International audienceThe purpose of the 1992 French Water Act is to encourage negotiation and dialogue among local stakeholderswithin a framework which is very similar to a patrimonial approach. Potential use of models in such post-normalapproaches is analyzed. Two kinds of models are compared: one is agent-based, the other follows a more classicalapproach. They are compared according to their contributions as negotiation support tools. This comparisonis based on a specific collective decision process dealing with water allocation at the sub-basin scale, in whichauthors are involved. Both are used to support collective decision processes through simulation of resource usedynamics. Agent-Based Models entail the broadening of spatial information of actors in the process, revealinginter-connected topics not taken into consideration earlier. This makes it possible to remain relevant, despite thesometimes rapidly evolving stakes. The central point of this paper is the implementation, within a practical application,of theories advocating the use of ABM as a collective decision support system. This application promotesa better understanding of the kind of support ABM provides and the way it does so. This is broughtabout more by re-framing the discussion and modifying the representation of the system on the part of thestakeholders than by providing specific agreements