Environmental Hazards 7 (2007) 399–418 Characterizing vulnerability to water scarcity: The case of a groundwater-dependent, rapidly urbanizing region Timothy W. Collins a,Ã , Bob Bolin b a Department of Sociology & Anthropology, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA b School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287-2402, USA Abstract Groundwater overdraft is a resource management issue that poses a threat for the security of communities. Impacts of groundwater overdraft are influenced by the biophysical and social contexts of water management. This paper presents a method for assessing vulnerability to water scarcity in spatial terms using biophysical and social indicators. A geographic information system was used to establish areas of vulnerability based upon hydrologic variability in water resource availability within a groundwater basin, three types of water management systems, and 10 sociodemographic characteristics. Our study area is in the rapidly urbanizing Arizona Central Highlands, located 150 km north of the Phoenix metropolitan region, USA. Results indicate that the most biophysically vulnerable places do not necessarily intersect with the most vulnerable populations and that local differences in vulnerability are interrelated, rather than independent, outcomes in a process of socioenvironmental transformation. Vulnerability is influenced by laws that deny access to local surface waters and lead to dependence on fossil groundwater, and by economic reliance on urbanization. Localities attempt to reduce vulnerability through the development of community water systems and the expansion of water frontiers. While such strategies may reduce local vulnerability, they are not sustainable solutions because they transfer risks to other places, and thus contribute to vulnerability elsewhere. r 2007 Elsevier Ltd. All rights reserved. Keywords: Water resources; Vulnerability; Urbanization; Arizona 1. Introduction Development of the Western United States (US) has depended on the acquisition of water resources; contesta- tion over rights to surface waters has been integral to regional history (Reisner, 1993). Because surface waters have been over-allocated in the arid US West (Reisner, 1993; Bates et al., 1993), the contemporary management task of increasing local water supplies frequently depends on the use of groundwater (Glennon, 2002; Smith, 1989; Ashley and Smith, 1999). This is not a situation unique to the US West, as groundwater is currently supporting urbanization across the globe. In contexts of rapid urbanization and climatic variability/change, concerns about the impacts of groundwater depletion have heigh- tened (Carter et al., 2002; Morehouse et al., 2002). Groundwater overdraft can have adverse biophysical consequences (with secondary social effects), including ecosystem degradation (Stromberg et al., 1996; MacKay, 2006) and land subsidence (Gelt, 1992; Zekster et al., 2005). Groundwater mining can also threaten long-term water security and has emerged as salient public policy issue (Alley et al., 1999; Foster and Chilton, 2003; US Bureau of Reclamation, 2003). While broad societal consequences are of legitimate concern, social and geographical impacts are not typically expressed evenly. Public policies are typically intended to ameliorate concerns about absolute scarcity; however, the effects of overdraft are typically expressed through localized patterns of relative scarcity. In cases of aquifer drawdown, it is particular people and places (rather than society as a whole) that experience a physical loss of access to usable groundwater, which is a defining ARTICLE IN PRESS www.elsevier.com/locate/hazards 1747-7891/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.envhaz.2007.09.009 Ã Corresponding author. Tel.: +915 747 6526; fax: +915 747 5505. E-mail addresses: twcollins@utep.edu (T.W. Collins), bob.bolin@asu.edu (B. Bolin).