Tapped out: how can cities secure their water future?
Brian D. Richtera, David Abellb, Emily Bachab, Kate Braumanc, Stavros Calosd, Alex Cohne, Carlos Dislad, Sarah Friedlander O'Briend, David Hodgesd, Scott Kaiserb, Maria Loughrand, Cristina Mestreb, Melissa Reardond and Emma Siegfriedd
Corresponding author. The Nature Conservancy, 5834 St George Avenue, Crozet, Virginia 22932, USA E-mail: email@example.com University of Virginia, School of Architecture, Charlottesville, Virginia 22904, USA University of Minnesota, Institute on the Environment, St Paul, Minnesota 55108, USA University of Virginia, School of Engineering and Applied Sciences, Charlottesville, Virginia 22904, USA University of Virginia, Department of Environmental Sciences, Charlottesville, Virginia 22904, USA
Cities around the world are struggling to access additional water supplies to support their continued growth because their freshwater sources are becoming exhausted. Half of all cities with populations greater than 100,000 are located in water-scarce basins, and in these basins agricultural water consumption accounts for more than 90% of all freshwater depletions. In this paper we review the water development histories of four major cities: Adelaide, Phoenix, San Antonio and San Diego. We identify a similar pattern of water development in these cities, which begins with the exhaustion of local surface and groundwater supplies, continues with importation of water from other basins, and then turns to recycling of wastewater or stormwater, or desalination of either seawater or brackish groundwater. Demand management through water conservation has mitigated, to varying degrees, the timing of water-system expansions and the extent to which cities rely on new sources of supply. This typical water development pattern in cities is undesirable from a sustainability perspective, as it is usually associated with serious ecological and social impacts as well as sub-optimal cost effectiveness. We highlight case examples and opportunities to invest in water conservation measures, particularly through urban–rural partnerships under which cities work with farmers to implement irrigation conservation measures, thereby freeing up water for ecological restoration and use by cities.
Keywords: Aquifer depletion; Desalination; Inter-basin transfers; Irrigation efficiency; River drying; Urban–rural partnerships; Urban water supply; Water conservation; Water scarcity