Hydrological and Precipitation Extremes and Trends over the Paraiba do Sul River Basin, Brazil

Round 1

Reviewer 1 Report

In this paper, the author conducted a systematic investigation on the extreme conditions and trends of hydrology and precipitation in the South Paraiba River Basin, Brazil. This report is presented in accurate way. All components of the structure of this paper (motivation (Introduction), Materials and Methods, Results, Discussion and Conclusions) are clear and concrete. Methodological combination for the analysis of time series assure the confidence of the results. Some questions and suggestions are as follows:

(1)   Most of the figures are lack of standardization. For example, the vertical coordinates of the two subgraphs in Figure 2 should at least have axis names. The third subgraph in Figure 2 is the spatial distribution of annual average precipitation produced by interpolation, and its corresponding legend should be represented by gradient colors instead of individual color blocks. This also applies to Figure 1 and Figure 3.

(2)   Figure 2b mentions typical drought years and their possible main influencing factors, but lacks analysis of typical flood years.

(3)   The manuscript lacks an introduction to human activities in the study region, such as the distribution of major cities, large reservoirs (Funil Reservoirs), and water diversion projects (transposition to the Guandu system). This is not conducive to readers' understanding of the analysis, such as in lines 351-374.

(4)   There are many inconsistencies in the reference format, please check carefully.

Author Response

Dear reviewer,

We sincerely appreciate your valuable suggestions and comments on our manuscript entitled "Investigation of hydrological extremes and trends in the South Paraiba River Basin, Brazil". Your insights have been extremely helpful in improving the quality of the paper. We would like to provide a detailed response and share the improvements we have made based on your suggestions:

Standardization of figures: Following your recommendation, we have revised all of them. The subgraph axes in Figure 2 are now properly labeled. Additionally, we have modified the legend of the spatial distribution of annual average precipitation (Figure 2 and other relevant figures) to use gradient colors, as suggested. We have also updated the legends of Figures 1 and 3 to adhere to this standard.

Inclusion of analysis for above-average precipitation years: We have taken into consideration your observation regarding the lack of analysis for above-average precipitation years in Figure 2b. The revised manuscript now includes a comprehensive analysis of these years and their possible influencing factors. With this addition, we aim to provide a more complete understanding of extreme hydrological conditions in the South Paraiba River Basin.

Consistency in reference formatting: We will thoroughly review all the references and ensure they are carefully formatted according to the MPDI guidelines.

We would like to thank you once again for your valuable contributions and the time and effort you dedicated to reviewing our work. We believe that the improvements we have made effectively address all the raised issues, and we hope that these changes have enhanced the quality and clarity of the manuscript.

Best regards,

Vanessa Silveira Barreto Carvalho

Reviewer 2 Report

The paper describes the climatology and long-term trends of extreme precipitation in the Paraiba do Sul River Basin (PSRB) in Brazil. The article will be accepted after revision.

[Main comments]

(1) Chapter 3 is entitled "Results and Discussions", while Chapter 4 is missing. It will be better to separate the chapters on results and discussions. For example, the following parts deserve to be written in a chapter of discussion.

@ Lines 284-297 "This was also confirmed by --- higher risks for this region."

@ Lines 384-398 "This mountainous region includes --- human systems in the PSRB."

@ Section 3.3.

(2) It is desired to add a map in order that readers can locate place names that appear in the text.

[Other comments]

@ It may be better to write in the abstract that the PSRB is in southeast Brazil.

@ Line 53 "ANA" --- It is better to spell out.

@ Line 149 "3.2 Source of Data" --- 2.2 Source of Data.

@ It will be better to write the percentage of valid data during the period.

@ Line 167 "IBGE" --- Please spell out.

@ Line 190 "precipitation (above zero)" --- Please write the smallest unit of precipitation (e.g., 0.1mm).

@ Line 254 --- Please add explanations in the caption of Figure 2-b as to what is indicated by the box plot. Does it indicate the variation among stations?

@ Line 230 "below 1000 mm/year" --- Do you mean spatially averaged values?

@ Line 272 "extreme precipitation" --- It may be better to say "extreme daily precipitation".

@ Line 275 "accumulated monthly rainfall rates" --- Please make clear the meaning of this phrase. Are they the six-month accumulated precipitation?

@ Line 337 --- Please add a unit in the caption in Fig.6.

@ Line 339 "average runoff" --- It may be better to say "average daily runoff".

Author Response

Dear reviewer,

We sincerely appreciate your comments on our article entitled "Climatology and trends of extreme precipitation in the Paraiba do Sul River Basin (PSRB), Brazil". We are grateful for your favorable assessment and are ready to make the necessary revisions. We would like to respond in detail and share the improvements we have implemented based on your suggestions:

We appreciate the suggestion to separate the chapters of Results and Discussion. However, due to the time available for the article revision, we have decided to keep Chapter 3 as "Results and Discussion" at this stage. Nevertheless, we are aware of this recommendation for future work and will ensure a clearer chapter structure in subsequent papers.

Abstract: We have explicitly mentioned that the Paraiba do Sul River Basin is located in southeastern Brazil.

We have spelled out the acronym "ANA".

We have corrected it to "2.2 Data Source".

We have spelled out the acronym "IBGE".

We clarified that the minimum unit of precipitation is 1 mm.

We included in the caption of Figure 2b that the boxplot represents the annual variation among the rainfall stations.

We replaced "extreme precipitation" with "extreme daily precipitation".

We have rewritten the sentence to clarify the meaning of "accumulated monthly rainfall rates". It refers to the accumulated precipitation over the month for both the rainy and dry seasons.

We added the unit to the caption of Figure 6.

We replaced "average runoff" with "average daily runoff".

We sincerely thank you for your time and effort in evaluating our article. We are committed to addressing all your suggestions comprehensively and accurately.

Best regards,

Vanessa Silveira Barreto Carvalho

Reviewer 3 Report

The paper is well-written and covers an important issue.

The introduction is adequate with relevant references.  The research design is good and on a sound base.

The results need more discussion about the effect of the reduced base flow on the future demand of the basin.

The conclusion is supported by the results.

The paper can be accepted after a succeful respond by the authors to the raised point.

Author Response

Dear reviewer,

We appreciate your feedback on our article. We value your positive comments regarding the quality of the writing and the significance of the topic. Your observations are valuable to us, and we have carefully considered them.

We acknowledge your suggestion to provide a more detailed discussion on the effect of reduced base flow on the future demand of the basin. We agree that this is an important aspect to consider and have expanded the discussion in our revised manuscript.

We thank you for your time and effort in evaluating our article. Your contribution has been invaluable in strengthening our work.

Best regards,

Vanessa Silveira Barreto Carvalho