Now in an extensively updated fourth edition, this essential text offers a comprehensive survey of all aspects of water resources planning and management. Utilizing an integrated water resources management (IWRM) framework, the authors show how this approach can clarify and help resolve resource management problems in ways that take into account complicated and interconnected social, economic, and environmental needs. Spanning the full planning process, the book considers legal and administrative issues; economic and forecasting factors; water quality, quantity, supply, use and demand; and model applications. The authors' goal throughout is to provide a practical foundation for improving ecological and human environmental systems for practitioners and students alike.