This paper reports on an experiment undertaken in the Office du Niger irrigation scheme (100,000 ha) in Mali, where the unprecedented development of irrigation driven by large scale investors is dramatically increasing uncertainty surrounding future water management. Coping with future uncertainty in irrigated systems is essential but existing approaches based on scenarios and decision support systems are mainly expert-driven, making them difficult for local users to understand and use on their own. The aim of this study was to design a participatory approach to help local and national stakeholders understand the possible future consequences for water management of scenarios they had built themselves in previous workshops. A role playing game called FOWIS (Future of water in irrigated systems) was designed for this purpose. Two groups (decision makers and local actors) took part and played the roles of family farmers, large scale investors, or the manager of the irrigation scheme. Playing FOWIS increased the players' awareness of each others' strategies and of land development issues, crop choices, and water management. In the local actors' group, applying land development strategies and choosing crops while failing to account for the inevitable increase in water demand led to serious water crises: total demand exceeded water availability by 75%, and the indicator of adequacy dropped to 0.5 for many players. In the decision makers' group, applying a collective strategy to limit water demand, as stipulated in their best case scenario, resulted in an equitable water supply. In this paper, we show how the game enabled participants to understand the interdependencies between future land development, crop choices, and water management, and, in addition, helped them design innovative strategies to limit water demand or to allocate water fairly. Indirectly, it also led them to question their current practices, choices and strategies that would have been impossible in the current context of open tensions concerning land and water allocation. The FOWIS experiment also provided useful information for the further development of non-computer-assisted role playing games in highly uncertain contexts, which is the case of most irrigated systems in developing countries. RPGs that take place in a virtual world could increase stakeholders' capacities to take action with respect to real world issues. (Résumé d'auteur)