Cities and other local authorities have a critical stake in the adaptation of water management to a changing climate. Virtually all the world's future population growth is predicted to take place in cities and their urban landscapes. The UN estimates a global increase from the 2.9 billion urban residents in the 1990s to a staggering 5.0 billion by 2030. By 2030, 1 in 4 persons will live in a city of 500,000 people, and 1 in 10 will live in a mega-city of 10 million or more. How will climate change and variability affect water services and water safety for these many millions? What actions should local governments take to adapt water management for climate change?