Preprints
https://doi.org/10.5194/egusphere-2022-431
https://doi.org/10.5194/egusphere-2022-431
23 Jun 2022
 | 23 Jun 2022

Droughts can reduce the nitrogen retention capacity of catchments

Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein

Abstract. In 2018–2019, Central Europe experienced an unprecedented multi-year drought with severe impacts on society and ecosystems. In this study, we analyzed the impact of this drought on water quality by comparing long-term (1997–2017) nitrate export with 2018–2019 export in a heterogeneous mesoscale catchment. We combined data-driven analysis with process-based modelling to analyze nitrogen retention and the underlying mechanisms in the soils and during subsurface transport. We found a drought-induced shift in concentration-discharge relationships, reflecting exceptionally low riverine nitrate concentrations during dry periods and exceptionally high concentrations during subsequent wet periods. Nitrate loads were up to 70 % higher, compared to the long-term load-discharge relationship. Model simulations confirmed that this increase was driven by decreased denitrification and plant uptake and subsequent flushing of accumulated nitrogen during rewetting. Fast transit times (<2 months) during wet periods in the upstream sub-catchments enabled a fast water quality response to drought. In contrast, longer transit times downstream (>20 years) inhibited a fast response but potentially contribute to a long-term drought legacy. Overall, our study reveals that severe multi-year droughts, which are predicted to become more frequent across Europe, can reduce the nitrogen retention capacity of catchments, thereby intensifying nitrate pollution and threatening water quality.

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Journal article(s) based on this preprint

13 Jan 2023
| Highlight paper
Droughts can reduce the nitrogen retention capacity of catchments
Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein
Hydrol. Earth Syst. Sci., 27, 303–318, https://doi.org/10.5194/hess-27-303-2023,https://doi.org/10.5194/hess-27-303-2023, 2023
Short summary Executive editor
Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-431', Anonymous Referee #1, 13 Jul 2022
    • AC1: 'Response to Reviewer 1', Carolin Winter, 17 Aug 2022
  • RC2: 'Comment on egusphere-2022-431', Anonymous Referee #2, 21 Jul 2022
    • AC2: 'Resonse to Reviewer 2', Carolin Winter, 17 Aug 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-431', Anonymous Referee #1, 13 Jul 2022
    • AC1: 'Response to Reviewer 1', Carolin Winter, 17 Aug 2022
  • RC2: 'Comment on egusphere-2022-431', Anonymous Referee #2, 21 Jul 2022
    • AC2: 'Resonse to Reviewer 2', Carolin Winter, 17 Aug 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Publish subject to revisions (further review by editor and referees) (20 Oct 2022) by Matthew Hipsey
AR by Carolin Winter on behalf of the Authors (31 Oct 2022)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (04 Nov 2022) by Matthew Hipsey
RR by Jens Lange (06 Dec 2022)
ED: Publish as is (19 Dec 2022) by Matthew Hipsey
AR by Carolin Winter on behalf of the Authors (02 Jan 2023)  Manuscript 

Journal article(s) based on this preprint

13 Jan 2023
| Highlight paper
Droughts can reduce the nitrogen retention capacity of catchments
Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein
Hydrol. Earth Syst. Sci., 27, 303–318, https://doi.org/10.5194/hess-27-303-2023,https://doi.org/10.5194/hess-27-303-2023, 2023
Short summary Executive editor
Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein
Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Understanding how catchments respond to change is a central theme of the work of many hydrologists around the world, however, it is fair to say that the vast majority of these studies have focused on water quantity. This study is unique in that it represents a very detailed treatment of how water quality changes due to drought, which is a topic that is becoming ever so important with the rapid changes happening in warming climate for many regions of the world. The authors very cleverly combine both complex models and data-driven analyses to elucidate the effects of extreme drought on river water quality.
Short summary
We investigated the impact of the severe 2018–2019 Central European drought on riverine nitrate pollution. We found that under severe drought, catchments can lose part of their nitrogen retention capacity due to decreased denitrification and plant uptake, but the time scale of riverine nitrate export responses to drought can be catchment specific. These results imply that severe and prolonged droughts can intensify nitrate pollution and threaten water quality.