Since 2020, a methodology has been developed at the interface of existing approaches, allowing implementing on a local scale a modeling approach aimed at providing a forward-looking aid to decision-making processes concerning water resource management. The methodology tested was (1) interdisciplinary, involving researchers from both the natural and social sciences; (2) participatory, involving a diversity of local stakeholders (users, managers and elected representatives); and (3) anticipatory, using modeling tools and scenarios to confront these stakeholders with the possible future hydroclimatic situation (2070 horizon). The aim of this article is to provide an overview of (1) this approach ‒ called “Water and Territory” ‒ as well as (2) a tool ‒ called “Trajectory Water and Territory” ‒ elaborated in order to support the implementation of the participative dimension and around which the transferability of this approach is organized. The "Water and Territory" approach was tested in Brittany, in the territory of “Lorient Agglomération” and the Scorff and Blavet watersheds. The approach comprises two types of participatory workshops and a modeling phase. A first workshop aims at (1) co-constructing a representation of the hydrosystem and share knowledge about water and global change locally; and (2) identifying solutions potentially suited to the territory. This step is carried out using “Trajectory Water and Territory” ‒ which was partly inspired from existing tools (e.g. Climate Fresk, Wat-a-Game) ‒ in order to provide participants with all the information (from scientific literature and local data) needed to understand the hydrological functioning of their territory. Then, the aim is to integrate a forward-looking dimension through a numerical modeling approach - combining surface water and groundwater with climate constraints and other future anthropogenic pressures (water withdrawals, changes in land cover and land use). Finally, a second participatory workshop aims at presenting modeling results, so that participants can identify desirable scenarios and reach agreements on water-sharing rules.