Climate change, population growth and migration, increasing urbanization and ageing infrastructure are all expected to impose significant strains on urban water cycle systems (UWCS) in Europe and elsewhere over the coming decades. Cities across the continent will experience increasingly frequent shortfalls in the supply and demand balance, particularly during the summer months. More intense rainfall events will lead to local flooding of properties and transport systems and to pollution of receiving waters. Sustainable solutions to these challenges need to be sensitive to long-term investment needs, but also to increasing energy prices, demands for low carbon intensity solutions, and the need to reducegas emissions from urban activities.