The World Water Development Report is part of an ongoing assessment project to measure progress towards achieving the goal of sustainable development formulated at Rio in 1992, and the targets set down in the UN Millennium Declaration of 2000. The international community pledged: to halve by 2015 the proportion of people who are unable to reach, or to afford, safe drinking water, and to stop the unsustainable exploitation of water resources, by developing water management strategies at the regional, national and local levels, which promote both equitable access and adequate supplies. This report is targeted at all those involved in the formulation and implementation of water-related policies and investment strategies, as well as to professionals at all levels. Although it offers a broad global picture, it focuses particularly on the situation in developing countries, where the need for better infrastructure and governance is highest. With this report, WWAP is aiming to show where systems are failing, and to provide the information needed for efficient and effective capacity-building throughout the world. The report encompasses a broad range of components, focusing on human stewardship of freshwater, that complex aggregation of policies, legislation, social programmes, economic approaches and management strategies through which we seek to achieve water sustainability. The report opens with a chapter describing the water crisis. It then: reviews progress and trends; proposes methodologies and indicators for measuring sustainability; assesses progress in 11 challenge areas, including: health, food, environment, shared water resources, cities, industry, energy, risk management, knowledge, valuing water and governance; and presents seven pilot case studies of river basins representing various social, economic and environmental settings. Each chapter ends with a comprehensive list of related references, as well as useful web sites.