterization of unsaturated zone hydrological processes to inform effective groundwater management policies.
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RC1: 'Comment on egusphere-2025-2623', Anonymous Referee #1, 03 Nov 2025
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AC1: 'Reply on RC1', Kashif Mahmud, 19 Dec 2025
We sincerely appreciate the time and effort the reviewers have devoted to creating an improved version of our paper. The major concern from the reviewers is the missing connection between the fine-scale high-resolution cave drip data and the behaviour of the larger-scale aquifer system. We believe the fine-scale drip data captures the nuances of the infiltration process (e.g., how different soil types and topographic features affect the rate of water entry), leading to better estimates of the total volume of recharge over a large area. Large-scale models often use coarse grid cells, which might oversimplify or average out significant variations in soil properties and landscape features. Fine-scale data allows for a more detailed representation of this heterogeneity, which is critical for simulating realistic water movement and distribution, as variations in soil type can cause significant differences in soil moisture and subsurface flow velocity. By incorporating detailed, high-resolution data, models can better quantify and reduce prediction uncertainty. This helps managers and stakeholders have greater confidence in the model’s outputs, such as predictions of future water levels or the impact of pumping, leading to more informed decision-making. Moreover, high-resolution field measurements such as the drip logger data provide robust datasets for calibrating and validating model performance against observed conditions. This ensures the model’s physical consistency and ability to accurately simulate real-world hydrologic responses. In essence, fine-scale infiltration data provides the necessary detail to ensure that the underlying processes are accurately captured, thereby increasing the fidelity and predictive power of the large-scale simulations. We will explain all these possible implications of fine-scale high-resolution drip data in the revised manuscript to justify the contributions of this work for sustainable groundwater management in karst aquifers.
The comments of the reviewer and the corresponding responses are below:
RC1: Anonymous Referee #1, 03 Nov 2025
The authors presented an approach for an in-depth analysis of the hydrological response in a Cretaceous karst formation. The authors use own data from 20 drip rate loggers deployed in the cave system. In addition, precipitation, soil water content and evapotranspiration data were obtained for one location outside the cave system. The investigated time spans only one year. This was correctly mentioned by the authors and convincingly justified. For data evaluation, multidimensional scaling and agglomerative hierarchical clustering was used to classify drip types and find unique drip regimes. Generally, the manuscript is very well written and easy to follow. I also believe that the authors invested a significant proportion of time in field work and data evaluation. However, there are major issues that need to be addressed.
Comment 1
First and most importantly, the introduction (which is too long) the geological background and the hydrological background (also too long) refer to a very large aquifer system.
Reply: Thank you for highlighting the lengthy nature of the introduction and background sections and being overly broad. Our revised manuscript will focus on these sections and modify the texts for clarity and brevity to highlight the most relevant factors to better align with the manuscript context.
Comment 2
A large proportion of text deals with the huge importance of this aquifer system as water source. The actual research work for this study, however, was done in one cave system by using loggers just a few meters apart. This is a substantial mismatch.
Reply: We agree with the reviewer and will condense the section on the importance of the Edwards Aquifer. In addition, we want to emphasize that Natural Bridge Caverns (NBC) are a living demonstration of karst infiltration, and a typical expression of the aquifer that sustains millions of people. Importantly, rainfall is the only source of recharge, and because of its position above the water table, this cave observatory is unaffected by groundwater abstraction. NBC lies within the Edwards Aquifer recharge zone, where rainfall and surface water infiltrate directly into the subsurface. The caverns provide a natural laboratory for studying how water moves through fractured limestone, conduits, and sinkholes. Periodic flooding within cavern passages demonstrates the immediate link between surface water and groundwater, offering rare opportunities for direct observation. Therefore, the drip logger’s measurement at NCB over time can be used as a proxy to understand the Edwards Aquifer recharge events.
Comment 3
Also, there is no interpretation of the drip water amount beyond the standard techniques mentioned above and the authors only confirm the findings of already published studies.
