Ecological network analysis for a virtual water network

Carbon metabolism mechanisms and evolution characteristics analysis of the food-water-energy nexus system under blue-green infrastructure changes

Food, water, and energy comprise a complex system (FWE nexus) that generates much carbon emissions during operation. At the same time, urban blue-green infrastructure (BGI) has a critical carbon sequestration function. This paper combines the functions of the FWE nexus and BGI and uses ecological network analysis (ENA) and the Markov model to measure the carbon metabolism (CM) mechanisms and evolutionary characteristics of BGI and FWE nexus (BGI-FWE nexus) complex systems. The results show that Guangzhou has high carbon emissions, and Zhaoqing and Huizhou have high carbon sequestration. Resident land and industrial and transportation land transfers to different land uses are more likely to produce positive carbon flows, while BGI transfers to other types are more likely to produce negative carbon flows. The study of CM mechanisms reveals a high proportion of competition relationships and a low proportion of mutualism relationships. The ecological utility index (EUI) tends to fall initially and then increase, peaking at 0.84 in 2015-2020, the highest value for the study period. The CM network has less system robustness (SR) and is in an unsustainable state of high redundancy and low efficiency. The mechanism evolution characterization study's findings show a decreased likelihood of remaining original and less stability in the spatial transfer probability matrices of EUI and SR. In this study, we constructed a BGI-FWE nexus research framework based on the different CM functions of BGI and FWE nexus. The research framework contributes to the realization of carbon reduction in the FWE nexus system and is essential for the planning and management of urban BGI.

Multiplex dependence analysis of China's interprovincial virtual water based on an ecological network

The interprovincial circulation of goods and services has formed virtual water flows between regions, which can redistribute water resources. Based on previous virtual water trade research, this study further explored the multiple dependencies of virtual water, i.e., direct, indirect, and complete dependence. This study examined the direct, indirect, and complete dependence of virtual water between provinces in China by constructing multilayer dependence networks and identified the key regions and paths of virtual water trade network. The results showed direct dependence was the densest and had the largest overall dependence degree, but indirect dependence was the most stable and orderly. Second, the dominant provinces were Guangxi, Hunan, Sichuan, Xinjiang, and Anhui, referred to as "core‒five‒region," and the flow relevant to them accounted for approximately 30% of the virtual water. The seven provinces of Shanxi, Zhejiang, Shandong, Hubei, Guangdong, Shaanxi, and Gansu depend both directly and indirectly on the "core‒five‒region." Shanxi and Zhejiang have close direct and indirect dependence, with more than one of the "core‒five‒region." Guangdong was the province with the most direct and indirect input of virtual water from the "core‒five‒region." The study provides a scientific basis for multiregional identification for the collaborative management of water resources in China from the perspective of dependence.

Decreasing resilience of China's coupled nitrogen-phosphorus cycling network requires urgent action

The coupled nature of the nitrogen (N) and phosphorus (P) cycling networks is of critical importance for sustainable food systems. Here we use material flow and ecological network analysis methods to map the N-P-coupled cycling network in China and evaluate its resilience. Results show a drop in resilience between 1980 and 2020, with further decreases expected by 2060 across different socio-economic pathways. Under a clean energy scenario with additional N and P demand, the resilience of the N-P-coupled cycling network would suffer considerably, especially in the N layer. China's socio-economic system may also see greater N emissions to the environment, thus disturbing the N cycle and amplifying the conflict between energy and food systems given the scarcity of P. Our findings on scenario-specific synergies and trade-offs can aid the management of N- and P-cycling networks in China by reducing chemical fertilizer use and food waste, for example.

Development of an industrial solid waste ecological analysis model in Shanghai, China

