Streamflow drought: implication of drought definitions and its application for drought forecasting

Sutanto, Samuel J.; Van Lanen, Henny A. J.

doi:https://doi.org/10.5194/hess-25-3991-2021

Articles | Volume 25, issue 7

https://doi.org/10.5194/hess-25-3991-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-25-3991-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 25, issue 7

Research article

|

08 Jul 2021

Research article |

| 08 Jul 2021

Streamflow drought: implication of drought definitions and its application for drought forecasting

Samuel J. Sutanto and Henny A. J. Van Lanen

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Final revised paper (published on 08 Jul 2021)
Supplement to the final revised paper
Preprint (discussion started on 05 Oct 2020)

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, 06 Nov 2020
- AC1: 'Authors response R1', Samuel Jonson Sutanto, 30 Nov 2020
- AC3: 'Executive Summary of author’s response to reviewer 1 and 2', Samuel Jonson Sutanto, 07 Dec 2020
RC2: 'Review', Anonymous Referee #2, 09 Nov 2020
- AC2: 'Authors response R2', Samuel Jonson Sutanto, 30 Nov 2020
- AC3: 'Executive Summary of author’s response to reviewer 1 and 2', Samuel Jonson Sutanto, 07 Dec 2020
AC3: 'Executive Summary of author’s response to reviewer 1 and 2', Samuel Jonson Sutanto, 07 Dec 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) (15 Dec 2020) by Elena Toth

AR by Samuel Jonson Sutanto on behalf of the Authors (08 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (08 Feb 2021) by Elena Toth

RR by Anonymous Referee #2 (02 Mar 2021)

Suggestions for revision or reasons for rejection

I would like to thank the authors for carefully considering my suggestions and comments. Overall, I found the revised version much improved, with the additional analyses adding very interesting insight on the topic.
I still have only one major concern with the presented paper. The authors stress the difference between monthly and daily methods in term of number of event, average duration and deficit, while also highlighting how many of the reported events (especially in the VTD) are basically only minor events.
Under such circumstances, average statistics may be not good proxy of the performance of the index, and in my opinion this is an issue that needs to be better addressed, with specific analyses. As an example, if the VTD reports 3 events, 1 very big (2 months) plus 2 minor (of 1 day each), whereas the VTM reports only the major event (2 months), are the two version so different at the end (3 events vs. 1)?
I think that a more “fair” comparison would be in terms of “total” quantities rather than average. Like: total deficit and total number of day under drought. I suggest to add to the mix those metrics as well, in order to better explain the differences between the different indices.
Similarly, when FTD and VTD are compared, you need to find a way to distinguish between the cases when VTD detects more actual events (i.e. events in different seasons) vs. the cases when FTD detects a single event while VTD “splits” the same in multiple smaller events (but close in time). Also in this case, total quantities may alleviate the problem.

As a final comment, I found the revised text a little unpolished. I report some minor issues and comments regarding the first pages of the manuscript, but I suggest a careful revision of the full text.

Minor comments

P1 L5. “The way, how…” is repetitive.
P1 L14. Here it should read “more than…”
P1 L21. “To the end…” sounds out of place.
P2 L29. “from among others drought…” is not clear. please rephrase.
P2 L31. Given the focus of the paper on streamflow drought over Europe, it may be worth to mention this recent study (HESS 24, 5919-5945).
P3 L82. Please spell our incl.
P3 L82. “Europa” should read “Europe”.
P4 L95. Looking at the maps, I’m assuming that only cells with a minimum contributing area are considered, especially because the threshold method may not work as intended in rivers with streamflow close to zero. This is a good place to mention that.
P4 L100. “Center” should read “Centre”.
P4 149-174. I suggest to summarize this discussion a bit, since is taking most of the methodology section even if this is not the key point on the analysis.
P7 L193. “… falls below -0.84…”Looking at the next section, it seems that also for SSI an event-based approach is adopted. Does an event start when SSI falls below the threshold and ends when it returns above (as for the threshold methods) or is each monthly value treated separately? Please clarify here.
P8 L252. Again, the criteria adopted to selected those 29,000 cells (i.e. minimum contributing area) need to be highlighted in the methodology. I’m sure that Europe is covered by much more than 29,000 5x5 km2 cells.

Authors: The suggested information about the VT method applied in EDO was added (P18L560-562).
The added reference is to the CDI index, and not to the streamflow drought index (Hydrol. Sci. J. 62(3), 346-358). In my opinion, a better place to refer to this operational index would be in the Lisflood section (since is based on these data).

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RR by Anonymous Referee #1 (10 Mar 2021)

ED: Publish subject to revisions (further review by editor and referees) (31 Mar 2021) by Elena Toth

AR by Samuel Jonson Sutanto on behalf of the Authors (06 May 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (07 May 2021) by Elena Toth

RR by Anonymous Referee #2 (10 May 2021)

RR by Anonymous Referee #1 (19 May 2021)

ED: Publish subject to technical corrections (11 Jun 2021) by Elena Toth

AR by Samuel Jonson Sutanto on behalf of the Authors (14 Jun 2021) Author's response Manuscript

Short summary

This paper provides a comprehensive overview of the differences within streamflow droughts derived using different identification approaches, namely the variable threshold, fixed threshold, and the Standardized Streamflow Index, including an analysis of both historical drought and implications for forecasting. Our results clearly show that streamflow droughts derived from different approaches deviate from each other in terms of drought occurrence, timing, duration, and deficit volume.