Since the UN water conference at Mar del Plata in 1977, there have been international debates about how water governance could and should respond to the challenges of sustainable development. New global institutions were established to promote universal norms of governance based on the 1992 'Dublin Principles' and its version of 'Integrated Water Resource Management' (IWRM). Many of these prescriptions were contested, not least because of their advocacy of marketbased approaches to address what were posed as challenges of scarcity and environmental sustainability. The paper examines the drivers that have informed different conceptualisations of water governance. It shows how 'scarcity' has become central to narratives that sought to focus governance at the river basin scale, to restrict water use in favour of the protection and restoration of water resource ecosystems and to prioritize economic efficiency through market mechanisms. It then reviews the experience of a diverse set of countries, some of which have implemented systemic governance reforms and others whose trajectories have been more evolutionary, driven by domestic contexts. These practical experiences, supported by a growing understanding of polycentric approaches and how networks cross and link a range of geographic and administrative scales, have given rise to alternatives to the normative IWRM, river basin-focused approaches to water governance. Despite continuing concerns about 'planetary environmental boundaries' and transboundary security, these are proving to be weak motivations for adoption of formal global systems of water governance. Instead, new narratives emphasise locally-diverse approaches that see water governed within "problem-sheds" rather than "water-sheds". Water governance remains a scene of contestation between local and 'global' criteria and developmental and environmental goals. But, in the face of challenges of complexity and diversity and the emerging understanding of network governance, emerging practitioner-oriented guidance is focusing on general principles and explicitly avoiding normative approaches. 1. Introduction Water and its governance has attracted increased attention as a policy concern in recent years. The United Nations has determined that water is a human right (United Nations 2010). The global business community, through the World Economic Forum's Annual Global Risks Report has repeatedly identified water crises 1 as one of its top global risks (WEF, 2016) A broad goal for governments and business is to achieve "water security" usefully defined as "the reliable availability of an acceptable quantity and quality of water for health, livelihoods, ecosystems and production, coupled with an acceptable level of water-related risks to people, environments and economies" (Grey & Sadoff, 2007, p547-8). This definition includes the risks of flood and drought posed by water as well as the maintenance of important ecosystems and recognises that communities may have different "acceptable" levels of risk and protection. Co...