Energy–water nexus of urban agglomeration based on multiregional input–output tables and ecological network analysis: A case study of the Beijing–Tianjin–Hebei region

Interdependent water and power infrastructure model (IWPIM): A modeling approach for water and energy resource management in rural communities

The importance of the dependencies between water and power systems is more acutely perceived when challenges emerge. As both energy and water supply are limited, efficient use is a must for any sustainable future, especially in rural areas. Although important, a modeling tool that can analyze water-energy systems interdependencies in rural systems, at the architectural level highlighting the physical interconnections and synergies of these systems, is still lacking. We present a multi-agent system model that captures the features of both systems, at the same levels of fidelity and resolution, with coordinated operations and contingency components represented. Unlike other models, ours captures architectural features of both systems and technical constraints of the systems' components, which is critical to capture physical intricacies of the interplay between systems components and shed light on the impacts of disruptions of either system on the other. This model, which includes multiple infrastructure components, shows the importance of a holistic understanding of the systems, for cooperation across systems physical boundaries and enhanced benefits at larger scales. This study looks to investigate water-power resource management in an irrigation system via the analysis of physical links and highlight strengths and vulnerabilities. The effects of water shortage, water re-allocation and load shedding are analyzed through scenarios designed to illustrate the utility of such a model. Results highlights the importance of inter-reservoir relationships for alleviating effects of disruption and unforeseen rise in energy demand. Water storage is also critical, helping to mitigate the impacts of water scarcity, and by extension, to keep the energy system unaffected. It can be a viable part of the solution to compensate for the negative impact of shortage for both resources.

Carbon footprint of farming practices in farmland ecosystems on the North and Northeast China plains

Fast development of farming practices in China is projected to result in additional carbon emissions and thus affect farmland ecosystems' environmental performance. Based on 454 farm surveys on the North and Northeast China Plain, the carbon footprint (CF) of two farmland ecosystems (irrigated system for wheat and maize on the North China Plain and rainfed system for maize on the Northeast Plain) were assessed and emission reduction pathways explored by quantifying greenhouse gas emissions of agricultural inputs and farm practices during the entire crop growing seasons with an agricultural footprint model. The results demonstrated that the GHG emissions from wheat and maize rotation in the irrigated system were 7.63 t CO2 eq ha-1 and 3.17 t CO2 eq ha-1 for single season maize in the rainfed system. While energy consumption accounted for 12.5%-21.3% of the carbon footprint in both systems, the group assessment found that the largest difference in GHG emissions between the high and low emission groups came from mechanical energy consumption. Approximately 50.6% and 39.2% of the mechanical carbon footprint of wheat and maize, respectively, were caused by irrigation practices in the irrigated system. Regarding the rainfed system, where 46.6% of mechanical carbon emissions were generated by maize tillage operations. In addition, scenario analysis indicated that the mechanical carbon footprint could be reduced to 56 kg CO2 eq t-1 for NCP-wheat and 26 kg CO2 eq t-1 for NCP-maize, respectively, by optimizing yields and irrigation practices in irrigated systems and that the mechanical carbon footprint of NEP-maize could be reduced to 25 kg CO2 eq t-1 by optimizing yields and tillage practices in rainfed systems. Therefore, improvement in mechanization in irrigation and tillage practices can contribute to reduce GHG emissions in China. Water-saving irrigation technology is recommended in irrigated area and conservation tillage is recommended in rainfed agricultural area to reduce carbon footprints.

Assessing the spatial spillover effects and influencing factors of carbon emission efficiency: a case of three provinces in the middle reaches of the Yangtze River, China

Studying urban carbon emission efficiency is vital for promoting city collaboration in combating climate change. Prior research relied on traditional econometric models, lacking spatial spillover effects understanding at the urban scale. To provide a more comprehensive and visually insightful representation of the evolving characteristics of carbon emission efficiency and its spatial clustering effects and to establish a comprehensive set of indicators to explore the spatial spillover pathways of urban carbon emission efficiency, we conducted an analysis focusing on 42 cities in the middle reaches of the Yangtze River. By employing the index decomposition method, the super-efficiency SBM model, spatial autocorrelation analysis, and the spatial Durbin model, the study calculates the urban carbon emission efficiency from 2011 to 2019 and analyzes the spatial spillover effects and influencing factors of urban carbon emission efficiency. The main conclusions are as follows: (1) Jiangxi Province displayed stable urban carbon emission efficiency evolution, while Hubei and Hunan showed significant internal disparities. (2) Positive spatial correlation exists in urban carbon emission efficiency, with an imbalanced distribution. (3) Various factors influence urban carbon emission efficiency. Technological innovation and economic development have positive direct and indirect impacts, whereas industrial structure, urbanization, population, and energy consumption have negative effects. Spatial spillover effects of vegetation coverage are insignificant. These methods and findings offer insights for future research and policy formulation to promote regional sustainable development and carbon emission reduction.

Modeling and exploring the coordination relationship between green infrastructure and land use eco-efficiency: an urban agglomeration perspective

In limited land space, improving the construction of infrastructure with ecological services can help to achieve the goal of promoting land use eco-efficiency (LUEE). In view of this, this study constructed interactive coordination relationship model of green infrastructure (GI) and LUEE that involves entropy method model, super-efficiency slack-based measure (SBM) model with undesirable outputs, and coupling coordination degree model. The interactive coordination relationship model can help to study and reveal the mechanisms of interaction and the coordination relationship between GI and LUEE from a land benefit and ecological perspective. We took the Beijing-Tianjin-Hebei urban agglomeration as the study area. The results showed that the assessment results of GI showed a decreasing trend from 2000 to 2020. LUEE in different cities displayed obvious variability with efficiency values ranging from 0.5666 to 2.4437. The relationship between GI and LUEE is in the stage of uncoordinated development in 53.8% of cities, mainly concentrated in the eastern and southern parts of the study area. The unnatural human activities are the critical factors affecting interactive coupling coordination degree of LUEE and GI. It is clarified that the level of coordination relationship of the two can be used as an important indicator to judge the sustainable development of urban agglomerations. Intensive use of land, optimal connection of geographic information, and localization of policies would help improve the balance and coordination between the two. This study provides interesting research ideas and novel modeling approaches for the study of green and sustainable development of urban agglomerations.