Reply: We appreciate this observation and will strengthen the interpretation of the drip-water data accordingly. In the revised manuscript, we will expand the discussion to provide a more detailed analysis of temporal variability in drip rates, relate the observed patterns to site-specific factors such as fracture geometry, rainfall–infiltration dynamics, and antecedent moisture conditions, to offer explanations based on the unique characteristics of the monitored locations. These additions will allow us to move beyond confirmation of existing work and highlight the specific hydrological behavior of the studied cave system.
Comment 4
A quantitative consideration which could justify the framework given in the introduction is completely missing. In summary, I am not convinced that this is sufficient for a publication in HESS.
Reply: Thank you for this constructive suggestion. In revising the manuscript, we will refine the introduction sections for clarity and conciseness, highlighting only the relevant factors to strengthen contextual alignment with the cave scale water infiltration data. The Edwards Aquifer is one of the most productive karst aquifers in the world, and recharge zones like NBC act as a proxy for the groundwater recharge process and are essential to study to maintain water supply to the Aquifer.
We are confident that the information presented herein is an important and necessary contribution to advancing the overall understanding of cave recharge dynamics within karst regions of Texas. With the ongoing revision, which includes further quantitative framing, we believe the rationale for the study area and its broader hydrogeological relevance will be more explicit and better-supported. We appreciate the reviewer’s thoughtful comments, which would allow us to significantly improve the manuscript’s quality.
Comment 5
Technical corrections: Figure 1B: Add scale.
Reply: A notation will be added to this diagram in the revised manuscript to indicate the scale.
Citation: https://doi.org/10.5194/egusphere-2025-2623-AC1
-
AC1: 'Reply on RC1', Kashif Mahmud, 19 Dec 2025
-
RC2: 'Comment on egusphere-2025-2623', Anonymous Referee #2, 22 Nov 2025
The manuscript begins with a broad description and consideration of a large karst aquifer region in Texas. The introduction (sections 1, 2) is long and detailed, but in the context of the actual focus and analysis in the methods and discussion sections, this introduction is far too long and contains far too much irrelevant detail.
The field measurements are limited to samples from 20 samplers, over a relatively small area, and for only one year. Justification for this limited dataset is provided, but nevertheless the dataset is limited especially after reading details in Sections 1 and 2 that describe an extremely large aquifer system.
It is clear from the cited literature that this aquifer system has been studied quite extensively. Here, too, the manuscript is seriously limited, as the results and analysis do not provide new insights, but instead reaffirm findings from previous studies (as the authors state).
The conclusions confirm that the results are analogous to similar studies (lines 526-533). The other two paragraphs describe behavior specific to the field site, and general comments about variability and the need for continued monitoring.
I therefore see this contribution as a limited, site-specific confirmation of known behavior at a well studied karst region. While I appreciate the considerable effort and time invested in obtaining these measurements and developing the analysis, I do not see the manuscript as representing a sufficiently significant and new contribution to support publication in HESS.
Citation: https://doi.org/10.5194/egusphere-2025-2623-RC2 -
AC2: 'Reply on RC2', Kashif Mahmud, 19 Dec 2025
We sincerely appreciate the time and effort the reviewers have devoted to creating an improved version of our paper. The major concern from the reviewers is the missing connection between the fine-scale high-resolution cave drip data and the behaviour of the larger-scale aquifer system. We believe the fine-scale drip data captures the nuances of the infiltration process (e.g., how different soil types and topographic features affect the rate of water entry), leading to better estimates of the total volume of recharge over a large area. Large-scale models often use coarse grid cells, which might oversimplify or average out significant variations in soil properties and landscape features. Fine-scale data allows for a more detailed representation of this heterogeneity, which is critical for simulating realistic water movement and distribution, as variations in soil type can cause significant differences in soil moisture and subsurface flow velocity. By incorporating detailed, high-resolution data, models can better quantify and reduce prediction uncertainty. This helps managers and stakeholders have greater confidence in the model’s outputs, such as predictions of future water levels or the impact of pumping, leading to more informed decision-making. Moreover, high-resolution field measurements such as the drip logger data provide robust datasets for calibrating and validating model performance against observed conditions. This ensures the model’s physical consistency and ability to accurately simulate real-world hydrologic responses. In essence, fine-scale infiltration data provides the necessary detail to ensure that the underlying processes are accurately captured, thereby increasing the fidelity and predictive power of the large-scale simulations. We will explain all these possible implications of fine-scale high-resolution drip data in the revised manuscript to justify the contributions of this work for sustainable groundwater management in karst aquifers.
