Sample Uncertainty Analysis of Daily Flood Quantiles Using a Weather Generator
Round 1
Reviewer 1 Report (New Reviewer)
I have read the manuscript number: water-2630142 with title: "Sample Uncertainty Analysis of Daily Flood Quantiles Using a Weather Generator ", and I found that, authors consider the following points before I recommend publication
1-The introduction is long, it can be written in brief form. The aim of the paper must be mentioned in the end of introduction.
2-Some abbreviations aren’t defined as for example “TETIS”, all abbreviation must be revised and labeled in a table.
3-The presentation and grammar need improvement.
Letter to editor in chief
Dear prof. Dr. Takayoshi Kobayashi
I have read the manuscript number: water-2630142 with title: "Sample Uncertainty Analysis of Daily Flood Quantiles Using a Weather Generator ", and I found that, authors consider the following points before I recommend publication
1-The introduction is long, it can be written in brief form. The aim of the paper must be mentioned in the end of introduction.
2-Some abbreviations aren’t defined as for example “TETIS”, all abbreviation must be revised and labeled in a table.
3-The presentation and grammar need improvement.
Author Response
Please refer to the attached document
Author Response File: 
Author Response.pdf
Reviewer 2 Report (New Reviewer)
Review of the manuscript entitled Sample Uncertainty Analysis of Daily Flood Quantiles Using a Weather Generator
Prediction of hydrological characteristics of flood events is one of the most important element for practitioners, because flood wave characteristics are used for the flood risk management process, hydrological infrastructure design. Prediction of the flood quantiles is a challenge task especially areas, where the hydro- and meteo-rological data are scare.
The authors in the article discussed on the aspects related to use of the Synthetic Continuous Simulation (SCS) method which combine of the Weather Generators (WG) and Hydrological Models (HM), trying to assess how different precipitation regimes, climate extremality or basin hydrological characteristics impact on the uncertainty of daily flood quantile estimates obtained by SCS method.
In rewiever’s opinion the topic is important, both from the scientific point of view and may potential for use in the practice. The article is an interesting case study in of the topic related to flood quantilies uncertainties analysis. The study confirmed many general outcomes reported in the literature. The novelty of this study is the fact that the authors analyze the uncertainty of flood quantiles estimated by SCS in different scenarios including different precipitation regimes, different climate extremality, and different hydrological characteristics of the basin. In rewiever’s opinion the article should be published because it contribute to knowledge extinction in this field.
The article is well written. The goals are clearly defined. The methodology clearly describe main elements of the investigation process, and the discussion sections explain the most important aspects in relation the goals. I recommend publication of the manuscript in this form.
Author Response
We want to thank the reviewer for their time and their nice words about our work
Reviewer 3 Report (New Reviewer)
In the article, please first define all abbreviations used, and also ??,? i and ??,?.
The text in the first column of Figure 3 is illegible. Please revise the image.
The methodology does not provide a complete explanation of the layers used. Some of the explanations can be found in the introduction. Therefore, it would be better to include the entire explanation in the methodology, stating which layers were used in the simulation.
Is the digital terrain model at too low a resolution? Does this not impact the simulation?
Figure 8 in Section 4.5 is not explained. In my opinion, any figure included in the text should be at least minimally interpreted.
Could you please proofread the English? There are some errors in the writing.
Author Response
Please refer to the attached document
Author Response File: Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Dear authors,
I read your manuscript “Sample Uncertainty Analysis of Daily Flood Quantiles Using a Weather Generator” submitted to ‘Water’ and was disappointed after reading it. While the goal of “improving the uncertainty of daily flood quantile estimates obtained by Synthetic Continuous Simulation is worthwhile exploring”, I do not feel that this journal article is up to standard for publication. Therefore, I recommend a rejection at this stage. The reason is that the article is full of assumptions, technical details and leaves readers wondering why this is even relevant.
However, I do have some suggestions on how to improve this work, after which I could be resubmitted:
· The bigger picture: why does this matter and what do you really add? Sure, precipitation regimes matter for estimating extremes and they have the biggest effect for the most extreme conditions. But what does this paper add? Also, could you give me a sense of relevance? An unnamed study area called ‘Study Area’ does not ring a bill to me.
· Validation: details on the accuracy of the data, fit, and eco-hydrological model are needed to give the reader confidence that you are doing something that is worthwhile. If you feel that these are too many details, use an appendix.
· Technical details: I want more details regarding the fitting, the relevance of the 18 base populations, etc. Ensure you give enough details so someone with a water engineering background can reproduce your work.
