Long-Term Stochastic Modeling of Monthly Streamflow in River Nile

Round 1

Reviewer 1 Report

(1)    The language needs to be improved. There are too many grammar errors, and language problem, I cannot list all of them here. My suggestion is authors should work with native English speaker, or seek help from the English language editing service, for English check throughout the manuscript. And this manuscript would benefit from a final close editing for language, grammar, word repeats, etc.

(2)    How this study is related to the topic of sustainability?

(3)    The title of this manuscript may be revised to be “Long-Term Stochastic Modeling of Monthly Streamflow in River Nile”

(4)    Please specify the purpose of this study in the Abstract. In the sentence “The purpose of this study was to use two stochastic time series approaches based on long-term historical data of the Nile river’s estimated synthetic streamflow at Aswan, Egypt.”, only the methods used in the study are highlighted, without pointing out the purpose of this study.

(5)    What materials are used? Does this study involve experiments using any material? If there is no any materials used in this study, please revise the title of the section “3. Materials and Methods”.  

(6)    The resolutions of the figures are too low.

(7)    Figure 2 can be adjusted to occupy less space.

(8)    The conclusions should be presented in an itemized manner.

(9)    It is recommended that a discussion of the applicability of the results obtained in this study is made.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript presents a case study that simulated the monthly streamflow of the Nile River using stochastic methods. The authors only simulated the streamflow series, but did not examined the performance of the methods in forecasting the streamflow. It is hard to find the practical significance or innovation point of this study. In my opinion, this manuscript cannot be accepted till the authors illustrate sufficient practice significance or innovation of the study. The major comments are given as follows:

1)     The authors just used a stochastic method to simulate the streamflow without concerning any predictors, such as rainfall, that are physically related to the runoff. This study is more like a mathematical game. It is not surprised that the model can achieve a not bad performance since the streamflow of the Nile has a clear periodicity.

2)     It is better to separate the whole streamflow series into two sub-series to calibrate and validate the model, respectively.

3)     The authors should use other metrics such as NSE, KGE to evaluate the performance of the methods.

4)     line 174: It should be Pearson III distribution rather than gamma.

5)     The quality of the figures of manuscript require a thorough improvement.

6)     This manuscript is not well organized. For example, section 3.2 is redundant.

7)     The discussion is not sufficient and comparisons with other results should be enhanced. Clarify what your contribution is?

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

General Overview

The authors focused on the generation of monthly synthetic streamflow data from long-term observed streamflow data of the River Nile from 1900 to 1999 using 2 methods namely: the Gamma distribution and the Discrete Fourier Transform. The methodology was to convert the streamflow data from time domain to frequency domain to make it easier to predict. This idea of the transformation of time series from time domain to frequency domain is a good practice especially in processes or models which find it difficult to incorporate the time variable into predictions. I recommend the manuscript be accepted after some minor modifications.

Comments to the Authors

1.      The authors only mention different literature used to produce synthetic streamflow but did not properly represent the gaps in literature in consideration of the methodology chosen for this process. The introduction is weak and need to be revised. The authors need to briefly explain why they chose the specific methodology considered in the manuscript.

2.      The authors state that the Nile River has been extensively studied, therefore there should exist more advanced literature regarding the research on the hydrological status of the Nile.  In light of this, it is assumed that the Nile River is not a data-scarce region and therefore much more hydrometeorological data variable should be available for use. Hence, why the need to produce synthetic hydrometeorological series if we can simply apply hydrological models from the sample of observed data to produce the same results with much better interpretability.

3.      The authors mentioned climate change as a factor in the overall water discharge of the Nile River. Using only streamflow as both the input and target variable for modeling and forecasting in the consideration of climate change effects is not recommended since changes in streamflow is a combination of several other factors directly affected by such climate change. It is suggested that the authors consider the addition of other hydrological variables to support the efficacy of their methodology. Otherwise, the novelty of this work is missing since the methodology chosen is not new and the climate change aspect is also vague.

4.      The authors should mention which software or modules utilized in the methodology for reproducibility.

5.      In the consideration of the impacts if climate change on streamflow, it is suggested that more recent data is utilized. If data from the 2000s are available, the authors could consider a comparison of the efficacy of the processes used in this manuscript (Gamma distribution and Discrete Fourier Transform) from 1900 to 1980 and from 1980 to the most recent data period available since the changes in the climate from 1980 have been shown to be of high impact to the globe. This suggestion in case of present data unavailability, could be a further research study for the authors based on future data availability.

Specific comments

1.      Line 24, Line 38: Fully state any terms in the text before using the abbreviated forms in later text.

2.      We find some sentences and paragraphs in the manuscript without references. See lines 95 to 110.

3.      Line 228: state the equation number (equation 17) before the reference.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for your improvement.

Author Response

On behalf of the authors, I would like to thank you for taking the time to review our submission and for your insightful comments.

Kind regards.

Reviewer 2 Report

For the comments in the first review cycle, the authors have made the corresponding modifications or given explanations. I think the conclusion section requires to be rewritten. You do not need to give so many points of conclusions.

Author Response

Dear reviewer,

Please find attached the response to your latest comment regarding the Conclusion section.

On behalf of the authors, I would like to thank you for your effort in reviewing our submission, and providing an insightful review that helped us in improving our submission.

Should you have further comments, please let us know.

Kind regards

Author Response File: Author Response.docx