Managing water-land-food nexus towards resource efficiency improvement: A superedge-based analysis of China

Challenges at the intersection of water conservation, land protection, food security, and economic growth cross industrial boundaries, and also involve synergies with multiple policy domains. Despite this, little is known about how system heterogeneity affects water, land, and food (WLF) consumption performance at a sectoral level. This study integrates superedge analysis with a flow interaction network, elasticity theory, and utility analysis to detect the WLF nexus with regard to resource efficiency gains. Three indicators (intra-sector recycling efficiency, trans-sector allocation efficiency, and symbiosis of system structure) are proposed as mechanisms by which to quantitatively explore intra-sector and trans-sector nexus, and formulate improvement strategies for sectoral WLF savings. The results show synergies between recycling efficiency and water/food productivity. Manufacturing servitization and agricultural industrialization can drive more efficient WLF allocation by minimizing resource misallocation, whilst positive industrial ecology enhances WLF circulation and facilitates reducing resource undue competition. In addition, the ability of industries to save resources under the nexus is examined. Approximately 93% of sectors suffer from resource waste, misallocation, and undue competition. Therefore, strategic paths enhance resource synergy and, through so doing, enable WLF efficiency gains.

Dual risk-aversion programming for regional industrial structure adjustment with water-energy nexus: A case study of Tianjin, China

The water-energy nexus (WEN) system is a large-scale complex system that comes with diverse forms of risks owing to many challenges in the process of maintaining economic-resource-environmental sustainability. First, the rapidly increasing demand for water and energy subjects many regions to the high risk of water and energy shortages. Second, decision makers face difficulties in weighing system benefits and loss risks under a series of stricter water-energy policies. To handle the aforementioned dual risks of WEN, in this study we propose copula-based stochastic downside risk-aversion programming (CSDP) for regional water-energy management. CSDP integrates the superiority of the copula analysis method and downside risk-aversion programming into a framework, which can not only reveal the risk interactions between water resources and energy demand by using copula functions under different probability distributions, even previously unknown correlations, but also control economic risk, tackle systemic uncertainties, and provide an effective linkage between system stability and conflicting economic benefits. The proposed model was applied to a water-energy system case study in Tianjin City, China. Optimal solutions for various water resources and energy demand copulas associated with different scenarios and hierarchical risk levels were examined in the CSDP model. The results showed that water resources have a greater influence than energy on industrial structure adjustment in Tianjin, with consequent effects on system benefits, optimal output value schemes, and environmental protection strategies. In addition, the tertiary industry provides a new opportunity for economic growth based on a large amount of water-energy consumption, and its potential resources and water-air pollution risks also deserve extensive attention.

Virtual Water Flow Pattern in the Yellow River Basin, China: An Analysis Based on a Multiregional Input-Output Model

Research on the Yellow River Basin's virtual water is not only beneficial for rational water resource regulation and allocation, but it is also a crucial means of relieving the pressures of a shortage of water resources. The water stress index and pull coefficient have been introduced to calculate the implied virtual water from intraregional and interregional trade in the Yellow River Basin on the basis of a multi-regional input-output model; a systematic study of virtual water flow has been conducted. The analysis illustrated that: (1) Agriculture is the leading sector in terms of virtual water input and output among all provinces in the Yellow River Basin, which explains the high usage. Therefore, it is important to note that the agricultural sector needs to improve its water efficiency. In addition to agriculture, virtual water is mainly exported through supply companies in the upper reaches; the middle reaches mainly output services and the transportation industry, and the lower reaches mainly output to the manufacturing industry. Significant differences exist in the pull coefficients of the same sectors in different provinces (regions). The average pull coefficients of the manufacturing, mining, and construction industries are large, so it is necessary to formulate stricter water use policies. (2) The whole basin is in a state of virtual net water input, that is, throughout the region. The Henan, Shandong, Shanxi, Shaanxi, and Qinghai Provinces, which are relatively short of water, import virtual water to relieve local water pressures. However, in the Gansu Province and the Ningxia Autonomous Region, where water resources are not abundant, continuous virtual water output will exacerbate the local resource shortage. (3) The Yellow River Basin's virtual water resources have obvious geographical distribution characteristics. The cross-provincial trade volume in the downstream area is high; the virtual water trade volume in the upstream area is low, as it is in the midstream and downstream areas; the trade relationship is insufficient. The Henan and Shandong Provinces are located in the dominant flow direction of Yellow River Basin's virtual water, while Gansu and Inner Mongolia are at the major water sources. Trade exchanges between the midstream and downstream and the upstream should be strengthened. Therefore, the utilization of water resources should be planned nationwide to reduce water pressures, and policymakers should improve the performance of agricultural water use within the Yellow River Basin and change the main trade industries according to the resource advantages and water resources situation of each of them.

Virtuous Cycle: An Idea of Water Resources Management and Top-Level Planning

Facing the conflict between human activities and the ecological environment, this study proposes a “Virtuous Cycle” concept of water resource management and top-level planning. By analyzing and summarizing typical experiences from both macro-policy and micro-practice, the characteristics and mechanisms of the Virtuous Cycle are discussed. According to the analysis method of “Problem-Attribution-Goal-Task-Measures” (PAGTM), taking the “Five Water Governance” water management project in Zhejiang Province of China as a case study, the specific measures and technical framework of the Virtuous Cycle are explored. This study hopes to provide a reference for the top-level planning and path design of harmonious and sustainable natural-social water resources management.

Analysis of the relationship between water and energy in China based on a multi-regional input-output method

The shortage of water and energy are hindering the rapid development of the regional economy in recent years. Therefore, exploring the synergy of water and energy and managing the two resources comprehensively is conducive to the sustainable development of the economy. Based on the multi-regional input-output (MRIO) model, this study proposed a new assessment framework for investigating the water-energy (WE) relationship. We used this novel framework to identify the relationships in different sectors. The achieved results are as follows. First, water and energy are closely related in many sectors, including agriculture, extractive sector, petroleum, coking, and nuclear fuel processing sector, and other sectors. However, the construction sector, textile and clothing sector, and wood processing and furniture manufacturing sector showed low correlation (p > 0.05). Second, on the whole, the WE relationship has been improving. Among the eight regions, the relationship varies greatly, and the Southern coastal region has the best relationship (r = 0.78). Third, the spatial distribution of water and energy footprints shows high agreement. Although the virtual water and energy flows alleviated the energy pressure in Coastal areas, it has aggravated the water and energy shortages in Central areas. Therefore, identification of key sectors and construction of suitable policies may help alleviate the contradiction between water and energy shortages and drive regional economic development.