Amid China's rapid economic expansion, the country's industrial solid waste (ISW) problem is escalating. As each sector generates distinct types of ISW, a multi-indicator assessment of each sector is essential to address China's New Solid Waste Policy. To investigate the ISW situation of each sector and perform a comprehensive assessment, we formulate an industrial solid waste ecological analysis framework based on ISW generation and ISW flow in the sector. Various indicators (i.e., solid waste utilization coefficient, solid waste threat coefficient, and solid waste threat intensity) are employed to assess the utilization of solid waste generated for each sector, as well as the threat of solid waste originating in each sector to society. Ecological network analysis probes the interrelationships between diverse sectors. Taking Shanghai in 2017 as an example, the study indicates that some sectors (e.g., production and supply of electric power and heat power (EH) and metal smelting and rolling processing sector (MS)) exhibit higher direct ISW generation and the direct industrial solid waste value-added coefficient (SVAC) for common industrial solid waste (CISW). Specifically, the direct CISW generation of EH and MS is 539.21Mt and 277.00Mt respectively. The direct SVAC of EH and MS is 157.06kg/103RMB and 126.27kg/103RMB respectively. These sectors should prioritize reducing emissions at the source. Additionally, the threats to society from various sectors are relatively insignificant for the CISW, while for the hazardous waste (HW), all sectors pose a considerable threat to Shanghai's society. Moreover, some sectors (e.g., mining industry) exhibit the highest mutualism relationships in the CISW and the HW. Enhancing mining sector technologies is a vital strategy for mitigating ISW sources. Specifically, MI has 9 pairs of mutualism relationships in the CISW and 8 pairs in the HW. These insights will provide empirical evidence for tackling the ISW problem in Shanghai.

Spatial and structural characteristics of the ecological network of carbon metabolism of cultivated land based on land use and cover change: a case study of Nanchang, China

This paper explored the ecological network of CMCL (carbon metabolism of cultivated land) of Nanchang City from 2000 to 2020 to promote the low-carbon land management and China's dual carbon goals. We found that vertical and horizontal net carbon flow of cultivated land was negative during 2000-2020, and harmful carbon flow was mainly generated by the conversion of cultivated land to transportation and industrial land. Cultivated land contributed the most of the total carbon throughflow, accounting for 56.16%. Furthermore, exploitation and control relationships made maximal contribution to ecological relationships (45.83%), followed by competition relationships and mutualism relationships. In addition, ecological utility index showed the ecological network of CMCL is unhealthy. We suggest that it is necessary to achieve healthy and orderly operation of the ecological network of CMCL to reduce carbon emissions.

Cross-media transfer of nitrogen pollution in the fast-urbanized Greater Bay Area of China: Trends and essential control paths

For urban agglomerations in the bay area, which concentrate multiple environmental elements and intense anthropogenic activities, comprehensive control of nitrogen pollution is particularly challenging due to diverse cross-media migration and transformation forms of nitrogen pollutants. Existing studies on urban nitrogen metabolism mainly focused on quantification of nitrogen flux, without systematic consideration of physiochemical changes of nitrogen between environmental media. This study conducted a dynamic simulation of nitrogen cross-media metabolism in urban agglomeration over 30 consecutive years, and recognized the types, quantities, and trends of cross-media transfer of nitrogen pollution as well as pollution control paths based on ecological network analysis and scenario analysis. Taking the Guangdong-Hong Kong-Macao Greater Bay Area as the case, results show that during its fast-urbanized stage in 1989-2018, more than 25% of the total nitrogen pollution emissions were transferred from other media. The higher degree of imbalance between the socioeconomic system and the soil in the nitrogen metabolic network emphasizes the increased pressure and necessity of pollution control of nitrogen in the solid state with urban development. Promoting fertilizer reduction and sludge land use are priority paths for collaborative control of cross-media nitrogen pollution. The study provides methods to systematically analyze the features of cross-media transfer of nitrogen pollution at the city level, and accordingly propose paths aiming at sustainable urban nitrogen management with multi-media integrity and synergy.

Water footprint and virtual water trade analysis in water-rich basins: Case of the Chaohu Lake Basin in China

Water footprints and virtual water are widely used as essential tools for water use and conservation analysis of basins worldwide. Despite the importance of water-rich basins as the main force for water-saving, water use analysis has been mainly for water-scarce basins rather than water-rich basins in the existing literature. To fill the gap, in this paper, we investigate the water footprint and virtual water trade in a water-rich basin, namely the Chaohu Lake Basin in China, from 2007 to 2017 using input-output analysis. The results show that: (1) Water use efficiency in the Chaohu Lake Basin was significantly improved. The overall trend of the water intensity was declining, decreasing by 10.21 % in 2017 versus 2012; (2) The internal and external water footprints showed an upward trend, and the growth rate of total water footprint was 36.66 %; (3) The basin was a net virtual water exporter, but the net export flows of virtual water has decreased significantly. The virtual water net export flow decreased by 0.12 billion m³ in 2017 versus 2012; (4) Water resources in the basin were mainly used locally, and its supply to other provinces was minimal. Compared with some water-scarce basins such as the Heihe River Basin and Haihe River Basin, the Chaohu Lake Basin shows significant gaps in the virtual water export flow per capita and behaves differently in the proportion of virtual water transfer. Based on the above findings, we conclude with some guidance and implications for local governments and policymakers.

