Unexpected spatial stability of water chemistry in headwater stream networks

Benjamin Abbott (1) , Gérard Gruau (2) , Jay P. Zarnetske (3) , Florentina Moatar (4) , Lou Barbe (1) , Zahra Thomas (5) , Ophélie Fovet (5) , Tamara Kolbe (6) , Sen Gu (2) , Anne-Catherine Pierson-Wickmann (2) , Philippe Davy (2) , Gilles Pinay (7, 1)

1 ECOBIO - Ecosystèmes, biodiversité, évolution [Rennes]
2 GR - Géosciences Rennes
3 Michigan State University [East Lansing]
4 GéHCO EA6293 - GéoHydrosystèmes COntinentaux
5 SAS - Sol Agro et hydrosystème Spatialisation
6 SLU - Swedish University of Agricultural Sciences
7 OSUR - Observatoire des Sciences de l'Univers de Rennes

Understanding how water and solutes enter and propagate through freshwater landscapes in the Anthropocene is critical to protecting and restoring aquatic ecosystems and ensuring human water security. However, high hydrochemical variability in headwater streams, where most carbon and nutrients enter river networks, has hindered effective modelling and management. We developed an analytical framework informed by landscape ecology and catchment hydrology to quantify spatiotemporal variability across scales, which we tested in 56 headwater catchments, sampled periodically over 12 years in western France. Unexpectedly, temporal variability in dissolved carbon, nutrients and major ions was preserved moving downstream and spatial patterns of water chemistry were stable on annual to decadal timescales, partly because of synchronous variation in solute concentrations. These findings suggest that while concentration and flux cannot be extrapolated among subcatchments, periodic sampling of headwaters provides valuable information about solute sources and subcatchment resilience to disturbance.

Keywords: critical source area; synoptic sampling; stream network; representative elementary area

Domains: Hydrology

Benjamin Abbott, Gérard Gruau, Jay P. Zarnetske, Florentina Moatar, Lou Barbe, et al.. Unexpected spatial stability of water chemistry in headwater stream networks. Ecology Letters, 2018, 21 (2), pp.296-308. ⟨10.1111/ele.12897⟩. ⟨insu-01674523⟩