Groundwater Quality and Health Risk Assessment Using Indexing Approaches, Multivariate Statistical Analysis, Artificial Neural Networks, and GIS Techniques in El Kharga Oasis, Egypt

Round 1

Reviewer 1 Report

In my opinion, the study investigates a very important and topical issue, the groundwater quality in El Kharga Oasis, Egypt. The results are also of international interest, so the article is valuable addition to the literature.

The authors are advised to make modifications, corrections and additions, as listed below:

 

Introduction:

Statements in Line 73-74 and 93-94 need to be referenced. Authors could cite following article:

The effects of uninsulated sewage tanks on groundwater. A case study in an eastern Hungarian settlement, DOI: 10.1515/jwld-2017-0027

Following sentence need to be reformulated ‘can be applied’, or move to materials and methods. Factor analysis (FA) was applied to examine the geochemical evolution, mineralization, and potential contamination of groundwater.

The authors should formulate hypothesises, and add to the end of the section introduction.

Materials and methods:

Please add information about the number of population living in the study area.

Provide information about drinking water supply (e.g. depth, consumption) and wastewater collection and treatment. Does it exist? could be a potential source of pollution?

The authors state in lines 176-178 the amount of extracted water, this is for irrigation only, or for drinking as well? Please clarify it in the text.

 Figure 1 need to be revised: Please use the correct English names of the Countries like: Egypt, Libya. Numbering of the sampling points is not clear, please modify. Remove the numbering, or enlarge the map to be able to add all numbers. Use “sampling points” instead of samples.

 Figure 2 need to be revised. The map is not readable, please replace with a new version. You could use the map from figure 1 that the reader can see the location of this wells. What is meant by “A” and A’ please clarify. Legend Use water level instead of W.L.

Subchapter 2.3.1. Please concretise the used Cluster Analysis. It exists more possibilities like: Hierarchical cluster analysis or two-step cluster analysis. Please also describe the used method

Subchapter 2.3.2. Please add information about the suitability of the dataset (KMO value)

Subchapter 2.4.1. Please reference the source of the drinking water quality indicy (DWQI). This seems to me similar to the index of Brown et al.

 Results:

Please clarify the following statement in lines 386-387: The classification of groundwater was carried out based on the physicochemical parameters deemed suitable for drinking by the NSSA.

For classification why only the suitable parameters were used?

Statement in line 398 need to be reformulated, I don’t think that with this relative low EC it is brackish water.

TDS can be calculated from EC, how is it possible the big difference between suitable/not suitable, EC 20%, TDS 38%. How is the minimum of EC lower than the minimum of TDS? TDS= EC*0,64 to 0,7

Chapter 3.2. In case of many samples clear differences can be seen in the Piper plot, several samples fall in type 5 and 3. What is the reason for that? Any separation by water level, location or well depth?

Chapter 3.3. The authors could create the cluster Dendogram for the monitoring wells. It is any separation by location?

 My overall evaluation is, that the manuscript is publishable after minor scientific revisions.

Author Response

In my opinion, the study investigates a very important and topical issue, the groundwater quality in El Kharga Oasis, Egypt. The results are also of international interest, so the article is valuable addition to the literature. The authors are advised to make modifications, corrections and additions, as listed below:

We greatly appreciate your critical observations as well as your constructive and helpful comments. We hope that we could address your questions/comments by the explanations and revisions made in the manuscript. We believe that the manuscript is substantially improved after making the suggested revisions.

Introduction:

1. Statements in Line 73-74 and 93-94 need to be referenced. Authors could cite following article: The effects of uninsulated sewage tanks on groundwater. A case study in an eastern Hungarian settlement, DOI: 10.1515/jwld-2017-0027.

Response: Many thanks for this comment. The references were added as your suggestion (Lines 89-92 – Page 3) and (Lines 124-127 – Page 4).

2. Following sentence need to be reformulated ‘can be applied’, or move to materials and methods. Factor analysis (FA) was applied to examine the geochemical evolution, mineralization, and potential contamination of groundwater.

Response: We greatly appreciate your critical observations. The sentence was reformulated as your suggestion (Line 164 – Page 4).

3. The authors should formulate hypothesises, and add to the end of the section introduction.

Response: Many thanks for this comment. A hypothesises was formulated and added in the end of the introduction section as your suggestion (Lines 197-207 – Page 5).

