This research develops a multistage stochastic linear programming (LP) model to assist in the process of water system planning and management under demographic and climate change in Amman, Jordan, over the next 75 years. Climate change is projected to have a gradual exacerbating effect on Amman's water stress over the next century, and water resources management strategies and policies put in place now will likely influence water use patterns for generations to come. A multistage decision model allows the identification of both adaptation strategies that should be implemented now and actions likely to be needed later, depending on future climate and demographic conditions. For Amman, the model recommends that household water reuse be expanded immediately, large-scale wastewater reclamation begin within 25 years, and mega-scale water import projects be postponed for several decades. Although these recommendations for the future will almost certainly change as additional information is acquired, by identifying now the actions most likely to be needed in the future, options for their implementation can be reserved, and feasibility studies begun.