The comments of the reviewer and the corresponding responses are below:
RC2: Anonymous Referee #2, 22 Nov 2025
Comment 1
The manuscript begins with a broad description and consideration of a large karst aquifer region in Texas. The introduction (sections 1, 2) is long and detailed, but in the context of the actual focus and analysis in the methods and discussion sections, this introduction is far too long and contains far too much irrelevant detail.
Reply: We thank the reviewer for this helpful observation. In the revised manuscript, we will substantially streamline the noted section to focus on the specific hydrogeologic processes relevant to our study area and remove any material that does not directly support our research questions and the processes investigated in this work. We anticipate that these revisions to shorten the introduction and background will improve the overall presentation of the manuscript and the analyses presented.
Comment 2
The field measurements are limited to samples from 20 samplers, over a relatively small area, and for only one year. Justification for this limited dataset is provided, but nevertheless the dataset is limited especially after reading details in Sections 1 and 2 that describe an extremely large aquifer system.
It is clear from the cited literature that this aquifer system has been studied quite extensively. Here, too, the manuscript is seriously limited, as the results and analysis do not provide new insights, but instead reaffirm findings from previous studies (as the authors state).
Reply: We appreciate the reviewer’s concern regarding the limited spatial and temporal extent of our dataset. Although our study area is small relative as it relates to the overall Edwards Aquifer system, the paper aimed to investigate fine-scale heterogeneity and short-term hydrologic variability that are not discussed in other existing regional studies. This research presents the first of its kind using drip loggers to document the hydrological response within a karst cave in Texas, and therefore the contributions emerging from our research are rather significant. While our results are consistent with regional observations, as we have acknowledged, this consistency strengthens the understanding of how larger-scale aquifer behavior manifests at fieldscale. We will further revise the manuscript to emphasize these contributions and to clarify the specific gaps the dataset helps to fill.
Comment 3
The conclusions confirm that the results are analogous to similar studies (lines 526-533). The other two paragraphs describe behavior specific to the field site, and general comments about variability and the need for continued monitoring.
Reply: Thank you for pointing out this limited scope within the manuscript. In response, we will revise the conclusions to better articulate the study’s key findings, clearly highlight the most important observations coming from the analysis, and explicitly detail how these findings advance understanding of site-scale variability within the broader karst system. We will remove any generalised statements and add a clearer discussion that focuses on the advantages of continued monitoring to better interpret the regional aquifer behavior from drip measurements. We will also propose a conceptual framework to illustrate the possible subsurface water infiltration pathways and fracture distribution above the cavern based on the flow classification utilizing drip logger data.
Comment 4
I therefore see this contribution as a limited, site-specific confirmation of known behavior at a well studied karst region. While I appreciate the considerable effort and time invested in obtaining these measurements and developing the analysis, I do not see the manuscript as representing a sufficiently significant and new contribution to support publication in HESS.
Reply: We appreciate the reviewer’s gracious evaluation of our work. Our intention with this study is not to just re-describe already established regional behavior, but rather to provide high-resolution, site-specific measurements that will help bridge the gap between already established conceptual models of the aquifer behaviour and small-scale hydrologic processes. This scale linkage is crucial for understanding the inter-relationships between the factors applied, the results obtained, and the impacts on processes such as recharge mechanisms. We believe the specific knowledge gap addressed by our fine-scale dataset is critical. There is much relevance within our findings for improving the interpretations based on monitoring data and developing better management strategies for karst systems that are linked to caves and caverns.