Shared network and supply chain features for synergetic control of carbon and air pollutant emissions

The synergetic control of carbon and air pollutant emissions will be an unflagging effort for China in its dual pursuit of air quality improvement and carbon neutrality. The shared features of sectoral emissions from network and supply chain perspectives, as well as the evolution of these features under policy intervention remain to be investigated. This study develops four ecological networks for CO₂ and SO₂ emissions targeting the period 2010-2015 with strengthened emission control implemented. By fusing input-output analysis, Ecological Network Analysis and Structural Path Analysis, the shared intersectoral linkages of emissions are examined, and the key supply chains are identified. The results indicate that most sectors have control over Transportation Equipment, Electronic Equipment, and Construction, and almost all sectors have dependence on Power and Heat. Exploitative relationships induced by emission flows along supply chains are predominant, accounting for over 60% for four emission flow networks. Eight shared supply chains are identified among the top 20 that generally induce larger than 50% emissions in both 2010 and 2015. The one with the largest emissions is "Total capital formation → Construction → Nonmetals". During 2010-2015, the critical evolution of network features is the decrease in the economy's control over Construction, dependence on Fossil Energy Mining, and emissions contained in the paths associated with exports. The findings help to more pertinently strategize on prescient regulation of key supply chains for a more effective carbon-pollution synergetic control.

Ecological network analysis of industrial wastes metabolism based on input-output model for Jiangsu, China

The enormous discharge of industrial waste seriously hinders the sustainable development of cities. However, most studies only involve a single or limited category of industrial pollutants, ignoring the environmental pressure caused by multiple resources and environmental factors. This paper combines input-output analysis and ecological network analysis to construct an industrial waste metabolic input-output (IWMIO) model, which explores the industrial waste discharge and discharge relationships among different sectors in Jiangsu Province from the three aspects of industrial wastewater, industrial waste gas, and industrial solid waste. The results show that the indirect discharge of industrial waste is greater than the direct discharge in the industrial waste metabolism system. TI (Tertiary industry), CI (Chemical industry), SPM (Smelting and pressing of metals), and PSEH (Production and supply of electricity and heat) dominate the industrial waste metabolism system. In addition, MWC (Mining and washing of coal), MNMP (Manufacture of non-metallic mineral products), SPM (Smelting and pressing of metals) have more mutualism and competition relationships with other sectors, so the control of industrial waste discharge in these sectors contributes to achieving emission reduction targets. Based on the research results, this paper proposes corresponding policy recommendations such as considering both direct and indirect emissions of sectors when formulating waste reduction policies and developing pertinent industrial waste reduction programs based on the characteristics of the identified sectors. The results of this paper are helpful to identify the dependence and influence relationships of various sectors in the industrial waste metabolism system, promote industrial waste discharge control, and provide theoretical support for the adjustment of industrial structure and the formulation of related policies in Jiangsu Province.

Sustainable conjunctive water management model for alleviating water shortage

Water shortage poses a great challenge to the health of population and environment and impedes socio-economic development. Therefore, a comprehensive model is necessary to promote the adaptation of the whole socio-economic system to limited water resources. To achieve it, a sustainable conjunctive water management model (SCWM) was developed. In SCWM, direct (physical) and indirect (virtual or embodied) water consumptions of multiple water resources in future scenarios are projected, and the sustainable performances of various water-saving scenarios are quantified from the perspectives of water resources, economy, and ecosystem under water capping policy. A case study of Shaanxi, a typical water shortage province in central-eastern China, is conducted aimed at conquering the irrational use of surface- and ground-water subjected to the constraint of future total water use quota. Key findings contain optimal possibility of adapting water shortage via saving water through increasing industrial water efficiency to 11.12 m³/10,000 CNY and reducing 40% of agricultural final demand (Summation of direct and indirect water savings of the two scenarios are 41.57 × 10⁸ m³ and 20.27 × 10⁸ m³, respectively.) and nonsynergistic effects of simultaneous decreasing final demand of multiple sectors on water consumption intensity (WCI) of total (all kinds of water) water, surface- and ground-water. To devise effective policies for conjunctive management of surface- and ground-water, positive utility, economic structure and water productivity should be heeded, and proposals emphasize trade-offs between surface water saving and groundwater conservation, water metabolic and socio-economic systems sustainability and negative interaction of multiple sectors on economy and WCI should be framed. The innovation of this study is the development of SCWM, which can provide sustainable solution for future multiple-source water saving management measures thoroughly concerning direct and indirect water and sectorial interactions. The model not only brings insights to Shaanxi's water management but also can be used for other similar arid area.

