Geomatics-Based Modeling and Hydrochemical Analysis for Groundwater Quality Mapping in the Egyptian Western Desert: A Case Study of El-Dakhla Oasis

Round 1

Reviewer 1 Report

Dear Authors,

Thank you for the submitted article. I believe that the research topic undertaken is very important. Especially now, when in many countries we are dealing with hydrolgogic droughts.

The structure of the article does not raise any objections, however, please respond to the following comments:

- please standardize the size of the fonts used (the different sizes in drawing captions are especially noticeable),

- there are stylistic errors, please correct them.

- Please add the item Discussion of results. I believe it is significant in a scientific article.

Kind regards.

Author Response

Response to the comments of Reviewer #1

We thank Reviewer #1 for his relevant comments on our manuscript. Below is the original comment from Reviewer#1 (in italic/bold), with our own responses withinin blue typeface. Changes to the manuscript are shown in red.

• Reviewer Comment: please standardize the size of the fonts used (the different sizes in drawing captions are especially noticeable).

Author's response: The size of the fonts used has been standardized especially drawing captions.

• Reviewer Comment: There are stylistic errors, please correct them.

Author's response: Thank you for pointing this out. Stylistic errors have been corrected as much as possible.

• Reviewer Comment: Please add the item Discussion of results. I believe it is significant in a scientific article.

Author's response: Thank you for this valuable comment. Discussion item has been added inside the revised article

Reviewer 2 Report

This manuscript is about the quality of groundwater used for agriculture and drinking using some standard indices in Egyptian desert area. I believe, this is important topic and would be interesting for readers. Also, findings are important which recommend treatment for groundwater considering high values of some parameters. 
Considering its scientific importance, I recommend it for publication.

Author Response

Response to the comments of Reviewer #2

Reviewer Comment: This manuscript is about the quality of groundwater used for agriculture and drinking using some standard indices in Egyptian desert area. I believe, this is important topic and would be interesting for readers. Also, findings are important which recommend treatment for groundwater considering high values of some parameters. Considering its scientific importance, I recommend it for publication.

Author's response: We are very happy about this comment, thank you very much.

Reviewer 3 Report

The paper reported by Dr. Hanaa A. Megahed et al. focused on Groundwater Quality in El-Dakhla Oasis of the Egyptian Western Desert via GIS-Based Modeling and Hydro-chemical Analysis. The topic is interesting and within the scope of Journal Water. However, there are some major issues. Firstly, information on hydrogeological conditions and groundwater sampling is too little. Secondly, discussion is little, and factors controlling groundwater quality in this study are unclear. I recommend authors use multivariate statistical techniques such as principal component analysis to discuss factors controlling groundwater quality. Thus, a major revision is recommended.

Specific comments

Title

Lines 2, please use full name of GIS in the title.

Abstract

Lines 19-34, please rewrote the abstract. At the beginning of the abstract, major (overarching) issue(s) or problem(s) addressed by the study, including a few sentences discussing why the issue(s)/problem(s) has(have) global importance or, at the very least, is of significant interest to readers of Water. Please use "groundwater" instead of "ground water". Please use "samples" instead of "specimens". "wells" rather than "groundwater wells".

Introduction

Lines 39, please use "groundwater" instead of  "GW" in the whole paper.

Lines 47-80, the introduction is not provide sufficient information for the reader to assess the extent and significance of the central issue(s) addressed in the manuscript. It does not sufficiently describe what is unique about the study area or the methodological/analytical approaches used in the manuscript. 

Study Area

Lines 93-105, what about surface water in the study area? what about hydrogeological conditions such as groundwater recharge, groundwater flow?

Materials and Methods

Lines 114-143, how to collect groundwater samples? filtered or not? what about the quality control for samples analyses?

Results

Lines 148-373, discussion is little, and factors controlling groundwater quality in this study are unclear. I recommend authors use multivariate statistical techniques such as principal component analysis to discuss factors controlling groundwater quality. 

At last, I recommend some references related to groundwater quality that may be useful to authors.

Assessing natural background levels of geogenic contaminants in groundwater of an urbanized delta through removal of groundwaters impacted by anthropogenic inputs: new insights into driving factors. Science of the Total Environment, 857, 159527, 2023

A sharp contrasting occurrence of iron-rich groundwater in the Pearl River Delta during the past dozen years (2006-2018): the genesis and mitigation effect. Science of the Total Environment, 829, 154676, 2022.

Natural background levels in groundwater in the Pearl River Delta after the rapid expansion of urbanization: A new pre-selection method. Science of the Total Environment, 813, 151890, 2022.

