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24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

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Le projet CRITEX


Innovative Equipment for the Critical Zone



Although the critical zone (i.e. the Earth’s permeable layer, from treetops to groundwater) is important for the future of human activities, we still know little about this thin veneer. We lack indirect investigation methods that allow us to observe it and monitor its dynamics in response to external forcing. We need to develop new and innovative techniques that allow it to be explored, like those used by doctors to visualize inaccessible parts of human body. This lack of powerful investigation tools strongly limits the ability to predict how the critical zone will respond to the new epoch of the Anthropocene.

CRITEX is an instrumental project for purchasing and building innovative instruments to better understand and examine the critical zone. CRITEX aims to develop new sensors and install commercial instruments in well-chosen critical-zone observatories by fostering collaboration among disciplines and approaches (e.g. geochemistry, geophysics, hydrology).

The AgrHyS Observatory, one of the OZCAR-RI INRAE Critical Zone Observatories, is managed by the SAS research unit. It hosts several pieces of CRITEX equipment:

  • A flux tower to measure land–surface exchanges (Kervidy-Naizin site). In Task 1.2 of CRITEX, turbulent exchanges between the surface and the atmosphere are monitored at the plot scale using the eddy-covariance method (“flux tower”).
  • A “River Lab” prototype to increase the temporal resolution of water-quality analysis for a wide range of chemical elements (Kervidy-Naizin site). Task 4.2 of CRITEX aims to develop a prototype of a “geochemical-lab-in-the-field”, called the “River Lab”, which can measure with unprecedented frequency the composition of major dissolved chemical elements in a river or groundwater. The main idea is to place laboratory facilities directly in the field to avoid drawbacks of the conventional chain of manipulation: sampling, filtration, conditioning, and analysis in the laboratory.


Floury, P., Gaillardet, J., Gayer, E., Bouchez, J., Tallec, G., Ansart, P., Koch, F., Gorge, C., Blanchouin, A., and Roubaty, J.-L.: The potamochemical symphony: new progress in the high-frequency acquisition of stream chemical data, Hydrol. Earth Syst. Sci., 21, 6153–6165, 2017

Tunqui Neira J.M., Tallec G., Andreassian V., Mouchel J-M. A combined mixing model for high-frequency concentration–discharge relationships. Journal of Hydrology, Elsevier, 2020, 591

SAS staff involved

  • Researchers: Ophélie Fovet, Chris Fléchard
  • Field Staff: Mikael Faucheux, Yannick Hamon, Beatrice Trinkler (2017-2020)
  • Post-doc: Nicolai Brekenfled (2021-2023)


Funding and Support

Funded by the ANR within the framework of the “Investment for the Future” program.