Materials and methods:

4. Please add information about the number of population living in the study area.

Response: Many thanks for this comment. The information about the number of population living in the study area was added as your suggestion (Lines 211-213– Page 6).

5. Provide information about drinking water supply (e.g. depth, consumption) and wastewater collection and treatment. Does it exist? Could be a potential source of pollution?

Response: We greatly appreciate for this comment. The information about drinking water supply (e.g. depth, consumption) was added as your suggestion and the main source of pollution due to the clay lenses in the aquifer composition and return flow of untreated irrigation waste water (Line 226 – Page 6) and (Lines 97-107 – Page 3 ).

6. The authors state in lines 176-178 the amount of extracted water; this is for irrigation only, or for drinking as well? Please clarify it in the text.

Response: We greatly appreciate your critical observations. The amount of extracted water for drinking and irrigation was added in the text as your suggestion (Line 222– Pages 6).

7. Figure 1 need to be revised: Please use the correct English names of the Countries like: Egypt, Libya. Numbering of the sampling points is not clear, please modify. Remove the numbering, or enlarge the map to be able to add all numbers. Use “sampling points” instead of samples.

Response: We greatly appreciate your critical observations. Figure 1 was corrected and modified as your suggestion (Line 247 – Page 8).

8. Figure 2 need to be revised. The map is not readable, please replace with a new version. You could use the map from figure 1 that the reader can see the location of these wells. What is meant by “A” and A’ please clarify. Legend Use water level instead of W.L.

Response: We greatly appreciate your critical observations. Figure 2 was corrected and modified as your suggestion (Line 269 – Page 11).

9. Subchapter 2.3.1. Please concretise the used Cluster Analysis. It exists more possibilities like: Hierarchical cluster analysis or two-step cluster analysis. Please also describe the used method.

Response: Many thanks for this comment. The Cluster Analysis was concretized and the used method was described as your suggestion (Lines 296-301 – Page 12).

10. Subchapter 2.3.2. Please add information about the suitability of the dataset (KMO value).

Response: Many thanks for this comment. The information about the suitability of the dataset (KMO value) was added as your suggestion (Lines 215-321– Page 12).

11. Subchapter 2.4.1. Please reference the source of the drinking water quality index (DWQI). This seems to me similar to the index of Brown et al.

Response: We greatly appreciate your critical observations. The reference was added as your suggestion (Line 325 – Page 12).

 

Results:

12. Please clarify the following statement in lines 386-387: The classification of groundwater was carried out based on the physicochemical parameters deemed suitable for drinking by the NSSA.

Response: Many thanks for this comment. This sentence was corrected and modified to clarify as your suggestion (Lines 448-458 – Page 17).

13. For classification why only the suitable parameters were used?

Response: Many thanks for this comment. This sentence was corrected and modified to clarify as your suggestion (Lines 448-458 – Page 17).

14. Statement in line 398 need to be reformulated, I don’t think that with this relative low EC it is brackish water.

Response: We greatly appreciate your critical observations. This sentence was reformulated as your suggestion (Line 464 – Page 18).

15. TDS can be calculated from EC, how is it possible the big difference between suitable/not suitable, EC 20%, TDS 38%. How is the minimum of EC lower than the minimum of TDS? TDS= EC*0,64 to 0,7

  Response: We greatly appreciate your critical observations. These errors in writing were corrected (Lines 457-458 – Page 17).

16. Chapter 3.2. In case of many samples clear differences can be seen in the Piper plot, several samples fall in type 5 and 3. What is the reason for that? Any separation by water level, location or well depth?

Response: Many thanks for this comment. The difference in the water type is related to the heterogenity of the aquifer and different cement materials between gains with wells depth  (Lines 514-516 – Page 19).

17. Chapter 3.3. The authors could create the cluster Dendogram for the monitoring wells. It is any separation by location?

Response: Many thanks for this comment. The cluster Dendogram for the monitoring wells was added and separation by location as your suggestion (Lines 613-628 – Pages 22-23).

