OZCAR, the French Critical Zone Research Infrastructure (RI) gathers observatories sampling various compartments of the Critical Zone. Given their long history, most of them have developed their own data/metadata portals. There is however a need to gather all the data in a common Information System (Theia-OZCAR IS) to make the data visible, findable and easy to explore; allow their preservation and their citation; favor their reuse and sharing; be interoperable with European infrastructures; respect the international standards. The project team visited the 22 observatories and 6 data centers to compile their needs. The consultation pointed out heterogeneous levels of data management maturity, variable names nomenclature and data exposition; and that finding data by variables is the point of interest of future users. The starting postulate is that databases stay next to data producers, which ensures the best data quality. A continuous information flow between observatories and the Theia-OZCAR IS will keep information up to date. Suppliers push data and metadata to the Theia-OZCAR IS using an extraction script maintained locally. To build the system, the following tasks were undertaken: 1. Work on variables names and categories that will serve as data search criteria • List all the variables measured by the observatories and match them with the GCMD Earth Science hierarchical vocabulary. About 300 in-situ measured variables of which half are chemical measurements were listed. • Identify the relevant published thesauri for the field (AGROVOC, EARTh Thesaurus, GACS Core Beta 3.1, NAL Thesaurus, UNESCO Thesaurus, ANAEE, EnvThes) to promote semantic interoperability, • Build a controlled vocabulary based on the GCMD hierarchical vocabulary and linked to the previous thesaurus concepts via SKOS semantic relations; 2. Work on metadata needed to set up interoperability and citation services • Identify the metadata proposed by different standards (ISO 19115 / Inspire, DataCite, DCAT, schema.org, SensorML, O&M, DOI) in order to establish a minimum set of metadata to be exchanged with the data providers; 3. Work on data flux between system • Define a pivot format that can convey all the metadata identified and adapted to the uses; The pivot format is currently discussed with data bases managers and will be progressively implemented in order to get a first prototype of the data portal by the end of 2018. The communication will present the approach that can be reused by other disciplines/data portals.