Identifying optimal virtual water management strategy for Kazakhstan: A factorial ecologically-extended input-output model

Virtual water is an important indicator measuring the amount of water needed from the perspective of consumption, which can help decision makers to identify desired system design and optimal management strategy against water resources shortage. In this study, a novel model named as factorial ecologically-extended input-output model (abbreviated as FEIOM) is developed for virtual water management. FEIOM integrates techniques of input-output model (IOM), ecological network analysis (ENA) and factorial analysis (FA) into a general framework. It is effective to evaluate the virtual water flows, reveal ecological inter-connections in virtual water system (VWS), and identify key water consumption sectors that have significant individual and interactive effects on VWS's performance. FEIOM is then applied to identifying optimal virtual water management strategies for Kazakhstan in Central Asia. The main findings are: (i) Kazakhstan is a net importer of virtual water (reaching up to 46.0 × 10⁹ m³), demonstrating that the national economic structure is reasonable, which can abate the national water scarcity and improve its eco-environmental protection; (ii) the virtual water of agricultural sector is net exporter, where vegetables, fruits and nuts occupy 86% of the total agricultural exports; the massive export of water-intensive products further squeezes the water for other users; (iii) the key factors affecting the national VWS are agriculture > primary manufacturing > advanced manufacturing > services. Therefore, from solving water resources shortage and facilitating sustainable development perspectives, Kazakhstan should stimulate the domestic primary manufacturing productions and improve agriculture and advanced manufacturing water-use efficiencies.

Ecological network analysis of an urban water metabolic system: Integrated metabolic processes of physical and virtual water

The contradiction between social economy and water environment has become increasingly prominent, and the analysis of urban water metabolism system (UWMS) represents a problem-solving approach from the perspective of the entire flow process. However, a comprehensive UWMS model that considers both physical and virtual water flows is currently lacking. This paper presents an innovative application of an ecological network model of the UWMS-integrated metabolic process of physical and virtual water in Xining during the 2002-2018 period. By analysing and screening the metabolic characteristics, metabolic structure and metabolic relationships, the sustainability of the UWMS is evaluated in depth, and the main causes and critical compartments of the unhealthy metabolic process are identified. The findings show that the UWMS in Xining maintains a moderate level of robustness (the average R = 0.48) with limited metabolic efficiency. Since 2012, the water management policies in Xining have been significantly strengthened, contributing to a slight increase in robustness by improving the water use efficiency and metabolic structure. The integrated metabolic process is unhealthy because the metabolic structure is not reasonable, and the systematic metabolic relationship tends to be antagonistic due to the network mutualism index dropping to 1.0 during 2016-2018. We conclude that efficient irrigation management, more infrastructure projects for the sewer network, wastewater treatment and recycling could provide effective support to enhance the coordinate development of the social economy and water environment in Xining.

Competition and Exploitation for Ecological Capital Embodied in International Trade: Evidence from China and Its Trade Partners

In order to identify ecological relationships of participating countries in the transfer system of ecological capital embodied in global trade, this paper takes the international trade of China and its partners from 2002 to 2017 as a case, and uses the ecological footprint (EF) measured by the optimized product land-use matrix (PLUM) method to quantify ecological capital for the value of macro-ecological resources, then uses the ecological network analysis (ENA) method to construct a complete transfer network of trade-embodied ecological capital and uses a utility analysis to identify ecological relationships between trading countries. Our results show that: (1) Throughout the study period, competition relationships with 61% dominated in the network, and the countries that have a pair-wise competition relationship with China are mainly located in central and western Europe, northeastern Europe, North America, southern Asia and eastern Asia. (2) Indirect utility determines the dominant ecological relationship in system, and it mainly converts dominant ecological relationships from control to competition by transforming exploit into competition. (3) China is looking to creating a more mutually beneficial trading environment at the expense of its own interests. (4) A global crisis event is likely to result in the control of ecological capital in more countries, and in its aftermath, the world is likely to be in a highly competitive environment. Reducing ecological capital consumption by improving energy efficiency and optimizing the global trading environment into a trading system dominated by mutualism relationships can be effective ways for countries around the world to achieve sustainable development post-COVID-19 crisis.

