Preprints
https://doi.org/10.5194/egusphere-2023-2214
https://doi.org/10.5194/egusphere-2023-2214
29 Nov 2023
 | 29 Nov 2023

Using high-frequency solute synchronies to determine simple two-end-member mixing in catchments during storm events

Nicolai Brekenfeld, Solenn Cotel, Mikaël Faucheux, Paul Floury, Colin Fourtet, Jérôme Gaillardet, Sophie Guillon, Yannick Hamon, Hocine Henine, Patrice Petitjean, Anne-Catherine Pierson-Wickmann, Marie-Claire Pierret, and Ophélie Fovet

Abstract. Stream water chemistry at catchment outlets is commonly used to infer the flow paths of water through the catchment and to quantify the relative contributions of various flow paths and/or end-members, especially during storm events. For this purpose, the number and nature of these flow paths or end-members are commonly determined with principal component analysis based on all available conservative solute data. Here, for a given pair of measured solutes, we propose a methodology to determine the minimum number of required end-members, based on the ion’s synchronous variation during storm events. This allows identifying solute pairs, for which a simple two end-member mixing model is sufficient to explain their variation during storm events and solute pairs, which show a more complex pattern, requiring a higher-order end-member mixing model. We analysed the concentration-concentration relationships of several major ion pairs on the storm-event scale, using multi-year, high-frequency (< 60 minutes) monitoring data from the outlet of two small (0.8 to 5 km²) French catchments with contrasting land-use, climate and geology. A large number of storm-events (56 to 92 %) could be interpreted as the result of the mixture of only two end-members, depending on the catchment and the ion pairs used. Even though some of these results could have been expected (e.g. a two-end-member model for the Na+/Cl- pair in a catchment close to the Atlantic coast), others were more surprising and in contrast to previous studies. These findings might help to revise or improve the perceptual catchment understanding of flow path or end-member contributions and of biogeochemical processes. In addition, this methodology can identify, which solute pairs are governed by identical hydro-biogeochemical processes and which solutes are modified by more complex and diverse processes.

Nicolai Brekenfeld, Solenn Cotel, Mikaël Faucheux, Paul Floury, Colin Fourtet, Jérôme Gaillardet, Sophie Guillon, Yannick Hamon, Hocine Henine, Patrice Petitjean, Anne-Catherine Pierson-Wickmann, Marie-Claire Pierret, and Ophélie Fovet

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2214', Anonymous Referee #1, 22 Dec 2023
    • AC1: 'Reply on RC1', Nicolai Brekenfeld, 12 Feb 2024
  • RC2: 'Comment on egusphere-2023-2214', Karl Nicolaus Van Zweel, 08 Jan 2024
    • AC2: 'Reply on RC2', Nicolai Brekenfeld, 12 Feb 2024
Nicolai Brekenfeld, Solenn Cotel, Mikaël Faucheux, Paul Floury, Colin Fourtet, Jérôme Gaillardet, Sophie Guillon, Yannick Hamon, Hocine Henine, Patrice Petitjean, Anne-Catherine Pierson-Wickmann, Marie-Claire Pierret, and Ophélie Fovet
Nicolai Brekenfeld, Solenn Cotel, Mikaël Faucheux, Paul Floury, Colin Fourtet, Jérôme Gaillardet, Sophie Guillon, Yannick Hamon, Hocine Henine, Patrice Petitjean, Anne-Catherine Pierson-Wickmann, Marie-Claire Pierret, and Ophélie Fovet

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Short summary
The proposed methodology consists of simultaneously analysing the concentration variation of any two solutes during a storm event, by plotting the concentration variation of one solute against the variation of another solute. For each solute pair and each storm event, this methodology can reveal, whether only two or whether more than two end-members contribute to the stream flow during a storm event. In consequence, conclusions can be drawn about hydro-biogeochemical processes in catchments.