Assessment of Climate Change Impacts for Balancing Transboundary Water Resources Development in the Blue Nile Basin

Round 1

Reviewer 1 Report

A clear and well written paper, describing the assessment of climate change impacts on trans-boundary water resources planning and management in the Blue Nile river basin.

The manuscript can be considered almost ready for publication. However, according to the reviewer, two issues should be addressed, namely:

1) the Authors should explain why they have carried out their analyses only for the worst-case scenario (RCP 8.5): although such hypothesis is definitely 'conservative', it is not the most likely, and an assessment of climate change impacts under different scenarios could be of interest, or at least a brief discussion about it.

2) In their manuscript, the Authors describe the beneficial effects that optimization of dam operations can have on the impacts of the inter-annual and spatial variability of dry and wet seasons, especially when extreme flood and drought events are considered. In addition, the Authors should mention the possibility (if any) of the presence of feedbacks on local climate change due to the presence of a large reservoir and the operation of the storage (like the Grand Ethiopian Renaissance Dam). In other words, is there any evidence of the influence that an artificial reservoir (especially those characterized by large volumes of stored water) may exert on local climate change ? and to what extent does the operation of such storage systems may alter the downstream river flows ? This could be of interest from the point of view of river restoration and eco-hydraulics impacts.

A minor issue: in the Bibliography section, citation [18] is not properly reported.

Author Response

Dear Reviewer,

We would like to thank you for the time you spent on our paper and for the detailed observations.

We hope to give you enough point-to-point clarification and explanations. Certainly, the paper now has a higher quality.

Author Response File: Author Response.pdf

Reviewer 2 Report

Greetings, Editor thank you for providing me with the opportunity to review the article. I reviewed the article with ID= sustainability-2004548. Overall, the article structure and content are suitable for the Sustainability journal. I am pleased to send you MODERATE level comments; there are some flaws, which need to be corrected before publication. Please consider these suggestions as listed below.

1. The title seems ok.
2. The abstract seems to be good. Please add one more introductory line of your objective in beginning of abstract.
3. Research gap should be delivered on more clear way with directed necessity for the future research work.
4. Remove `` GCM`` from keywords.
5. Introduction section must be written on more quality way, i.e., more up-to-date references addressed. Please target the specific gap such as 2015-2021 etc.
6. The novelty of the work must be clearly addressed and discussed, compare previous research with existing research findings and highlight novelty.
7. What is the main challenge?
8. The main objective of the work must be written on the more clear and more concise way at the end of introduction section.
9. Please check the abbreviations of words throughout the article. All should be consistent.
10. Please provide space between number and units. Please revise your paper accordingly since some issue occurs on several spots in the paper.
11. Overall result section is well explained.
12. Regarding the replications, authors confirmed that replications of experiment were carried out. However, these results are not shown in the manuscript, how many replicated were carried out by experiment? Results seem to be related to a unique experiment. Please, clarify whether the results of this document are from a single experiment or from an average resulting from replications. If replicated were carried out, the use of average data is required as well as the standard deviation in the results and figures shown throughout the manuscript. In case of showing only one replicate explain why only one is shown and include the standard deviations.
13. Please add a comparative discussion section. It would be more better for reader.
14. Section 5 should be renamed by Conclusion and Future perspectives. Conclusion section is missing some perspective related to the future research work, quantify main research findings, highlight relevance of the work with respect to the field aspect.
15. To avoid grammar and linguistic mistakes, moderate level English language should be thoroughly checked. Please revise your paper accordingly since several language issue occurs on several spots in the paper.
16. Reference formatting need carefully revision. All must be consistent in one formate. Please follow the journal guidelines.

 These are comments to improve the manuscript and not necessarily to down the quality of work, which is very good.

Author Response

Dear Reviewer,

We would like to thank you for the time you spent on our paper and for the detailed observations.

We hope to give you enough point-to-point clarification and explanations. Certainly, the paper now has a higher quality.

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Reviewer 2

Greetings, Editor thank you for providing me with the opportunity to review the article. I reviewed the article with ID= sustainability-2004548. Overall, the article structure and content are suitable for the Sustainability journal. I am pleased to send you MODERATE level comments; there are some flaws, which need to be corrected before publication. Please consider these suggestions as listed below.

1. The title seems ok.

Okay.

1. The abstract seems to be good. Please add one more introductory line of your objective in beginning of abstract.

We added one introductory sentence in the abstract.

1. Research gap should be delivered on more clear way with directed necessity for the future research work.

We have edited the introduction part including the research gap covered in this study with the indication of the future research direction.

1. Remove `` GCM`` from keywords.

The keyword is removed.