Economic environmental imbalance in China - Inter-city air pollutant emission linkage in Beijing-Tianjin-Hebei (BTH) urban agglomeration

Production fragmentation makes the air pollution policy no longer at the local scale but requires accounting more about embodied emissions cross-region through supply chains. Here, we map the consumption-driven NO_x networks of Beijing-Tianjin-Hebei urban agglomeration (BTH) in China using the city-level multi-regional input-output model. The results show that the construction, service, and equipment manufacturing sectors in Beijing and Tianjin indirectly drive more than half of BTH NO_x emissions (54%). Moreover, 75% of NO_x flows in the supply chains are traded from cities with low efficiency (high intensity) to cities with high efficiency (low intensity), which reflects the economic environmental imbalance in BTH. Especially, for the metals smelting and pressing sector and nonmetal mineral products sector, there is a wider gap in emission intensity between production-oriented cities (1.03-4.43 Mt/million yuan) and consumer-oriented cities (0.08-0.45 Mt/million yuan), which leads to additional emissions of air pollutants to increase. At the same time, for the provinces in the south and north China, the role of BTH in the supply chain is different, which leads to an economic environmental imbalance between the north and the south. Synchronous outsourcing of production and technology is the key to solving the economic environmental imbalance. The consumption-oriented high-income cities are suggested to increase the financial and technical support to improve the efficiency of pollution control in production-oriented cities.

Temporal Understanding of the Water–Energy Nexus: A Literature Review

Guaranteeing reliable access to water and clean energy has been one of the most debated topics to promote sustainable development, which has made the Water–Energy Nexus (WEN) a relevant field of study. However, despite much development of the WEN, there are still many gaps to be addressed. One of these gaps is the understanding of temporal features. To address this, this study aimed to identify, categorize, and analyze the main temporal features applied in WEN studies based on a review of academic publications from 2010 to 2021. The results showed that most of the recent literature has focused on understanding the WEN from a quantitative perspective, often does not provide clear motivations for their choice of time, and lacks understanding of the role of historical processes. To improve the temporal understanding in WEN research, there is a need to include more methodological diversity, enhance the understanding of historical developments, and diversify the data use. The presented measures provide a chance to improve the evaluation of key issues, enhance the understanding of drivers of trade-offs between the water and energy sectors, and ground the discussion besides quantification. Moreover, these measures help the scientific community better communicate results to a broader audience.

Water-Energy-Food Accessibility and Tracking Progress towards Achieving Sustainable Development Goals in the Savannah Region of Katsina State, Nigeria

Although remarkable progress has been achieved in reducing hunger and poverty and improving people’s health in the past couple of decades, humanity still faces considerable socio-economic and sustainability challenges. Ensuring sustainable access to safe and sufficient water, improved sanitation facilities, clean energy sources and healthy food is a necessary requirement for ending hunger and poverty, advancing health and achieving all the goals of the sustainable development agenda. Socio-economic variables are determinant factors of water, energy and food accessibility. Ecological region, income and education are measures used in this study, which aims to examine a pairwise comparison of water and energy sources, sanitation facilities and food accessibilities in six sampling communities and tracking progress towards achieving the sustainable development goals (SDG) at a local scale using nine specific SDG indicators. A study involving questionnaire administration covering 1785 households across the three ecological regions of Katsina state was performed. Two communities representing urban and rural households from each of the ecological regions were selected. An analysis of variance was used to test the equality of resource accessibility across the investigated communities followed up by a post hoc analysis to identify significant mean groups. The results showed that the overall access level to safely manage water and sanitation facilities were 16.5% and 28.1%, respectively. Access indices of 1.83 and 1.24 for electricity and cooking fuel, respectively, were calculated in the study area. The study revealed that location, education and income are the key drivers of water, energy and food access and choice.

Assessment of the water-energy-food nexus under spatial and social complexities: A case study of Guangdong-Hong Kong-Macao

Water, energy, and food resources are indispensable and irreplaceable resources for the survival and development of human society. This study systematically assessed the three resources system in Guangdong, Hong Kong, and Macao based on constructed direct and nexus-oriented, multi-regional input-output, and ecological network analysis models. Various network analysis (e.g., control, utility, hierarchy, and robustness) was adopted to identify the critical factors of inter-regional resources trade from a perspective of supply-demand. The results indicated that Guangdong, Hong Kong, and Macao have complex control linkages in the three resources trade network, and Guangdong is the key to improving the three resources network structure. The three resources network existed highly competition and exploitation in the three regions. Industrial development is unbalanced and competitive for the three resources. The wholeness water-energy-food trade network of the three regions stayed in a positive environment, but the positive effect level was relatively weak. The three resources network robustness in the three regions is at a medium level. Hong Kong and Macao's water-energy-food network systems have a high vulnerability, and the lowest system robustness was food-related energy in Hong Kong. Finally, we provide some measures to help the sustainable development of the water-energy-food resource system in the three regions, such as cross-regional coordinated management, integration industries development, seawater toilets-flushing, sea rice, and renewable energy.

Understanding the Sustainability of the Energy–Water–Land Flow Nexus in Transnational Trade of the Belt and Road Countries

Increasing economic and population growth has put immense pressure on energy, water and land resources to satisfy national and supra-national demand. Through trade, a large proportion of such a demand is fulfilled. With trade as one of its key priorities, the China Belt and Road Initiative is a long-term transcontinental investment program. The initiative gained significant attention due to greater opportunities for economic development, large population and different levels of resource availability. The nexus approach has appeared as a new viewpoint in discussions on balancing the competing sectoral demands. However, following years of work, constraints exist in the scope and focus of studies. The newly developed multi-regional input–output (MRIO) models covering the world’s economy and its use of resources permit a comprehensive analysis of resource usage by production and consumption at different levels, and bring more knowledge about resource nexus problems. Using the MRIO model, this work simultaneously tracks energy, water and land use flows and investigates the transnational resource nexus. A nexus strength indicator is proposed which depends on ternary diagrams to grade countries based on their combined resources’ use and sectoral weighting. Equal sectoral weighting is assigned. The analysis presented a sectorally balanced nexus approach. Findings support existing work by recognizing energy, water and land as the robust transnational connections, from both production and consumption points of view. Resource nexus issues differ from country to country owing to inequalities in industrial set-up, preferences in economic policy and resource endowments. The paper outlines how key resource nexus problems can be identified and prioritized in view of alternative and often opposing interests.

