Big river basins are complex systems of people and nature. This article explores the resilience of nine case studies of big river basins. A system description and generic conceptual model suggests that resilience to changes in water quantity is critical. When water becomes limiting, the social-ecological system must adapt rapidly if key elements (for example, communities, biodiversity) are to be maintained. Water limitation imposes a water economy and alters political and institutional links between actors. Pro-active management for resilience demands politically acceptable participatory processes that use the best possible science and incorporate social, ecological and economic elements in problem definition and solution.