Abstract
Imposing an environmentally well defined territorial framework (wetland, catchment, groundwater), the environmental legislation gives a real power to the manager in charge to locally implement the program of conservation, protection or improvement. On the contrary, the participative approaches make him depending on local decision-makers with scattered willingness to reach the environmental objectives. So, for the manager, obtaining a “good decision” implies an accurate view on the local challenges. Some tool can help him to reveal these challenges. We propose such an instrument to simulate how impact on the collective decision (agreement), various negotiation structures including the possibility to deal with alliances among the parties.