We have offered an estimate of fine-scale subsurface water infiltration that can significantly improve large-scale groundwater model predictions by providing more accurate estimates of groundwater recharge, which is a primary input to models. The drips counted by the loggers are able to capture the spatial variability and heterogeneity of subsurface properties within a fine cave-scale study, which is also vital to incorporate into the large-scale groundwater models for better accuracy. To our knowledge, this is the only fine-scale high-resolution water infiltration measurement study conducted within the recharge zone of Edwards Aquifer, providing vital information about aquifer water infiltration and spatial heterogeneity within the subsurface limestone formation.
Overall, in conclusion, we hope that these clarifications demonstrate the value of this contribution, even within the context of an already well-studied aquifer system. We believe the revised manuscript will clearly convey the significance of the research paper.
Citation: https://doi.org/10.5194/egusphere-2025-2623-AC2
-
AC2: 'Reply on RC2', Kashif Mahmud, 19 Dec 2025
Status: closed
-
RC1: 'Comment on egusphere-2025-2623', Anonymous Referee #1, 03 Nov 2025
General comments:
The authors presented an approach for an in-depth analysis of the hydrological response in a Cretaceous karst formation. The authors use own data from 20 drip rate loggers deployed in the cave system. In addition, precipitation, soil water content and evapotranspiration data were obtained for one location outside the cave system. The investigated time spans only one year. This was correctly mentioned by the authors and convincingly justified. For data evaluation, multidimensional scaling and agglomerative hierarchical clustering was used to classify drip types and find unique drip regimes. Generally, the manuscript is very well written and easy to follow. I also believe that the authors invested a significant proportion of time in field work and data evaluation. However, there are major issues that need to be addressed.
First and most importantly, the introduction (which is too long), the geological background and the hydrological background (also too long) refer to a very large aquifer system. A large proportion of text deals with the huge importance of this aquifer system as water source. The actual research work for this study, however, was done in one cave system by using loggers just a few meters apart. This is a substantial mismatch.
Also, there is no interpretation of the drip water amount beyond the standard techniques mentioned above and the authors only confirm the findings of already published studies. A quantitative consideration which could justify the framework given in the introduction is completely missing.
In summary, I am not convinced that this is sufficient for a publication in HESS.
Technical corrections:
Figure 1B: Add scale.
Citation: https://doi.org/10.5194/egusphere-2025-2623-RC1 -
AC1: 'Reply on RC1', Kashif Mahmud, 19 Dec 2025
We sincerely appreciate the time and effort the reviewers have devoted to creating an improved version of our paper. The major concern from the reviewers is the missing connection between the fine-scale high-resolution cave drip data and the behaviour of the larger-scale aquifer system. We believe the fine-scale drip data captures the nuances of the infiltration process (e.g., how different soil types and topographic features affect the rate of water entry), leading to better estimates of the total volume of recharge over a large area. Large-scale models often use coarse grid cells, which might oversimplify or average out significant variations in soil properties and landscape features. Fine-scale data allows for a more detailed representation of this heterogeneity, which is critical for simulating realistic water movement and distribution, as variations in soil type can cause significant differences in soil moisture and subsurface flow velocity. By incorporating detailed, high-resolution data, models can better quantify and reduce prediction uncertainty. This helps managers and stakeholders have greater confidence in the model’s outputs, such as predictions of future water levels or the impact of pumping, leading to more informed decision-making. Moreover, high-resolution field measurements such as the drip logger data provide robust datasets for calibrating and validating model performance against observed conditions. This ensures the model’s physical consistency and ability to accurately simulate real-world hydrologic responses. In essence, fine-scale infiltration data provides the necessary detail to ensure that the underlying processes are accurately captured, thereby increasing the fidelity and predictive power of the large-scale simulations. We will explain all these possible implications of fine-scale high-resolution drip data in the revised manuscript to justify the contributions of this work for sustainable groundwater management in karst aquifers.
