Methodologies for Locating Suitable Areas for Rainwater Harvesting in Arid Regions: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review of the manuscript entitled “GIS methodology for locating suitable areas for rainwater harvesting in arid regions: A review” submitted to MDPI water. The manuscript offers a comprehensive analysis of siting methods for rainwater harvestings (RWH) in arid regions. It is a topic both critically relevant to urban water management and sustainable urban development. The manuscript is well-written and well-structured, making it a joy to read. It is highly suitable for the journal's readership, and overall, the paper is extremely interesting and worthy of publication.  Applying a bibliometric methodology and synthetising the findings of 37 peer reviewed papers, its addresses the very important issue and provides valuable findings. It in itself fills an important and clear knowledge gap, however, there are a large number of corrections that should be addressed. Including:

Please add a few sentences which outline the reasons why the authors selected Methodi Ordinatio Verus other bibliometric approaches

The authors should allude to limitations of selecting only Science Direct and Scopus databases for articles selection. Why were databases such as Web of Science, google scholar and grey literature not included? Do the authors expect different results?

"Metodi” Ordinatio is often misspelled as “Methodi” Please check the entire document.

Lines 17-19, 186-188, 193-200, 254-158 all repeat the description of AHP. Please avoid, merge or rephrase too many repetitions.  

Line 56, empty space between references.

Line 14, please rephrase for clarity

Line 102, please state how many of the 291 articles were yielded from Science Direct and how many from Scopus.

Many figures lack clear axis.

Please improve captions.

Geographical results of the articles. The authors find many studies from India, Egypt and Iraq etc but do not reflect on what missing. Why are certain rid reasons, underdressed in the RWH literature despite also facing acute water stress (Sahel, western USA, Australia). 

Please make sure all Figueres are clearly mentioned and interpreted in the main text body. Figure 1 caption should be more descriptive.

Only a small number of the reviewed articles actually validate their GIS based analysis maps using ground-truthing or field data. This should be emphasised as a major knowledge gap, which is recommended to fill in future studies which integration validation using hydrological monitoring and/or ground-truthing.

Table 5 provides a great comparison of how different studies have weighted thematic layers. Please discuss it more in the text the heterogeneity in layer weighting across studies.

Please suggest directions for future research.

Author Response

Dear reviewers, in order to facilitate the identification of the points addressed in the manuscript, a color was assigned to each of the reviewers, which are: Reviewer 1, Reviewer 2, Reviewer 3, Reviewer 4.

 

Reviewer 1

Thank you for all suggestions.

1. Please add a few sentences which outline the reasons why the authors selected Methodi Ordinatio Verus other bibliometric approaches

We agree with this comment. The justification for choosing the Methodi Ordinatio was added to the 1st paragraph of topic 2..

2. The authors should allude to limitations of selecting only Science Direct and Scopus databases for articles selection. Why were databases such as Web of Science, google scholar and grey literature not included? Do the authors expect different results?

We agree with this comment. The justification for the choice of databases was added to the 1st paragraph of topic 2.

3. "Metodi” Ordinatio is often misspelled as “Methodi” Please check the entire document.

We agree with this comment. The term “Methodi” was adopted.

4. Lines 17-19, 186-188, 193-200, 254-158 all repeat the description of AHP. Please avoid, merge or rephrase too many repetitions.  

We agree with this comment. Unnecessary repetitions were avoided.

5. Line 56, empty space between references.

We agree with this comment. Fixed.

6. Line 14, please rephrase for clarity

We agree with this comment. The sentence was reworded.

7. Line 102, please state how many of the 291 articles were yielded from Science Direct and how many from Scopus.

The total number of articles selected was 356, of which 291 were from the Science Direct database and 65 from Scopus. Lines 102 and 103 specify the number of articles selected in each database.

8. Many figures lack clear axis.

We agree with this comment. The figures have been revised..

9. Please improve captions.

We agree with this comment. The captions have been rewritten.

10. Geographical results of the articles. The authors find many studies from India, Egypt and Iraq etc but do not reflect on what missing. Why are certain rid reasons, underdressed in the RWH literature despite also facing acute water stress (Sahel, western USA, Australia). 