A Comprehensive Review on Types, Methods and Different Regions Related to Water-Energy-Food Nexus

Water, food, and energy are three of the most important resources for long-term survival and development. The term “nexus” is used to underline the need of controlling these primary components collectively rather than separately because they are interconnected and linked. With the purpose of better understanding nexus thinking and showcasing nexus analysis approaches and tools, this study explores the current state of the approach to the water–energy–food relationship, which has gotten a lot of attention in recent years. Water–energy, water–food, water–energy–food, water–energy, and climate are the four forms of nexus. This paper examines a variety of methodologies based on their principal objectives and provides a basic overview of a wide range of currently available methods and instruments for analyzing the water–energy–food (WEF) nexus. According to this study, the quantity of studies on the water–energy–food nexus has increased significantly, as the scientific community’s ability to analyze water, food, and energy interlinkages at a greater resolution. The integration and optimization of this multi-centric nexus is explored, with focus on four regions—Asia, Europe, America, and Africa—as a case study. The WEF nexus should be used in case studies to help illustrate its intricacies. Furthermore, this study builds a methodology and frameworks to find study linkages between water, energy, food, and other components, for a nexus analysis and discuss the major challenges and its solutions. This study also includes a scientometric analysis that looks at the countries and keyword mapping. Furthermore, the study is being planned, with an emphasis on quantitative analysis of the water–energy–food nexus which is helpful for the water security at local and global scale. This study aids in the coordination of research efforts to solve the difficult issues in nexus research and create sustainable and adaptable water, energy, and food systems.

Dynamic metabolism network simulation for energy-water nexus analysis: A case study of Liaoning Province, China

Faced with gradually serious energy and water crisis, the exploration of energy-water nexus metabolism relationships could provide a new direction for achieving the resources conservation and consumption reduction. In this paper, a comprehensive assessment for energy-water metabolic network is proposed to search the dynamic evolution and quantify the sectoral metabolic processes in Liaoning Province, China. Input-output analysis (IOA) and ecological network analysis (ENA) are integrated to clarify the embodied linkages and the complicated system interactions in the energy-water nexus network. The coefficients of "water-related energy" and "energy-related water" are explored through the system dynamics model (SDM) based on the consecutive input-output tables from 2012 to 2018. In addition, energy-water nexus efficiency index (EWEI) is constructed to evaluate the metabolism circulation efficiency of energy-water nexus network. The results indicate that (a) the energy and water outflow sectors mainly concentrate in primary industries and tertiary industries, while inflow sectors mainly concentrate in secondary industries; (b) the sectoral relationship provides effective pathways to implement collaborative resource saving and efficiency improvement measures, and the key sectors with the highest correlation with other sectors in energy-water nexus are AGR (agriculture), MIN (mining) and WRC (wholesale, retail and catering services). (c) the EWEI shows a gradually downward trend and the state of the energy system would determine the health of the energy-water nexus metabolism more strongly than water system.

Is the Water System Healthy in Urban Agglomerations? A Perspective from the Water Metabolism Network

Urban agglomerations are a primary spatial focus of socioeconomic activity and inherently include large volumes of embodied water. We have applied the concept of water metabolism health to comprehensively evaluate the overall operation of water systems in urban agglomerations and propose an innovative assessment framework. In particular, we constructed a water metabolism network (WMN) model to simulate a water system in which different cities and sectors are integrated, combining a newly compiled multiregional input-output (MRIO) table of water flow with ecological network analysis (ENA). A case study considering the Pearl River Delta (PRD) urban agglomeration in 2015 demonstrates that its network is well synergic but highly dependent, with considerable negative effects. Highly developed cities in southeastern of the PRD exhibit higher embodied water productivity and robustness but impose considerable negative effects on the water system. We found the agricultural sector to be a dominant controller of the network; the construction and service sectors represent the primary beneficiaries with strong competition. We suggest measures at various scales to improve water utilization efficiency and promote positive interactions between components, thus improving water metabolism system health for urban agglomerations.

Quantifying economic-social-environmental trade-offs and synergies of water-supply constraints: An application to the capital region of China

Sustainable water management is one of the sustainable development goals (SDGs) and is characterized by a high level of interdependencies with other SDGs from regional to global scales. Many water assessment studies are restricted to silo thinking, mostly focusing on water-related consequences, while lacking a quantification of trade-offs and synergies of economic, social, and environmental dimensions. To fill this knowledge gap, we propose a "nexus" approach that integrates a water supply constrained multi-regional input-output (mixed MRIO) model, scenario analysis, and multi-criteria decision analysis (MCDA) to quantify the trade-offs and synergies at the sectoral level for the capital region of China, i.e. the Beijing-Tianjin-Hebei urban agglomeration. A total of 120 industrial transition scenarios including nine major industries with high water-intensities and water consumption under current development pathways were developed to facilitate the trade-off and synergy analysis between economic loss, social goals (here, the number of jobs) and environmental protection (with grey water footprint representing water pollution) triggered by water conservation measures. Our simulation results show that an imposition of a tolerable water constraint (a necessary water consumption reduction for regional water stress level to move from severe to moderate) in the region would result in an average economic loss of 68.4 (± 16.0) billion Yuan (1 yuan ≈ 0.158 USD$ in 2012), or 1.3 % of regional GDP, a loss of 1.94 (± 0.18) million jobs (i.e. 3.5 % of the work force) and a reduction of 1.27 (± 0.40) billion m³ or about 2.2% of the regional grey water footprint. A tolerable water rationing in water-intensive sectors such as Agriculture, Food and tobacco processing, Electricity and heating power production and Chemicals would result in the lowest economic and job losses and the largest environmental benefits. Based on MCDA, we selected the 10 best scenarios with regard to their economic, social and environmental performances as references for guiding future water management and suggested industrial transition policies. This integrated approach could be a powerful policy support tool for 1) assessing trade-offs and synergies among multiple criteria and across multiple region-sectors under resource constraints; 2) quantifying the short-term supply-chain effects of different containment measures, and 3) facilitating more insightful evaluation of SDGs at the regional level so as to determine priorities for local governments and practitioners to achieve SDGs.

