Assessing Groundwater Sustainability in Siwa Oasis, Egypt: Evaluating Physico-Chemical and Hydrochemical Suitability for Human and Agricultural Use

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This research is very important, escpecially for the Siwa Oasis, considering all the problems related to drinking and irrigating water, which are also very well explained in the article.

The Introduction gives a good overview of the topic. It gives a detailed insight into todays problems regarding this topic and is relevant to the field.

The Materials and Methods section as a whole gives a precise explanation of the methodical framework in this study. The 2.1 subsection should contain a map for easy understanding of the study site. In the 2.4 subsection, the map would benefit from including a gridline containing latitude and longitude for a clear spatial perception.

The Results section is backed with Figures and Tables which provide a clear summary of the results. In subsection 3.2, when the wells deemed suitable for drinking and irrigation are listed, well W03 is incorrectly written.

In Table 2 equation 7, precisely in the classification for the SAR indice, it is stated that ranges below 10 are excellent, whereas ranges between 10 and 18 are good. In Table 5, 20 out of 20 samples are ranging from 1.27 to 17.72 which means the samples are either classified as  "excellent" or "good" considering the classification from Table 2. The abstract and conclusion argue that the SAR indice (among others) classified the wells as not suitable for irrigation, which contradicts the results from Table 5 and the classification from Table 2. The water from the wells is indeed not suitable for irrigation, but the SAR indice doesn`t support that fact. 

All in all, this study gives a comprehensive insight into the properties and the very states of the studied wells in this region. The theoretical background is relevant to the topic and distinctively exhibited through Tables and Figures. 

Comments on the Quality of English Language

This article contains a few grammatical errors mostly in sections Introduction and Materials and Methods and some inconsistent uses of brackets when citing Tables and data in Tables.

Author Response

Reviewer #1:

Comments to the Corresponding Author

This research is very important, especially for the Siwa Oasis, considering all the problems related to drinking and irrigating water, which are also very well explained in the article.

 

We sincerely appreciate the reviewer's positive assessment. We value your feedback and will carefully consider your suggestions for improvement to enhance the quality of the manuscript.

 

1. The Introduction gives a good overview of the topic. It gives a detailed insight into today's problems regarding this topic and is relevant to the field.

Response: Thank you for your positive evaluation of the Introduction. We appreciate the reviewer’s acknowledgment that it provides a clear and relevant overview of the topic and addresses current issues in the field.

 

2. The Materials and Methodssection as a whole gives a precise explanation of the methodical framework in this study. The 2.1 subsectionshould contain a map for easy understanding of the study site. In the 2.4 subsection, the map would benefit from including a gridline containing latitude and longitude for a clear spatial perception.

 

Response: Thank you for your constructive and helpful suggestion regarding the inclusion of a map in Section 2.1. In our revised manuscript, we have clarified that Section 2.1 provides an overview of the study area, while the detailed map is intentionally presented in Section 2.4 to avoid duplication. The map in Section 2.4 has been updated to include latitude–longitude gridlines for clearer spatial interpretation. Additionally, Table 1 including sampling sites and coordinates that complements this map.

 

3. The Resultssection is backed with Figures and Tables which provide a clear summary of the results. In subsection 3.2, when the wells deemed suitable for drinking and irrigation are listed, well W03 is incorrectly written.

 

Response: Thanks for Reviewer's careful observation. We are very sorry for our negligence for the typographical error in listing well W03 in subsection 3.2. It has now been corrected and the change is highlighted in the revised manuscript.

 

4. In Table 2 equation 7, precisely in the classification for the SAR indice, it is stated that ranges below 10 are excellent, whereas ranges between 10 and 18 are good. In Table 5, 20 out of 20 samples are ranging from 1.27 to 17.72 which means the samples are either classified as  "excellent" or "good" considering the classification from Table 2. The abstract and conclusion argue that the SAR indice (among others) classified the wells as not suitable for irrigation, which contradicts the results from Table 5and the classification from Table 2. The water from the wells is indeed not suitable for irrigation, but the SAR indice doesn`t support that fact. 

