Emergent Properties of Water Resources and Associated Watershed Systems Abstract: A challenge to managing water resources is characterizing the heterogeneity created by the interactions among hydrological, ecological and anthropological processes. An option applied to other scientific disciplines includes identifying and analyzing emergent phenomena in complex systems, whose components self-organize into novel structures or processes via their collective interactions with each other and the environment. A new level of organization and complexity emerges that cannot be predicted from or attributed to the components alone. Predictions based on the functionally emergent properties of watershed systems (top-down) differ from predictions based on reductionist models (bottom-up). This presentation reviews the ways in which emergent properties may be applied to water resources and associated systems.