Identifying the key sectors for regional energy, water and carbon footprints from production-, consumption- and network-based perspectives

Energy consumption, water use and carbon emission targets are important for promoting sustainable development. This study presents a multi-goal analytical framework based on an environmental input-output analysis, structural path analysis and correspondence analysis to identify the key sectors for energy, water and carbon footprints. Using Guangdong Province as a case study, the energy, water and carbon footprints are modelled from production-based, consumption-based and network (betweenness)-based perspectives. The results show that (1) the construction sector is a key sector for energy use/water use/carbon emissions from the three perspectives. The electricity and heat power production and supply sector emitted the most production-based CO₂ (283.4 Mt), accounting for 52.3% of the total CO₂ emissions. (2) The key sectors in terms of energy, water and carbon differ. The transport, storage and post sector is an important sector for energy consumption, and the agriculture sector and food and tobacco sector are important sectors for freshwater withdrawal. (3) The key sectors differ according to the three perspectives. For example, the energy production sector ranked first in production-based CO₂ emissions (286.2 Mt), but heavy manufacturing ranked first in consumption-based CO₂ emissions (146.3 Mt). This study recommends paying more attention to the abovementioned sectors, specifically concerning the transmission role of light manufacturing in freshwater withdrawal, and reducing energy consumption-intensive but low value-added exports (such as metal smelting and pressing). The findings highlight the need to consider multiple angles and elements to identify the key sectors and help decision makers better understand the relationships and flows among the industries.

Virtual Water Trade in the Yellow River Economic Belt: A Multi-Regional Input-Output Model

The sustainable and efficient use of water resources has gained wide social concern, and the key point is to investigate the virtual water trade of the water-scarcity region and optimize water resources allocation. In this paper, we apply a multi-regional input-output model to analyze patterns and the spillover risks of the interprovincial virtual water trade in the Yellow River Economic Belt, China. The results show that: (1) The agriculture and supply sector as well as electricity and hot water production own the largest total water use coefficient, being high-risk water use sectors in the Yellow River Economic Belt. These two sectors also play a major role in the inflow and outflow of virtual water; (2) The overall situation of the Yellow River Economic Belt is virtual water inflow, but the pattern of virtual water trade between eastern and western provinces is quite different. Shandong, Henan, Shaanxi, and Inner Mongolia belong to the virtual water net inflow area, while the virtual water net outflow regions are concentrated in Shanxi, Gansu, Xinjiang, Ningxia, and Qinghai; (3) Due to higher water resource stress, Shandong and Shanxi suffer a higher cumulative risk through virtual water trade. Also, Shandong, Henan, and Inner Mongolia have a higher spillover risk to other provinces in the Yellow River Economic Belt.

Unveiling land footprint of solar power: A pilot solar tower project in China

Land occupation by solar power installations has become a rising concern that may cause adverse impacts on natural ecosystems and biodiversity. Existing studies mainly adopt a local perspective to view land use requirements of solar power and forget that the solar-based electricity system is subordinate to the macro economy and nourished by the material, machinery and service support by various economic sectors. To manifest a key aspect of the footprint of solar power on land resources, this study uncovered the extensive industrial land use initiated by the infrastructure of a representative pilot solar-based electricity plant using a systems perspective. The results in this study show that in magnitude, land footprint by the infrastructure of the pilot solar plant amounts to three times as much as the onsite land area. Also, the land footprint calculated is revealed as one order of magnitude larger than a previous finding that includes primary materials only, and four to seven times higher than the onsite land use by coal-based electricity plants. The outcome implies that existing environmental management policies need to be re-evaluated by putting enough emphasis on the land displacement by solar power systems along the production chain.

The economic loss of public health from PM2.5 pollution in the Fenwei Plain

At present, the concentration of PM_2.5 in the Fenwei Plain has become the second highest in China, ranking second to the Beijing-Tianjin-Hebei region. At the same time, China began to monitor and control the PM_2.5 concentration in the Fenwei Plain, but the data indicated that the concentration of PM_2.5 in the Fenwei Plain rose instead of falling. PM_2.5 concentrations in 6 cities from the Fenwei Plain ranked highest among the 20 cities in 2018 in China, and PM_2.5 pollution can cause some health economic loss. Based on this background, the exposure-response model is used to estimate the impact of PM_2.5 pollution on the health economic loss in the Fenwei Plain, and PM_2.5 concentration in 2020, 2025, and 2030 is also predicted based on the setting of three scenarios: baseline scenario, emission reduction scenario, and enhanced emission reduction scenario. Then, according to the estimated results, the paper provides suggestions for reducing public health loss in the Fenwei Plain in the future.

Energy—Water Nexus: Integration, Monitoring, KPIs Tools and Research Vision

The relationship between water and energy is a strong one characterized as having integration and coupling as two important features. While energy is responsible for delivering water to the end-users, it needs energy in order to be generated, and water. In this paper, a thorough review is presented regarding the different relationships between water and energy in terms of (i) the significance of the close relationship between water and energy by means of water/energy generation and consumption. Water consumption, water cooling and heating must be taken into account in order to avoid the obstacles related to future use of water for energy generation; (ii) the measuring and monitoring technologies for the energy-water nexus, focusing attention on the variables that are interrelated in the water and energy sectors. In addition, the consequences of finding several parameters, unknown variables and unclear dependencies in measuring of energy usage in the applications of water usage should also be taken into account. Innovative developments including nanotechnology, biotechnology, and wireless networks, as sensor technologies, may resolve the challenges of sensing; (iii) the different key performance indication tools for assessing and quantifying this nexus by analyzing and categorizing recent case studies of the water energy nexus and applicable evaluation methods; and (iv) the different research dimensions conducted on this nexus. Hopefully, this review will contribute to the development of this nexus adding value to the field while reducing duplication efforts.

