the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Regional difference in runoff regimes and changes in the Yarlung Zangbo river basin
Abstract. An improved understanding of runoff regimes and flow changes in the Yarlung Zangbo (YZ) river basin in the southern Tibetan Plateau (TP) is crucial for water resources management. However, regional characteristics in runoff regimes and changes are not comprehensively investigated in the YZ mostly due to the lack of hydrometeorological observations. Here, we comprehensively investigated runoff regimes and changes across six sub-basins in the YZ for 1971–2020 with a particular focus on the comparison between the upstream of the Nuxia (NX) basin and the downstream NX-Pasighat (NX-BXK), based on a newly generated precipitation dataset and a well-validated model with streamflow, glacier mass and snow cover observations. Our results reveal that large regional differences in runoff regimes and changes exist in the YZ basin. Firstly, runoff generation is dominated by rainfall in the entire YZ, and glacier runoff plays more important role in annual total runoff (19 %) in the NX-BXK than other sub-basins. Secondly, annual runoff shows an increasing trend in the NX basin but a decreasing trend in the NX-BXK due to rain-induced runoff changes, resulting in a weak increasing trend (3.1 mm/10 yr) in the YZ basin. Thirdly, total runoff increases of 5 %–22 % in the NX but decreases of 3 %–20 % in the NX-BXK in all seasons in 1998–2020 relative to the period 1971–1997. Finally, the NX basin faces a considerably hazard from extreme flood, but the NX-BXK basin faces more severe hydrological droughts. Glacier runoff shows limited roles in mitigating water shortages caused by drought in dry seasons, but it intensifies the flood frequency and severity among the basins in wet season. Our study offers a basic framework for clarifying the runoff regimes and flow changes in the TP basins.
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Status: closed
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RC1: 'Comment on hess-2023-16', Anonymous Referee #1, 26 Mar 2023
General comments:
This paper offers an hydrological modeling of the Yarlung Zangbo River (also named upper Brahmaputra), and five sub-basins, over a long period of time, by using the VIC- Glacier model forced by the ERA5 reanalysis data.
This work is a good contribution to the knowledge of hydro-systems in the Tibetan Plateau, in particular regarding the question of partitioning the rainfall and glacial melt contributions.The scientific approach is good, with a rigorus description of input data and results. Sources of uncertainties are also described in the results section, which is good.
Number and quality of tables and figure is good, despite the accuray of legends needs to be improved.Scientific significance: Fair
Scientific quality: Good
Presentation quality: FairSpecific comments:
My main remark stands on the description of the calibration process, and in particular the time periods. Degree-Day factor (DDF) and 6 parameters of the VIC model are calibrated. Please provide more information and syntetic explaination of the process. What are the intial ranges of tested parameters? What are the method/tool employed for the optimization process? Please add a table with this info.
Also, regarding the periods of time: Is the whole analysis performed over the calibration period? Is there any calibration/validation periods? Please make this clear. In table 2: several period of time are quoted. What are they used for? Glaciar coverage and observed runoff are not availaible over the same period, so which period is used for the calibration process?
A real clarification of this is needed.
Technical corrections:l68: 0.3-0.4°C: over wich period?
l83: at a rate of 48.2m yr−1: over wich period?
l106: which may be due to
l150: annual precipitation increases from upstream (283 mm) to downstream (1465 mm): what do you mean?
l155 snow cover fraction (SCF) = annual mean or winter maximum coverage?
l186 (eq 1): give the reference/source for this equation
l211: please give calibration period and validation period
l231: what is figure S2?
l244: Snow cover is considered on average over the basin?
l452: Zhang et al 2013 applyed the same model?Figure 2: please quote data source in the legend
Figure 3: 1971-1980 is the whole calibration period of the model?
Figure 5: 'The asterisk indicates 95% significance confidence level.': not clear. why is there a confidence interval for correlation coeficient? Please clarify
Figure 6: please quote data source in the legend. please clarify '95% significance confidence level'table 1: please give reference/product for the precipitation and temperature data and for DFF, SCA and SCF values. Are they results from the calibration process?
Citation: https://doi.org/10.5194/hess-2023-16-RC1 -
AC1: 'Reply on RC1', He Sun, 29 Mar 2023
Dear editors and reviewers:
On behalf of my co-authors, thank you very much for your attention to our paper “Regional difference in runoff regimes and changes in the Yarlung Zangbo river basin”. My co-authors and I think that all the comments are valuable and very helpful for us to improve the manuscript. We have carefully revised the manuscript according to the reviewers’ comments.Revision note was also included in the Supplement.
We hope this manuscript will satisfy the requirement of the Hydrology and Earth System Sciences.