We agree with this comment. The justification was added in the paragraph after figure 2.

11. Please make sure all Figueres are clearly mentioned and interpreted in the main text body. Figure 1 caption should be more descriptive.

We agree with this comment. This point has been revised.

12. Only a small number of the reviewed articles actually validate their GIS based analysis maps using ground-truthing or field data. This should be emphasised as a major knowledge gap, which is recommended to fill in future studies which integration validation using hydrological monitoring and/or ground-truthing.

We agree with this comment. The point was added in the penultimate paragraph of the conclusion.

13. Table 5 provides a great comparison of how different studies have weighted thematic layers. Please discuss it more in the text the heterogeneity in layer weighting across studies.

We agree with this comment. A comment on the suggestion has been added in the first paragraph after table 5.

14. Please suggest directions for future research.

We agree with this comment. The penultimate paragraph of the conclusion addresses the suggestion.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

A sentence such as ‘This study provides a methodological roadmap for future research, particularly emphasizing that AHP-based analyses are predominant and that researcher sensitivity in the selection of thematic strata significantly affects the results’ can be added to the end of the abstract.

In the conclusion section, the applicability of water management policies, rural planning or disaster risk reduction strategies can be discussed in accordance with the information obtained.

Comments for author File: Comments.pdf

Author Response

Dear reviewers, in order to facilitate the identification of the points addressed in the manuscript, a color was assigned to each of the reviewers, which are: Reviewer 1, Reviewer 2, Reviewer 3, Reviewer 4.

 

Reviewer 2

Thank you for all suggestions.

1. A sentence such as ‘This study provides a methodological roadmap for future research, particularly emphasizing that AHP-based analyses are predominant and that researcher sensitivity in the selection of thematic strata significantly affects the results’ can be added to the end of the abstract.

We agree in part with the comment. The use of the study as a systematic roadmap for future studies was added to the end of the abstract. It was not possible to conclude how the model is affected by the use of a particular number and type of thematic maps, so it is not possible to state that they significantly affect the results.

2. In the conclusion section, the applicability of water management policies, rural planning or disaster risk reduction strategies can be discussed in accordance with the information obtained.

We agree with this comment. A comment on this was added to the 5th paragraph of the conclusion.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

General comments: The subject is of interest to water community but I believe this paper was not able to conduct this mission and give effective guide lines to water community. In order to reach this goal first of all the methodology (Metodi Ordinatio) has to be explained in details (in section 2). Also the advantages and disadvantages of the different MCDM employed within the literature have to be part to the review so that the researchers can apply it in real world. In addition The most commonly used thematic layers in the literature need justification within the context. Also, I believe the authors have to drop a conclusion about the area in this investigation.

Other comments are assigned within the paper context which need to be noticed.

Comments for author File: Comments.pdf

Author Response

Dear reviewers, in order to facilitate the identification of the points addressed in the manuscript, a color was assigned to each of the reviewers, which are: Reviewer 1, Reviewer 2, Reviewer 3, Reviewer 4.

 

Reviewer 3

Thank you for all suggestions.

1. General comments: The subject is of interest to water community but I believe this paper was not able to conduct this mission and give effective guide lines to water community. In order to reach this goal first of all the methodology (Metodi Ordinatio) has to be explained in details (in section 2).

We agree with this comment. In the 1st paragraph of section 2 the Methodi Ordinatio was explained and its use was justified.

2. Also the advantages and disadvantages of the different MCDM employed within the literature have to be part to the review so that the researchers can apply it in real world.

We agree with this comment. In the penultimate paragraph of section 3.2.2, a comparison was added between the MCDM models most used in the articles, which will serve as a parameter for future applied research.

3. In addition The most commonly used thematic layers in the literature need justification within the context.

The justification for using thematic maps is supported by the researchers' sensitive analysis and the availability of data for the region studied. The explanation is given in the 3rd paragraph of the conclusion.

4. Also, I believe the authors have to drop a conclusion about the area in this investigation.

We agree with this comment. A paragraph about the area of ​​study has been added to the last paragraph of the conclusion.