The comments of the reviewer and the corresponding responses are below:
RC1: Anonymous Referee #1, 03 Nov 2025
The authors presented an approach for an in-depth analysis of the hydrological response in a Cretaceous karst formation. The authors use own data from 20 drip rate loggers deployed in the cave system. In addition, precipitation, soil water content and evapotranspiration data were obtained for one location outside the cave system. The investigated time spans only one year. This was correctly mentioned by the authors and convincingly justified. For data evaluation, multidimensional scaling and agglomerative hierarchical clustering was used to classify drip types and find unique drip regimes. Generally, the manuscript is very well written and easy to follow. I also believe that the authors invested a significant proportion of time in field work and data evaluation. However, there are major issues that need to be addressed.
Comment 1
First and most importantly, the introduction (which is too long) the geological background and the hydrological background (also too long) refer to a very large aquifer system.
Reply: Thank you for highlighting the lengthy nature of the introduction and background sections and being overly broad. Our revised manuscript will focus on these sections and modify the texts for clarity and brevity to highlight the most relevant factors to better align with the manuscript context.
Comment 2
A large proportion of text deals with the huge importance of this aquifer system as water source. The actual research work for this study, however, was done in one cave system by using loggers just a few meters apart. This is a substantial mismatch.
Reply: We agree with the reviewer and will condense the section on the importance of the Edwards Aquifer. In addition, we want to emphasize that Natural Bridge Caverns (NBC) are a living demonstration of karst infiltration, and a typical expression of the aquifer that sustains millions of people. Importantly, rainfall is the only source of recharge, and because of its position above the water table, this cave observatory is unaffected by groundwater abstraction. NBC lies within the Edwards Aquifer recharge zone, where rainfall and surface water infiltrate directly into the subsurface. The caverns provide a natural laboratory for studying how water moves through fractured limestone, conduits, and sinkholes. Periodic flooding within cavern passages demonstrates the immediate link between surface water and groundwater, offering rare opportunities for direct observation. Therefore, the drip logger’s measurement at NCB over time can be used as a proxy to understand the Edwards Aquifer recharge events.
Comment 3
Also, there is no interpretation of the drip water amount beyond the standard techniques mentioned above and the authors only confirm the findings of already published studies.
Reply: We appreciate this observation and will strengthen the interpretation of the drip-water data accordingly. In the revised manuscript, we will expand the discussion to provide a more detailed analysis of temporal variability in drip rates, relate the observed patterns to site-specific factors such as fracture geometry, rainfall–infiltration dynamics, and antecedent moisture conditions, to offer explanations based on the unique characteristics of the monitored locations. These additions will allow us to move beyond confirmation of existing work and highlight the specific hydrological behavior of the studied cave system.
Comment 4
A quantitative consideration which could justify the framework given in the introduction is completely missing. In summary, I am not convinced that this is sufficient for a publication in HESS.
Reply: Thank you for this constructive suggestion. In revising the manuscript, we will refine the introduction sections for clarity and conciseness, highlighting only the relevant factors to strengthen contextual alignment with the cave scale water infiltration data. The Edwards Aquifer is one of the most productive karst aquifers in the world, and recharge zones like NBC act as a proxy for the groundwater recharge process and are essential to study to maintain water supply to the Aquifer.
We are confident that the information presented herein is an important and necessary contribution to advancing the overall understanding of cave recharge dynamics within karst regions of Texas. With the ongoing revision, which includes further quantitative framing, we believe the rationale for the study area and its broader hydrogeological relevance will be more explicit and better-supported. We appreciate the reviewer’s thoughtful comments, which would allow us to significantly improve the manuscript’s quality.
Comment 5
Technical corrections: Figure 1B: Add scale.
Reply: A notation will be added to this diagram in the revised manuscript to indicate the scale.
Citation: https://doi.org/10.5194/egusphere-2025-2623-AC1
-
AC1: 'Reply on RC1', Kashif Mahmud, 19 Dec 2025
-
RC2: 'Comment on egusphere-2025-2623', Anonymous Referee #2, 22 Nov 2025
The manuscript begins with a broad description and consideration of a large karst aquifer region in Texas. The introduction (sections 1, 2) is long and detailed, but in the context of the actual focus and analysis in the methods and discussion sections, this introduction is far too long and contains far too much irrelevant detail.
