Climate change impacts on Yangtze River discharge at the Three Gorges Dam

Birkinshaw, Steve J.; Guerreiro, Selma B.; Nicholson, Alex; Liang, Qiuhua; Quinn, Paul; Zhang, Lili; He, Bin; Yin, Junxian; Fowler, Hayley J.

doi:https://doi.org/10.5194/hess-21-1911-2017

Articles | Volume 21, issue 4

https://doi.org/10.5194/hess-21-1911-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-21-1911-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 21, issue 4

Research article

|

05 Apr 2017

Research article |

| 05 Apr 2017

Climate change impacts on Yangtze River discharge at the Three Gorges Dam

Steve J. Birkinshaw, Selma B. Guerreiro, Alex Nicholson, Qiuhua Liang, Paul Quinn, Lili Zhang, Bin He, Junxian Yin, and Hayley J. Fowler

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Final revised paper (published on 05 Apr 2017)
Preprint (discussion started on 23 May 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Climate Change Impacts on Yangtze River Discharge at the Three Gorges Dam', Anonymous Referee #1, 26 Jun 2016
- AC1: 'Response to Anonymous Referee #1', Steve Birkinshaw, 28 Aug 2016
RC2: 'Interesting study but the processes leading to changes in discharge and to the uncertainty in the projections need to be better discussed.', Anonymous Referee #2, 07 Jul 2016
- AC2: 'Response to Anonymous Referee #2', Steve Birkinshaw, 28 Aug 2016
EC1: 'Valuable comments and promising author responses', Jan Seibert, 04 Sep 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (04 Sep 2016) by Jan Seibert

AR by Steve Birkinshaw on behalf of the Authors (15 Nov 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Nov 2016) by Jan Seibert

RR by Anonymous Referee #2 (11 Dec 2016)

Suggestions for revision or reasons for rejection

I thank the authors for the revised version of their manuscript and for their detailed response to my comments. I think that their study is much improved and that both the methodology and their results gained in clarity. I would like to congratulate them for this new set of discharge projections and for their efforts to characterize its uncertainties. I particularly appreciate the distributed SWE changes they now show in Figure 5.

Before I can recommend their study for publication, I encourage them to consider the following suggestions:

Line 14, page 3: “Within each polygon there is no simple relationship between elevation and precipitation to improve this approach.” This sentence is unclear. I would simply state that precipitation and temperature are considered to be uniform within each polygon.

Caption of Figure 7: Since this Figure shows temperature simulations, its caption should be “largest and smallest temperature bias” instead of “largest and smallest totals”.

Lines 5-7, page 20: “One of the major sources of uncertainty when predicting future discharge as a result of climate change is model uncertainty. In this work the main uncertainties in using Shetran is predicting discharges for precipitation outside the limits of the model calibration and validation period”. This sentence is confusing, because the source of uncertainty that this study is focusing on is the uncertainty stemming from the climate models, and uncertainties in the hydrological model (Shertan) are not explicitly considered (the authors only use one model and one parameter set). I would suggest to rephrase this sentence as follows: “Discharge simulations under future climate are uncertain, because of uncertainties in future greenhouse gas emissions, climate models, downscaling methods and hydrological models. This study focuses on the uncertainty stemming from the climate models because of its significant influence on the uncertainty in discharge projections (e.g. Ragettli et al., (2013); Addor et al., (2014))”

Lines 23-24, page 21: “An improvement in climate model performance would also allow PET to be calculated using the Penman-Monteith equation which would deliver more reliable projections of change in PET”. Penman-Montheith could already be used with the current set of climate projections. I would simply state that using a more-process based formulation of PET (e.g. Penman-Monteith) would improve the realism of the discharge projections.

Figure 10 has now three panels, the two bottom ones (a and b) are described in the caption but the not the top one. Please modify the figure and/or the caption.

Suggested references

Addor, N., Rössler, O., Köplin, N., Huss, M., Weingartner, R. and Seibert, J.: Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments, Water Resour. Res., 50, 7541–7562, doi:10.1002/2014WR015549, 2014.

Ragettli, S., Pellicciotti, F., Bordoy, R. and Immerzeel, W. W.: Sources of uncertainty in modeling the glaciohydrological response of a Karakoram watershed to climate change, Water Resour. Res., 49(9), 6048–6066, doi:10.1002/wrcr.20450, 2013.

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RR by Anonymous Referee #3 (03 Feb 2017)

Suggestions for revision or reasons for rejection

Climate Change Impacts on Yangtze River Discharge at the Three Gorges Dam
By Birkinshaw et al. for possible publication in HESS

In the paper, the authors tried to analyze future impacts of climate change on the flow regime of the Yangtze river using a distributed hydrological model, based on GCM projections. Overall, this is a useful work, given the importance of the study region in China. The paper is reasonably structured, although I am a little bit uncomfortable with the writing style. However, I will leave this to the authors and editors to decide. The authors also replied most of the referees’ comments in a satisfactory way, but I hope that the authors can resolve some of my concerns before its acceptance.

First, I am not very familiar with the distributed model the authors used. My understanding is that although it is a distributed model, the parameters calibrated in Table 2 had the same values for all the grid cells. Is this correct? Also, I am not comfortable with the values for other parameters used by the authors, meaning that physical processes might not be correctly represented in the model. For instance, in Table 1, LAI for evergreen forest is from 0.5 to 1.0 and canopy storage capacity is 3 mm. Those values are more like for grass! For actual/potential ET ratio, the value of 1 seems unrealistic, even for the humid region like the Yangtze River basin. I would encourage the authors to provide a supplemental table to show the details on the temporal dynamics of those parameters.

Secondly, the authors claimed that the land use change does not have important impacts on the flow discharges in the Yangtze River. However, there are numerous studies that beg the difference in the same region. More importantly, the reference of Hansen et al. (2013) as cited by the authors is not appropriate here, which only shows changes in forest. Instead, as also noticed by the authors, Liu et al. (2010) shows considerable land use changes in the study region. In terms of the orographic effect on precipitation, I am not conceived by the authors’ argument. I would suggest, at least, the authors to plot elevation vs. precipitation in the paper to support their claim.

Lastly, the authors attributed the differences in projected discharge to the differences in projected spatial distributions of future precipitation from different GCMs; however, little explanations behind the physical mechanism is offered by the authors. Given it is the key finding of this study, I would invite the authors to do so in the next revision.

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ED: Publish subject to minor revisions (further review by Editor) (09 Feb 2017) by Jan Seibert

AR by Steve Birkinshaw on behalf of the Authors (17 Feb 2017) Author's response Manuscript

ED: Publish subject to technical corrections (08 Mar 2017) by Jan Seibert

AR by Steve Birkinshaw on behalf of the Authors (10 Mar 2017) Author's response Manuscript

Short summary

The Yangtze River basin in China is home to more than 400 million people and susceptible to major floods. We used projections of future precipitation and temperature from 35 of the most recent global climate models and applied this to a hydrological model of the Yangtze. Changes in the annual discharge varied between a 29.8 % decrease and a 16.0 % increase. The main reason for the difference between the models was the predicted expansion of the summer monsoon north and and west into the basin.