Today, three sets of challenges - water-related risks, ageing infrastructures and trends in institutional reforms - are calling this model into question. The chapter review's these challenges sequentially and outlines a framework for organising policy responses. It proposes criteria cities can use to compare their water management policies and practices w'ith those of other cities. Similarly, the OECD (2013b) defines water security as the management of four water risks: scarcity, floods, pollution and freshwater ecosystem resilience.