Understanding and seasonal forecasting of hydrological drought in the Anthropocene

Yuan, Xing; Zhang, Miao; Wang, Linying; Zhou, Tian

doi:https://doi.org/10.5194/hess-21-5477-2017

Articles | Volume 21, issue 11

https://doi.org/10.5194/hess-21-5477-2017

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

Special issue:

Observations and modeling of land surface water and energy...

https://doi.org/10.5194/hess-21-5477-2017

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

Articles | Volume 21, issue 11

Research article

|

07 Nov 2017

Research article |

| 07 Nov 2017

Understanding and seasonal forecasting of hydrological drought in the Anthropocene

Xing Yuan, Miao Zhang, Linying Wang, and Tian Zhou

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Final revised paper (published on 07 Nov 2017)
Preprint (discussion started on 15 Nov 2016)

Interactive discussion

Status: closed

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

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RC1: 'review', Anonymous Referee #1, 07 Dec 2016
- AC1: 'Responses to the comments from Reviewer #1', Xing Yuan, 07 Jan 2017
RC2: 'comment on hess-2016-592', Anonymous Referee #2, 12 Dec 2016
- AC2: 'Responses to the comments from Reviewer #2', Xing Yuan, 07 Jan 2017

Peer-review completion

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

ED: Reconsider after major revisions (further review by Editor and Referees) (03 Feb 2017) by Dennis Lettenmaier

AR by Xing Yuan on behalf of the Authors (22 Mar 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Apr 2017) by Dennis Lettenmaier

RR by Anonymous Referee #3 (04 May 2017)

Suggestions for revision or reasons for rejection

Review of HESS-2016-592 “Understanding and seasonal forecasting of hydrological drought in
the Anthropocene” by Yuan et al.

General comments:

This paper aims to understand the effect of human activities on the occurrence of hydrological droughts. By making use of this understanding and the seasonal climate forecasts from multiple GCMs, the paper also aim to demonstrated potential of performing seasonal forecasting of hydrological droughts. I think the authors did a reasonable job on highlighting the importance of accounting for human activities in understanding and forecasting hydrological droughts, especially in Yellow River basin in North China, where human activities have significant effects on hydrological processes. After reading through the paper, the authors seem to have ignored a couple of huge factors, that is, the groundwater overdraft can cause significant leakage of surface water to groundwater, and Yellow river is famous for its changing geomorphology due to heavy sediments from the Loess Plateau carried downstream, which would elevate the riverbed over the years, making streamflow time series non-stationary, i.e., even without human activities, hydrological response to the same meteorological forcing could change over time. I don't think the authors have considered those factors adequately.

Also, I echo with editor’s concern on how naturalized streamflow is computed. Based on the paper, it is hard to figure how naturalized streamflow is truly computed. I wonder if the authors have access to the paper version of Water Resources Bulletins for all years between 1961-2010, because the website http://www.yellowriver.gov.cn/zwzc/gzgb/ has only annual observed streamflow, annual water withdrawals and consumptions for 1998 to 2015. Further the bulletins have only annual numbers, not the monthly numbers used in the study, so I wonder how they are obtained. Besides, I don’t see direct naturalized data from the website. So the authors basically estimated the natural streamflow themselves by adding water consumptions by different sectors. I don’t know if such a simple addition/substraction is proper because of the complex interactions between surface water and subsurface water and changing geomorphology, as mentioned above.

Except for my concerns on how to account for full effect of human activities and non-stationarity, I have no big problem on the design on figuring out the relational between meteorological drought and hydrological drought, nor do I question hydrological forecasting experiments. I tend to agree that human activities worsen the hydrological droughts. The questions the authors need to address if those quantitative numbers measuring the effects of human activities are truly reliable.

In summary, I think that the authors still to clarify those points to make sure all effects of human activities are comprehensively considered and naturalized streamflow are truly reflective of natural conditions. My recommendation is to return for further revision.

Some specific comments:

P1, Abstract, line 14-15: Something is missing in this phrase: “… make the hydrological drought respond to longer time scale of meteorological drought especially during rainy seasons”. Especially what?

P1, line 27: I am not sure if “recursive” is the right word for describing an event occurred repeatedly. According to www.thefreedictionary.com, “Recursive” is term “relating to a repeating process whose output at each stage is applied as input in the succeeding stage.” Estimation of future soil moisture can be recursive as future soil moisture can use current soil moisture as input. This doesn’t apply to droughts as future drought cannot use current drought condition as input.

P3, line 34-35: see my comments above. I feel how naturalized streamflow is obtained needs further clarification.

P4, line 10-15: Again, I would like to point out that the lower natural streamflow can also be due to riverbed leakages because of the overdraft of groundwater and of changing geomorphology due to sediment accumulation downstream.

P5, line1-24: here, the streamflow non-stationarity question needs to be addressed.

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ED: Publish subject to revisions (further review by Editor and Referees) (05 May 2017) by Dennis Lettenmaier

AR by Xing Yuan on behalf of the Authors (07 May 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (24 Jul 2017) by Dennis Lettenmaier

RR by Anonymous Referee #3 (16 Aug 2017)

Suggestions for revision or reasons for rejection

Review of Hess-2016-592 “Understanding and seasonal forecasting of hydrological drought in the Anthropocene” by Yuan

General comments:
This latest revised manuscript has responded to all the comments of the last version. Particularly, the authors answered the questions related to my concerns about non-stationarity caused by natural elements such as sedimentations of the Loess Plateau on downstream channels and human elements such as over-pumping of groundwater on surface-subsurface interactions. They also provided a reply to the concern about how naturalized streamflow was created. I have no problem with the writing of the paper. It is mostly well presented.

Reading those replies, however, I found that the authors are too eager to dismiss the issues raised in previous comments, instead of acknowledging and opening up to the limitations of the study in the revision. For example, naturalized streamflow has obvious limitations as they are derived under very strong assumptions. Based on what I read from the manuscript, the way the naturalized streamflow is derived in this study is simple summations and deductions and it did not consider the interactions different elements. Nobody knows for sure how naturalized streamflow compared to streamflow under the natural conditions. This is a given fact no matter how the creator of the naturalized streamflow data defends it. Granted, naturalized streamflow is probably the best information available to us, but there is considerable uncertainty associated with it, and the uncertainty is probably not easy to quantify. I think the authors should just acknowledge this limitation explicitly in the text where naturalized streamflow first appeared and in the conclusion sections.

Overall, I recommend further revision.

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ED: Publish subject to minor revisions (further review by Editor) (26 Sep 2017) by Dennis Lettenmaier

AR by Xing Yuan on behalf of the Authors (29 Sep 2017) Author's response Manuscript

ED: Publish as is (04 Oct 2017) by Dennis Lettenmaier

Short summary

Understanding and forecasting of hydrological drought in the Anthropocene are grand challenges. Human interventions exacerbate hydrological drought conditions and result in earlier drought onset. By considering their effects in the forecast, the probabilistic drought forecast skill increases for both climate-model-based and climatology methods but their difference decreases, suggesting that human interventions can outweigh the climate variability for drought forecasting in the Anthropocene.