Vulnerability Mapping of Groundwater Resources of Mekelle City and Surroundings, Tigray Region, Ethiopia

Round 1

Reviewer 1 Report

The authors improved the article, taking into account the reviewers' suggestions

Author Response

Dear Reviewer,

Thank you so much for your time and all the valuable comments. Please find below your reproduced comments (plain text, black font color) and our responses (plain text, red font color).

1. The authors improved the article, taking into account the reviewers' suggestions

 We thank you very much for your valuable input.

Reviewer 2 Report

All changes have been considered and the text has been improved.

I would suggest of considering for the introduction the below papers concerning anthropogenic and geogenic pollution:

Water 13, no. 20: 2809. https://doi.org/10.3390/w13202809)

Environ Monit Assess 191, 509 (2019). https://doi.org/10.1007/s10661-019-7655-1

Author Response

Dear Reviewer,

Thank you so much for your time and all the valuable comments. Please find below your reproduced comments (plain text, black font color) and our responses (plain text, red font color).

All changes have been considered and the text has been improved.

We thank you very much for your valuable input.

I would suggest of considering for the introduction the below papers concerning anthropogenic and geogenic pollution:

Water 13, no. 20: 2809. https://doi.org/10.3390/w13202809)

Environ Monit Assess 191, 509 (2019). https://doi.org/10.1007/s10661-019-7655-1

Thank you so much again for recommending us these important articles and we have included them (lines 35 to 36 and lines 43 to 44).

Reviewer 3 Report

I found this research work very interesting and suitable for Water journal. However, authors need to address following points before it can be considered for the publication:

1. At present abstract is very poorly written with lots of grammatical errors. It must be rewritten to summarize the objectives and key findings. 

2. In the introduction section, authors need to add one paragraph to write about information or research gap in this study area and motivation to carry this research work.

3. Figure 2 needs to be revised for better explanation of all the symbols used to generate this map.

4. Line number 383-386 is very confusing as aquifer media and hydraulic conductivities are showing different and opposite effective weightings? Please recheck your result outcome.    

5. Information about gathering nitrate data should be added in line number 444.

Please see the reviewed paper attached herewith for more comments.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you so much for your time and all the valuable comments. Please find below your reproduced comments (plain text, black font color) and our responses (plain text, red font color).

I found this research work very interesting and suitable for Water journal. However, authors need to address following points before it can be considered for the publication

                    Thank you so much for your valuable input.

At present abstract is very poorly written with lots of grammatical errors. It must be rewritten to summarize the objectives and key findings.

 The abstract provides the objectives (lines 13 to 15) and the key findings (lines 16 to 24 and 19 to 22). However, changes have been made on the abstract to rectify grammatical errors, and typos following your suggestion. Keywords of the previous version are also changed.

In the introduction section, authors need to add one paragraph to write about information or research gap in this study area and motivation to carry this research work.

Dear reviewer, would you please check lines (94 to 99) The research gap and motivations to carry out this research are already available there. For clarity, the words ‘Mekelle area’ are added (line 97) to introduce readers to the location of Ellala-Aynalem catchments.

Figure 2 needs to be revised for better explanation of all the symbols used to generate this map.

The map in Figure 2 is a modified map, mainly used to show the regional fractures which cross the study area and the lithological distributions. The sampling locations are already shown on the location map (Figure1.). Showing the sampling locations on this map (Figure 2, which is of a different scale) overcrowds the map. Moreover, it would be a redundancy.  However, the previous mismatch in color between the points on the map and the legend, ‘localities’, is fixed. The fonts are also edited for readability. Thank you for the feedback.

Line number 383-386 is very confusing as aquifer media and hydraulic conductivities are showing different and opposite effective weightings? Please recheck your result outcome.

We believe the result is correct; the effective weightings depend on the ‘ratings and weightings’ that we have used. Even though the same weight was assigned to both the Aquifer media and Hydraulic conductivity; it is not mandatory to get the same or similar final result.   Moreover, the difference in effective weighting between the aquifer and hydraulic conductivity can also be witnessed from different published articles (look ref.# 65, 66, and 67 in the manuscript) and the previously conducted research work in the area ( ref .# 44).

Information about gathering nitrate data should be added in line number 444.

