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Urban Surface Water Supply Vulnerability

Project Leads: 
Julie Padowski
Steven Gorelick
Abstract:  "This study presents a global analysis of urban water supply vulnerability in 70 surface water-supplied cities, with populations exceeding 750 000. Vulnerability represents the failure of an urban supply-basin to simultaneously meet demands from human, environmental and agricultural users. We assess a baseline (2010) condition and a future scenario (2040) that considers increased demand from urban population growth and projected agricultural demand under normal climate conditions. We do not account for climate change, which can potentially exacerbate or reduce urban supply vulnerability. In 2010, 36% of large cities are vulnerable as they compete with agricultural users. By 2040, without additional measures 44% of cities are vulnerable due to increased agricultural and urban demands. Of the vulnerable cities in 2040, the majority are river-supplied with mean flows so low that the cities experience ‘chronic water scarcity’ (1200 l p−1 d−1). Reservoirs supply the majority of cities facing individual threats to future freshwater supply, revealing that constructed storage potentially provides tenuous water security. In 2040, of the 31 vulnerable cities, 13 would reduce their  vulnerability via reallocating water by reducing environmental flows, and 15 would similarly benefit by transferring water from irrigated agriculture. Approximately half remain vulnerable under either potential remedy."

Figure, caption, and abstract from: Padowski and Gorleick (2014), Global analysis of urban surface water supply vulnerability, Environ. Res. Lett. 9 104004 (corrigendum)

Figure Caption: "City supply system vulnerability. Cities are represented on the world map by circles where color indicates the degree to which each city faces water supply issues. Cities that change status over the time period studied are demarcated with a coloured outer ring (2010) and inner circle (2040). Vulnerable cities (red) are those who suffer from both environmental and urban water scarcity. Threatened cities (yellow are those that have either environmental or urban water scarcity issues. Cities with no water supply issues (non-threatened) are symbolized by a light blue fill. Numbered locations represent those cities-of-concern which become vulnerable by 2040. Insets of these particular cities accompany the world map. Dark blue circles represent the general location of urban supply sources in inset maps. Basin color denotes the primary sectoral water user in each system, whereas dark gray areas indicate city extents. City names may be found in the supplementary information of the paper."



Padowski, J.C. and S.M. Gorelick, 2015, Global analysis of urban surface water supply vulnerability, Environmental Research Letters 9 (10), 104004, doi:10.1088/1748-9326/9/10/104004 (also see corrigendum).