Agriculture practices are increasingly disconnected from their lo cal non-agricultural socio- environmental context. As a consequence, agriculture is considered to day as having major impacts on water quality in river basins and coastal areas. Tensions emerge between agricultural sector and some civic organizations. Transition from this situation to a better integration of agricultural practices in their environment is sought by many stakeholders and policy makers, from water, land development and also agriculture sectors. Efforts for increasing water quality while maintaining a sustainable agriculture may be expensive. With the on-going research project Exp'Eau (LTSER-FR Réseau des Zones Ateliers), our purpose is (1) to raise awareness on the opportunities to handle agricultural sources of water pollution collectively, and (2) to compare them in various watersheds. Our main hypothesis is that collective pathways thought at the territorial level may bring as many b enets as a farm level fo cus, and are less divisive. To that end, we are developing a serious game featuring activities and relations between farmers, municipalities and river basin organization on a virtual river basin to be generated from actual datasets for topography, soil properties, and climate. For comparison sake, the game is generic as it features a framed number of entities and possibilities of action, and the process of transforming actual datasets is standardized. Within any LTSER site, we consider a representative small basin (ca. 100 km2) that we discretize into three sub-basins, each of them representing a municipality as the first level for collaboration. Each subbasin counts about 30 hexagons elementary tiles with a single land use for each, under control of players. To facilitate the gaming phase, we develop a hybrid game comprising a physical board and playing action cards, as well as a twin on-line game. During the game, the players access to the information on their environment and carry out cultural practices thanks to a smartphone. A local server computes the impacts of these actions in terms of production, collective well-being and contamination, and up dates the players' data. Players can discuss, negotiate and experiment solutions collectively. During the game session, they can see the virtual watershed, the land use and the infrastructures on the physical board. According to their role, they receive information on their production, on territorial well-being and water quality and quantity at the outlets of subbasin, or water quality and quantity at the outlet of the whole basin. Each game session is followed by a debriefing on the spot that could produce (1) a lo cal understanding on the interactions between agriculture and water quality and their potential evolutions, and (2) socio-ecosystem data to feed a cross LTSER analysis of these interactions. This poster presents the specification process, the game structure and elements, the connection between players in the hybrid setting and the results of initial tests realized for the Moderbach watershed (Région Grand-Est, France). Other watersheds will be considered in a next future.