The field measurements are limited to samples from 20 samplers, over a relatively small area, and for only one year. Justification for this limited dataset is provided, but nevertheless the dataset is limited especially after reading details in Sections 1 and 2 that describe an extremely large aquifer system.
It is clear from the cited literature that this aquifer system has been studied quite extensively. Here, too, the manuscript is seriously limited, as the results and analysis do not provide new insights, but instead reaffirm findings from previous studies (as the authors state).
The conclusions confirm that the results are analogous to similar studies (lines 526-533). The other two paragraphs describe behavior specific to the field site, and general comments about variability and the need for continued monitoring.
I therefore see this contribution as a limited, site-specific confirmation of known behavior at a well studied karst region. While I appreciate the considerable effort and time invested in obtaining these measurements and developing the analysis, I do not see the manuscript as representing a sufficiently significant and new contribution to support publication in HESS.
Citation: https://doi.org/10.5194/egusphere-2025-2623-RC2 -
AC2: 'Reply on RC2', Kashif Mahmud, 19 Dec 2025
We sincerely appreciate the time and effort the reviewers have devoted to creating an improved version of our paper. The major concern from the reviewers is the missing connection between the fine-scale high-resolution cave drip data and the behaviour of the larger-scale aquifer system. We believe the fine-scale drip data captures the nuances of the infiltration process (e.g., how different soil types and topographic features affect the rate of water entry), leading to better estimates of the total volume of recharge over a large area. Large-scale models often use coarse grid cells, which might oversimplify or average out significant variations in soil properties and landscape features. Fine-scale data allows for a more detailed representation of this heterogeneity, which is critical for simulating realistic water movement and distribution, as variations in soil type can cause significant differences in soil moisture and subsurface flow velocity. By incorporating detailed, high-resolution data, models can better quantify and reduce prediction uncertainty. This helps managers and stakeholders have greater confidence in the model’s outputs, such as predictions of future water levels or the impact of pumping, leading to more informed decision-making. Moreover, high-resolution field measurements such as the drip logger data provide robust datasets for calibrating and validating model performance against observed conditions. This ensures the model’s physical consistency and ability to accurately simulate real-world hydrologic responses. In essence, fine-scale infiltration data provides the necessary detail to ensure that the underlying processes are accurately captured, thereby increasing the fidelity and predictive power of the large-scale simulations. We will explain all these possible implications of fine-scale high-resolution drip data in the revised manuscript to justify the contributions of this work for sustainable groundwater management in karst aquifers.
The comments of the reviewer and the corresponding responses are below:
RC2: Anonymous Referee #2, 22 Nov 2025
Comment 1
The manuscript begins with a broad description and consideration of a large karst aquifer region in Texas. The introduction (sections 1, 2) is long and detailed, but in the context of the actual focus and analysis in the methods and discussion sections, this introduction is far too long and contains far too much irrelevant detail.
Reply: We thank the reviewer for this helpful observation. In the revised manuscript, we will substantially streamline the noted section to focus on the specific hydrogeologic processes relevant to our study area and remove any material that does not directly support our research questions and the processes investigated in this work. We anticipate that these revisions to shorten the introduction and background will improve the overall presentation of the manuscript and the analyses presented.
Comment 2
The field measurements are limited to samples from 20 samplers, over a relatively small area, and for only one year. Justification for this limited dataset is provided, but nevertheless the dataset is limited especially after reading details in Sections 1 and 2 that describe an extremely large aquifer system.
It is clear from the cited literature that this aquifer system has been studied quite extensively. Here, too, the manuscript is seriously limited, as the results and analysis do not provide new insights, but instead reaffirm findings from previous studies (as the authors state).
Reply: We appreciate the reviewer’s concern regarding the limited spatial and temporal extent of our dataset. Although our study area is small relative as it relates to the overall Edwards Aquifer system, the paper aimed to investigate fine-scale heterogeneity and short-term hydrologic variability that are not discussed in other existing regional studies. This research presents the first of its kind using drip loggers to document the hydrological response within a karst cave in Texas, and therefore the contributions emerging from our research are rather significant. While our results are consistent with regional observations, as we have acknowledged, this consistency strengthens the understanding of how larger-scale aquifer behavior manifests at fieldscale. We will further revise the manuscript to emphasize these contributions and to clarify the specific gaps the dataset helps to fill.