Author Response File: Author Response.docx

Reviewer 2 Report

Groundwater Quality and Health Risk Assessment Using  Indexing Approaches, Multivariate Statistical Analysis,  Artificial Neural Networks and GIS Techniques in El Kharga Oasis, Egypt

It focuses on Groundwater Quality and Health Risk Assessment Using Indexing Approaches, Multivariate Statistical Analysis, Artificial Neural Networks and GIS Techniques in El Kharga Oasis, Egypt. The author addresses a fascinating topic. The manuscript in its current form is adequate to be published. The author is requested to revise it and follow the following suggestions to improve their work. In my opinion, some details on the experiment should be presented in a methodology that validates your results with filed data. This study introduction section looks very localized and needs to add some literature on other countries or regions which have faced the same problem and make it more readable globally.

Other comments

Revise your abstract.

*       What is the key finding?

*       What are the practical implications of your research (how can the results be utilized by e.g., readers, community)?

 

Line 43-44 The results of HI indicated that there is a potential health risk 43 due to ingesting of water, with the risk being higher for children in only one location.?

Why is it only for children

Introduction

An introduction is poorly framed. Very localized introduction! I suggest the authors revise it completely into a new format. The authors need to clarify the novelty in the introduction section. This section is not clearly explaining the overall picture of your paper. It is suggested to add some literature globally and make it more attractive for readers. The specific issue of your study area and finally problem formulation and scope of the research.

It is suggested that include a paragraph that indicates your study's importance from the perspective of the Red Sea region.

 

These are the following question that needs to address from your end.

 

 

1.      What are your suggestions to improve water management and quality control in your study area?

2.      Author should make a comparative analysis of regional countries and present an effective solution that is vital to cater to such situations.

 Conclusions

 

The current form is very large in length. It is suggested to revise this section and make it more concise to reflect your study. 

Author Response

It focuses on Groundwater Quality and Health Risk Assessment Using Indexing Approaches, Multivariate Statistical Analysis, Artificial Neural Networks and GIS Techniques in El Kharga Oasis, Egypt. The author addresses a fascinating topic. The manuscript in its current form is adequate to be published. The author is requested to revise it and follow the following suggestions to improve their work. In my opinion, some details on the experiment should be presented in a methodology that validates your results with filed data. This study introduction section looks very localized and needs to add some literature on other countries or regions which have faced the same problem and make it more readable globally.

We greatly appreciate your critical observations as well as your constructive and helpful comments. We hope that we could address your questions/comments by the explanations and revisions made in the manuscript. We believe that the manuscript is substantially improved after making the suggested revisions.

Abstract:

1. What is the key finding?

Response: Many thanks for this comment. The key findings were added in the abstract section as your suggestion (Lines 48-55– Page 2) and (Lines 66-70– Page 2).

2. What are the practical implications of your research (how can the results be utilized by e.g., readers, community)?

Response: We greatly appreciate your critical observations. The practical implications of our research were added as your suggestion (Lines 66-70– Page 2).

3. Line 43-44. The results of HI indicated that there is a potential health risk due to ingesting of water, with the risk being higher for children in only one location? Why is it only for children?

Response: Many thanks for this comment. The answer was added to the text. Children may be more sensitive to certain contaminants than adults. For example, their developing bodies may be more susceptible to the effects of certain chemicals or toxins such as Fe and Mn. The contaminants could be from natural sources, such as minerals leaching from rocks and soil, or from human activities (Lines 709-713– Page 27).

Introduction:

4. An introduction is poorly framed. Very localized introduction! I suggest the authors revise it completely into a new format. The authors need to clarify the novelty in the introduction section. This section is not clearly explaining the overall picture of your paper. It is suggested to add some literature globally and make it more attractive for readers. The specific issue of your study area and finally problem formulation and scope of the research.

Response: Many thanks for this comment. The novelty and the overall picture of our paper were explained, also some literature globally were added as your suggestion (Lines 94-107– Page 5), (Lines 122-127– Page 3-4) and (Lines 197-207– Page 5).

5. It is suggested that include a paragraph that indicates your study's importance from the perspective of the Red Sea region.

Response: Many thanks for this comment. There is difference between the western desert (Kharga Oasis) and the region in eastern desert (red sea region). Kharga Oasis is covered by sedimentary rocks while the red sea region is covered by basement rocks and it is different in the aquifer condition.

6. What are your suggestions to improve water management and quality control in your study area?

Response: Many thanks for this comment. To improve water management and quality control from the current investigation, the exploitation of groundwater in production wells should be limited and replacing flood irrigation with more advanced irrigation methods, such as drip and sprinkle irrigation.