Multi-regional industrial wastewater metabolism analysis for the Yangtze River Economic Belt, China

Enormous wastewater discharges have significantly impeded the sustainable development. As several economic belt has been formed in China, systematic analysis of multi-regional wastewater metabolic system is required for advancing wastewater mitigation effectively and efficiently. In this study, a distributive environmental input-output model (DEIO) is developed for the Yangtze River Economic Belt (YREB) to provide bases for supporting sustainable development from inter-regional and inter-sectoral perspectives. The discharges and flows of wastewater and related pollutants (i.e., chemical oxygen demand (COD) and ammonia nitrogen (AN)) among sectors and regions are analyzed to providing solid bases for wastewater management within the YREB. The results show that the industrial wastewater mitigation in YREB is desired urgently. The industrial wastewater discharges in Jiangsu and Zhejiang provinces are numerous, while Hunan and Yunnan provinces are more inclined to suffer from serious COD and AN pollution. In addition, the manufacture of food, tobacco, chemical materials, and pharmaceutical are the typical sectors with a large amount of direct wastewater discharge, and the tertiary industry is ranked at the first in indirect wastewater discharge. According to the analysis, the implementation of the "Supply-side Structure Reform" and the "Replace Subsidies with Rewards" policy can benefit the wastewater mitigation in the YREB.

A factorial emission-focused general equilibrium model for investigating composite effects of multiple environmental policies

With the rapid growth of the economy, there are increasing conflicts between economic development and environmental protection. Among these conflicts, the wastewater emission management as one of the significant ways to alleviate water scarcity has been paid increasing attention across the developing countries, such as China. It is thus essential to comprehensively investigate the enviro-economic effects induced by wastewater-related policies. In this study, a factorial emission-focused general equilibrium model (FEGE) is first developed to facilitate examine the composite enviro-economic effects of multiple policy scenarios with regards to wastewater-related environmental taxes and the related subsides. A special case study for the Municipality of Chongqing, China, is conducted to illustrate the potential benefits of its use in the formulation of wastewater-related policies. It is found that the impacts of various wastewater-related policies (i.e., environmental taxes and the related subside) on GDP are different. In detail, green tax policies on GDP are negative, while wastewater emission intensity (WEI) improvement policies on GDP are positive. When green tax reaches 14 yuan/tonne, which is the maximum proposed by the Chinese government, the GDP will drop by 0.37%, which would be deemed acceptable for the Municipality of Chongqing. In addition, the impacts on rural households' consumption are greater than those on urban households' consumption whichever the application of wastewater-related policies; it is because the rural households in the Municipality of Chongqing have a relatively unitary income source. It is thus recommended that the rural household in Chongqing should be paid more attention. For example, some extra allowances could be considered to the rural household to help them cope with the negative economic impacts induced by a new environmental policy. It is expected that the outputs would provide bases for formulating desired wastewater-related policies.

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.

Social network analysis of virtual water trade among major countries in the world

This study utilizes multi-region input-output model to calculate the virtual water trade among 19 major countries (the Group 20 countries, except the EU) from 2006 to 2015. Moreover, this paper uses network analysis method to study the characteristics of virtual water trade networks. Results show that: (1) the import and export of the virtual water trade among 19 major countries in 2015 increased in varying degrees. Among them, the growth rates of China's import and Russia's export were the highest. (2) The density(average value) and asymmetry(differences between import and export)of the virtual water trade network among the major countries in 2006-2015 increased throughout the whole industry and the three major industries. In comparison with the secondary and tertiary industries, the virtual water trade network formed by the primary industry is denser. (3) The Out-Degree(corresponding to export) and In-Degree(corresponding to import)of countries in the virtual water trade network of the whole industry increased in varying degrees in 2015. Major countries exhibited the largest export and import within the primary industry, except for Japan and South Korea. Therefore, in order to alleviate the contradiction between supply and demand of water resources in various countries, it is necessary to further strengthen the construction of transportation facilities and reduce the logistics cost of trade in industrial and agricultural products, especially the trade cost of agricultural products such as grain, so as to further expand the virtual water import and export trade to expand the import and export trade of the virtual water network further.

