The world 's governments agreed at the Millennium Summit to halve the number of people who lack access to safe water, mainly in the world 's cities, by 2015. With rapidly growing urban populations the challenge is immense.This is a comprehensive and authoritative assessment of the problems and how they can be addressed. It sets out in detail the scale of inadequate provision of water and sanitation, it describes the impacts on health and economic performance, showing the potential gains of remedial action, it analyzes the proximate and underlying causes of poor provision and identifies information gaps affecting resource allocation, it outlines the consequences of further deterioration, and it explains how resources and institutional capacities -- public, private, and community -- can be used to deliver proper services through integrated water resource management.