Hydrological impacts of climate change on small ungauged catchments – results from a global climate model–regional climate model–hydrologic model chain

Tsegaw, Aynalem T.; Pontoppidan, Marie; Kristvik, Erle; Alfredsen, Knut; Muthanna, Tone M.

doi:https://doi.org/10.5194/nhess-20-2133-2020

Articles | Volume 20, issue 8

https://doi.org/10.5194/nhess-20-2133-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Integrated assessment of climate change impacts at selected...

https://doi.org/10.5194/nhess-20-2133-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 8

Research article

|

10 Aug 2020

Research article |

| 10 Aug 2020

Hydrological impacts of climate change on small ungauged catchments – results from a global climate model–regional climate model–hydrologic model chain

Aynalem T. Tsegaw, Marie Pontoppidan, Erle Kristvik, Knut Alfredsen, and Tone M. Muthanna

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Final revised paper (published on 10 Aug 2020)
Preprint (discussion started on 04 Dec 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'review', Anonymous Referee #1, 12 Jan 2020
- AC1: 'Responses to comments of reviewer 1', Aynalem Tsegaw, 13 Mar 2020
RC2: 'RC', Anonymous Referee #2, 06 Feb 2020
- AC2: 'Responses to the comments of reviewer 2', Aynalem Tsegaw, 13 Mar 2020

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (17 Mar 2020) by Henning Rust

AR by Aynalem Tsegaw on behalf of the Authors (31 Mar 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Apr 2020) by Henning Rust

RR by Anonymous Referee #1 (14 Apr 2020)

RR by Anonymous Referee #2 (29 Apr 2020)

Suggestions for revision or reasons for rejection

The manuscript has improved with the first revision, especially with regard to a better embedding of the results with other research on climate change impacts in Norway and also the shortening of the DDD-model description is appreciated.
However, further improvements are required.
What I find somewhat discouraging here from the point of view of the reviewer is that many comments I made in the first PDF were simply ignored.
I will only list a few examples here and expect that if the authors get the chance to resubmit the manuscript, the comments of the first round will also be taken into account.

(1) Examples of comments from the first round of reviews not addressed by authors
On page 3, line 57. It was already commented in the previous review that this sentence is not really elegant: "Climate change adverse results upon streamflow regimes worldwide..." Better start like this: "Adverse effects of climate change on river regimes worldwide..."

There is still the sentence in the introduction (page 3, line 61): "Projected increase in the frequency and intensity of heavy localized precipitation events, based on climate models, contributes to increasing in precipitation-generated local flooding, ..."
To me, this sounds like the "projected increase of heavy localized precipitation events" itself cause an increase of local flooding in reality. Maybe it is simply the term "contributes", which is not used properly in this context.

Page 4, line 84: "Climate impact assessment on hydrology ... is challenging..." More correct or precise: "Assessing the impacts of climate change on hydrology...is callenging..." Moreover, the sentence is way too long.

(2) Description of bias correction method
page 9 (bottom) and page 10 (top): From the description, it is not clear to me how the bias correction was performed. I could only guess.
The sentence: "For the reference period the 6-hourly NorESM1-M input data were split into a monthly mean term and the deviation from this." is not clear.
First of all, the reader does not know whether the mean monthly time series is composed of twelve values, representing the 30-years mean or if it is a time series composed of 12*30 values.
I would also not use the term "split into". Explain first how the monthly mean time series was computed and then how the deviations were calculated.
The equations 1-3 are not referred to in the text and are not self-explanatory, because the variabels are not explained. Which variable represents the mean, which the deviation?

(3) Proper and / or imprecise use of English language
It seems to me that the manuscript was not corrected by a native speaker. There are still sentences, which are grammatically not entirely correct. Sometimes it is only a missing "the" ...

(4) Discussion
It seems that there is quite some redundancy between Discussion and Results and sometimes one and the same results are referred to too often.
For example: "the magnitude of the 200-year flood changees range from 16% to 43%" (page 28, line 610 and page 29, line 631). So, there is some space for improvement.

