The current human use of global natural resources exceeds the long-term sustainable capacity of the planet. New and more sustainable ways of building cities and providing urban water services are needed. The Australian city of Sydney is expected to grow by more than 1 million people over the next 30 years. Water use from the Hawkesbury-Nepean River system already exceeds system capacity. Current proposals to allocate a greater proportion of low flows to meet environmental flow needs will limit urban water allocations and require the development of more efficient water and sewerage systems for new and existing urban development. This paper presents a hypothetical case study of how water supply and sewerage services might be provided for an additional 1 million people over a 25-year period. It compares traditional service provision with alternative scenarios incorporating water conservation measures, rainwater harvesting and water reuse. The paper presents both economic and environmental comparisons. The economic comparisons include valuations of environmental externalities in the form of environmental levies. It shows that the extra capital costs of water conservation, alternative water sources and water reuse scenarios are offset by operating savings and environmental benefits. Ecological footprints are reduced because of lower water diversions, discharges, energy use and CO2 emissions. The paper also discusses the implication of alternative infrastructure ownership and water pricing arrangements, and the opportunities to create incentives for additional investment in water conservation and reuse projects.