Multi-dimensional diagnosis model for the sustainable development of regions facing water scarcity problem: A case study for Guangdong, China

Freshwater consumption and wastewater discharge of economic activities have caused water scarcity problem in many regions. This study aims to develop a multi-dimensional diagnosis model (MDDM) to provide new insights for the sustainable development of regions which face water scarcity problem. In detail, the sectorial blue water, grey water and total water consumptions are assessed to reveal the direct effects of economic activities on water quantity and water quality. Then, hypothetical extraction method is integrated into input-output model and ecological network analysis to quantify the system-based effects of sectors in three dimensions: economy, water and metabolism. A case study of Guangdong province, China is conducted to illustrate the availability of the developed model. We found that the multi-dimensional performances of Guangdong's socioeconomic system are dominated by a few sectors. Wastewater, especially that discharged from the primary industry, is the main reason for the local water scarcity. Specifically, the unique role that every sector plays in the socioeconomic system is quantitatively revealed by MDDM, which could guide the relevant policy development at sectorial level.

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.

Water Pipeline Leakage Detection Based on Machine Learning and Wireless Sensor Networks

The detection of water pipeline leakage is important to ensure that water supply networks can operate safely and conserve water resources. To address the lack of intelligent and the low efficiency of conventional leakage detection methods, this paper designs a leakage detection method based on machine learning and wireless sensor networks (WSNs). The system employs wireless sensors installed on pipelines to collect data and utilizes the 4G network to perform remote data transmission. A leakage triggered networking method is proposed to reduce the wireless sensor network’s energy consumption and prolong the system life cycle effectively. To enhance the precision and intelligence of leakage detection, we propose a leakage identification method that employs the intrinsic mode function, approximate entropy, and principal component analysis to construct a signal feature set and that uses a support vector machine (SVM) as a classifier to perform leakage detection. Simulation analysis and experimental results indicate that the proposed leakage identification method can effectively identify the water pipeline leakage and has lower energy consumption than the networking methods used in conventional wireless sensor networks.

A Systems Approach To Assess Trade Dependencies in U.S. Food-Energy-Water Nexus

We present a network model of the United States (U.S.) interstate food transfers to analyze the trade dependency with respect to participating regions and embodied irrigation impacts from a food-energy-water (FEW) nexus perspective. To this end, we utilize systems analysis methods including the pointwise mutual information (PMI) measure to provide an indication of interdependencies by estimating probability of trade between states. PMI compares observed trade with a benchmark of what is statistically expected given the structure and flow in the network. This helps assess whether dependencies arising from empirically observed trade occur due to chance or preferential attachment. The implications of PMI values are demonstrated by using Texas as an example, the largest importer in the U.S. grain transfer network. We find that strong dependencies exist not only just with states (Kansas, Oklahoma, Nebraska) providing high volume of transfer to Texas but also with states that have comparatively lower trade (New Mexico). This is due to New Mexico's reliance on Texas as an important revenue source compared to its other connections. For Texas, import interdependencies arise from geographical proximity to trade. As these states primarily rely on the commonly shared High Plains aquifer for irrigation, overreliance poses a risk for water shortage for food supply in Texas. PMI values also indicate the capacity to trade more (the states are less reliant on each other than expected), and therefore provide an indication of where the trade could be shifted to avoid groundwater scarcity. However, some of the identified states rely on GHG emission intensive fossil fuels such as diesel and gasoline for irrigation, highlighting a potential tradeoff between crop water footprint and switching to lower emissions pumping fuels.

