Résumé
In the environmental field, water management provides examples of the move towards participative democracy. Indeed, French water policy promotes participative river basin management devices. Such devices allow confrontation of several forms of knowledge and raise the issue of composing these different forms within decision making process. How to compose scientific, lay and diverse cultural forms of knowledge? "Hybrid fora" (Callon, Lascoumes and Barthes 2001) are political devices which tackle this issue using the principle of symmetry. Following this pragmatic stance, this communication paper studies how "participants" compose different forms of knowledge, specifically focussing on plural cognitive formats; from the most familiar ones to the public ones. How do people cope with their attachments to the environment while participating in "governance" practices? How do they cope with the necessity of making people and things equivalent and general? This paper focuses on these tensions relying on Thévenot`s framework of "regime of engagement" (Thévenot 2000). This author analyses people's shifts between different "pragmatic regimes of engagement" ("familiarity", "regular planned action" and "justification") and moral treatments of their attachments to the world. He pays attention to the familiar engagement which is wrecked by the publicisation processes. The Lentilla and the Llech are two Mediterranean rivers in the south of France where the predominancy of agricultural water uses is questionned by environmental issues and the development of recreational water uses. Sharing water is at stake. The existing political modalities of management are of community type and lean on interpersonal arrangements. Based on strong social links, they have proved efficient. But today they reach some limits as they are required to integrate new people affected with certain water issues. As a consequence, some of these people (neo-rurals and the French water agency) ask for public debates and the development of formal devices (management plans, rules and regulations, contracts, standards~) in order to guarantee the integration of their good (including stakes and moral principles). This paper focuses on participants` "engagement" and the composition of knowledge forms in the Lentilla and Llech participative water management devices. Interviews, observations of meetings, as well as an experimental game, are used. This game aims to make people shift between pragmatic regimes; from familiar engagement to public formats; and between water management logics in order to elaborate "compromises" (Boltanski and Thévenot 1991). The game is assumed to be suitable for simulating the composition of heterogeneous pieces of knowledge and for supporting participative management. The paper presents the case study, the game, its theoretical background and the first results of its experimentation.