5. Other comments are assigned within the paper context which need to be noticed.

The suggestions were appreciated and adopted.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Review Comments

Title:  GIS methodology for locating suitable areas for rainwater harvesting in arid regions: A Review

It is a review paper. It has reviewed articles presently being published in the field of identifying appropriate zones for Rainwater Harvesting (RWH) systems in arid regions. There is always high interest of researchers in this area of specialization because of water scarcity in such areas. The Methodi Ordinatio has been applied to identify some of articles published between 2020 and 2025. The manuscript needs a lot of improvements. Kindly see my comments below:

Comments to improve the manuscript:

1. The title of the manuscript needs improvement, the manuscript is very much different from its title. GIS and rainwater harvesting have not been discussed in detail in the manuscript.
2. Line 15: Kindly change “ Metodi Ordinatio” to Methodi Ordinatio ------Also kindly check Line 122: and change “Metodi” into “Methodi”
3. Line 63: Kindly change “A RWH includes the collection, conveyance, storage, and use of rainwater runoff” to “A RWH system includes the collection, conveyance, storage, and use of rainwater runoff”.
4. Kindly check the sentence on line 98: “The search on Science Direct was conducted on February 2, 2025, and on Scopus on June 2, 2025”-----------------We are still in April 2025. How search on Scops was done on June 2, 2025.
5. Line 70 to 72: According to the authors, “to identify potential zones for large-scale implementation of RWH, the most commonly used methodologies today include Remote Sensing (RS), Geographic Information Systems (GIS) [24], Multi-Criteria Decision Analysis (MCDA), and hydrological modeling, with the latter assisting the other methodologies”, however, the manuscript is kept limited to the search on GIS. My suggestion is to keep it vast open covering all the methods, because it is difficult to find innovations in GIS and rainwater harvesting only.
6. Line 79 to 90: Water moves on the planet in its 79 solid, liquid, and gas phases----------, this whole paragraph does not add any value to this review manuscript-------All this information is very basic, known and simple, so, it may be deleted.
7. Line 102-103: The result was 291 articles in Science Direct and 65 in Scopus. The alignment of titles and abstracts was then verified, resulting in 37 articles. Kindly describe in a little more detail how (291+65) articles resulted in only 37 articles for review.
8. Total papers from Science Direct and Scopus are 356 whereas citations are about 374. It means that there might be some other important papers which have cited these 37 papers. So, the search and review in this manuscript might have missed some important papers. Kindly elaborate.
9. Kindly write some explanations for Figure 2. Only 15 countries have done research on rainwater harvesting throughout the globe. China has only 4 publications on rainwater harvesting. USA has zero. The data looks very strange. Kindly elaborate.
10. Line 132-133: “There is a predominance of studies in Egypt (5 articles), India (6 articles) and Iraq (5 articles), with the Indian articles obtaining the highest total number of citations. The articles from Libya and Bangladesh were not cited”----------According to figure 2, India has only 6 articles and 6 citations. These articles might have cited in other countries, kindly elaborate how it was determined that the Indian articles obtained the highest total number of citations.
11. Kindly explain figures 4 and 5. What do different line colors mean? How to determine the highest cited word/author from these figures. Can these figures be replaced by a table for easy reading.
12. Kindly define all symbols before these appear first time in the text. For example, Table 2, “LULC” needs to be defined.
13. Kindly explain briefly what is difference between the keywords given in Figure 4 and “thematic layers” given in Table 2?
14. Kindly improve English of “It is noteworthy that some layers that were little used”--------
15. Line 253, 254: “the BRT and RF methods presented more effective results and the AHP method was the one that provided less effective results”.---------Kindly elaborate what is meant by “more effective results” and “less effective results”
16. Kindly write a paragraph on description of table 6. For example, the first row of table 6 is as under--------Kindly explain these results with respect to rainwater harvesting      Table 6: Suitability for article  (Suitability%)

    Author

    High or very high

    Moderate

    Low or unsuitable

    Hashim and Sayl [35]

    6

    4

    90

17. Kindly add a section in the manuscript for “Discussion”. Critical discussion on various aspects of rainwater harvesting is very important for future research.
18. It is very difficult to conclude that this manuscript is novel. So kindly describe explicitly the novelty of this review paper.

