For the purposes of this paper, water resources management is defined in its broadest terms and deemed to encompass all water-related aspects of river-basin management from long-term planning through to real-time operational control. Bearing in mind the increasing pressure on finite resources, an integrated, multifunctional approach is advocated in which different analytical procedures are used at various stages of decision making. These include mathematical programming, large-scale simulation and optimal control theory. By way of example, the application of these techniques to water resources in the United Kingdom is briefly described.