Food, Energy and Water Nexus: A Brief Review of Definitions, Research, and Challenges

Vast expansion in consumption is leading to natural resource scarcity and global warming. The integrated management of natural resources, such as food, energy, food (FEW) as one of the most important aspects has been proposed as a solution to meet these challenges. The FEW nexus is a world-wide solution for simultaneously assessing the development and implementation of various approaches focusing on energy, water and food security, sufficiency. This approach is intended to foster sustainable development and improve the quality of life of communities while preserving the natural, human and social capital, address the long-term sustainability challenges and protecting all-natural resources. This paper tries to review some recent research on this topic. For this purpose, first, we describe some facts about demand growth and exponential consumption in these three areas, with emphasis on presented statistics. Then, the most critical research published in this field is reviewed, considering that it took a decade or so before that the original idea was introduced. The most important policymakers of this emerging concept, including committees and conferences, and finally significant challenges and opportunities to the implementation along with future insights, are addressed.

Taiwan has shifted to being a net CO2 exporter since the mid-1990s

With the integration of the global economy and increased international trade, CO₂ emissions embodied in trade have attracted broad attention. In this study, we examined Taiwan's CO₂ emissions embodied in its imports and exports with its 167 trade partners from 1970 to 2015 using the emissions embodied in bilateral trade (EEBT) method. The results show that since the mid-1990s, Taiwan has shifted to being a net CO₂ emissions exporter. The share of Taiwan's CO₂ emissions exported to developed countries has decreased. However, the share exported to Mainland China, Hong Kong special administrative region and many developing countries in Southeast Asia has increased. The results of a structural decomposition analysis show that emissions intensity changes were the main driving force for Taiwan's exported CO₂ emissions during 1970-1996, while increased export volumes were the largest driving force for Taiwan's exported CO₂ emissions during 1996-2015. Emissions intensity changes and population growth are the main driving factors for Taiwan's CO₂ emissions produced and consumed by itself increases. Based on the SDA results, environmentally friendly policies, such as energy efficiency and industrial structure optimization, are suggested to help Taiwan shift towards a sustainable economy.

Study on industrial selection of counterpart cooperation between Jilin province and Zhejiang province in China from the perspective of low carbon

Counterpart cooperation is a major innovative measure in China's strategy for revitalizing north-eastern China. While promoting economic progress, regional counterpart cooperation should also focus on low-carbon economy and sustainable development. Under the background of China's proposed innovative cooperation strategy, using a multi-regional input-output (MRIO) model and structural decomposition analysis (SDA), this study takes Jilin province and its counterpart Zhejiang province as an example and decomposes the change in carbon emission intensity (CEI), which is a widely used indicator to measure regional carbon emission performance. The decomposition spans the years 2007 to 2012, at the level of two provinces and departments. By comparing the factors that drive and inhibit CEI in the two provinces, it was found that the production technology effect in Jilin province primarily drove the growth in CEI, while in Zhejiang province, the opposite occurred. Second, the structural effects of agriculture and heavy industry in Jilin province accounted for the largest proportion of this change, and the pulling effect on the increase in CEI in Jilin was significantly higher than that in Zhejiang province. Third, the scale effect of agricultural demand in Zhejiang province was much higher than that in Jilin province, and the same trend was observed for the scale effect of heavy industrial exports.

Dynamic Input–Output Analysis of a Carbon Emission System at the Aggregated and Disaggregated Levels: A Case Study in the Northeast Industrial District

Research on carbon emissions of complex interactive activities in urban agglomerations is one of the hotspots of global climate change research. A comprehensive analysis of the urban agglomeration system’s carbon emissions is essential to reveal strategies for reduction and support sustainable development. The objective of this research is to develop an integrated carbon emission network model to explore the impact of different energy types on the Northeast Industrial District (NID), China. Four representative energy groups are considered. Specifically, at the aggregated sector-level, this research quantified the relative contributions of socioeconomic factors to carbon emission changes using structural decomposition analysis and examined the system efficiency and redundancy through robustness analysis. At the disaggregated level, the research investigated carbon emissions of different sectors from production-based, consumption-based, and income-based viewpoints. Moreover, emissions from specific categories of final demand and primary input were quantified. It was found that the increase of final demand level will proceed to push up the carbon emissions of the NID. Changing the production structure contributes to reducing emissions. The carbon emissions system has a high redundancy and low efficiency, illustrating that there are many emission pathways within the system. In addition, the use of crude oil significantly increases system redundancy and inhibits system efficiency. However, the major limitation of the model is that the long-term changes of the system are not considered. Moreover, considering the actual policies, emission reduction simulations could be added in the future.

Performance assessment of water reuse strategies using integrated framework of urban water metabolism and water-energy-pollution nexus

This paper evaluates the metabolism-based performance of a number of centralised and decentralised water reuse strategies and their impact on integrated urban water systems (UWS) based on the nexus of water-energy-pollution. The performance assessment is based on a comprehensive and quantitative framework of urban water metabolism developed for integrated UWS over a long-term planning horizon. UWS performance is quantified based on the tracking down of mass balance flows/fluxes of water, energy, materials, costs, pollutants, and other environmental impacts using the WaterMet² tool. The assessment framework is defined as a set of key performance indicators (KPIs) within the context of the water-energy-pollution nexus. The strategies comprise six decentralised water reuse configurations (greywater or domestic wastewater) and three centralised ones, all within three proportions of adoption by domestic users (i.e. 20, 50, and 100%). This methodology was demonstrated in the real-world case study of San Francisco del Rincon and Purisima del Rincon cities in Mexico. The results indicate that decentralised water reuse strategies using domestic wastewater can provide the best performance in the UWS with respect to water conservation, green house gas (GHG) emissions, and eutrophication indicators, while energy saving is almost negligible. On the other hand, centralised strategies can achieve the best performance for energy saving among the water reuse strategies. The results also show metabolism performance assessment in a complex system such as integrated UWS can reveal the magnitude of the interactions between the nexus elements (i.e. water, energy, and pollution). In addition, it can also reveal any unexpected influences of these elements that might exist between the UWS components and overall system.

Unfolding interregional energy flow structure of China's construction sector based on province-level data

The construction sector is a critical part in achieving energy conservation targets in China, as it accounts for approximately 30% of the annual national energy supply for building construction. Therefore, this study integrates multi-regional input-output analysis and ecological network analysis to track energy fluxes and pathways from the construction sector, aiming to facilitate the configuration of the energy-flow structure and improve understanding of the region's responsibilities. Results of a spatial distribution analysis show that the eastern area of China leads in fossil energy consumption (e.g., coal and crude oil), whereas western China is the largest consumer of natural gas. Spatial relationship analyss indicate that eastern areas are located at the top of the trophic structure, implying that these regions are prioritized in energy consumption over the surrounding regions. By contrast, most regions located in the northern parts of China are characterized by resource-abundant areas and are at the bottom of the trophic structure, thereby indicating their comparatively weak role in an exploitation relationship. An investigation of major metropolitan areas demonstrates that mandatory targets set by national instruments are stratified in accordance with their diverse role and status in energy consumption at the beginning of the 12th Five-Year Plan period. However, these targets remain insignificant in the context of the inner area.

