Urbanization and population growth increase demands for commodities such as food, energy, and water in cities. Energy and food production depend on water resources, and piped treated water and wastewater systems depend on energy resources, representing aspects of the food-energy-water nexus. Because water resources are used outside of cities to produce the goods that are eventually consumed in cities, the water stress of cities is impacted by local water shortages and indirectly by physical water stress in locations in the supply chain. As a result, determining cities' consumption of resources and their implications can act as a powerful tool in informing resource managers and policy makers. The main research question in this work is: How can the resource usage of cities be quantified, and what are the implications associated with these urban resource flows? In this work, the local and indirect water stress of 69 metropolitan statistical areas (MSAs) within the contiguous United States is determined and compared. In addition, electricity-water interdependencies are further broken down at an urban scale by spatially and temporally quantifying direct and indirect water and electricity consumption for households in the urban area of Chicago, Illinois, USA. This analysis synthesizes data of various sources and resolutions and can act as a decision-support tool in advancing food-energy-water nexus literature and informing nexus-related policy.
The urban direct and indirect water stress quantification results show that cities typically import commodities from nearby locations with similar water resource constraints, and generally have similar local and indirect water stress. In particular, cities in the Western United States have stressed local water resources and also import commodities from water-stressed locations. Individual contributions of food, fuel, and electricity imports to urban water stress vary from city to city, and do not necessarily reflect their geographical locations.
The quantification of Chicago's electricity-water nexus highlights that the direct consumption of water and electricity greatly exceed their respective indirect consumption when considering the urban electricity-water nexus. In addition, while direct electricity consumption and drinking water consumption are largest in the summer (June-August), wastewater treated and its associated indirect electricity peak during the spring (March-May). While the area's electricity provider has installed smart electricity meters, Chicago's water sector has comparatively lagged in advances, struggling with challenges of limited drinking water withdrawals from Lake Michigan and massive gray infrastructure investment and overflow restrictions with a combined sewer system. This work quantifies resource flows and their interdependencies in the urban environment, and can be used as a decision-making basis in future resource management initiatives and policy making
