Addressing modern water management challenges requires the integration of physical, environmental and socio-economic aspects, including diverse stakeholders’ values, interests and goals. Early stakeholder involvement increases the likelihood of acceptance and legitimacy of potential solutions to these challenges. Participatory modelling allows stakeholders to co-design solutions, thus facilitating knowledge co-construction/social learning. In this work, we combine integrated modelling and participatory modelling to develop and deploy a digital platform supporting decisionmaking for water management in a semiarid basin under contentious water use. The purpose of this tool is exploring “on-the-fly” alternative water management strategies and potential policy pathways with stakeholders. We first co-designed specific water management strategies/impact indicators and collected local knowledge about farmers’ behaviour regarding groundwater regulation. Second, we coupled a node–link water balance model, a groundwater model and an agent-based model in a digital platform (SimCopiapo) for scenario exploration. This was done with constant input from key stakeholders through a participatory process. Our results suggest that reductions of groundwater demand (40%) alone are not sufficient to capture stakeholders’ interests and steer the system towards sustainable water use, and thus a portfolio of management strategies including exchanges of water rights, improvements to hydraulic infrastructure and robust enforcement policies is required. The establishment of an efficient enforcement policy to monitor compliance on caps imposed on groundwater use and sanction those breaching this regulation is required to trigger the minimum momentum for policy acceptance. Finally, the participatory modelling process led to the definition of a diverse collection of strategies/impact indicators, which are reflections of the stakeholders’ interests. This indicates that not only the final product—i.e., SimCopiapo—is of value but also the process leading to its creation.