# How are the data from the OZCAR RI critical zone observatories used by local stakeholders?

Isabelle Braud, Marie-Claire Pierret, Laurent Longuevergne, Pierre-Alain Ayral, Laurie Boithias, Brice Boudevillain, Jean-Martial Cohard, Guillaume Couloumat, Ophélie Fovet, Hocine Henine, et al.

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Isabelle Braud, Marie-Claire Pierret, Laurent Longuevergne, Pierre-Alain Ayral, Laurie Boithias, et al.. How are the data from the OZCAR RI critical zone observatories used by local stakeholders?. 3rd OZCAR TERENO Conference, Sep 2025, Paris, France. . hal-05397531

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Submitted on 4 Dec 2025

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# How are the data from the OZCAR RI critical zone observatories used by local stakeholders?

Isabelle Braud(1), Marie-Claire Pierret(2), Laurent Longuevergne(3), Pierre-Alain Ayral(4), Laurie Boithias(5), Brice Boudevillain(6), Jean-Martial Cohard(6), Guillaume Couloumat(7), Ophélie Fovet(8), Hocine Henine(9), Eric Lajeunesse(10), Caroline Le Bouteiller(6), Cédric Legout(6), Jean-Christophe Maréchal(11), Jérôme Molénat(7), Jean-Sébastien Moquet(12), Jean Nabucet(13), Guillaume Nord(5), Olivier Payrastre(14), Agnès Rivière(15), Fabrice Rodriguez(14)

(1) INRAE, RiverLy, Lyon, isabelle.braud@inrae.fr; (2) ITES, Strasbourg; (3) Géosciences Rennes, Rennes; (4) ESPACE, St-Christol les Alès; (5) GET Toulouse; (6) IGE, Grenoble; (7) LISAH, Montpellier; (8) SAS, Rennes; (9) HYCAR, Antony; (10) IPGP, Paris; (11) G-EAU, Montpellier; (12) ISTO/OSUC, Orléans; (13) LETG, Rennes; (14) GERS-LEE, Bouguenais; (15) MINES PARIS - PSL, Fontainebleau

## 1. THE OZCAR RI NETWORK

### The critical zone:

* The thin layer of the Earth's surface, from the un-weathered bedrock up to the top of the atmospheric boundary layer (Fig. 1)

* A critical interface where rocks, soil, water, air and living organisms interact using the sun's energy and the Earth's internal energy to transform their environment (Gaillardet, 2023)

* With processes acting from the second (biological processes) to the million years (geological processes)

* A Critical Zone for humanity, because it's where we live and where we draw our vital resources (water, soil, air)

* Diversity of objects of Interest (watersheds, rivers, aquifers, glaciers, peatland, land surface) and observations (water, energy, chemical elements, nutrients cycles) (Fig. 2)

<figure><img src="image_4.png" /><figcaption>Figure 1: Schematic view of the critical zone with the various sampled compartments and objects @ Joël Dion, IPGP</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Figure 2: Location of the OZCAR RI observation sites colored according to their main object of interest</figcaption></figure>

### OZCAR-RI (https://www.ozcar-ri.org/, Gaillardet et al., 2018):

* A network of 22 long-term observatories for the understanding and integrated simulation of the evolution of the Critical Zone and its various compartments (Fig. 2)

* Observatories that also address issues of societal and/or local interest (flash floods, surface water or groundwater pollution, acid rain, etc.)

* Observatories that monitor the system in real conditions, including its changes, but also conduct experiments with stakeholders to help it evolve

* More than 100 sites around the world, documenting the cycles of water, energy, chemical elements and nutrients (Fig. 2)

* Sites open to collaboration

* Keywords: water and soil resources (quantity, quality), risks (floods, droughts, avalanches)

## 2. WP1: TOWARDS A UNIQUE ACCESS TO DATA

### More than 300 measured variables (see one example in Fig. 3)

* Point time series: meteorology, hydrology, hydrogeology, glaciology, surface energy balance, sediment fluxes, geochemical elements and contaminant concentrations

* Soil cores, 2D/3D geophysical profiles, LiDAR DTM; Maps (raster or vector) characterizing the sites: land use, DTM, soil physical properties, surveys: crop rotations, fertilizers application

<figure><img src="image_6.png" /><figcaption>Figure 3: An example of monitored variables in the Kamech watershed (Tunisia, OMERE observatory)</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Figure 4: The Theia/OZCAR data portal giving access to metadata and to data very soon (https://in-situ.theia-land.fr)</figcaption></figure>

### The Theia/OZCAR Information System (IS) to make data FAIR:

* Objective: make data from OZCAR RI FAIR and build a single entry point to access data by making the best use of existing IS (Braud et al., 2020)

* Harmonization of metadata using a pivot data model and a FAIR thesaurus of variables' names (I-ADOPT framework) (Coussot et al., 2024)

* Organization of data flux between observatories IS and Theia/OZCAR IS (Figure 5) that provides services (search portal (Fig. 4), cataloguing web service, ...)