Evaluation of the Water–Energy–Land Nexus (WELN) Using Exergy-Based Indicators: The Chilean Electricity System Case

The competition and interlinkages between energy, water, and land resources are increasing globally and are exacerbated by climate change and a rapid increase in the world population. The nexus concept has emerged for a comprehensive understanding related to the management and efficiency of resource use. This paper assesses water–energy–land nexus (WELN) efficiency through integration of the principles of Life Cycle Assessment (LCA) and exergy analysis, using the Chilean energy sector (CES) as a study case. The cumulative exergy consumption (CExC) and cumulative degree of perfection (CDP) are used as indicators for WELN efficiency. The results show the production of 1 MWh of electricity required 17.3 GJex, with the energy component of WELN (fossil and renewable energy sources) being the main contributor (99%). Furthermore, the renewable energy technologies depicted higher CDP of the water–energy–land nexus due to lower CExC and higher technology efficiency concerning non-renewables. The water and land resources contributed slightly to total exergy flow due to low quality in comparison with the energy component. Nevertheless, water availability and competition for land occupation constitute important issues for reducing environmental pressures and local conflicts. This study demonstrated the feasibility of exergy analysis for the evaluation of WELN efficiency through a single indicator, which could facilitate the comparison and integration with different processes and multi-scales.

A Literature Review to Propose a Systematic Procedure to Develop “Nexus Thinking” Considering the Water–Energy–Food Nexus

There is a growing interest in the literature on the theme of the water–energy–food nexus, as there is growing recognition that sectors that share natural resources have interdependent and interconnected systems. Despite the widespread popularity of nexus thinking, it still lacks standardized procedures and methodologies to assist in its development. Therefore, this paper proposes, from a literature review, a systematic procedure to assist in the development of management models based on nexus thinking. To this end, 304 papers were analyzed using the following criteria: nexus concept, type of approach, geographic scale, elements in the nexus system, application context, and types of assessment methods and tools. The results of the review served as the basis for determining the procedure, which consisted of four steps: (a) understanding nexus thinking, (b) identification of composing variables, (c) evaluation (diagnosis and prognosis), and (d) decision-making. In addition to the standardization of these steps, the main information used to compose the procedure was organized and synthesized with a mind map.

Ten principles to integrate the water-energy-land nexus with climate services for co-producing local and regional integrated assessments

The water-energy-land nexus requires long-sighted approaches that help avoid maladaptive pathways to ensure its promise to deliver insights and tools that improve policy-making. Climate services can form the foundation to avoid myopia in nexus studies by providing information about how climate change will alter the balance of nexus resources and the nature of their interactions. Nexus studies can help climate services by providing information about the implications of climate-informed decisions for other economic sectors across nexus resources. First-of-its-kind guidance is provided to combine nexus studies and climate services. The guidance consists of ten principles and a visual guide, which are discussed together with questions to compare diverse case studies and with examples to support the application of the principles.

The Water-Energy Nexus of Megacities Extends Beyond Geographic Boundaries: A Case of Beijing

The water-energy nexus (WEN) is dynamic and complicated in megacities, most of which are challenged by water scarcity and the mandate to reduce energy consumption. A salient feature of water and energy services in megacities is that they are supported by a web of regional infrastructure, extending far beyond the geographic boundaries of the cities, resulting in a strong dependence on resources imported from outside. Understanding the WEN of megacities has implications not only for more efficient resource utilization but also for synergistic regional development and corporation. This study provides a quantitative assessment of the WEN of Beijing within and beyond its geographic boundaries. Results show that water for local internal energy production and transformation accounts for 220 million m³/year, or 5.6% of its total freshwater use in 2016, and the energy for local water abstraction, supply, and treatment is 3.06 billion kWh, accounting for 1.1% of its total energy consumption for the same year. The external water for "imported" energy is 290 million m³/year, 1.3 times of Beijing's freshwater use for internal energy. This means that more water for energy is consumed outside Beijing than that within Beijing. The energy for external water is negligible because the bulk of the water transfer into Beijing relies on gravity and because the energy for construction of the transfer infrastructure is not included. Analysis of the WEN revealed the contradiction between the two independently conceived policies of Beijing: to meet the "three-red-line" target in the water sector, recycled water and transferred water use will rise, making it more difficult to meet the carbon emission control targets. Therefore, adopting low energy intensity, nature-based water recycling is a wise policy choice.

Research on the synergy of urban system operation-Based on the perspective of urban metabolism

Cities have been posing threats to local environment due to intensive human activities. Disordered urban metabolism can lead to unhealthy urban system operation. Studying urban metabolism can identify the characteristics and structure of urban system operations, thereby promoting sustainable development. We construct an ecological network to model the energy/material flows among the sectors of urban system in Beijing, Shanghai, Tianjin, and Chongqing, which are the most representative cities of China. Ecological network analysis was introduced to survey the system's characteristic of structure and function. Results show that Shanghai's urban metabolic system has the highest synergism with a value of 5.04, followed by Beijing, Chongqing, and Tianjin. Different cities vary considerably in terms of the relationships among the sectors. In Beijing and Chongqing, there is mutualistic relationship between environment and primary industry. Transportation forms a mutualistic relationship with tertiary industry and other sectors Only in Chongqing. The good relationships between primary industry and construction are merely seen in Beijing and Shanghai. However, some relationships are similar in the four cities, for instance, all the relationships between primary industry and advanced industry, and between construction and advanced industry are competition; All the relationships between environment and transportation are mutualism. We further explored the network stability and found that the studied urban systems are all located in a stable status relatively. Our research could reveal the synergy of urban operation, and provide a theoretical basis for optimizing urban metabolic processes by regulating the flows and guidance for sustainable urban development.

