Towards a FAIR Water Data Ecosystem: The OneWater FAIR Water Data Platform

The French national research and innovation program OneWater – Eau Bien Commun (2022–2032) addresses key scientific and societal challenges related to the protection and sustainable management of water as a common good. The program brings together a large number of interdisciplinary projects producing highly heterogeneous datasets, including in-situ sensor measurements, Earth Observation products, model outputs, samples, and social/citizen science data. These datasets are complemented by long-term observations from research infrastructures, environmental observatories, and national public monitoring services. However, a significant part of these data is not yet compliant with the FAIR principles (Findable, Accessible, Interoperable, Reusable), limiting their reuse and cross-disciplinary exploitation.To address these challenges, the OneWater FAIR Water Data Platform, maintained by the DATA TERRA research infrastructure through its thematic Datahub on Continental Surfaces THEIA, aims to go beyond a traditional data catalogue by fostering a FAIR Water Data ecosystem based on international standards and semantic interoperability. The platform promotes the production of FAIR-compliant data by design, enabling efficient data sharing, integration, and reuse across scientific and operational communities.On top of research data, the OneWater Data Platform also interfaces with national public policy data services and associated monitoring networks. At the international level, the initiative contributes to and benefits from the global FAIR Water community through collaborations with the OGC Hydrology Domain Working Group, WMO, UNEP, UNESCO-IGRAC, eLTER, TERENO, and the Water4All partnership, ensuring alignment with international best practices.This contribution presents the OneWater FAIR approach, including: (i) the definition of a framework to achieve high FAIRness levels for water data by interpreting the FAIR principles in the context of existing standards and best practices (OGC, W3C, INSPIRE, RDA); (ii) the development of FAIR Implementation Profiles and FAIRness analysis templates applied to datasets from the French water community (research, public monitoring) including THEIA/OZCAR; and (iii) the design of a FAIR Data Platform architecture relying on state-of-the-art interoperability standards, open-source solutions, and recent FAIR Open Science prototyping initiatives; and (iv) the active support to help water observatories climb up the stairway to FAIR”.