EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Water as a critical zone currency: linking water storage and age to root uptake and biogeochemical transport

Sylvain Kuppel1,2, Isabelle Braud2, Yves Goddéris3, Sekhar Muddu4,5, Jean Riotte3, and Laurent Ruiz5,6
Sylvain Kuppel et al.
  • 1Institut de Physique du Globe de Paris, CNRS - University of Paris, Paris, France
  • 2INRAE, Villeurbanne, France
  • 3Géosciences Environnement Toulouse, CNRS - Université Paul Sabatier - IRD, Toulouse, France
  • 4Indian Institute of Science, Bengalore, India
  • 5Indo-French Cell for Water Sciences, IISc-IRD Joint International Laboratory, Bangalore, India
  • 6INRAE, Rennes, France

Efforts to grasp hydrological functioning in landscapes have gradually been evolving from inferring when water output fluxes respond to precipitation and energy inputs in catchments, towards tracking down which water is present in the different flow pathways of the critical zone (CZ). In the CZ where almost all terrestrial life developed, quantifying water storage and age (residence times in stores and transit times in fluxes) is key to the understanding of how water is i) available to supply root uptake, ii) in interaction with regolith minerals and biota, and iii) a medium for solute transport. We propose an approach to characterize the dynamics and non-linearities of CZ functioning first by mapping time-varying transit times of water exiting as plant transpiration as well as soil evaporation and stream discharge, against the corresponding water storage states. This picture is then extended by assessing the resulting relationships between hydrological states and patterns of nutrient concentration in, and export out of, the critical zone. This analysis considers several spatial scales, from the hillslope to the whole catchment. To this end, we use simulations from a cascade of spatially-distributed numerical tools: a process-based ecohydrological model – accounting for the coupling between energy balance, critical zone hydrology and vegetation dynamics, and a modular chemical weathering model – simulating dissolution/precipitation rates of mineral phases based on kinetics laws. We particularly focus on the long-term experimental tropical catchment of Mule Hole in Peninsular India (part of both the Indian Kabini CZ observatory and the French CZ observatory network OZCAR), with a highly seasonal hydroclimate and deep unsaturated profile, and where extensive hydrometric and chemical datasets are available for model calibration and evaluation. We discuss the interplay between distinctively mobilized critical zone compartments for each output flux, and the time-varying spatial organization of flow pathways.

How to cite: Kuppel, S., Braud, I., Goddéris, Y., Muddu, S., Riotte, J., and Ruiz, L.: Water as a critical zone currency: linking water storage and age to root uptake and biogeochemical transport, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15958,, 2020

Comments on the presentation

AC: Author Comment | CC: Community Comment | Report abuse

Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-15958, Paul Hallett, 05 May 2020

    Did you find any evidence of hydraulic lift by deeper roots?  Thanks.  Paul Hallett

    • CC2: Reply to CC1, Sylvain Kuppel, 05 May 2020

      Hi Paul, the ecohydrological model does not explicitly simulate hydraulic redistribution at this stage. Hopefully in future versions!

    • CC3: Reply to CC1, Jean Riotte, 05 May 2020

      Hello, we could evidence deep root uptake in the watershed from long term data of tree growth and inversion of a water stress model. The results show that the main tree species share water vertically from fe meters depth to about 20m (Chitra-Tarak et al. 2018 J. Ecol)

      • CC4: Reply to CC3, Paul Hallett, 05 May 2020

        Great thanks.  I will have a look at the paper you provided.