Résumé
At the end of Apartheid, South Africa has been pioneering the recognition of a right to water. This right is now enshrined in the democratic Constitution of the country (1996). South Africa is also perceived as a world leader with one of the most ambitious water Act, granting " water for the environment " (or an " ecological reserve ") alongside a human reserve (minimum water for daily human needs). This kind of environmental flow requirement has been experimented elsewhere too, in France amongst other countries. Yet, comparing environmental flows across countries can prove tricky as environmental flow indicators describe a reality that can differ greatly depending on the socio-historical context. In this paper, we put into perspective, in both countries, the implementation of environmental flows undertaken by water agencies in France and by their equivalent in South Africa, catchment management agencies. Despite enjoying different prerogatives, both organisations share the task of performing functions at the periphery of State regulatory action, which implies most often than not to master a more accommodating governing style. Indeed, in South Africa, if environmental flow requirements were initially determined by hydro-ecology experts commissioned by the department of Water Affairs, soon they were re-conceptualised by water managers who had to operationalise environmental flows when dealing with water allocation demands by different users. Environmental flows thus shifted from a hydro-ecology science towards more socio-hydrology knowledge taking into consideration various economic uses and mitigating ecological requirements with socio-economic goals for each river. It eventually led to a more adaptive management approach applied to environmental flows. In France, and more specifically in the southwest, designing and implementing minimum flows indicators can be understood as a dynamic process of co-production between specific knowledge about -and representation of- rivers on the one hand, and water sharing mechanisms between users on the other hand. Such indicators and the regulatory science that inform them, are instruments deployed by the Adour-Garonne Water Agency for the last 50 years. Their goal is to negotiate water flows that have been significantly framed, temporally and spatially, by electricity producers and by irrigators. These indicators are quite regularly contested within diverse local arenas. This, however, never leads to broadening the debate on the logics and legitimacy of the productive activities such indicators support. It has also often contributed to disarm environmental concerns. Such paradox can be explained because, in both countries, environmental flows not only produce knowledge about rivers but simultaneously they tend to sanction specific allocations of water amongst users-–although in a more concealed and discreet way-. Eventually we reflect on how environmental flow indicators rests on a type of knowledge allowing more space for trade-offs and negotiations among water users.