Image Added Collaborative modeling promotes the fruitful engagement and participation of decision makers and stakeholders in the analysis and assessment of policy options. Water resources systems are complex and encompass a variety of competing technical, ecological, economic, and social dimensions. Often experts and stakeholders do not fully understand or cannot agree upon the reasons why water-related challenges occur, let alone upon the actions that should be taken to adapt to or mitigate their impacts. Ownership and acceptance of strategic plans by national and local authorities are critical preconditions for ensuring sustainable development objectives are met. Deltares’ collaborative modelling approaches offer an effective means to address and resolve these knowledge- and values-based conflicts between experts, water users, stakeholders and decision makers. They consist of interactive and iterative processes for decision support that combine stakeholder engagement with analytical modelling, visualisation and communication tools.