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This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 17922
To cite this version : Probst, Jean-Luc Experimental catchments as
observatories of the hydrological and biogeochemical functioning of the critical Zone. (2017) In: List water lectures seminar series, 12 June 2017 - 15 June
2017 (Luxembourg, Luxembourg). (Unpublished)
Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@listes-diff.inp-toulouse.fr
LIST WATER LECTURES Seminar Series
13
thJune 2017, 15.00
Room F011A
41, rue du Brill, L-4422 Belvaux
Dr. Jean-Luc Probst, EcoLab, Centre national
de la recherche scientifique and University of
Toulouse, France
Experimental Catchments as observatories of the hydrological and
biogeochemical functioning of the Critical Zone
The catchments are geographic, geomorphologic and hydrologic unities, today recognized to be relevant natural infrastructures for supporting the development of new research and the management of water resources and soil protection at continental scale, as well as at regional or local scales. The long term survey of rivers allows to determine the impacts of climatic changes and anthropogenic activities on the hydrological and biogeochemical functioning of their drainage basin, but also on soil erosion, pollutant transfers, biogeochemical cycles, soil and water quality, living organisms and terrestrial and aquatic ecosystems. They allow also to assess the relationships between biodiversity and ecosystem functioning, ecosystem services and finally, the relationships between man, societies and their environments at different scales. A better understanding of mechanisms and a better estimation of mass balances at the scale of catchments require to set up long term surveys, at least during 10 years to take into account the recurrence of dry and humid periods, which exhibit on average a 10-year periodicity for most rivers in the world. These surveys must be done with a high resolution or even continuously (using multi-parameter probes with different sensors) during the flood events (“hot moments”) which are the main periods of soil erosion and river transports. Inputs and outputs of water and sediment fluxes and of their chemical and isotopic composition must be evaluated in relation with changes in climate, hydrology, land cover and agricultural practices. These global surveys make these catchments real environmental Observatories of the continental surfaces and interfaces, and particularly, of what we call today, the Critical Zone (see figure below).
We show through some results obtained on different catchments how we can assess hydroclimatic fluctuations from river discharge variations, physical and chemical soil erosion and CO2 uptake by rock weathering from the chemical composition of river waters and fluvial sediments. We also show how an anthropogenic perturbation can change the chemical and isotopic composition of river fluxes and CO2 consumption by chemical erosion.
Several Observatories already exists on different catchments in France, in Europe and in the world and they are organized in network at the scale of the different countries (SOERE RBV and IR OZCAR in France), but also at the European (like eLTER) or international levels (ILTER, CZEN).
In France, the experimental catchment network (RBV) was recently grouped with other networks on the Critical Zones (Peat, Ground Water, Glaciers, Regional Spatial Observatory…), to form a French Research Infrastructure (IR OZCAR). At the end of 2017, OZCAR will be grouped with the French LTER network (Zone Atelier) to integrate an European Strategy Forum on Research Infrastructure (ESFRI) on eLTER.