· Readability: let co-workers review the article to see if they understand the logic and have a native speaker review it before submission.
I hope this helps the authors. I know it takes much time to do research and write papers.
See comments above
Author Response
Comment 1: The bigger picture: why does this matter and what do you really add? Sure, precipitation regimes matter for estimating extremes and they have the biggest effect for the most extreme conditions. But what does this paper add? Also, could you give me a sense of relevance? An unnamed study area called ‘Study Area’ does not ring a bill to me
Reply: We thank the reviewer for the comment, which means that our explanations in the document can certainly be improved. Flood quantiles are commonly used in the design of hydraulic infrastructures and to establish flood risk areas. In many cases, the economic and social implications (including the possible loss of human lives) make it necessary to obtain these quantiles with the minimum possible uncertainty. In other words, knowledge of this uncertainty is mandatory in order to be able to propose methodologies for its reduction. In this context and as a result of the short length of the available hydrometeorological records, the Synthetic Continuous Simulation (SCS) approach is rapidly gaining importance among practitioners when it comes to estimate flood quantiles. However, no studies could be found by these authors evaluating the uncertainty of these estimations related to the amount of available information. In a previous paper (https://doi.org/10.1080/02626667.2023.2208754), for the uncertainty reduction in the estimation of annual maximum daily precipitation quantiles using SCS with a meteorological generator, we proposed the incorporation of additional information obtained in an independent regional extreme precipitation study. In this present paper, the aim is to evaluate the uncertainty of flood quantiles to the sample length in different climate/watershed conditions, encompassing potential catchments that can be found all over the world, which we believe is the major contribution of this novel research.
In order to perform this study and following the methodology proposed (no uncertainty is introduced by the modelling, meteo and hydrological, since the aim of this works was to evaluate purely the sample information), a synthetic case study was defined from an existing watershed by setting the Hydrological Model parameters based on the authors experience. Nevertheless, the uncertainty propagation of the quantile estimates from the Weather Generator to the Hydrological Model was also analyzed in Section 3.5.
Concerning the “Study Area”, this is not one: actually, there are 18 different synthetic or made-up scenarios trying to represent a wide range of hydro-climatic conditions.
Notwithstanding this, it is clear from the reviewer's comment that more explanation and/or emphasis is needed in the manuscript, especially in the introduction..
Modification: A track-changes document has been resubmitted to the journal incorporating all the necessary modifications to make this clearer and avoid potential misleading.
Specific comments
Comment 1: Validation: details on the accuracy of the data, fit, and eco-hydrological model are needed to give the reader confidence that you are doing something that is worthwhile. If you feel that these are too many details, use an appendix
Reply: As explained in the previous answer, the objective is the estimation of the uncertainty of the methodology, independently of the selected models. Therefore, we believe that detailed information on the Weather Generator GWEX and the Eco-hydrological Model TETIS is not necessary since these have been only tools for developing our methodology, and in any case, it has not been the aim of this work to assess their performance. This methodology can be easily replicable using a different Weather Generator and a different Hydrological Model. Nevertheless, information regarding the Eco-Hydrological Model TETIS and the Weather Generator GWEX can be found in the respective citation of the document.
In terms of calibration and/or validation results of the Eco-Hydrological Model, these do not apply in the present work since the case study is synthetic. I.e., this paper is based on the construction of 18 synthetic scenarios, where the HM model is “perfect”. Therefore, there is neither calibration nor validation. Something similar, but not exactly the same, happens with the Weather Generator. . Although in this case we did modified the shape parameter of the E-GPD for increasing the torrentiality, we consider that the main statistics shown in Table 1 are sufficient and more information could lead to confusions among readers.
Modification: part from the corrections derived from the previous comments include the necessary modifications from this comment.
Comment 2: Technical details: I want more details regarding the fitting, the relevance of the 18 base populations, etc. Ensure you give enough details so someone with a water engineering background can reproduce your work.
Reply: With regards to the precipitation, the main statistics of the nine different synthetic populations (climate and extremality) are shown in Table 1 of the former and new manuscript. Precipitation generation is explained in Section 1.2, which is similar to that in Beneyto et al. (2023) (https://doi.org/10.1080/02626667.2023.2208754). The authors did not consider of interest to show all parameters involved in the precipitation modelling since this will depend on the Weather Generator the user decides to use. To be free of the WG selected, the hypothesis is that the WG conceptualization is “perfect”. However, we did find of interest to show how we introduced the climate extremality with the E-GPD shape parameter used in the WG GWEX and the WG calibration process, which are explained Stochastic Weather Generator: GWEX Section
These nine precipitation populations feed an HM with two different sets of parameters (representing a permanent and an ephemeral river as described in Section 3.2), resulting in 18 different discharge “base” populations. Each population represents a specific climate and watershed conditions (e.g. an ephemeral river in a humid climate with low extremality or a permanent river in an extremely humid climate with high extremality), thus, trying to represent the conditions that can be found not just in a specific location but all over the world. These two different sets of parameters were set by the authors based on their experience representing a typical permanent and ephemeral river, with no need of calibration and validation given the synthetic nature of the watershed.