* Visualization and downloading tools to access to data in harmonized formats (in progress)

<figure><img src="image_8.png" /><figcaption>Figure 5: Principles of the Theia/OZCAR IS: 1/ Different data producers (green rectangles) with different types of databases exchange information with the central Theia/OZCAR IS (yellow rectangle). 2/ A continuous information flux is organized through the implementation of the pivot data model and using controlled vocabulary (red rectangle). 3/ Users (either humans or machines) can consume the services provided by the Theia/OZCAR IS for different purposes (blue rectangles)</figcaption></figure>

Plain line: already implemented, dotted line, in progress).

## 3. HOW IS OZCAR RI DATA USED?

### 3. Expert use (consultancy, design offices, electricity companies)

* Proposals for tools for design offices (e.g. structural dimensioning, intensity/duration/frequency curves for design offices (Fig. 8), studies for flood and low water management, drafting of regulatory texts such as a water resilience plan)

* Reanalysis of extreme events that have caused damage (local authorities, Flood monitoring service)

* Calibration of hydrological or hydro-sedimentary models (hydroelectric operators) developed at the AMMA-CATCH observatory.

<figure><img src="image_9.png" /><figcaption>Figure 6: Practical work during the OZCAR 2023 summer school on the Strengbach watershed (OHGE). @ C. Heimlich</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Figure 8: Excerpt from the web page presenting the method for estimating intensity-duration-frequency curves</figcaption></figure>

### 2. Arts and sciences / general public / journalists

* Work with artists, residencies

* Exhibitions for the general public

* Popular science books

* Participatory science (e.g. smartphone app for measuring nitrate levels, snow cover monitoring)

* Summary publications for stakeholders (Fig. 7) or journalists: increased demand on this topic

<figure><img src="image_11.png" /><figcaption>Figure 7: BHalf-yearly bulletin from the OMERE observatory summarizing the site's hydro-meteorological situation and explaining scientific findings in layman's terms.</figcaption></figure>

### 5. Co-construction of research (beyond data)

* PhD theses with industrial partners (e.g. new instrumentation)

* Co-constructed research programs (e.g. Lyon Métropole and OTHU on rainwater management in urban areas, Fig. 9; territorial foresight with Lorient agglomeration)

* Pooling of resources for data acquisition (basin managers, natural parks, municipalities)

* Facilitation of funding for stakeholders (scientific endorsement)

* Needs regarding the impact of global change and territorial transformations

* Need for mediators between scientists and stakeholders

<figure><img src="image_12.png" /><figcaption>Figure 9: Partnership agreement between OTHU and Lyon Métropole. @ OTHU</figcaption></figure>

### 4. Use by managers

* Close relationship with the owners of the plots equipped with instruments

* Direct use of data on rainfall, flow rates, temperature and water conductivity (local authorities, parks, basin managers, partners in the South)

* Knowledge of soil properties and quality (local authorities, forest managers, natural parks) and recommendations for their use (gardening)

* Access to research results via publications, but need for 'translations' to answer their questions

* Flood management (near real-time data, forecasting model): e.g. Nîmes (ESPADA, Fig. 10), Yzeron basin

* Drinking water supply for municipalities (Aubure) or larger cities (Lorient, Montpellier)

* Wetland restoration (use of research results rather than data)

* Often needs for management at the mesoscale, fed by knowledge derived from data and models, even on small-scale sites

<figure><img src="image_13.png" /><figcaption>Figure 10: Extract from the ESPADA flood forecasting system web page in Nîmes (https://www.nimes.fr/habitat/prevention-des-risques/inondations.html)</figcaption></figure>

## 5. Conclusions and perspectives

* OZCAR RI data used by regional stakeholders, but unevenly across sites

* Need to enrich observatories with new professions (scientific mediation, site manager in liaison with stakeholders)

* Need to develop certain sites to become experimental areas for regional transformation?

* What new uses will emerge when data downloads via the Theia/OZCAR IS portal and the Data Terra catalogue become operational?

### References:

Braud, I., et al., 2020. Building the information system of the French Critical Zone Observatories network: Theia/OZCAR-IS. Hydrological Sciences Journal: 1-19. DOI:10.1080/02626667.2020.1764568

Coussot, C., et al., 2024. Implementing a new Research Data Alliance recommendation, the I-ADOPT framework, for the naming of environmental variables of continental surfaces, Earth Science Informatics, 17(5), 4261-4277, DOI:10.1007/s12145-024-01373-9

Gaillardet, J.: La terre habitable: ou, l'épopée de la zone critique, La Découverte, Paris, 2023.

Gaillardet, J. et al., 2018. OZCAR: The French Network of Critical Zone Observatories. Vadose Zone Journal, 17(1). DOI:10.2136/vzj2018.04.0067

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ADVANCING CRITICAL ZONE SCIENCE

OZCAR – TERENO international conference

September 29th to October 2nd, 2025, in Paris (France)