[Departement_IRSTEA]Territoires [TR1_IRSTEA]DTAMIn the field of water, in France, envisionning future has long been the exclusive duty of state strategists and water managers. Yet since 2006, the French law for local and participatory water planning has hold that “trends and scenarios” should be collectively built and made explicit before choosing a strategy. This article draws lessons learned from a vision building exercice implemented in 2010 in the Thau basin (Hérault, France). The authors assisted the process and facilitated some workshops. The article discusses what made the experience possible and successful. It argues that a specific framing fostered individual and collective exploration. It consisted in welcoming...