【Objective】Food production is the primary consumer of water resources in many countries. At the catchment and basin scale, understanding the spatiotemporal variation of food production and the underlying determinants is crucial for improving water resource use efficiency and promoting sustainable development. We propose a new method in this paper to analyze this issue.【Method】Our study focuses on the Yangtze River Basin. The water used for food production and its spatiotemporal variation from 2000 to 2020 in the basin were calculated based on crop water demand. Path analysis was used to elucidate the underlying determinants affecting the blue and green water footprint per unit area.【Result】① The annual average grain water footprint in the basin from 2000 to 2020 was 205.25×109 m3, with the green water footprint accounting for 66%. ② Due to differences in cultivation scales, the upper, middle, and lower reaches contributed 36.5%, 46.8%, and 16.7%, respectively, to the total grain water footprint of the basin. Additionally, the grain water footprints in the middle and lower reaches have increasingly relied on green water. ③ Meteorological factors positively influenced the density of the green water footprint and negatively affected the density of the blue water footprint. Social development and economic factors significantly impacted the density of the blue water footprint. 【Conclusion】 The middle reaches of the Yangtze River Basin, where irrigation demand for grain crop production is high, are likely to face growing pressure due to land and water resource shortages. This challenge is particularly acute in Henan, Hubei, Hunan, and Jiangxi provinces, where investments in agricultural infrastructure, such as irrigation systems and advanced water management technologies, are essential. In Gansu, Qinghai, and Henan provinces, where water scarcity and pollution persist, adopting technologies such as soil mulching, rainwater harvesting and water storage can enhance green water utilization and alleviate regional water resource pressures.

With the increasing urbanization but growing resource scarcities, the securing provision of fundamental resources as food, energy and water (FEW) has become a unique challenge for urban sustainability. This is not only because of continuous demand of resource imports from different regions for urban areas, but also due to the complex interrelationships among FEW systems. In such context, exploring the interactions between FEW resources and economic activities when investigating FEW provisions to meet urban demand through trade is very essential to find effective policy intervention points and priority areas for actions. This paper investigates external binding FEW resource flows with internal certain interlinkages driven by final demand of Beijing city at different nodes along their supply chains, by combing structural path analysis and multi-regional input-output model of China 2010. The results show that the key source regions present overall neighborhood pattern that Hebei, Inner Mongolia, Anhui, Jiangsu, and Shandong near Beijing are the five leading contributors of tran-regional FEW provisions. The top 20 nexus paths are identified and the most important nexus pathways start with the other services in Beijing. Besides this, the critical supply chains appear divergent directions for FEW flows, driven by food, construction and agriculture industries respectively. Moreover, the key nodes mainly concentrate on less developed regions and energy-related sectors. For example, non-metal products manufacturing in Hebei, petroleum refining and coking in Heilongjiang, and coal mining and washing in Inner Mongolia have larger impacts on all of FEW flows across the supply chains. These results are very informative to targeting our efforts to address the urban FEW nexus issue both from the perspective of supply side and demand side.

Secure and efficient supply for the food, energy and water resources is essential for sustainable urban development. Due to the close interaction of food, energy and water systems, it is necessary to analyze food-energy-water nexus from an integrated perspective. Taking the Detroit Metropolitan Area as a case, this study first constructs a food-energy-water physical input-output model to quantify food, energy and water flows. Then, structural path analysis is adopted to identify critical supply chain paths driven by the final demand of key sectors. Quantitative results of food-energy-water flows show that major inputs of food and energy in the Detroit Metropolitan Area are from outside through imports, while water use is predominately extracted from local sources. Local consumption activities for the food, energy, and water systems are mainly concentrated downstream of the supply chain. Structural path analysis results show that intermediate processes use relatively large amounts of food, energy and water, and should be more concerned. Also, identifying sectors involving multiple systems, such as Food Processing, Domestic Consumption, Solid Waste Management, Wastewater Treatment, and Residual Processing, can promote co-benefit opportunities. This holistic view on urban FEW nexus presented in this study can facilitate better decisions and help avoid unintended consequences.

The rapid population growth in China has increased the demand for limited water, energy and food resources. Because the resource supply is constrained by future uncertainties such as climate change, it is necessary to examine the connections among water, energy and food resources from the perspective of the relevant final demands. Based on an input-output model and structural path analysis, this study aims to explore the hidden connections among water, energy and food resources by identifying important final demands and examine how these resources are embodied in upstream production and downstream consumption processes along the supply chain. The water-energy-food nexus approach in this research identifies where and how these resources intersect in economic sectors. By simultaneously considering the water, energy and food footprints, synergistic effects can be maximized among these resource systems. The results reveal that urban household consumption and fixed capital formation have large impacts on water-energy-food resources. Besides, agriculture, construction and service sectors have the largest water-energy-food footprints. For each resource, we rank the top-20 supply chain paths from the final demands to the upstream production sectors, and six critical supply chain paths are identified as important contributors to the consumption of all these resources. Compared with independent approach to manage water, energy and food resources, the nexus approach identifies the critical linkages of the water, energy and food systems and helps to formulate integrated policies to effectively manage these resources across sectors and actors. Synergistic strategies for conserving water, energy, and food resources can be achieved through avoiding unnecessary waste in end uses and improving resource use efficiency along critical supply chains. This research can help consumers, industries and the government make responsible consumption and production decisions to conserve water, energy and food resources.

The safety of food-energy-water (FEW) systems in mega-urban regions (MURs) is an urgent issue for achieving regional sustainable development. However, with the rapid growth of the population, the economy and urbanization and uncertainty inherent in climate change and international politics, FEW systems in MURs face tremendous challenges not only because of increasing demands and inadequate resources but also because of the dependence on imports from other regions. Therefore, it is essential to identify the critical connections and change features in FEW systems from economic actions to better meet these challenges. Taking the Bohai MUR as a case study, this study explores FEW changes embodied in trade, final demands and supply chains during 2002–2012 and identifies important nodes and critical supply chains by combining a three-scale input-output (IO) model with structural path analysis (SPA). The results show that FEW flows embodied in trade were significantly increased during the 10 years. The Bohai MUR turned from a net importer to a net exporter in embodied food and energy from 2002 to 2012. In final demands, the ratios of consumption and investment in embodied FEW obviously decreased, but exports increased significantly. Exports were always the largest consumer of embodied FEW, and urban households also consumed them. The top 20 critical supply chains from the final demands to the upstream production sectors for food, energy and water systems in 2002 and 2012 are listed. One and three common routes in the top 5 critical supply chains strongly impact embodied FEW. The common critical routes of each subsystem in time are also identified. Embodied FEW change factors and coping strategies are explored as well. This study will help stakeholders make responsible production and consumption decisions to improve the resilience of FEW systems and achieve sustainable development goals (SDGs) at the mega-urban scale.