Water scarcity is an increasing problem in many parts of the world, yet conventional supply-side economics and management are insufficient to deal with it. One of the key water management options for water demand is water trading. Water trading can contribute to water reallocation and in this way improve efficiency of water use and decouple economic growth and the use of water resources, thus contributing also to improve environmental river flows. This book explores the role of water trading, as an instrument of integrated water resources management.