Best regards
He Sun
-
AC1: 'Reply on RC1', He Sun, 29 Mar 2023
-
RC2: 'Comment on hess-2023-16', Anonymous Referee #2, 10 Jun 2023
This study presents modeling results of the hydrological regime in subbasins of the YZ basin from 1971 to 2020. The authors compare the variations in runoff components and their change trends across the subbasins. I have a couple of concerns regarding the motivation, methodology, and discussion, which the authors may consider for further improvement of their work:
-
The authors should reduce the number of self-citations in the introduction and discussion sections. The frequency of citing works published by their own group is too high in the text. It would be more appropriate to include a wide range of peer research from other groups in the same study area. Citing research findings from other groups can provide more robust evidence for their statements.
-
The authors need to provide more evidence or references to support their claims about the novelty of this work (lines 133-138). They should explain why spatially varied runoff regimes are important and novel compared to previous studies. Additionally, they should clarify why model validation using an observational hydrometeorological network is considered new. It would also be helpful to explain the novelty of using their own precipitation dataset for model running.
-
It is necessary to include a methodology section to provide more details on how the change trend of runoff was tested, how the change point of 1997-1998 was identified, and how the change trends were attributed.
-
In the discussion, the authors should compare their results of runoff component contributions with findings from other studies. Although Table 4 is listed, it is not discussed in the text. Moreover, the authors should also compare their runoff change trend in subbasins up to the NX station with other studies.
-
The conclusions section is lengthy and wordy. It would be beneficial to make it more concise and present the novel findings in a straightforward manner.
Specific comments:
- Line 80: "Less" - Please provide examples.
- Line 95: Cite research from other groups.
- Line 105: Existing studies - cite more research from other groups.
- Line 112: Most studies - cite relevant studies in the study area. Moreover, Duethmann et al. (2014) ran their model in central Asia, which is not suitable for this study.
- Line 130: Adaptation strategies.
- Line 221: What does "adjusted" mean?
- Line 238: Are there references for these thresholds?
- Lines 437-458: Add references from other groups.
- Figures 2a-b: Why not show a direct comparison between simulated and observed GMB (without normalization)? RGI is not satellite-based.
- Figures 3-6: Show results separately for the calibration and validation periods. Readers would be more interested in seeing the performance during the validation period.
- Figure 6: How was the snow area coverage simulated in the model? Please specify in the methodology section.
- Figure 8: Remove the table and refine the sub-figures (colors, fonts, lines...).
- Figure 11: How was the change rate calculated? Please specify in the methodology.
- Table 1: What are the periods for snow cover area and fraction?
- Tables 2-3: Add bottom lines for the first column.
- Table 3: How were the change trends tested? Please specify in the methodology.
- Add a table to compare and discuss hydrological model parameters in the subbasins.
Citation: https://doi.org/10.5194/hess-2023-16-RC2 -
AC2: 'Reply on RC2', He Sun, 14 Jun 2023
Dear editors and reviewers:
On behalf of my co-authors, thank you very much for your attention to our paper “Regional difference in runoff regimes and changes in the Yarlung Zangbo river basin”. My co-authors and I think that all the comments are valuable and very helpful for us to improve the manuscript. We have carefully revised the manuscript according to the reviewers’ comments.
We hope this manuscript will satisfy the requirement of the Hydrology and Earth System Sciences.
Best regards
He Sun
-
Status: closed
-
RC1: 'Comment on hess-2023-16', Anonymous Referee #1, 26 Mar 2023
General comments:
This paper offers an hydrological modeling of the Yarlung Zangbo River (also named upper Brahmaputra), and five sub-basins, over a long period of time, by using the VIC- Glacier model forced by the ERA5 reanalysis data.
This work is a good contribution to the knowledge of hydro-systems in the Tibetan Plateau, in particular regarding the question of partitioning the rainfall and glacial melt contributions.The scientific approach is good, with a rigorus description of input data and results. Sources of uncertainties are also described in the results section, which is good.
Number and quality of tables and figure is good, despite the accuray of legends needs to be improved.Scientific significance: Fair
Scientific quality: Good
Presentation quality: FairSpecific comments:
My main remark stands on the description of the calibration process, and in particular the time periods. Degree-Day factor (DDF) and 6 parameters of the VIC model are calibrated. Please provide more information and syntetic explaination of the process. What are the intial ranges of tested parameters? What are the method/tool employed for the optimization process? Please add a table with this info.
Also, regarding the periods of time: Is the whole analysis performed over the calibration period? Is there any calibration/validation periods? Please make this clear. In table 2: several period of time are quoted. What are they used for? Glaciar coverage and observed runoff are not availaible over the same period, so which period is used for the calibration process?
A real clarification of this is needed.