We appreciate you raised that, and we have added the information (lines 453 to 454).

 Please see the reviewed paper attached herewith for more comments

Our responses for the comments on the attached paper

Dear reviewer, thank you for your effort in improving our manuscript. We have addressed all your suggestions on the updated manuscript, and your major comments and our replies are reiterated below;

On lines 14 to 18: How index classification is represented in km2? Authors are confused between index classes and its distribution in this study area? Please recheck 

It is not that we represented index class in Km²; rather we wanted to indicate how much of a spatial coverage each index class has in the study area. For example, if the ‘very high’ vulnerable area covers only 1 km² out of about a total of 1023 Km², then the magnitude of risk or remedial actions can be thought of accordingly. Therefore, our intent was to show the areal extent of each index class (indirectly the % can also be considered). There are published papers also reporting it that way. To avoid confusion to readers the word areal coverage is added to clarify what the values in brackets represent.

 On lines 16 to 18: Hard to understand

We have performed the conventional DRASTIC and modified DRASTIC to assess the vulnerability of groundwater resources in the study area. In the modified DRASTIC index, two more input layers are added. Therefore, the numerical values for the range in the modified DRASTIC obviously become higher. Our objective was also to compare both versions, as to which one better fits the study area. In our work, we have done that using the nitrate concentration and Pearson’s correlation coefficient.

On lines 95 to 98: Before this paragraph, authors are suggested to write a short paragraph about Mekelle city, information gap and motivation behind carrying this study.

This comment is related to your main comment on ‘number 2’. So, our response is partly put there. Moreover, information about Mekelle is available on lines 106 to 110 i.e on the study area description.

On lines 129 to 130: Legends used to show sampling locations is not clear in this map? Also what are green dots as it is not mentioned in the legends?

Comment similar to main comment on ‘number 3. Our reply is addressed there.  Thank you for noting the color mismatch on the point data. The green dots are used to show localities (in the legend, it was wrongly in red color now it is corrected). Thank you.

On lines 444 to 445:  Did authors have analyzed this data or its a secondary data collected? Please clarify it.

Similar to main comment ‘number 5’. The data were collected from Tigray Water Resources Bureau.

On line 478: what is car station?

The two words ‘car stations’ are replaced by ‘garages’.

Thank you again for all the valuable inputs! 

Round 2

Reviewer 3 Report

Authors did a great job to revise the manuscript. I don't have any further comments and hence vote for its acceptance for the publication

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The topic addressed is interesting for the journal. However, few sections of the current version of paper should be improved. The article should be modified taking into account the suggestions indicated below.

• Line 128: please check the references [5, 6, 12, 14, 17, 18, , 15, ].
• Line 175: please provide more information on the Drastic Index. In particular provide a description of the parameters considered in Eq. 1 (Dr, Dw, Rr, etc…), and, if possible, of the application of Drastic on other similar case studies.
• Line 175: provide more information on IDW technique. Report the equation considered for IDW and the related parameters, in particular the power parameter that affects the area of influence of each data point.
• Based on the conclusion section, what is further research direction?

Reviewer 2 Report

The author have used a simple additive model without calculating the weight and rank. They have applied the weight and rank of Aller et al. 1987 which might be not applicable to their study sites. The authors must have calculated own weight and rank using different decision making criteria. This is the major drawback in the manuscript. The authors have not validated their DRASTIC model and did not performed the sensitivity and uncertainty in their developed out put map is second major limitation of their study. Why authors have applied IDW method is also not provide a logical region behind the study?

Reviewer 3 Report

The literature in the introduction is poor

Lines 42-43: rephrase

Lines 47-48: rephrase

Lines 67-69 rephrase, a little confused

Lines 70-73: It is not clear the reason of mention the critical situation in this country, regarding the topic of the paper and how these are associated

Lines 77-81: rephrase, the war is a very difficult situation which can change  everything in an environment but the vulnerability of the aquifer is something else , I am not sure that I can fully understand the aim of this paper.

Figure 1. Is there any reason for including this picture?

Line 89 Figure 1 must be moved below 2.1.1 section , also Fig. 2 below 2.1.2.

Figure 3 North arrow is missing

Line 136-139 rephrase

Line 152 wrong figure

Many sentences begin with ''to''  I suggest to change it