Description:    Globally, urban growth will add 1.5 billion people to cities by 2030, making the difficult task of urban water provisions even more challenging. In this article, we develop a conceptual framework of urban water provision as composed of three axes: water availability, water quality, and water delivery. For each axis, we calculate quantitative proxy measures for all cities with more than 50,000 residents, and then briefly discuss the strategies cities are using in response if they are deficient on one of the axes. We show that 523 million people are in cities where water availability may be an issue, 890 million people are in cities where water quality may be an issue, and 1.3 billion people are in cities where water delivery may be an issue. Tapping into groundwater is a widespread response, regardless of the management challenge, with many cities unsustainably using this resource. The strategies used by cities deficient on the water delivery axis are different than for cities deficient on the water quantity or water quality axis, as lack of financial resources pushes cities toward a different and potentially less effective set of strategies. Content Type Journal Article Pages 1-10 DOI 10.1007/s13280-011-0152-6 Authors Robert I. McDonald, Worldwide Office, The Nature Conservancy, 4245 N. Fairfax Drive, Arlington, VA 22203, USA Ian Douglas, School of Environment and Development, University of Manchester, Oxford Road, Manchester, M13 9PL UK Carmen Revenga, Worldwide Office, The Nature Conservancy, 4245 N. Fairfax Drive, Arlington, VA 22203, USA Rebecca Hale, School of Life Sciences, Arizona State University, 1711 South Rural Road, Tempe, AZ 85287, USA Nancy Grimm, Faculty of Ecology, Evolution, & Environmental Science, Arizona State University, 1711 South Rural Road, Tempe, AZ 85287, USA Jenny Grönwall, 110 Marlyn Lodge, Portsoken St, London, E1 8RB UK Balazs Fekete, CUNY Research Foundation, The City College of New York, 160 Convent Avenue, New York, NY 10031, USA Journal AMBIO: A Journal of the Human Environment Online ISSN 1654-7209 Print ISSN 0044-7447