Response: We appreciate the reviewer’s careful observation regarding the SAR classification. In the revised manuscript, we clarified this point to avoid any perceived contradiction. Although Table 2 classifies samples with SAR <10 as “excellent” and <18 as “good,” only three wells (≈20%) fall below 10 and can be confidently considered suitable for irrigation. The remaining wells, while technically within the “good” category (<18), have SAR values approaching the upper limit of this class and are close to the threshold of the “doubtful” category. Moreover, other irrigation indices (such as %Na) collectively indicate that most wells are not suitable for irrigation despite their SAR values. We have revised the abstract and conclusion to clearly reflect that the unsuitability of the wells is supported by the combined interpretation of multiple indices rather than SAR alone.

 

5. All in all, this study gives a comprehensive insight into the properties and the very states of the studied wells in this region. The theoretical background is relevant to the topic and distinctively exhibited through Tables and Figures. 

Response: We sincerely appreciate the reviewer's supportive comments regarding the study's insight into the regional wells and the effective use of tables and figures to present the theoretical background and presentations.

 

6. This article contains a few grammatical errors mostly in sections Introduction and Materials and Methods and some inconsistent uses of brackets when citing Tables and data in Tables.

Response: Thank you for highlighting these languages and formatting issues. We have carefully proofread the entire manuscript, with particular attention to the Introduction and Materials and Methods sections, to correct grammatical errors and ensure consistent formatting. The changes have been highlighted in yellow color

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents important work on groundwater assessment in the Siwa Oasis and

The manuscript presents important work on groundwater assessment in the Siwa Oasis and contains several strong elements, particularly in outlining the study’s value, summarizing key findings, and providing classification of groundwater groups. However, a number of editorial, structural, and scientific issues should be addressed to improve clarity, consistency, and accuracy.  Overall I enjoyed this simple but comprehensive (with respect to major cations and anions) because it provides a menu for others to apply a variety of basic methods in a similar way.

The title is quite long.  I would drop “comprehensive” from the title because there are many drinking water parameters that could be done, including organics and trace elements

Abstract – These ecosystems or “these natural hydrological systems and aquifer”

Introduction.  Freshwater has become “a” critical……….

Not rocks erosion.   Maybe “natural geological factors such as mineral dissolution

Several sentences in the abstract are overly long and should be split for readability.

Editing is needed in the introduction.    Some phrasing needs tightening. For example, “pollution controlling should be revised to pollution control efforts, and redundant statements about groundwater salinization should be removed.  There are quite a number of examples where editing will strengthen the paper and a good editor should be employed to take care of these minor-moderate  editing issues.  Citation formatting is inconsistent. References appear as [7-8] in some places and [7, 8] in others

Care were taken” should be corrected to “Care was taken.”

I will not add much more on editing because there are many examples needed to be fixed. 

Citation needed for Oven Drying Method

The Figure 1 map.  Upper Panel.  It is impossible to read the lables of the figures.

The authors should include a geological map and a geological description table so the geological factors on salinity may be noted, and because it is standard in a groundwater investigation.

I like table 2 because it is available to other scientists for use.  However, where is F1 and W defined on equations 1 and 2?

Significant figures for DO.  If they have two after decimal, 4 should be 4.00 for average.

To compare Nitrate to Ammonia/Ammonium.  You need to convert all values to NO3-N and NH3-N.  Otherwise, the weights are not a reliable comparison

Hydrogeochemical criteria of groundwater”   this is why you need a geologic map and understanding of aquifer minerals

Ion balance error is good. Almost all under 5%.

Could the statements “Only about 5% of the oasis area is used for cultivation”  Can a citation provided?

Ion notation should be checked for consistency throughout the manuscript (Ca²⁺, Mg²⁺, HCO₃⁻, SO₄²⁻).