7. Author should make a comparative analysis of regional countries and present an effective solution that is vital to cater to such situations.

Response: Many thanks for this comment. A comparative analysis of regional countries and an effective solution were presented as your suggestion (Lines 502-526 – Pages 18-19).

Conclusions:

8. The current form is very large in length. It is suggested to revise this section and make it more concise to reflect your study.

Response: Many thanks for this comment. The conclusion section was revised to make it more concise as your suggestion (Lines 748-774 – Pages 30-31).

Author Response File: Author Response.docx

Reviewer 3 Report

General comments

Robust research that fits well the scope of either journal or session. However, all the specific comments need to be addressed before publication

 

Specific comments

Line 38. “Rock weathering”. Which types of rocks are you treating? Be more specific in the abstract

Lines 49-50. “Its value of R2 was 0.99 for training, Cross validation (CV), and test data”. Please, do not start a sentence with “its”. Revise the language

Lines 92-93. “At present, one of the top environmental issues that the world is grappling with is the pollution of water”. Insert the following review papers on groundwater contamination on other areas of the world. One review paper is specific on sandstone

- Medici, G. and West, L.J., 2022. Review of groundwater flow and contaminant transport modelling approaches for the Sherwood Sandstone aquifer, UK; insights from analogous successions worldwide. Quarterly Journal of Engineering Geology and Hydrogeology, 55(4), https://doi.org/10.1144/qjegh2021-176

- Mackay, D.M. and Cherry, J.A., 1989. Groundwater contamination: Pump-and-treat remediation. Environmental Science & Technology, 23(6), pp.630-636.

 

Line 157. (i), (ii), and (iii) are specific objectives. Revise the sentence, and state the principal aim of the paper

Line 182. The Quseir Formation is part of the Nubian Sandstone?

Line 188. The Nubian Aquifer System also represents a group of geological formations?

Line 188. Possible inserting the transmissivity values (ranges, and arithmetic average)?

Lines 204-210. You need to insert several references

Line 219. More detail on pH analysis. Did you determine the pH in the field? What about alkalinity another parameter typically measured in the field?

Line 371. Which software did you use? You mention a software in the title, but not in the main body of the paragraph

Line 440-441. You need to specify the previous geochemical studies. Please, insert references

Line 562. The data points are aligned along a line? Why? Did you target a fault zone?

Lines 630-631. “Ca-Mg-SO4, mixed Ca-Mg-Cl-SO4, Na-Cl, Ca-Mg-HCO3, and mixed 630 Na-Ca-HCO3 types” You have lots of Ca and HCO3, did you specify processes of dissolution of calcite cement in your sandstone? Please, do that in the previous paragraphs, and refer to the relevant paper below:

- Tellam, J. H., & Barker, R. D. (2006). Towards prediction of saturated‐zone pollutant movement in groundwaters in fractured permeable‐matrix aquifers: The case of the UK Permo‐Triassic sandstones. In R. D. Barker, & J. H. Tellam (Eds.), Fluid flow and solute movement in sandstones: The onshore UK Permo‐Triassic red bed sequence (Vol. 263) Geological Society, London, Special Publication.

 

Line 664. Insert the three relevant references suggested above. Two are specific on the hydrogeology of sandstones

 

Figures and tables

Figure 2a. This figure is un-readable. Please, increase the graphic resolution (more dpi), and enlarge it

Figure 9. You can enlarge a lit bit this figure. Also, increase the graphic resolution to improve the readability

Author Response

Robust research that fits well the scope of either journal or session. However, all the specific comments need to be addressed before publication. 

We greatly appreciate your critical observations as well as your constructive and helpful comments. We hope that we could address your questions/comments by the explanations and revisions made in the manuscript. We believe that the manuscript is substantially improved after making the suggested revisions.

1. Line 38. “Rock weathering”. Which types of rocks are you treating? Be more specific in the abstract.

Response: Many thanks for this comment. The types of rocks were added as your suggestion (Line 43 – Page 2).

2. Lines 49-50. “Its value of R² was 0.99 for training, Cross validation (CV), and test data”. Please, do not start a sentence with “its”. Revise the language.

