Water resources professionals have an obligation to conceive and manage water resource systems such that they will fully contribute to an improved quality of life for all humans, now and into the future. Those water resource systems that will be able to satisfy the changing demands that will inevitably be placed on them, without significant system degradation, can be called 'sustainable'. An international group of experts have reviewed various guidelines for achieving greater degrees of sustainability and the extent to which they have been applied in a number of case studies. Approaches for measuring and modelling sustainability are provided. Ways in which these measures and models might be used when evaluating alternative designs and operating policies are illustrated. The monograph will be particularly valuable for practising engineers and planners, and as a supplementary text for graduate students in civil and environmental engineering, hydrology, geography and economics.