Modelling the Effects of Dam Reservoir Backwater Fluctuations on the Hydrodynamics of a Small Mountain Stream
Round 1
Reviewer 1 Report
caption of Figure 7 is wrong, same like Figure 6
Author Response
Dear Reviewer #1,
We would like to thank you for your comments.
- caption of Figure 7 is wrong, same like Figure 6
Answer: Please note that the figures refer to mean water depth (Fig. 6) and mean flow velocity (Fig. 7), and the captions are written accordingly. The statistical analysis performed on both these quantities is the same, and this is also stated in the figures' captions. During revision we have only shorten the caption of Figure 7 using "All statistical descriptions are the same like on the Figure 6" to avoid repetitions of the statistical description presented in both figures.
Reviewer 2 Report
This manuscript studies the effects of dam backwater fluctuations on the hydrodynamics of mountain rivers through a two-dimensional hydrodynamic model. By simulating the hydrodynamic characteristics of the fluctuating backwater area of the dam under different scenarios, the influence of backwater fluctuation on the velocity and water level of the river channel and floodplain area was explained. The hydrodynamic characteristics of the intersection area of rivers and reservoirs are pretty complex, which is the focus of attention. This study is related to today's scenario.
Major suggestions:
I am very worried that the introduction part of this manuscript does not clearly explain the motivation of this study. It is crucial to emphasize writing motivation and raise key scientific issues in the introduction. The introduction of this manuscript does not show the difference or advancement between this study and previous scholars' research on the backwater fluctuation region. I suggest that the author can revise the introduction to explain how this study is different from previous scholars' research, why this manuscript should be studied, and its importance. Secondly, it is suggested to add references for recent three years in the introduction.
The hydrodynamic characteristics of reservoir backwater fluctuation areas are very complex, especially for mountainous rivers. In the summary of 2.2.3, this study only explained that the planar two-dimensional hydrodynamic model was used for simulation, which I think is very unreasonable, and the correctness of the method completely affects the analysis of the results. Whether the reservoir backwater fluctuation areas simulated in this study had the characteristics of wide and shallow, otherwise, it is necessary for the author to explain why the planar two-dimensional hydrodynamic model was used. The hydrodynamic characteristics of the backwater confluence area are complex, and it is possible that the flow velocity direction of the surface water is opposite to that of the bottom. The related research generally adopts a laterally averaged two-dimensional hydrodynamic model or three-dimensional hydrodynamic model. In addition, this study did not seem to verify the hydrodynamic calculation with field monitoring data, and it is suggested to supplement the verification of hydraulic calculation.
It is suggested that the author explains in the method whether this study was directly solving the shallow water equation or considering the Reynolds stress. If the Reynolds stress was considered, what turbulence model was used in this study?
Minor suggestions:
Ln 25-27: Does the velocity here refer to the average velocity of the cross section?
Ln 67-69: What is the basis for defining one-year flood as a small flow scenario?
Ln 152: The fluctuation area of reservoir return water is unsteady. In this study, the steady flow was used for hydrodynamic simulation, please explain the reason.
Ln 173-174: The sediment transport equation was used in the model, but the analysis of sediment calculation results was lacking in the results and discussion of the manuscript.
Ln 185-188: It is suggested to supplement the grid sensitivity test, the influence of grid size and simulation step size on the model accuracy.
Author Response
Dear Reviewer #2,
We would like to thank you very much for your comments.
Our responses to your questions are attached.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
this is a good paper and mostly well-written. I am not sure if there is much novelty in the paper, but I think the case study data will be of regional importance and hence should be considered for publication.
I think the paper needs to add more to justify the method and the model used. I also think that your literature review is very narrow and brief and will require conducting a gap analysis. In recent years (2020-2022), some studies used advanced numerical modeling or ML-based techniques to investigate open-channel flow-related problems and specifically hydrodynamic modeling which is missing from the literature (doi.org/10.1038/s41598-020-68830-5; doi.org/10.1016/j.jwpe.2020.101411;doi.org/10.1016/j.ecoleng.2022.106702;doi.org/10.3390/hydrology9020036; doi.org/10.1038/s41598-022-08417-4). A brief discussion of these methods is essential to provide a more comprehensive narrative of the available methods.
Your method only mentions the names of the model used. However, the expectation is to describe the models at an appropriate depth, so the reader can understand the fundamental equations used in the model without the need for reading other papers. You can't publish the work without having a clear and detailed method description. Another important element missing from the method is justifications of why the proposed model is used rather than alternative hydrodynamic modeling techniques.
The revised manuscript should have clear and in-depth information showing that the model is calibrated and validated, i.e. why should we trust your results? what kind of measured data are used to confirm/validate model prediction? This info needs to be clear in the manuscript.
uncertainty quantification of the results obtained in this study is important, as you don't have detailed measured data to validate the model. Your conclusion should acknowledge the necessity of capturing further data for validation and using robust uncertainty quantification methods to ensure the results will make sense in real-life scenarios.
I think the abovementioned revisions should be straightforward and help the authors to improve the impact of their manuscript. Proofreading of the manuscript is necessary to revise English writing and grammatical mistakes.
Author Response
Dear Reviewer #3,
We would like to thank you very much for your comments.
Our responses to your questions are attached.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Thank you for preparing a revised manuscript. However, it is not possible to readily understand the revised material as the authors did not provide track changes document.
Referencing in the manuscript is very poor, the authors cited 19 papers in one paragraph without robust discussion. This is surely not acceptable.
Some of the authors have Self-Cited more than 9 papers (i.e. Reference No. 8, 11, 13, 18, 19, 21, 28, 33, 43) while failing to discuss recent studies. Following the comment from the previous round of reviews the literature needs enhancement. see my comments from the previous round of revision.
There is a serious methodological problem which is about the validity and robustness of the numerical solver you used - the response to my question, didnt provide any sound scientific discussions on why MFlow-02 can be used without any validation?! and the authors seem not to describe/know the underlying equations governing the model. This is a very serious flaw and without properly addressing this it is not possible to consider the paper.
Author Response
Dear Reviewer,
Thank you very much for your comments on our manuscript. Our responses and manuscript with tracked changes are attached.
Best Regards,
Author Response File: 
Author Response.docx
Round 3
Reviewer 3 Report
The model validation and uncertainty quantification of the results remain a major concern regarding the method.
self-citations are not appropriate and must be removed.
Author Response
Our Response to reviewer comments is attached below.
Author Response File: Author Response.docx