Response: Thank you for your guidance and support for our manuscript. The phrase has been revised. “The R² value for the training, cross-validation (CV), and test data was 0.99”. (Lines 61-62 – Page 2).

3. Lines 92-93. “At present, one of the top environmental issues that the world is grappling with is the pollution of water”. Insert the following review papers on groundwater contamination on other areas of the world. One review paper is specific on sandstone.

• Medici, G. and West, L.J., 2022. Review of groundwater flow and contaminant transport modelling approaches for the Sherwood Sandstone aquifer, UK; insights from analogous successions worldwide. Quarterly Journal of Engineering Geology and Hydrogeology, 55(4), https://doi.org/10.1144/qjegh2021-176 (Lines – Pages  ).
• Mackay, D.M. and Cherry, J.A., 1989. Groundwater contamination: Pump-and-treat remediation. Environmental Science & Technology, 23(6), pp.630-636.

Response: Many thanks for this comment. The review papers on groundwater contamination on other areas of the world were added as your suggestion (Lines 122-124 – Pages 3-4).

4. Line 157. (i), (ii), and (iii) are specific objectives. Revise the sentence, and state the principal aim of the paper.

Response: Many thanks for this comment. The principal aim of the paper was highlighted as your suggestion (Lines 197-206 – Page 5).

5. Line 182. The Quseir Formation is part of the Nubian Sandstone?

Response: We greatly appreciate for this comment. The Quseir Formation is part of the Nubian Sandstone (Lines 229-231 – Page 6).

6. Line 188. The Nubian Aquifer System also represents a group of geological formations?

Response: We greatly appreciate for this comment. This phrase was modified in the text (Lines 239-240 – Page 6).

7. Line 188. Possible inserting the transmissivity values (ranges, and arithmetic average)?

Response: We greatly appreciate for this comment. The transmissivity values were added as your suggestion (Lines 232-233 – Page 6).

8. Line 219. More detail on pH analysis. Did you determine the pH in the field? What about alkalinity another parameter typically measured in the field?

Response: We greatly appreciate for this comment. The pH parameter was measured in the field, which revealed alkaline water (Lines 273-274 – Page 11).

9. Line 371. Which software did you use? You mention a software in the title, but not in the main body of the paragraph

Response: We greatly appreciate for this comment. We have already mentioned the study's software” The Python 3.7.3 programming language was utilized for data analysis, model construction, and data preparation”. (Lines 439-441 - Page 17).

10. Line 440-441. You need to specify the previous geochemical studies. Please, insert references.

Response: We greatly appreciate for this comment. The previous geochemical studies were added and documented with references as your suggestion (Lines 510-526 – Page 19).

11. Line 562. The data points are aligned along a line? Why? Did you target a fault zone?

Response: Many thanks for this comment. The data points are aligned along a line because drilling wells in the western desert (El Kharga Oasis) depend on the availability of fertile soil for agriculture as well as the upward movement of the groundwater is through the fault plane in the NSSA Fig 2. (Lines 213-215 - Page 6).

12. Lines 630-631. “Ca-Mg-SO₄, mixed Ca-Mg-Cl-SO₄, Na-Cl, Ca-Mg-HCO₃, and mixed Na-Ca-HCO₃ types” You have lots of Ca and HCO₃, did you specify processes of dissolution of calcite cement in your sandstone? Please, do that in the previous paragraphs, and refer to the relevant papers.

Response: Many thanks for this comment. The processes of dissolution of calcite cement in sandstone were be specified and the relevant papers were added as your suggestion (Lines 502-526 – Pages 18-19).

13. Line 664. Insert the three relevant references suggested above. Two are specific on the hydrogeology of sandstones.

Response: Many thanks for this comment. The three relevant references were added as your suggestion (Line 817 – Page 32).

Figures and tables

14. Figure 2a. This figure is un-readable. Please, increase the graphic resolution (more dpi), and enlarge it.

Response: We greatly appreciate for this comment. Figure 2a was modified and the graphic resolution (more dpi) was increased as your suggestion (Line 270 – Pages 11).

15. Figure 9. You can enlarge a lit bit this figure. Also, increase the graphic resolution to improve the readability.

Response: Many thanks for this comment. We regret that this figure was not clear. So, we included another figure that is easier to understand for readers (Line 746 – Pages 30).

Author Response File: Author Response.docx