Recognising Australia's need for water management that better supports urban populations facing increasing socio-ecological challenges, the study on which this article is based brought together professionals from Sydney's water sector to understand what they believe is entailed in transitioning Sydney to a water sensitive city. Participants called for new institutional arrangements requiring collaboration and leadership from various levels of government, community groups and individual community members. We adopt Tainter's model of social complexification as an analytical framework for considering the implications of the research findings. From the perspective of this model, we argue that the proposed arrangements would involve, along with the envisioned benefits, increasing complexity and commensurate costs, with important consequences for the forms that water sensitive cities might take. Considerations relating to the costs of complexity take on particular importance in futures for which reduced material affluence appears increasingly possible. The costs of complexity under such conditions may be more readily ameliorated via pathways that entail increased local responsibility for meeting water needs, such as decentralised rainwater harvesting. We argue that increased participation in water-related governance and responsibility for related infrastructure will follow more readily from measures to foster local enthusiasm than from mandated approaches that themselves require increased complexity. (C) 2014 Elsevier Ltd. All rights reserved.