The historical roots of environmental engineering and water-quality management are traced to mid-19th century London when engineers and public health workers worked to control and manage the major water-quality problems derived from urbanization. This is followed by a brief review of the field’s subsequent century-plus evolution. The talk then turns to the current state of the art and a delineation of key research issues and frontiers. These include the modelling of “black water”, scum formation, the nepheloid layer, floatables (plastics & weeds), macrophytes, zooplankton, and uncertainty analysis of large model frameworks. Beyond specific research needs, global warming and mega-urbanization mean that, in the future, water-quality management must be expanded beyond the traditional reduction of pollutant inputs with novel approaches essential to maintain acceptable water quality in a sustainable fashion. Several case studies are used to illustrate possible approaches including dissolved oxygen bubblers, pure oxygen injection, lake hypolimnetic electron acceptor injection, boom deployment to capture floatables, flushing flows for oxygen and pathogen control, and deep lake siphons. Many of these schemes will be facilitated by coupling improved observational technology such as drones, robots, and sensors with water quantity and quality models. Real time, model-based distributed control could allow the development of “smart waters” where in situ interventions could be implemented in a sustainable fashion.