The BOD method should be described as a 5-day BOD test, dropping “5-days incubation process.”

Percentages of major cations (Na⁺ = 59.3%, Mg²⁺ = 26.8%, Ca²⁺ = 8.7%, K⁺ = 5.2%) sum to 99%. 

Does WHO set limits for all major cations and anions or only some of them? 

Figure 6 shows values in microsiemens but throughout the data is referred to as millisiemens.  And TDS changing from mg/L to g/L.  Most authors use uS/cm3 and mg/L and I think the authors should consider this change thoughout. 

Please expand on conclusions where authors say optimizing pumping rate will affect artesian flow.  That should be mentioned with more details in discussion.  With explanations and clarifications.    Can the aquifer quality be improved?  If it is largely geologic, there may not be any remedy except using desalting of water.  Please discuss with more details.  

Comments on the Quality of English Language

A moderate amount of editing is needed.  However, it is not all that far off if a good editor is employed to look over the editing issues.

Author Response

The manuscript presents important work on groundwater assessment in the Siwa Oasis and The manuscript presents important work on groundwater assessment in the Siwa Oasis and contains several strong elements, particularly in outlining the study’s value, summarizing key findings, and providing classification of groundwater groups. However, a number of editorial, structural, and scientific issues should be addressed to improve clarity, consistency, and accuracy.  Overall I enjoyed this simple but comprehensive (with respect to major cations and anions) because it provides a menu for others to apply a variety of basic methods in a similar way.

Response:

Thank you for your thoughtful and constructive review of our manuscript. We sincerely appreciate your positive assessment of the study's importance. We have carefully considered all your comments and fully agree that addressing the structural, and scientific issues you raised will significantly improve the manuscript's clarity, and accuracy. Below is our point-by-point response

1. The title is quite long.  I would drop “comprehensive” from the title because there are many drinking water parameters that could be done, including organics and trace elements

Response:

Thank you for your constructive comment. We have revised and modified the title of the manuscript to " Assessing Groundwater Sustainability in Siwa Oasis, Egypt: Evaluating Physico-Chemical and Hydrochemical Suitability for Human and Agricultural Use".

2. Abstract – These ecosystems or “these natural hydrological systems and aquifer”

Response:

Thank you for your important comment. We have revised and modified the abstract insight your comments, the modifications were highlighted in Yellow color

3. Introduction.  Freshwater has become “a” critical……….

Not rocks erosion.  Maybe “natural geological factors such as mineral dissolution

Several sentences in the abstract are overly long and should be split for readability.

Editing is needed in the introduction.  Some phrasing needs tightening. For example, “pollution controlling should be revised to pollution control efforts, and redundant statements about groundwater salinization should be removed.  There are quite a number of examples where editing will strengthen the paper and a good editor should be employed to take care of these minor-moderate  editing issues.  Citation formatting is inconsistent. References appear as [7-8] in some places and [7, 8] in others

Care were taken” should be corrected to “Care was taken.”

I will not add much more on editing because there are many examples needed to be fixed. 

Response:

Thank you for your constructive comment. We have revised and modified the introduction section insight your comments, the modifications were highlighted in Yellow color

4. Citation needed for Oven Drying Method

Response:

We thank the reviewer for highlighting the need for a citation regarding the Oven Drying Method. For clarity, the primary methodological citation is indeed provided at the beginning of the paragraph in the reference [21] "American Public Health Association, APHA"

5. The Figure 1 map.  Upper Panel.  It is impossible to read the lables of the figures.

Response:

Thank you for your constructive comment. We have revised and modified the map and re-write the labels in clear manner and adding the Lat. and Long. coordinates of the lower map for better readability

6. The authors should include a geological map and a geological description table so the geological factors on salinity may be noted, and because it is standard in a groundwater investigation.

Response:

Thank you for your constructive comment. We have added a geological map of Siwa Oasis showing the major formation and structures.