Comment 3
The conclusions confirm that the results are analogous to similar studies (lines 526-533). The other two paragraphs describe behavior specific to the field site, and general comments about variability and the need for continued monitoring.
Reply: Thank you for pointing out this limited scope within the manuscript. In response, we will revise the conclusions to better articulate the study’s key findings, clearly highlight the most important observations coming from the analysis, and explicitly detail how these findings advance understanding of site-scale variability within the broader karst system. We will remove any generalised statements and add a clearer discussion that focuses on the advantages of continued monitoring to better interpret the regional aquifer behavior from drip measurements. We will also propose a conceptual framework to illustrate the possible subsurface water infiltration pathways and fracture distribution above the cavern based on the flow classification utilizing drip logger data.
Comment 4
I therefore see this contribution as a limited, site-specific confirmation of known behavior at a well studied karst region. While I appreciate the considerable effort and time invested in obtaining these measurements and developing the analysis, I do not see the manuscript as representing a sufficiently significant and new contribution to support publication in HESS.
Reply: We appreciate the reviewer’s gracious evaluation of our work. Our intention with this study is not to just re-describe already established regional behavior, but rather to provide high-resolution, site-specific measurements that will help bridge the gap between already established conceptual models of the aquifer behaviour and small-scale hydrologic processes. This scale linkage is crucial for understanding the inter-relationships between the factors applied, the results obtained, and the impacts on processes such as recharge mechanisms. We believe the specific knowledge gap addressed by our fine-scale dataset is critical. There is much relevance within our findings for improving the interpretations based on monitoring data and developing better management strategies for karst systems that are linked to caves and caverns.
We have offered an estimate of fine-scale subsurface water infiltration that can significantly improve large-scale groundwater model predictions by providing more accurate estimates of groundwater recharge, which is a primary input to models. The drips counted by the loggers are able to capture the spatial variability and heterogeneity of subsurface properties within a fine cave-scale study, which is also vital to incorporate into the large-scale groundwater models for better accuracy. To our knowledge, this is the only fine-scale high-resolution water infiltration measurement study conducted within the recharge zone of Edwards Aquifer, providing vital information about aquifer water infiltration and spatial heterogeneity within the subsurface limestone formation.
Overall, in conclusion, we hope that these clarifications demonstrate the value of this contribution, even within the context of an already well-studied aquifer system. We believe the revised manuscript will clearly convey the significance of the research paper.
Citation: https://doi.org/10.5194/egusphere-2025-2623-AC2
-
AC2: 'Reply on RC2', Kashif Mahmud, 19 Dec 2025
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General comments:
The authors presented an approach for an in-depth analysis of the hydrological response in a Cretaceous karst formation. The authors use own data from 20 drip rate loggers deployed in the cave system. In addition, precipitation, soil water content and evapotranspiration data were obtained for one location outside the cave system. The investigated time spans only one year. This was correctly mentioned by the authors and convincingly justified. For data evaluation, multidimensional scaling and agglomerative hierarchical clustering was used to classify drip types and find unique drip regimes. Generally, the manuscript is very well written and easy to follow. I also believe that the authors invested a significant proportion of time in field work and data evaluation. However, there are major issues that need to be addressed.
First and most importantly, the introduction (which is too long), the geological background and the hydrological background (also too long) refer to a very large aquifer system. A large proportion of text deals with the huge importance of this aquifer system as water source. The actual research work for this study, however, was done in one cave system by using loggers just a few meters apart. This is a substantial mismatch.
Also, there is no interpretation of the drip water amount beyond the standard techniques mentioned above and the authors only confirm the findings of already published studies. A quantitative consideration which could justify the framework given in the introduction is completely missing.
In summary, I am not convinced that this is sufficient for a publication in HESS.
Technical corrections:
Figure 1B: Add scale.