Technical corrections:l68: 0.3-0.4°C: over wich period?
l83: at a rate of 48.2m yr−1: over wich period?
l106: which may be due to
l150: annual precipitation increases from upstream (283 mm) to downstream (1465 mm): what do you mean?
l155 snow cover fraction (SCF) = annual mean or winter maximum coverage?
l186 (eq 1): give the reference/source for this equation
l211: please give calibration period and validation period
l231: what is figure S2?
l244: Snow cover is considered on average over the basin?
l452: Zhang et al 2013 applyed the same model?Figure 2: please quote data source in the legend
Figure 3: 1971-1980 is the whole calibration period of the model?
Figure 5: 'The asterisk indicates 95% significance confidence level.': not clear. why is there a confidence interval for correlation coeficient? Please clarify
Figure 6: please quote data source in the legend. please clarify '95% significance confidence level'table 1: please give reference/product for the precipitation and temperature data and for DFF, SCA and SCF values. Are they results from the calibration process?
Citation: https://doi.org/10.5194/hess-2023-16-RC1 -
AC1: 'Reply on RC1', He Sun, 29 Mar 2023
Dear editors and reviewers:
On behalf of my co-authors, thank you very much for your attention to our paper “Regional difference in runoff regimes and changes in the Yarlung Zangbo river basin”. My co-authors and I think that all the comments are valuable and very helpful for us to improve the manuscript. We have carefully revised the manuscript according to the reviewers’ comments.Revision note was also included in the Supplement.
We hope this manuscript will satisfy the requirement of the Hydrology and Earth System Sciences.
Best regards
He Sun
-
AC1: 'Reply on RC1', He Sun, 29 Mar 2023
-
RC2: 'Comment on hess-2023-16', Anonymous Referee #2, 10 Jun 2023
This study presents modeling results of the hydrological regime in subbasins of the YZ basin from 1971 to 2020. The authors compare the variations in runoff components and their change trends across the subbasins. I have a couple of concerns regarding the motivation, methodology, and discussion, which the authors may consider for further improvement of their work:
-
The authors should reduce the number of self-citations in the introduction and discussion sections. The frequency of citing works published by their own group is too high in the text. It would be more appropriate to include a wide range of peer research from other groups in the same study area. Citing research findings from other groups can provide more robust evidence for their statements.
-
The authors need to provide more evidence or references to support their claims about the novelty of this work (lines 133-138). They should explain why spatially varied runoff regimes are important and novel compared to previous studies. Additionally, they should clarify why model validation using an observational hydrometeorological network is considered new. It would also be helpful to explain the novelty of using their own precipitation dataset for model running.
-
It is necessary to include a methodology section to provide more details on how the change trend of runoff was tested, how the change point of 1997-1998 was identified, and how the change trends were attributed.
-
In the discussion, the authors should compare their results of runoff component contributions with findings from other studies. Although Table 4 is listed, it is not discussed in the text. Moreover, the authors should also compare their runoff change trend in subbasins up to the NX station with other studies.
-
The conclusions section is lengthy and wordy. It would be beneficial to make it more concise and present the novel findings in a straightforward manner.
Specific comments:
- Line 80: "Less" - Please provide examples.
- Line 95: Cite research from other groups.
- Line 105: Existing studies - cite more research from other groups.
- Line 112: Most studies - cite relevant studies in the study area. Moreover, Duethmann et al. (2014) ran their model in central Asia, which is not suitable for this study.
- Line 130: Adaptation strategies.
- Line 221: What does "adjusted" mean?
- Line 238: Are there references for these thresholds?
- Lines 437-458: Add references from other groups.
- Figures 2a-b: Why not show a direct comparison between simulated and observed GMB (without normalization)? RGI is not satellite-based.
- Figures 3-6: Show results separately for the calibration and validation periods. Readers would be more interested in seeing the performance during the validation period.
- Figure 6: How was the snow area coverage simulated in the model? Please specify in the methodology section.
- Figure 8: Remove the table and refine the sub-figures (colors, fonts, lines...).
- Figure 11: How was the change rate calculated? Please specify in the methodology.
- Table 1: What are the periods for snow cover area and fraction?
- Tables 2-3: Add bottom lines for the first column.
- Table 3: How were the change trends tested? Please specify in the methodology.
- Add a table to compare and discuss hydrological model parameters in the subbasins.
Citation: https://doi.org/10.5194/hess-2023-16-RC2 -
AC2: 'Reply on RC2', He Sun, 14 Jun 2023
Dear editors and reviewers:
On behalf of my co-authors, thank you very much for your attention to our paper “Regional difference in runoff regimes and changes in the Yarlung Zangbo river basin”. My co-authors and I think that all the comments are valuable and very helpful for us to improve the manuscript. We have carefully revised the manuscript according to the reviewers’ comments.
We hope this manuscript will satisfy the requirement of the Hydrology and Earth System Sciences.
Best regards
He Sun
-
Data sets
Daily precipitation data with 10km resolution in the upper Brahmaputra (Yarlung Zangbo River) Basin-V2 (1951-2020) He Sun https://doi.org/10.11888/Atmos.tpdc.272885
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