Urbanization, land subsidence and sea level rise will increase vulnerability to droughts in the urbanized low-lying areas in the western part of the Netherlands. In this paper a possibility is explored to decrease vulnerability of urban areas by implementing an alternative water supply option. A four component vulnerability framework is presented that includes threshold capacity, coping capacity, recovery capacity and adaptive capacity. By using the vulnerability framework it is elaborated that current water supply strategies in the Netherlands mainly focus on increasing threshold capacity by constructing improved water storage and delivery infrastructure. A complete vulnerability decreasing strategy requires measures that include all four components. Adaptive capacity can be developed by starting experiments with new modes of water supply. A concept which is symbolically called 'the closed city' uses local urban rainfall as the only source of water supply. The 'closed city' can decrease the water dependence of urban areas on (1) the surrounding rural areas that are diminishing in size and that are increasingly under strain and (2) river water resources that will probably be less constant and reliable as a result of climate change.