Distributions, origins, and health-risk assessment of nitrate in groundwater in typical alluvial-pluvial fans, North China Plain. Environmental Science and Pollution Research, 29, 17031-17048, 2022

Distributions and origins of nitrate, nitrite, and ammonium in various aquifers in an urbanized coastal area, south China. Journal of Hydrology 582, 124528, 2020

Groundwater quality in the Pearl River Delta after the rapid expansion of industrialization and urbanization, Distributions, main impact indicators, and driving force, Journal of Hydrology, 577, 124004, 2019

Author Response

Response to the comments of Reviewer #3

We thank Reviewer #3 for his relevant comments on our manuscript. Below is the original comment from Reviewer#3 (in italic/bold), with our own responses withinin blue typeface. Changes to the manuscript are shown in red.

• Reviewer Comment: Title: Lines 2, please use full name of GIS in the title.

Author's response: We would like to thank the reviewer for his comment. The search title has been modified within the revised manuscript

Reviewer Comment: Abstract:Lines 19-34, please rewrote the abstract. At the beginning of the abstract, major (overarching) issue(s) or problem(s) addressed by the study, including a few sentences discussing why the issue(s)/problem(s) has(have) global importance or, at the very least, is of significant interest to readers of Water. Please use "groundwater" instead of "ground water". Please use "samples" instead of "specimens". "wells" rather than "groundwater wells".

Author response: The manuscript was adjusted on the journal template in all sections.

• Reviewer Comment: Please, insert all corrected axes and labels, in order to guide the reader properly in understanding the whole manuscript. In addition, please improve the contrast between colours.

Author's response: We would like to thank the reviewer for his constructive comment. The abstract has been rearranged in the desired order within revised article.

• Reviewer Comment: Introduction: Lines 39, please use "groundwater" instead of "GW" in the whole paper. Lines 47-80, the introduction is not provided sufficient information for the reader to assess the extent and significance of the central issue(s) addressed in the manuscript. It does not sufficiently describe what is unique about the study area or the methodological/analytical approaches used in the manuscript. 

Author's response: We would like to thank the reviewer for his valuable comment. Introduction has been improved to include information about the study area, methodological/analytical approaches and for significance of the study.

• Reviewer Comment: Study Area: Lines 93-105, what about surface water in the study area? what about hydrogeological conditions such as groundwater recharge, groundwater flow?

Author's response: We would like to thank the reviewer for his valuable comment. Hydrogeological conditions, groundwater recharge and groundwater flow have been added in the study area section.

• Reviewer Comment: Materials and Methods: Lines 114-143, how to collect groundwater samples? filtered or not? what about the quality control for samples analyses?

Author response: We would like to thank the reviewer for his valuable comment.

The recommended procedure for collecting water samples: (Water samples put in labelled suitable container or clear glass (label should be written in waterproof ink) depending on laboratory requirement. Ensuring that the bottle is adequately labelled, so it can be identified at all stages of the transport and analytical process. - The laboratory requirements for analysis are a minimum of 500-mL depending on required analyses (one liter would be suitable). - Rinsing the bottle at least 4 times with the water to be sampled. Taking 2 sub-samples (100-200 mL each) to make up the full sample. - Filling the bottle to the top, leaving little or no air space and seal tightly with the cap.- All information about water samples is recorded on the sample container and in the field log book, e.g., the number with the site code, time and date of collection, parameter to be tested, sampler’s name, and other details to avoid mix-ups. Each sample is given a laboratory number. The information sheet should be clearly written with copying pencil. - Using the plastic bottles (Sterile containers). - Filtering for samples if a preservative is being used. - Containers closed until ready for analysis. -  All water samples stored in chilled cool-boxes prior to dispatch to the laboratory

• Reviewer Comment:Results: Lines 148-373, discussion is little, and factors controlling groundwater quality in this study are unclear. I recommend authors use multivariate statistical techniques such as principal component analysis to discuss factors controlling groundwater quality. 

Author response:

We thank the reviewers for the comments.

The factors are more explored and added a section for soil quality parameters as we used the spatial model to correlate all parameters.

• Reviewer Comment: At last, I recommend some references related to groundwater quality that may be useful to authors.

Author's response. Thank you very much for these references, it is very useful and these were cited in the revised article

Round 2

Reviewer 3 Report

All my concerns were answered. Now, it is acceptable. One minor mistake for the reference list. References 46 and 47 are repeated. I guess one of them is "Natural background levels in groundwater in the Pearl River Delta after the rapid expansion of urbanization: A new pre-selection method. Science of the Total Environment, 813, 151890, 2022". Please check it.