Analysis of the Water-Energy Coupling Efficiency in China: Based on the Three-Stage SBM-DEA Model with Undesirable Outputs

Although the relationships between water and energy systems have been widely researched globally, such studies have not properly considered the coupling and driving mechanisms of the nexus between water and energy. Based on panel data from 30 Chinese provinces and cities, we used a three-stage Slacks-Based Measure model for Data Envelopment Analysis (SBM-DEA) to estimate the Water-Energy coupling efficiency in China from 2003–2015. Using the Stochastic Frontier Approach (SFA) regression model, we constructed an index of environmental factors that affect the Water-Energy coupling efficiency from the four aspects of resource environment, social environment, economic environment, and ecological environment. The results indicate that the Water-Energy coupling efficiency scores in most provinces in China are high and stable, and that the coupling efficiency of water and energy in China has a distribution pattern of northeast > east > west > central. Compared to the results in the first stage of analysis, the efficiency values in the third stage (after removal of environmental and stochastic factors) were smaller, illustrating that the coupling efficiency of water and energy in China depends on a favorable external environment. In the sample period, we also found that the improvement of the resource and social environments was the most conducive way to improve the Water-Energy coupling efficiency. Overall, the management level of technological innovation in China still has some room for improvement.

Urban weight and its driving forces: A case study of Beijing

Massive resource and energy consumption greatly increase a city's domestic material consumption (its "weight"), resulting in proportionally large pressure on the environment. Understanding the causes and driving forces behind urban weight can therefore promote more sustainable urban development. To improve our understanding, we analyzed the composition of Beijing's urban weight from 2000 to 2015. We then defined the key metabolic processes (including both metabolic components and paths between them) that contributed to weight changes during this period using the logarithmic mean Divisia index model to identify the underlying driving forces. Beijing's weight grew by 82.6% during the study period, with non-metallic minerals being the material most consumed (about 45% of the total weight). Beijing depended heavily on imports, and extraction within the city's administrative boundaries has gradually declined. The Construction and Industry sectors were the dominant metabolic components; their material exchanges with both the internal and external environments of the city represented the largest flow pathways. The largest proportion of urban weight that was dissipated was air pollution, which therefore represents the biggest environmental challenge facing Beijing. Economic activity was the largest driver of urban weight growth, followed by population growth, with decreasing material consumption intensity (per unit GDP) somewhat reducing the city's weight. The results help us to understand the characteristics of urban weight change over a long period, and this knowledge can be used to prioritize structural adjustment, determine targets for regulation, refine processes, and guide future policy development to focus on the drivers of weight change.

Life-cycle water uses for energy consumption of Chinese households from 2002 to 2015

China's household energy demands' life-cycle water uses from 2002 to 2015 are quantified with an Input-Output analysis disaggregating rural and urban impacts. 9.73 and 1.60 km³ of water was withdrawn and consumed respectively in the life cycle of Chinese household energy demands in 2015, which was dominated by power and heat uses. An average urbanite's household energy uses, including coal, gas, petroleum products, power and heat, require about four times of life-cycle water uses than its rural counterpart. Among all upstream sectors, while agricultural sectors accounted for the largest shares for all energy uses, oil and gas extraction made significant contributions to petroleum products and gas consumption. A Structural Decomposition Analysis is conducted to disentangle the impacts of four driving factors, i.e. population, demand, economic structure and technology. Population change reduced energy consumption's life-cycle water use for rural households but increased that for urban households. Each economic sector's water intensity decreases, which represent technology advancement, played the dominant role curbing household energy consumption's life-cycle water uses. While power and heat dominates the household energy use profile, urbanization is accompanied by household consumption shifting from coal to gas and petroleum products. In order to reduce household energy consumption's impacts and reliance on water resources, it is imperative to reduce energy production's water use by adopting water-saving technologies, such as air cooling, as well as to reduce upstream sectors' water intensities, such as by promoting drip irrigation.

Urban Metabolic Analysis of a Food-Water-Energy System for Sustainable Resources Management

Urban metabolism analyzes the supply and consumption of nutrition, material, energy, and other resources within cities. Food, water, and energy are critical resources for the human society and have complicated cooperative/competitive influences on each other. The management of interactive resources is essential for supply chain analysis. This research analyzes the food-water-energy system of urban metabolism for sustainable resources management. A system dynamics model is established to investigate the urban metabolism of food, water, and energy resources. This study conducts a case study of Shihmen Reservoir system, hydropower generation, paddy rice irrigation of Taoyuan and Shihmen Irrigation Associations, and water consumption in Taoyuan, New Taipei, and Hsinchu cities. The interactive influence of the food-water-energy nexus is quantified in this study; the uncertainty analysis of food, water, and energy nexus is presented.

Critical sectors and paths for climate change mitigation within supply chain networks

Certain sectors and paths along supply chains play a critical role in climate change mitigation. We develope a consumption-based framework, which combines input-output analysis, a power-of-pull approach and structural path analysis, and applied it to supply chain networks derived from 2010 and 2012 Jing-Jin-Ji interregional input-output tables. The aim of this study is to identify (1) the key economic sectors for controlling carbon emissions and their changes, (2) the critical directions from a carbon-pulling sector to the emissions of key economic sectors, and (3) the paths with the largest carbon emissions flux in these critical directions. Our results show that the key sectors are from Hebei and Tianjin, more concentrated in Hebei. Most sectors have the largest pulling power over their own carbon emissions, and within-region connections dominated in the emission network, with a stronger tie between Beijing and the other two regions. Critical paths along carbon-pulling directions are located in tiers 0 and 1. Our framework can provide new insight into the creation of carbon emissions control policies.

A network analysis of indirect carbon emission flows among different industries in China

Indirect carbon emissions account for a large ratio of the total carbon emissions in processes to make the final products, and this implies indirect carbon emission flow across industries. Understanding these flows is crucial for allocating a carbon allowance for each industry. By combining input-output analysis and complex network theory, this study establishes an indirect carbon emission flow network (ICEFN) for 41 industries from 2005 to 2014 to investigate the interrelationships among different industries. The results show that the ICEFN was consistent with a small-world nature based on an analysis of the average path lengths and the clustering coefficients. Moreover, key industries in the ICEFN were identified using complex network theory on the basis of degree centrality and betweenness centrality. Furthermore, the 41 industries of the ICEFN were divided into four industrial subgroups that are related closely to one another. Finally, possible policy implications were provided based on the knowledge of the structure of the ICEFN and its trend.