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Securing adequate water supply for the future is an increasingly critical concern in the urban United States. This concern was clearly expressed in the 2008 American Water Works Association “State of the Industry” report of the top priorities and issues facing the water industry in the US. A survey of water suppliers found that the industry's top-ranked concern, for both the short- and long-term future, is the availability of adequate quantities of clean or treatable water to meet both current and prospective needs in an increasingly uncertain future. The amount of water available to an urban area is a product of both the local environmental context and the overlying anthropogenic framework for water supply regulation and distribution. To better understand the drivers of source water vulnerability in urban areas, this study quantified the relationship between water production and urban consumption in the 262 largest US cities (all those with population greater than 100,000). Water availability for each urban area was assessed by spatial analyses of climatic and hydrologic data, and was broken into two components: naturally available water from local rivers, lakes, or aquifers, and managed water available from the construction of reservoirs, aqueducts, or imported sources. The baseline water vulnerability of each city was quantified as a ratio of local consumptive demands to natural water production. The effect of hydraulic infrastructure was evaluated as changes in vulnerability through the incorporation of artificial water production. Comparisons both between baseline (natural) vulnerabilities and incorporated (anthropogenic) vulnerabilities allow sources of vulnerability not necessarily captured by local hydrologic conditions to be identified and therefore better express the range of vulnerability faced by US cities. |