The fulfilment of basic human needs, our environment, socio-economic development and poverty reduction are all heavily dependent on water. Good management of water is especially challenging due to some of its unique characteristics: it is unevenly distributed in time and space, the hydrological cycle is highly complex and perturbations have multiple effects. Rapid urbanization, pollution and climate change threaten the resource while demands for water are increasing in order to satisfy the needs of a growing world population, now at over seven billion people, for food production, energy, industrial and domestic uses. Water is a shared resource and its management needs to take into account a wide variety of conflicting interests. This provides opportunities for cooperation among users.