Specific comments
page 2, line 26: RCPs are not "emission" scenarios but"greenhouse gas concentration" scenarios. It is also used somewhere else in the text.

page 5, line 110: How can the performance of a simulation been measured if there are no observations? "Even if the DDD model predicts flow at ungauged catchments satisfactory 0.5<=Kling-Gupta Efficiency < 0.75)..."

page 6, line 137 "...dominated by rain floods..." I think, "rain flood" is not a proper term, it is either a river flood, if you want to distinguish from e.g. "coastal flood" or a flood caused by (heavy) rainfall.

page 9, line 207: Reference Bruyere et al. 2015 is not in the references. Is it Bruyere et al. 2014?

page 11, line 246: Be more specific: "catchments from small to large", what does it mean in terms of km2? "Temporal resolution from low to high", what is low what is high?

page 14: The brackets in equation 5 are in my opinion superfluous.

page 14, line 315-320: You could simply say that the 3-hourly time series were converted to annual time series instead of writing 5 lines.

page 17, lines 388f. ...temperature rises "in" <-- "by". The mean annual flow increases "from" <-- "between"

page 19, line 410: Abbreviation "CV" not introduced before usage

page 22, line 471: "moderate increase in temperature". 3 degrees increase is not moderate in my point of view, only if you compare it to other world regions, where increase in air temperature might be much higher at the end of the 21st century.

page 24, line 515: ...increase of...-9% to 17%... is it really -9%, if yes, increase would be the wrong term

page 28, line 610: You present the value of the 50-year flood by another study and compare it to the 200-year flood from your study. Why don't you refer to the 50-year flood value from your study?

page 29, line 642: "...and perhaps this is the data..." Don't you know or why are you saying "perhaps"? I recommend to reformulate this and to be more precise.

page 30, line 659: "...will be higher water available" <-- more water

page 31, line 678: "...that we are not totally off..." <-- This is colloquial language

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ED: Publish subject to minor revisions (review by editor) (10 May 2020) by Henning Rust

Dear Aynalem Tsegaw and co-authors,
thanks for submitting a revised manuscript! We have now received the reports of the same two referees as from the first round. Referee #1 is satisfied with your revised manuscript and suggests publication. Referee #2 has some minor issues which are to be resolved prior to publication. In particular, referee #2 complains that not all of the comments from the first round are taken up and addressed in your revised version. Please do so in the next round. Addressing referees' comments does not necessarily imply to accept all their suggestions. But you should either accept it or give reasons why you do not want to accept them.
Referee#2 noted that the language and presentation of results is not sufficiently precise in some places of the manuscript. He gave a few examples (already in the first review) in the beginning of the second review. I strongly support aiming for a precise language in a scientific paper! In particular, Referee #2 points towards the difficulties to understand (and reproduce) the bias correction (pp. 9,10). You start your description with "Mathematically, the bias correction ...", however, there is not much math in your text. Mathematical equations help other to unambiguously understand and reproduce your results. With equations, you could formulate your bias adjustment approach very clearly and precise. It definitively helps to accompany this with written text, as you do. I strongly advocate to extend your description with clear definitions written as equations. Your start in Eqs. (1-3) is good. However, it is not clear what is ERAI' or GCM' and how you handle seasonality (one could guess form the text but it is not unambiguous, e.g. what to do with the daily cycle?). Please give clear definitions of what you "keep" as a climatology, based on the sampling frequency of the data (6 hourly). I am aware of the difficulties in precisely representing bias adjustment algorithms using equations. However, this makes research transparent and reproducible and is thus indispensable for a research paper.
Referee#2 also suggest to have the language checked, preferably by a native speaker.

Looking forward to your revised version!
Best,
Henning

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AR by Aynalem Tsegaw on behalf of the Authors (20 May 2020)

ED: Publish subject to minor revisions (review by editor) (05 Jun 2020) by Henning Rust

AR by Aynalem Tsegaw on behalf of the Authors (10 Jun 2020) Author's response Manuscript

ED: Publish as is (26 Jun 2020) by Henning Rust

AR by Aynalem Tsegaw on behalf of the Authors (30 Jun 2020) Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Aynalem Tsegaw on behalf of the Authors (29 Jul 2020) Author's adjustment Manuscript

EA: Adjustments approved (03 Aug 2020) by Henning Rust

Short summary

Hydrological impacts of climate change are generally performed by following steps from global to regional climate modeling through data tailoring and hydrological modeling. Usually, the climate–hydrology chain primary focuses on medium to large catchments. To study impacts of climate change on small catchments, a high-resolution regional climate model and hydrological model are required. The results from high-resolution models help in proposing specific adaptation strategies for impacts.