The provision of a safe and reliable water supply is a major challenge for the world's growing urban populations. This book investigates the implications of different developments in water technology and infrastructure for urban sustainability and the relationship between cities and nature. The book begins by outlining a framework for analysing water technologies and systems, based on theories from critical urban geography, environmental philosophy and the philosophy of technology. It then analyses in detail what the sustainability implications are of different technical developments in water systems, specifically: water efficiency, water reuse, desalination, water sensitive urban design and ecological sanitation. The main purpose of the book is to draw out the social, political and ethical implications of technical changes that are occurring in urban water systems around the world, with positive and negative impacts on sustainability.