The 63-year changes in annual streamflow volumes across  Europe with a focus on the Mediterranean basin

Masseroni, Daniele; Camici, Stefania; Cislaghi, Alessio; Vacchiano, Giorgio; Massari, Christian; Brocca, Luca

doi:https://doi.org/10.5194/hess-25-5589-2021

Articles | Volume 25, issue 10

https://doi.org/10.5194/hess-25-5589-2021

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

Special issue:

Changes in the Mediterranean hydrology: observation and...

https://doi.org/10.5194/hess-25-5589-2021

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

Articles | Volume 25, issue 10

Research article

|

25 Oct 2021

Research article |

| 25 Oct 2021

The 63-year changes in annual streamflow volumes across Europe with a focus on the Mediterranean basin

Daniele Masseroni, Stefania Camici, Alessio Cislaghi, Giorgio Vacchiano, Christian Massari, and Luca Brocca

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Final revised paper (published on 25 Oct 2021)
Preprint (discussion started on 27 Jan 2020)

Interactive discussion

Status: closed

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

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SC1: 'A possibly useful reference', Ryan Teuling, 27 Jan 2020
- AC1: 'Reply to SC1', Daniele Masseroni, 26 Jun 2020
RC1: 'Interesting paper that needs a more detailed data description', Anonymous Referee #1, 15 Mar 2020
- AC2: 'Reply to RC1', Daniele Masseroni, 26 Jun 2020
RC2: 'Review of „65-year changes of annual streamflow volumes across Europe with a focus on the Mediterranean basin”', Anonymous Referee #2, 19 Mar 2020
- AC3: 'Reply to RC2', Daniele Masseroni, 26 Jun 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 Jul 2020) by María José Polo

AR by Anna Mirena Feist-Polner on behalf of the Authors (05 Oct 2020) Author's response

ED: Referee Nomination & Report Request started (21 Oct 2020) by María José Polo

RR by Anonymous Referee #1 (05 Nov 2020)

RR by Anonymous Referee #2 (24 Nov 2020)

ED: Publish subject to revisions (further review by editor and referees) (14 Dec 2020) by María José Polo

AR by Daniele Masseroni on behalf of the Authors (22 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (25 Apr 2021) by María José Polo

RR by Anonymous Referee #2 (04 May 2021)

Suggestions for revision or reasons for rejection

1) The authors analysed trends over one common time period, 1950-2013, and allowed a maximum of two years missing data. 3485 stations of their original 3913 stations fulfilled this criterion (and further quality criteria). Unfortunately, they decided to keep the new Fig. 1 instead of a figure that shows the number of available stations over time (similar to the previous Fig. 2a). In the previous Fig. 2a the number of stations during the 1950s is around 1000-1500 and always smaller than 2500 during the studied period. It is unclear how 3485 stations could be found that have less than two years missing between 1950-2013. Could the authors please clarify? If the series have different length, this needs to be described very clearly in the methods and be taken into account for the interpretation of the results.

2) The authors have amended their discussion on the causes of the streamflow trends. In their discussion on precipitation changes as a driver they state “Concerning rainfall changes, the southern regions are affected by a marked negative trend (even below -3 mm/decade), while the northern regions are characterized by a positive trend which can overcome 10 mm/decade. The spatial distribution over the 230 continent of both patterns appears perfectly congruent with the findings in annual streamflow volumes, as shown in Fig.6.” I still strongly disagree with “perfectly congruent” changes in spatial patterns of streamflow and precipitation changes. For example over Germany, precipitation has largely slightly decreased while discharge has increased. What could be the possible reasons for this pattern? This needs to be discussed in the manuscript.

3) While the authors already agreed with many of the referee comments in their previous version of their responses to the referee’s comments, these changes could not be found in their revision 1 text. In the second revision, more of the changes that are described in the author responses are actually implemented in the text. However, this does not apply to all changes and it is annoying to see that the authors state in two rounds of revisions in their replies that changes were undertaken that in the end cannot be found in the text. Is it the reviewer’s responsibility to check one by one that authors are not only pretending to undertake changes? I ask the authors to go very carefully through their replies and check whether really all of them are also in the text.
Here are examples that I could not find in the text:

Reviewer: The calculation of the Sen’s slope from annual streamflow anomalies is described as innovative, but if I do not overlook something this should not affect trends (and has probably been done in many studies).
Reply: By using anomalies to detect trends, the absolute random error is minimized (Pandžić and Trninić, 1992), but the reviewer is right in that it does not affect the trend (i.e., regression slope against time). Also, it is routinely carried out in both hydrologic and climatologic research. The methods section has been amended accordingly.
New Reply: The term “innovative” was removed. We modified as follows:
“Theil-Sen’s line, known as Theil-Sen’s slope or Sen’s slope, was calculated on the annual anomalies in streamflow volumes, an alternative modality with respect to the common application on direct streamflow data (Birsan et al. 2005). “
=> Not implemented in the text.

Reviewer: P6, L151: The unit of annual streamflow per area is length/time (e.g. m3/(km2 year), or mm y-1). Therefore the change in runoff over a certain period is length/time2 (e.g. m3/(km2 year2)).
Reply: Accepted – the values and units will be updated to reflect yearly change expressed in m3/(km2 year2).
New Reply: Done.
=> Not implemented in the text.

Reviewer: P7, L170; legend and caption of Fig. 5: replace rainfall by precipitation (assuming that snow is included).
Reply: Snow is included. Suggestion accepted.
New Reply: Done. We modified the caption as follows:
“Fig. 8. Comparison between annual streamflow volume trends and daily mean temperature (a) and rainfall (included snow-to-liquid equivalent) (b) trends over the European continent. Only significant trend are shown.”
=>Not implemented in the text.
Please also replace rainfall with precipitation in the main text.

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ED: Reconsider after major revisions (further review by editor and referees) (09 Jun 2021) by María José Polo

AR by Daniele Masseroni on behalf of the Authors (17 Jun 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (19 Jul 2021) by María José Polo

RR by Anonymous Referee #2 (22 Aug 2021)

ED: Publish subject to minor revisions (review by editor) (09 Sep 2021) by María José Polo

AR by Daniele Masseroni on behalf of the Authors (20 Sep 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (03 Oct 2021) by María José Polo

Short summary

We evaluate 63 years of changes in annual streamflow volume across Europe, using a data set of more than 3000 stations, with a special focus on the Mediterranean basin. The results show decreasing (increasing) volumes in the southern (northern) regions. These trends are strongly consistent with the changes in temperature and precipitation.