 

7. I like table 2 because it is available to other scientists for use.  However, where is F1 and W defined on equations 1 and 2?

Response:

Thank you for your constructive comment. We have revised and added the definition of various variables in Eq1 and Eq 2 in table 2, the modification was highlighted with yellow color

8. Significant figures for DO.  If they have two after decimal, 4 should be 4.00 for average.

Response:

Thank you for your valuable comment. We have revised the manuscript accordingly and we adjusting the decimal configuration of average. The modification was highlighted with yellow color

9. To compare Nitrate to Ammonia/Ammonium.  You need to convert all values to NO3-N and NH3-N.  Otherwise, the weights are not a reliable comparison

Response

Thank you for your valuable comment. We would like to clarify that; all nitrogen species were already calculated according to their nitrogen-based forms. Nitrate was expressed as NO₃–N, nitrite as NO₂–N, and ammonium as NH₄⁺–N. we correct these terms in the revised version. Therefore, the comparison and weighting of nitrogen parameters were conducted on a consistent nitrogen basis, ensuring reliable and accurate evaluation.

10. Hydrogeochemical criteria of groundwater”   this is why you need a geologic map and understanding of aquifer minerals

Response

 

11. Ion balance error is good. Almost all under 5%.

Response

Thank you for your comment. We appreciate your observation and are pleased to note that the ion balance error values fall below 5%

 

12. Could the statements “Only about 5% of the oasis area is used for cultivation”  Can a citation provided?

Response

Thank you for your comment. We would like to inform you that. We confirm that the statement is indeed supported by the reference mentioned at the end of the paragraph. The sentence, “Only about 5% of the oasis area is used for cultivation...” is part of the description in the Study Area section, which is primarily based on the work of Abdel-Gawad et al. (2020), cited as reference [20] at the paragraph's end.

13. Ion notation should be checked for consistency throughout the manuscript (Ca²⁺, Mg²⁺, HCO₃⁻, SO₄²⁻).

Response:

Thanks for Reviewer's careful observation. We are very sorry for our negligence for the typographical error. It has now been corrected and the change is highlighted in the revised manuscript.

14. The BOD method should be described as a 5-day BOD test, dropping “5-days incubation process.”

Response:

Thanks for Reviewer's observation. We are corrected this term and the change is highlighted in the revised manuscript.

15. Percentages of major cations (Na⁺ = 59.3%, Mg²⁺ = 26.8%, Ca²⁺ = 8.7%, K⁺ = 5.2%) sum to 99%. 

Response:

Thank you for your comment. We have double-checked the calculations, and the percentages of the major cations (Na⁺ = 59.3%, Mg²⁺ = 26.8%, Ca²⁺ = 8.7%, K⁺ = 5.2%) correctly sum to 100%, not 99%. We appreciate your attention to detail and have ensured this is clearly presented in the revised version.

16. Figure 6 shows values in microsiemens but throughout the data is referred to as millisiemens.  And TDS changing from mg/L to g/L.  Most authors use uS/cm3 and mg/L and I think the authors should consider this change thoughout. 

Response:

Thank you for your helpful comment. We have corrected Figures 6 and 7 and standardized the conductivity units by converting µS/cm to mS/cm. Additionally, we ensured consistent use of mg/L for TDS throughout the manuscript. These adjustments have been incorporated in the revised version."

 

17. Please expand on conclusions where authors say optimizing pumping rate will affect artesian flow.  That should be mentioned with more details in discussion.  With explanations and clarifications.    Can the aquifer quality be improved?  If it is largely geologic, there may not be any remedy except using desalting of water.  Please discuss with more details.  

Response:

Thank you for this important comment. We have expanded and clarified the conclusion in the revised manuscript to provide a more detailed explanation of how optimizing pumping rates can influence artesian flow conditions. These points have been thoroughly addressed in the updated conclusion section.