Diversity analysis of water sources, uses, and flows from source to use in the USA

Diversifying a system can reduce risk from- and increase resilience to perturbation. For this reason, the concept of diversity has been used in many different fields but its use in analyzing engineering infrastructure has been limited. In particular, the diversity of water sources and uses and the diversity of how sources are connected to uses (flow) have never been analyzed. In addition, the relationships between diversity and economic efficiency of water systems remain uncertain. In this study, we addressed these topics by conceptualizing and quantifying water source, use, and flow diversity in the USA. Water source and water use data were collected from the US Geological Survey for 2000, 2005, and 2010. Diversity was calculated with the Shannon Weaver Index. The overall mean water use diversity by state was 0.79 ± 0.31 (N = 150) and increased from 0.63 ± 0.31 in 2000 to 0.89 ± 0.28 by 2010, reflecting overall decreases in high-use categories, like thermonuclear power, and relative increases in already low domestic use. In contrast, source diversity showed no change over time, with an overall state mean of 0.82 ± 0.28 (N = 150) but varying between states largely due to differences in geographic and climatic factors influencing regional water sources. Water flow diversity also showed no change over time, averaging 1.00 ± 0.43 (N = 150), higher than both source and use diversity. The mean water use efficiency for all states over the study period was 52 ± 60 $/m³ of water and was positively and strongly related to both source and use diversity. Thus, the USA water system diversity is sensitive to factors logically expected to influence both source and use, and directly affects water use efficiency.

Ecological network analysis of growing tomatoes in an urban rooftop greenhouse

Urban agriculture has emerged as an alternative to conventional rural agriculture seeking to foster a sustainable circular economy in cities. When considering the feasibility of urban agriculture and planning for the future of food production and energy, it is important to understand the relationships between energy flows throughout the system, identify their strengths and weaknesses, and make suggestions to optimize the system. To address this need, we analyzed the energy flows for growing tomatoes at a rooftop greenhouse (RTG). We used life cycle assessment (LCA) to identify the flows within the supply chain. We further analyzed these flows using ecological network analysis (ENA), which allowed a comparison of the industrial system to natural systems. Going beyond LCA, ENA also allowed us to focus more on the relationships between components. Similar to existing ENA studies on urban metabolism, our results showed that the RTG does not mimic the perfect pyramidal structure found in natural ecosystems due to the system's dependency on fossil fuels throughout the supply chain and each industry's significant impact on wasted energy. However, it was discovered that the RTG has strong foundational relationships in its industries, demonstrating overall positive utility; this foundation can be improved by using more renewable energy and increasing the recycling rates throughout the supply chain, which will in turn improve the hierarchy of energy flows and overall energy consumption performance of the system.

Ecological network analysis for an industrial solid waste metabolism system

Faced with an increasing amount of industrial solid waste (ISW) in the process of rapid industrialization, it is indispensable to carry out ISW metabolism study to realize source and waste reduction. In this study, a new composite waste input-output (WIO) model is developed to examine ISW production and production relationships among different sectors. In particular, the extended methods of network control analysis and network utility analysis are used in the ecological network analysis under two ISW scenarios (i.e. common industrial solid waste (CISW) and hazardous waste (HW) scenarios). Furthermore, comprehensive utilization analysis is first developed to evaluate the ISW utilization level and to guide the planning of sectors with large proportion of ISW production. A case study of Guangdong, China shows that indirect flow analysis can be used to understand the internal ISW metabolism structure. The mining sectors produce a large amount of direct ISW and perform a low level of comprehensive utilization, but they have mutualism relationships with other sectors. The energy transformation (EH) sector in the CISW system has high direct generation intensity and plays as a main controller. The situation of paper manufacturing (MP) sector in HW system is similar to that of EH. Therefore, it is expected that the results of this study will provide scientific foundations for these sectors to formulate future ISW reduction policies.

Network structure impacts global commodity trade growth and resilience

Global commodity trade networks are critical to our collective sustainable development. Their increasing interconnectedness pose two practical questions: (i) Do the current network configurations support their further growth? (ii) How resilient are these networks to economic shocks? We analyze the data of global commodity trade flows from 1996 to 2012 to evaluate the relationship between structural properties of the global commodity trade networks and (a) their dynamic growth, as well as (b) the resilience of their growth with respect to the 2009 global economic shock. Specifically, we explore the role of network efficiency and redundancy using the information theory-based network flow analysis. We find that, while network efficiency is positively correlated with growth, highly efficient systems appear to be less resilient, losing more and gaining less growth following an economic shock. While all examined networks are rather redundant, we find that network redundancy does not hinder their growth. Moreover, systems exhibiting higher levels of redundancy lose less and gain more growth following an economic shock. We suggest that a strategy to support making global trade networks more efficient via, e.g., preferential trade agreements and higher specialization, can promote their further growth; while a strategy to increase the global trade networks' redundancy via e.g., more abundant free-trade agreements, can improve their resilience to global economic shocks.

