Many rivers worldwide have been progressively engineered for agriculture, energy, transportation, flood control and navigation. Dams, in particular, have played a major role in controlling and harnessing large volumes of water to support these anthropogenic uses. While dams have undoubtedly contributed to human development, this has often come at a heavy price to downstream communities and the natural environment. The provision of environmental flows (e-flows), freshwater flows for the environment, is a means to restore or protect the benefits of naturally flowing rivers. Since the 1940s, e-flows science has grown, however, actual implementation remains relatively limited. This research investigated how dams are re-operated for the implementation of e-flows. It began with a systematic literature review and survey of practical cases of dam re-operation followed by a case study of the Lower Volta River, Ghana. The research has generated knowledge on the process of dam re-operation for e-flows, the enabling factors for success and hurdles which typically stall the process, as well as inter-sectoral trade-offs inherent in delivering environmental flows in a unique case study. These insights inform attempts to scale up efforts in e-flows implementation towards the sustainable operation of dams for people and the environment.