Organisation for Economic Co-operation and Development (OECD) survey and report setting out the climate adaptation challenge for freshwater management, and providing policy guidance. Climate change is reshaping the future for freshwater, aggravating pressures and complicating planning, management, and investment in water infrastructure. This report is drawn from the results of an OECD-wide survey designed to gauge progress on climate change adaptation in the water sector. The paper presents the need for a risk-based approach to climate change adaptation in the water sector, so as to most effectively deal with the inherent uncertainties that are present. This is expanded into a "know", "target", and "manage" framework that incorporates building an evidence base with strategic policy and financing approaches. The final section concerns improving flexibility through adaptive governance, policies, and finance options. The paper makes a number of conclusions and recommended actions in its final section: The scientific evidence on the significance of climate change on freshwater is compelling and growing. Yet despite the potential threat to a string of key policy domains, reliable information on the potential impacts are generally lacking. Effective and timely adaptation that accounts for uncertainty can significantly lower the costs of climate change impacts. Adaptation must be flexible, dynamic, and account for both climate variability and changes in human systems, over both the near- and long-term. Where information is unreliable or highly uncertain, a risk-based approach can accommodate a range of possible scenarios by identifying priorities and least-cost approaches. Governments should "know", "target", and "manage" water risks, such as drought, floods, poor quality freshwater, and threats to sensitive ecosystems. It is crucial that climate change be systematically integrated into water management policies, as well as considered in a broader, multi-sectoral manner. The survey of OECD member states shows that all report observed changes to freshwater systems, and anticipate rising risks. While progress has been made to “know” the risks, more must be done to “target” and “manage” them. Information-based policies are by far the most widely used, with significant potential to scale up economic instruments, ecosystem-based approaches, and green infrastructure. Most countries have yet to explicitly address financing issues for adaptation. The annex to the report includes detailed profiles of each member state, including observed and projected climate change impacts, key policy documents and instruments, main research programmes and financing mechanisms, and innovative initiatives.