1. Introduction section must be written on more quality way, i.e., more up-to-date references addressed. Please target the specific gap such as 2015-2021 etc.

The introduction part is re-written adding recent references. We hope the entire introduction part is improved.

1. The novelty of the work must be clearly addressed and discussed, compare previous research with existing research findings and highlight novelty.

Thank you. We revised the introduction and discussion section adding more recent research gaps to highlight the novelty of this research. In the discussion part, we elaborate on the results in comparison with the previous study's results.

1. What is the main challenge?

The main challenge was the reliability and presentation of climate change projections. Also, previous studies reported different directions in precipitation projection, however, they did not include the difference in the GCMs mechanism. To overcome this challenge, in this study, we used the DIAS system to assess the CMIP5 GCMs mechanism and identify the difference in the precipitation projection. This study also assessed the extreme climate risks by incorporating bias-corrected GCMs and 30 years of observed datasets using different parametric and non-parametric trend analyses.

1. The main objective of the work must be written in a more clear and more concise way at the end of the introduction section.

We added a new paragraph at the end of the introduction section to explain the objective of the study. We hope the new paragraph summarizes the unique features of this study in comparison with previous study outputs.

1. Please check the abbreviations of words throughout the article. All should be consistent.

We re-checked the abbreviations in the paper.

1. Please provide space between number and units. Please revise your paper accordingly since some issue occurs on several spots in the paper.

Thank you, we corrected this part.

1. Overall result section is well explained.

Thank you

1. Regarding the replications, authors confirmed that replications of experiment were carried out. However, these results are not shown in the manuscript, how many replicated were carried out by experiment? Results seem to be related to a unique experiment. Please, clarify whether the results of this document are from a single experiment or from an average resulting from replications. If replicated were carried out, the use of average data is required as well as the standard deviation in the results and figures shown throughout the manuscript. In case of showing only one replicate explain why only one is shown and include the standard deviations.

The results of this study are from a single experiment in the Blue Nile basin. The methodology developed in this study can be replicated in sub-basins in the Nile system. This will enable climate change impact assessment in the whole Nile basin which is characterized by highly diversified hydro-climatic conditions. We discussed the replication of this work indicating the possibility of assessing climate change impact in other regions following the case presented in this study.

1. Please add a comparative discussion section. It would be more better for reader.

We modified the discussion section adding more comparative discussion with the previous study's results. Hopefully, it is better now, thank you.

1. Section 5 should be renamed by Conclusion and Future perspectives. Conclusion section is missing some perspective related to the future research work, quantify main research findings, highlight relevance of the work with respect to the field aspect.

We re-wrote the conclusion part, quantified the main findings in the field and highlighted the relevance of the work to future studies. We keep the section title “conclusion” as it is the journal’s format.

1. To avoid grammar and linguistic mistakes, moderate level English language should be thoroughly checked. Please revise your paper accordingly since several language issue occurs on several spots in the paper.

We undergo English language editing by professionals.

1. Reference formatting need carefully revision. All must be consistent in one formate. Please follow the journal guidelines.

We have re-formatted the reference section according to the journal’s guidelines.

These are comments to improve the manuscript and not necessarily to down the quality of work, which is very good.

Thank you so much for the constructive comments. We have gone through the comments one by one and the language is also revised by professionals. The paper improved a lot now.

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Reviewer 3 Report

This paper presents a modeling study in the Blue Nile Basin to assess the climate change impacts on water resources in the region. The authors selected five GCMs for precipitation and temperature change assessment. Then the GCM outputs are coupled with a hydrologic model WEB-RRI for hydrologic impact assessment. The results show that frequency of flood and drought will both increase in the future. Therefore, dam operations become crucial for water resources management under the impacts of more frequent extreme events. This study is on a topic of interest to the audience of this journal. I only have one minor comment: In figure 1, use a different color for the names of stream gauges. It is hard to see. Also, remove the “@” symbol.

Author Response

Dear Reviewer,

We would like to thank you for the time you spent on our paper and for the detailed observations.

We hope to give you enough point-to-point clarification and explanations. Certainly, the paper now has a higher quality.

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Reviewer 3

This paper presents a modeling study in the Blue Nile Basin to assess the climate change impacts on water resources in the region. The authors selected five GCMs for precipitation and temperature change assessment. Then the GCM outputs are coupled with a hydrologic model WEB-RRI for hydrologic impact assessment. The results show that frequency of flood and drought will both increase in the future. Therefore, dam operations become crucial for water resources management under the impacts of more frequent extreme events. This study is on a topic of interest to the audience of this journal. I only have one minor comment: In figure 1, use a different color for the names of stream gauges. It is hard to see. Also, remove the “@” symbol.

Thank you for the constructive feedback. The figure is modified according to the comments.