Trajectories of nitrate input and output in three nested catchments along a land use gradient

Ehrhardt, Sophie; Kumar, Rohini; Fleckenstein, Jan H.; Attinger, Sabine; Musolff, Andreas

doi:https://doi.org/10.5194/hess-23-3503-2019

Articles | Volume 23, issue 9

https://doi.org/10.5194/hess-23-3503-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-23-3503-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 23, issue 9

Research article

|

02 Sep 2019

Research article |

| 02 Sep 2019

Trajectories of nitrate input and output in three nested catchments along a land use gradient

Sophie Ehrhardt, Rohini Kumar, Jan H. Fleckenstein, Sabine Attinger, and Andreas Musolff

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Final revised paper (published on 02 Sep 2019)
Supplement to the final revised paper
Preprint (discussion started on 22 Oct 2018)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of Ernhardt et al.', Anonymous Referee #1, 06 Nov 2018
- AC1: 'Response to anonymous Referee #1', Andreas Musolff, 14 Jan 2019
RC2: 'Review of Ehrhardt et al. - Decadal trajectories of nitrate input and output in three nested catchments along a land use gradient', Anonymous Referee #2, 23 Nov 2018
- AC2: 'Response to anonymous Referee #2', Andreas Musolff, 14 Jan 2019

Peer-review completion

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

ED: Publish subject to revisions (further review by editor and referees) (06 Feb 2019) by Nandita Basu

AR by Andreas Musolff on behalf of the Authors (20 Mar 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Apr 2019) by Nandita Basu

RR by Anonymous Referee #2 (13 May 2019)

Suggestions for revision or reasons for rejection

The authors managed to clearly improve the manuscript based on the first reviews. I only have a few more suggestions:

P2 L27-29: In many cases, surface water quality does improve quickly after reducing the N inputs. See for example Rozemeijer et al., 2014
Rozemeijer, J.C., J Klein, HP Broers, TP van Tol-Leenders, B Van Der Grift, 2014. Water quality status and trends in agriculture-dominated headwaters; a national monitoring network for assessing the effectiveness of national and European manure legislation. Environmental monitoring and assessment 186 (12), 8981-8995.

P4 L5-6: Chemostatic behavior after decades of N inputs is not what we’ve observed in the Netherlands. We still see changing concentrations during events. Quite often, the concentration dips shortly during events due to fast runoff of water that did not have time to take up nitrate from the subsurface. But also: unless decades of N inputs, we see decreasing groundwater concentrations with depth, due to denitrification. This still leads to higher concentrations during the wet season. For chemostatic behavior you would need similar concentrations in all flow routes from the deep groundwater to the direct runoff. We haven’t seen that yet.

P8 L7: What crops are grown and what type of fertilizer is used?

P9L29: What are ‘in situ parameters’?

P11 L11-18: Do you have information about the performance of this method for interpolating concentration data? Is it better than a more straightforward linear or stepwise interpolation? And why is it better?

P13 L 6: 97% of agricultural N is quite a lot given that the input from atmospheric deposition usually is in the range of 20% (L17-18). What is the remaining 3%?
Mention again here that you left out the effluent from the sewage treatment plants.

P15 Figure 3: Consider to add some more detailed information about the NO3 concentrations in time. It would be good to see the year-to-year variations and the seasonal variations as well.

P16 L6: You only use the export via surface water. Could there be export via (regional) groundwater as well? Why is it legitimate to neglect this?

P21 L23: Export via groundwater can be a third explanation for the missing N.

P25 Figure 7: I still don’t understand the way that you’ve visualized this conceptual model. It’s not clear what sections of the subsurface contribute which water during HFS and LFS. Why don’t you use or modify the visualization by Rozemeijer & Broers, 2008?

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RR by Anonymous Referee #1 (25 May 2019)

ED: Publish subject to minor revisions (review by editor) (28 May 2019) by Nandita Basu

AR by Andreas Musolff on behalf of the Authors (20 Jun 2019)

ED: Publish as is (06 Jul 2019) by Nandita Basu

AR by Sophie Ehrhardt on behalf of the Authors (09 Jul 2019) Manuscript

Short summary

This study shows quantitative and temporal offsets between nitrogen input and riverine output, using time series of three nested catchments in central Germany. The riverine concentrations show lagged reactions to the input, but at the same time exhibit strong inter-annual changes in the relationship between riverine discharge and concentration. The study found a strong retention of nitrogen that is dominantly assigned to a hydrological N legacy, which will affect future stream concentrations.