Evaluating the evolution of the Heihe River basin using the ecological network analysis: Efficiency, resilience, and implications for water resource management policy

One of the most critical challenges in the anthropocentric age is the sustainable management of the planet's increasingly strained water resources. In this avenue, there is a need to advance holistic approaches and objective tools which allow policy makers to better evaluate system-level properties and trade-offs of water resources. This research contributes to the expanding literature in this area by examining the changes to system-level network configurations of the middle reaches of the Heihe River basin from 2000 to 2009. Specifically, through the ecological network analysis (ENA) approach, this research examines changes to the system-level properties of efficiency, redundancy, and evaluates the trade-offs to the resiliency of ecosystem water services of the middle reaches of the Heihe River basin. Our results indicate that while the efficiency of the middle reaches has increased from 2000 to 2009 by 6% and 78% more water is released to the lower reaches, the redundancy of the system has also decreased by 6%. The lower level of redundancy, particularly due to the changes in the groundwater body levels, has critical long-term consequences for the resilience of the water ecosystem services of the middle reaches. In consideration of these holistic trade-offs, two hypothetical alternative scenarios, based on water recycling and saving strategies, are developed to improve the long-term health and resilience of the water system.

Tracking Inter-Regional Carbon Flows: A Hybrid Network Model

The mitigation of anthropogenic carbon emissions has moved beyond the local scale because they diffuse across boundaries, and the consumption that triggers emissions has become regional and global. A precondition of effective mitigation is to explicitly assess inter-regional transfer of emissions. This study presents a hybrid network model to track inter-regional carbon flows by combining network analysis and input-output analysis. The direct, embodied, and controlled emissions associated with regions are quantified for assessing various types of carbon flow. The network-oriented metrics called "controlled emissions" is proposed to cover the amount of carbon emissions that can be mitigated within a region by adjusting its consumption. The case study of the Jing-Jin-Ji Area suggests that CO2 emissions embodied in products are only partially controlled by a region from a network perspective. Controlled carbon accounted for about 70% of the total embodied carbon flows, while household consumption only controlled about 25% of Beijing's emissions, much lower than its proportion of total embodied carbon. In addition to quantifying emissions, the model can pinpoint the dominant processes and sectors of emissions transfer across regions. This technique is promising for searching efficient pathways of coordinated emissions control across various regions connected by trade.

The effect of inter-annual variability of consumption, production, trade and climate on crop-related green and blue water footprints and inter-regional virtual water trade: A study for China (1978-2008)

Previous studies into the relation between human consumption and indirect water resources use have unveiled the remote connections in virtual water (VW) trade networks, which show how communities externalize their water footprint (WF) to places far beyond their own region, but little has been done to understand variability in time. This study quantifies the effect of inter-annual variability of consumption, production, trade and climate on WF and VW trade, using China over the period 1978-2008 as a case study. Evapotranspiration, crop yields and green and blue WFs of crops are estimated at a 5 × 5 arc-minute resolution for 22 crops, for each year in the study period, thus accounting for climate variability. The results show that crop yield improvements during the study period helped to reduce the national average WF of crop consumption per capita by 23%, with a decreasing contribution to the total from cereals and increasing contribution from oil crops. The total consumptive WFs of national crop consumption and crop production, however, grew by 6% and 7%, respectively. By 2008, 28% of total water consumption in crop fields in China served the production of crops for export to other regions and, on average, 35% of the crop-related WF of a Chinese consumer was outside its own province. Historically, the net VW within China was from the water-rich South to the water-scarce North, but intensifying North-to-South crop trade reversed the net VW flow since 2000, which amounted 6% of North's WF of crop production in 2008. South China thus gradually became dependent on food supply from the water-scarce North. Besides, during the whole study period, China's domestic inter-regional VW flows went dominantly from areas with a relatively large to areas with a relatively small blue WF per unit of crop, which in 2008 resulted in a trade-related blue water loss of 7% of the national total blue WF of crop production. The case of China shows that domestic trade, as governed by economics and governmental policies rather than by regional differences in water endowments, determines inter-regional water dependencies and may worsen rather than relieve the water scarcity in a country.