Comment 3: Readability: let co-workers review the article to see if they understand the logic and have a native speaker review it before submission
Reply: Authors experience (F. Francés: Scopus h-index: 24, associated editor in a international hydrological journal, visiting research at Colorado State University, UC-Irvine and Princeton U., etc.) along with the demonstrable English proficiency of the author C. Beneyto (Council of Europe Level C1 – Cambridge and 5 years working in a Scottish Engineering Consultancy) and the opinion of the other reviewer proof that only a fine/minor spell check is required. Therefore, we do not consider necessary to improve the English of the manuscript by a native English speaker. Of course, always any text can be improved, and this reviewer have found more errors than he expected. Therefore, a fully review of the manuscript has been carried out by all authors and a throughout grammar check has been performed, correcting the misspellings and refining sentence structure and grammar as suggested by the reviewer.
Author Response File: 
Author Response.docx
Reviewer 2 Report
It is a good work. However, some additional explanations are required as below.
It concluded that no significant differences could be found between ephemeral and perennial river with regards to the quantile estimates accuracy. Could this indifference result from the synthetic design of watershed?
How rainfall patterns generated are different between ephemeral and perennial river?
How infiltration capacity are different between ephemeral and perennial river?
Author Response
Comment 1: It concluded that no significant differences could be found between ephemeral and perennial river with regards to the quantile estimates accuracy. Could this indifference result from the synthetic design of watershed?
Reply: We thank the reviewer for the comment. In these authors’ point of view, this indifference would not be attributable to the synthetic design of the watershed. Being the watershed synthetic it is assumed to be “perfect”, this is, no uncertainty is added. Then, any difference in flood quantile estimations introduced by the hydrological model should be the same for an ephemeral and for a perennial river.
Comment 2: How rainfall patterns generated are different between ephemeral and perennial river?
Comment 3: How infiltration capacity are different between ephemeral and perennial river?
Joint Reply: Ephemeral and perennial rivers have been simulated by modifying the hydrological characteristics of the basin. Basically this means modifying the base flow and connecting/disconnecting the deep aquifer flow. In terms of the hydrological model TETIS, this translates into modifying the adequate Correction Factors (CF) to obtain two different basin responses for a given rain:
- Ephemeral: 70% of overland flow and 30% of interflow, being the aquifer disconnected
- Perennial: 30% of overland flow, 40% of interflow and the remaining 30% feeds the aquifer or reach the river channel.
Correction Factors correspond to the factors which multiply the parameters of the catchment forming the effective parameters of the model. In this sense, Correction Factors related to the base flow (CF-8) and interflow velocity (CF-6) were initially amended as per the table below. Lastly, slight tweaks were made to Correction Factors related to percolation capacity (CF-5) and gravitational infiltration (CF-3) to refine the abovementioned desired percentages, being the first three CFs the ones changing the behavior of the river. The authors understand that the way it is written in the document might be confusing and we have rephrased the paragraph
|
Description |
Values |
|
|
Perennial |
Ephemeral |
|
|
Static storage* |
1 |
1 |
|
Evapotranspiration |
1 |
1 |
|
Gravitational infiltration** |
0.14 |
0.2 |
|
Overland flow velocity |
1 |
1 |
|
Percolation capacity |
0.012 |
0.4 |
|
Interflow velocity |
70 |
10 |
|
Base flow |
50 |
200 |
|
River flow velocity |
1 |
1 |
* This storage takes into account the detention of water in pools (it could also include the interception) and the water retained in soil by capillary forces.
** Gravitational infiltration is related to the capacity of soil to allow the infiltration of water at soil moisture higher than field capacity conditions. Gravitational infiltration at soil moisture lower than field capacity is infinite.
Although it is true that undoubtedly rainfall patterns influence the way rivers respond, the hydrological characteristics of the basin can also be a key factor. Thus, since different precipitation regimes had already been considered in the study (i.e. different climates and different extremality), the authors defined ephemeral and perennial river only with