Author Response

Dear reviewers, in order to facilitate the identification of the points addressed in the manuscript, a color was assigned to each of the reviewers, which are: Reviewer 1, Reviewer 2, Reviewer 3, Reviewer 4.

 

Reviewer 4

Thank you for all suggestions.

1. The title of the manuscript needs improvement, the manuscript is very much different from its title. GIS and rainwater harvesting have not been discussed in detail in the manuscript.

We agree with this comment . The title has been changed to “Methodologies for locating suitable areas for rainwater harves-ting in arid regions: A Review”

2. Line 15: Kindly change “ Metodi Ordinatio” to Methodi Ordinatio ------Also kindly check Line 122: and change “Metodi” into “Methodi”

We agree with this comment. The term “Methodi” was adopted.

3. Line 63: Kindly change “A RWH includes the collection, conveyance, storage, and use of rainwater runoff” to “A RWH system includes the collection, conveyance, storage, and use of rainwater runoff”.

We agree with this comment. The change has been made.

4. Kindly check the sentence on line 98: “The search on Science Direct was conducted on February 2, 2025, and on Scopus on June 2, 2025”-----------------We are still in April 2025. How search on Scops was done on June 2, 2025.

We agree with this comment. The mistake has been corrected.

5. Line 70 to 72: According to the authors, “to identify potential zones for large-scale implementation of RWH, the most commonly used methodologies today include Remote Sensing (RS), Geographic Information Systems (GIS) [24], Multi-Criteria Decision Analysis (MCDA), and hydrological modeling, with the latter assisting the other methodologies”, however, the manuscript is kept limited to the search on GIS. My suggestion is to keep it vast open covering all the methods, because it is difficult to find innovations in GIS and rainwater harvesting only.

We agree with this comment. Necessary changes were made throughout the manuscript to maintain the vast methodology.

6. Line 79 to 90: Water moves on the planet in its 79 solid, liquid, and gas phases----------, this whole paragraph does not add any value to this review manuscript-------All this information is very basic, known and simple, so, it may be deleted.

We agree with this comment. The information has been deleted.

7. Line 102-103: The result was 291 articles in Science Direct and 65 in Scopus. The alignment of titles and abstracts was then verified, resulting in 37 articles. Kindly describe in a little more detail how (291+65) articles resulted in only 37 articles for review.

We agree with this comment . The excerpt "The alignment of titles and abstracts was then verified, resulting in 37 articles." in the 1st paragraph of section 2 explains how the 365 (291+65) were limited to 37. A following excerpt was added to reinforce the reason for the exclusion of the remaining articles.

8. Total papers from Science Direct and Scopus are 356 whereas citations are about 374. It means that there might be some other important papers which have cited these 37 papers. So, the search and review in this manuscript might have missed some important papers. Kindly elaborate.

The total number of citations is actually 374, however, the citations are linked to articles that are not specifically included in studies in arid zones.

9. Kindly write some explanations for Figure 2. Only 15 countries have done research on rainwater harvesting throughout the globe. China has only 4 publications on rainwater harvesting. USA has zero. The data looks very strange. Kindly elaborate.

In fact, when defining the search for arid zones and limiting the analysis horizon to studies between 2020 and 2025, studies from the United States are not reported in the Science Direct and Scopus databases.

10. Line 132-133: “There is a predominance of studies in Egypt (5 articles), India (6 articles) and Iraq (5 articles), with the Indian articles obtaining the highest total number of citations. The articles from Libya and Bangladesh were not cited”----------According to figure 2, India has only 6 articles and 6 citations. These articles might have cited in other countries, kindly elaborate how it was determined that the Indian articles obtained the highest total number of citations.

We agree with this comment. An error occurred in Figure 2. In fact, the Indian articles received a total of 40 citations. Figure 2 has been corrected.

11. Kindly explain figures 4 and 5. What do different line colors mean? How to determine the highest cited word/author from these figures. Can these figures be replaced by a table for easy reading.

