摘要
Urban growth and development depends on both the local hydrologic conditions and how water resources are procured and managed. The objective of this study was to assess the water security of large urban areas based on their physical hydrology, existing water supply infrastructure, and water management institutions. This study examined 108 large cities (>750,000 people) in the United States (n = 50) and Africa (n = 58), encompassing a broad range of hydrologic and socio-economic conditions, including degrees of institutional complexity. Urban water availability was estimated as the volume of water available from local, natural water sources, as well as water captured via infrastructure such as reservoirs, wellfields, or water transfers. Urban institutional complexity was assessed based on ability to provide, regulate and maintain urban water supplies. Over half of the cities in this study rely on captured water to meet urban demands and maintain high levels of institutional complexity in doing so. Cities able to adequately supply water from local natural sources (37 %) maintain significantly lower institutional complexity than cities using water captured from non-local sources. Cities categorized as water insecure (7 %) had minimal access to either local or captured water resources and operated using the simplest water institutions. Results suggest that low local availability drives the urban response for capturing additional water supplies, and is both the cause and product of more complex institutional frameworks. Efforts to address urban water insecurity should focus more attention on meeting not only the physical but managerial needs of a city.