With increasing water scarcity, pressure to re-allocate water from agriculture to other uses mounts, along with a need to put in place institutional arrangements to promote "higher value" uses of water. Many developing countries are now experimenting with establishing new institutional arrangements for managing water at the river basin level. This book, based on research by IWMI and others, reviews basin management in six developed and developing countries. It describes and applies a functional theory of river basin management, based on the idea that there is a minimum set of functions required to manage basins effectively and a set of basic conditions that enable effective management institutions to emerge. The book examines the experiences of both developed and developing countries in order to see what lessons can be learned and to identify what constitutes the core of a "theory of river basin management". It concludes that although it is difficult for developing countries to adopt approaches and institutional designs directly from developed countries, basic principles and lessons are transferable.