One of the great challenges of developing sustainable water management is to integrate water and land use issues, and to favor stakeholders’ involvement in the process of designing a solution to the specific issues of water basins. This study aims to help reach these objectives: we present the outcomes of a methodology that aims to design, with stakeholders of a watershed facing quantitative water manage- ment issues, alternative agricultural landscapes that they each consider as potential solutions. Our design approach combines (1) facilitation of participatory workshops for designing changes in cropping systems and their spatial distributions at the landscape level with (2) formalization of these alternatives in a GIS. The formalized alternatives provide precise information about fields, farms and areas concerned by the designed changes. We present two sample results of this methodology implemented in a 840 km2 irri- gated landscape located in a water-deficient watershed in southwestern France. We discuss how our design approach may be useful for a wider design-and-assessment methodology involving researchers and stakeholders with conflicting interests. We show that our co-design approach provides fertile ground for the emergence of salient, credible and legitimate change options.