This book provides a solid foundation for a comprehensive, systemic and water-centric approach to water management. Said approach integrates two performance principles essential for sustainable water use systems, namely equity and efficiency. Further, it decreases the policy space for decision-making encountered by water managers and makes it easier to arrive at reasonable solutions because of the bounded rationality inherent in its development. By combining the distributive and aggregative principles, the approach offers a transparent and autonomous structure for gathering water data and enabling stakeholder involvement. Lastly, it employs and promotes a unifying language for all types of water use systems, e.g. urban, agricultural and industrial.