In Figures 4 and 5, the graphic resource of the VOSviewer software was used to group and correlate the occurrences of keywords (Figure 4) and authors (Figure 5). The correlation between the occurrences would be lost if the presentation were done in table format.

12. Kindly define all symbols before these appear first time in the text. For example, Table 2, “LULC” needs to be defined.

We agree with this comment. Fixed in the text.

13. Kindly explain briefly what is difference between the keywords given in Figure 4 and “thematic layers” given in Table 2?

The keywords observed in Figure 4 are the words associated with the articles delimiting their central theme, while Table 2 expresses how many times each thematic layer was used by the 37 articles.

14. Kindly improve English of “It is noteworthy that some layers that were little used”--------

We agree with this comment. The section has been improved.

15. Line 253, 254: “the BRT and RF methods presented more effective results and the AHP method was the one that provided less effective results”.---------Kindly elaborate what is meant by “more effective results” and “less effective results”

We agree with this comment. A comment has been added to complement the cited excerpt.

16. Kindly write a paragraph on description of table 6. For example, the first row of table 6 is as under--------Kindly explain these results with respect to rainwater harvesting Table 6: Suitability for article  (Suitability%)

Author  High or very high         Moderate          Low or unsuitable

Hashim and Sayl [35]   6          4          90       

We agree with this comment. A paragraph was added after and before Table 6 commenting on it.

17. Kindly add a section in the manuscript for “Discussion”. Critical discussion on various aspects of rainwater harvesting is very important for future research.

This article is limited to addressing modeling methodologies, thus the discussion regarding other aspects of rainwater harvesting is a topic for another article.

18. It is very difficult to conclude that this manuscript is novel. So kindly describe explicitly the novelty of this review paper.

We agree with this comment. A justification of the contribution and innovation of this article has been added in the last paragraph of section 5.

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

1) According to authors "In fact, when defining the search for arid zones and limiting the analysis horizon to studies between 2020 and 2025, studies from the United States are not reported in the Science Direct and Scopus databases". ---------It will be appropriate if authors may kindly explain the reason for this ---why studies from the United States are not reported in the Science Direct and Scopus databases?-----How these studies can be searched?

2) Kindly explain what do colors of various lines mean in Figures 4 and 5?

3) Kindly add a section in the manuscript for “Discussion”. Critical discussion on various aspects of modeling methodologies for rainwater harvesting is very important for future research. In review papers the most important part of the paper is critical discussions from the authors. It is lacking in this manuscript. 

Author Response

Dear reviewer, the changes made are highlighted in yellow in the manuscript.

Thank you for all suggestions.

1. According to authors "In fact, when defining the search for arid zones and limiting the analysis horizon to studies between 2020 and 2025, studies from the United States are not reported in the Science Direct and Scopus databases". ---------It will be appropriate if authors may kindly explain the reason for this ---why studies from the United States are not reported in the Science Direct and Scopus databases?-----How these studies can be searched?

We agree with this comment. In applying the Methodi Ordinatio, titles and abstracts that were not aligned with the theme were excluded. Thus, studies conducted in the United States that did not fit methodologically or within the stipulated period were excluded. A section was added before Figure 2 in this regard.

2. Kindly explain what do colors of various lines mean in Figures 4 and 5?

We agree with this comment. A comment has been added after Figure 4 to explain the function of dividing lines by color.

3. Kindly add a section in the manuscript for “Discussion”. Critical discussion on various aspects of modeling methodologies for rainwater harvesting is very important for future research. In review papers the most important part of the paper is critical discussions from the authors. It is lacking in this manuscript. 

In this article, the discussion is elaborated throughout the item "3. Results and Discussion". Specifically for this review study, the criticism between the authors must have some reservations, since the studies address different methodologies, areas and regions. Thus, the discussion present in this article is based on the comparison of the methodologies used by each author, the thematic maps used (Table 2. Most used thematic layers) and their quantity (Table 3. Number of layers and total area studied per article), and the weights used (3.2.2. Weighting methods). The articles that used more than one methodology in their development were criticized (lines 281 to 291, 294 to 298 and 299 to 301).

Author Response File: Author Response.pdf