For over three decades the methods of systems analysis have been applied to solving problems involved in managing the water environment. The fundamental principles of the subject remain relevant, and the techniques-e.g. optimisation, mathematical modelling, simulation, etc-are more highly developed than ever, yet the context in which systems analysis seems to be changing rapidly and radically. The 42 papers selected for these proceedings set out the latest developments in the various techniques of systems analysis and also show the direct links from the abstract and mathematical to the practical and applicable. The following themes are included: the identification and characterization of systems; analysis of series-time data and the impact of uncertainty; simulation methods; planning and optimization, operations and control; and methods for understanding and dealing with transient pollution events. The papers may each have case-specific aspects, but they also highlight matters of methodology that are common to all, with a distinctly interdisciplinary character. These proceedings take stock of the current research in systems analysis, review the strategic achievements in applications to water quality management, and provide a platform for charting new directions for research in the future.