Reviewer 3 Report

Comments and Suggestions for Authors

The article deals with the highly topical issue of assessing the potential of using underground non-renewable water resources for various purposes (drinking water source, irrigation water source).

The authors used methods and calculations that correspond to other published case studies to assess the potential of use and assess the suitability of water for selected purposes. I have no reservations about them. They are adequate for the purpose of the study and to achieve the results that are necessary to resolve the established hypotheses.

I have no comments on the structure and organization of the article.

I agree with the presentation of the results of water monitoring and analytical analyses.

The article has a clear structure and presentation procedure for the achieved monitoring results and subsequent statistical analyses, which are suitably displayed graphically. They allow the reader to have a good orientation and interpretation of the presented results.

I agree with the conclusions of the study.

I have no comments on the literature used. The authors discuss their findings and conclusions within all chapters of the article with appropriate sources of information.

I recommend the article for publication, after considering the suggested recommendations for corrections of typos and ambiguities.

I came across typos and areas for clarification in the article. I have marked all of this in the form of revisions and comments directly in the submitted version of the article, which I am attaching to the review for easier editing by the authors in the final version of the article.

 

Comments for author File: Comments.pdf

Author Response

Reviewer: 2

 

Comments and Suggestions for Authors

The article deals with the highly topical issue of assessing the potential of using underground non-renewable water resources for various purposes (drinking water source, irrigation water source).

The authors used methods and calculations that correspond to other published case studies to assess the potential of use and assess the suitability of water for selected purposes. I have no reservations about them. They are adequate for the purpose of the study and to achieve the results that are necessary to resolve the established hypotheses.

I have no comments on the structure and organization of the article.

I agree with the presentation of the results of water monitoring and analytical analyses.

The article has a clear structure and presentation procedure for the achieved monitoring results and subsequent statistical analyses, which are suitably displayed graphically. They allow the reader to have a good orientation and interpretation of the presented results.

I agree with the conclusions of the study.

I have no comments on the literature used. The authors discuss their findings and conclusions within all chapters of the article with appropriate sources of information.

I recommend the article for publication, after considering the suggested recommendations for corrections of typos and ambiguities.

I came across typos and areas for clarification in the article. I have marked all of this in the form of revisions and comments directly in the submitted version of the article, which I am attaching to the review for easier editing by the authors in the final version of the article.

 

Response:

We sincerely thank the reviewer for his positive and thorough evaluation of our manuscript and for their recommendation for publication. We are grateful for their careful reading and for providing specific editorial suggestions and comments directly in the manuscript. We have incorporated all of the suggested corrections to address typos and clarify any ambiguities in the revised version. The modification was highlighted with yellow color

 

1. Please consider formatting the table differently or arranging it differently. Not all monitored parameters are visible.

Response:

We thank the reviewer for this helpful suggestion. We have reformatted the concerned table by aligning the entire page in landscape orientation to ensures that all monitored parameters are clearly visible without truncation.

2. we corrected the typographical error in listing well W03 in subsection 3.2.
3. I think; it could be named Eq 10.

Thank you for your valuable comment, In the revised version of the manuscript, Equation 9 from the previous draft has been removed. Therefore, the current equation retains its numbering as Equation 9.

4. There is no information about monitored microbiological parameters in the chapter If they were monitored, please add the information to the sub-chapter. Ideally, create a chapter 2.4 that follows on from chapter 2.3. The original chapter 2.4 will be marked 2.5

 

We thank the reviewer for highlighting the absence of microbiological parameter details in Chapter 2. In the revised manuscript, we have clarified that the microbiological data were obtained from the previously published study by Abdelkarim et al. (2025), which investigated the biological characteristics of the same sampling sites. To address the reviewer’s suggestion, we have added this information in the Section 2.4, describing the source of the microbiological data.

5. we corrected all typographical errors in the revised version. The modifications were highlighted with yellow color

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

As long at the values of NH3-N and NO3-N are shown as such in the relevant graphs and data I am satisfied with the final paper!