Lifting China's water spell

A high-resolution multi-scale industrial water use dataset in China

Water is crucial for achieving the UN Sustainable Development Goals, particularly SDG 6. As a major source of water use and pollution, industrial sector requires improved water management based on more systematic and refined analysis. Such analysis, however, is compromised by the accuracy, granularity, and coverage of industrial water data. Here we present an open dataset of China's industrial water use, compiled from 1,480,265 plant-level reports. This high-resolution multi-scale dataset offers unparalleled details, supporting multi-scale analysis at the province, city, and county levels, and across 2-digit, 3-digit, and 4-digit industrial classifications. It provides comprehensive information on water use, recycling, pollution, and wastewater processing. Such data enables further macro- and micro-level analysis, including multi-regional input-output analysis, structural decomposition analysis, statistical analysis, machine learning, as well as many other advanced analytical methods. This dataset can equip researchers and policymakers with a valuable tool to advance sustainable water management, fostering alignment with global sustainability goals.

Increasing role of transboundary food-related water footprints by regional income groups

Income group heterogeneity and transboundary food-related water footprints are essential for water resource management. Previous studies have not fully characterized the transboundary food-related water footprints by regional income groups. Taking Guangdong as an example, this study calculates the local and transboundary food-related water footprints by income groups and explores relevant socioeconomic factors during 2007-2017. Results show that the proportion of transboundary food-related water footprints by income groups has increased during 2007-2017. By 2017, nearly half of food-related water footprints of income groups happened in external regions. In particular, the high-income groups of Guangdong transferred large amounts of food-related water footprints to specific northern regions (e.g., Heilongjiang and Jilin). However, socioeconomic changes of these northern regions contributed to the increase of food-related water footprints by income groups. Fortunately, the transitions of food consumption structures of income groups helped to reduce the external food-related water footprints. We also observed that the effects of dietary behavior changes were group heterogeneous. The findings of this study can provide scientific foundations for group-targeted dietary behavior optimization to reduce water footprints, as well as interregional collaboration for sustainable food and water resource management.

Multidimensional occurrence and diet risk of emerging contaminants in freshwater with urban agglomerations

Freshwater systems near highly urbanized areas are extremely susceptible to emerging contaminants (ECs), yet their stereoscopic persistence in aquatic ecosystems and related risks remain largely unknown. Herein, we characterized the multi-mediums distribution of 63 ECs in Baiyangdian Lake, the biggest urban lake in the North of China. We identified variations in the seasonal patterns of aquatic EC levels, which decreased in water and increased in sediment from wet to dry seasons. Surprisingly, higher concentrations and a greater variety of ECs were detected in reeds than in aquatic animals, indicating that plants may contribute to the transferring of ECs. Source analysis indicated that human activity considerably affected the distribution and risk of ECs. The dietary risk of ECs is most pronounced among children following the intake of aquatic products, especially with a relatively higher risk associated with fish consumption. Besides, a comprehensive scoring ranking method was proposed, and 9 ECs, including BPS and macrolide antibiotics, are identified as prioritized control pollutants. These findings highlight the risks associated with aquatic ECs and can facilitate the development of effective management strategies.

An integrated simulation-optimization approach for combined allocation of water quantity and quality under multiple uncertainties

Multiple uncertainties such as water quality processes, streamflow randomness affected by climate change, indicators' interrelation, and socio-economic development have brought significant risks in managing water quantity and quality (WQQ) for river basins. This research developed an integrated simulation-optimization modeling approach (ISMA) to tackle multiple uncertainties simultaneously. This approach combined water quality analysis simulation programming, Markov-Chain, generalized likelihood uncertainty estimation, and interval two-stage left-hand-side chance-constrained joint-probabilistic programming into an integration nonlinear modeling framework. A case study of multiple water intake projects in the Downstream and Delta of Dongjiang River Basin was used to demonstrate the proposed model. Results reveal that ISMA helps predict the trend of water quality changes and quantitatively analyze the interaction between WQQ. As the joint probability level increases, under strict water quality scenario system benefits would increase [3.23, 5.90] × 109 Yuan, comprehensive water scarcity based on quantity and quality would decrease [782.24, 945.82] × 106 m3, with an increase in water allocation and a decrease in pollutant generation. Compared to the deterministic and water quantity model, it allocates water efficiently and quantifies more economic losses and water scarcity. Therefore, this research has significant implications for improving water quality in basins, balancing the benefits and risks of water quality violations, and stabilizing socio-economic development.

City level water withdrawal and scarcity accounts of China

In the context of China's freshwater crisis high-resolution data are critical for sustainable water management and economic growth. Yet there is a dearth of data on water withdrawal and scarcity regardless of whether total or subsector amount, for prefectural cities. In administrative and territorial scope, we accounted for water withdrawal of all 63 economic-socio-environmental sectors for all 343 prefectural cities in China, based on a general framework and 2015 data. Spatial and economic-sector resolution is improved compared with previous studies by partitioning general sectors into industrial and agricultural sub-sectors. Construction of these datasets was based on selection of 16 driving forces. We connected a size indicator with corresponding water-withdrawal efficiency. We further accounted for total blue-water withdrawal and quantitative water scarcity status. Then we compared different scopes and methods of official accounts and statistics from various water datasets. These disaggregated and complete data could be used in input-output models for municipal design and governmental planning to help gain in-depth insights into subsector water-saving priorities from local economic activities.

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.

Water pollution scenarios and response options for China

China has formulated several policies to alleviate the water pollution load, but few studies have quantitatively analyzed their impacts on future water pollution loads in China. Based on grey water footprint (GWF) assessment and scenario simulation, we analyze the water pollution (including COD, NH3-N, TN and TP) in China from 2021 to 2035 under different scenarios for three areas: consumption-side, production-side and terminal treatment. We find that under the current policy scenario, the GWF of COD, NH3-N, TN, and TP in China could be reduced by 15.0 % to 39.9 %; the most effective measures for GWF reduction are diet structure change (in the consumption-side area), and the wastewater treatment rate and livestock manure utilization improvement (in the terminal treatment area). However, the GWF will still increase in 8 provinces, indicating that the current implemented policy is not universally effective in reducing GWF across all provinces. Under the technical improvement scenario, the GWF of the four pollutants will decrease by 54.9 %-71.1 % via improvements in the current measures related to current policies and new measures in the production-side area and the terminal treatment area; thus, GWF reduction is possible in all 31 provinces. However, some policies face significant challenges in achieving full implementation, and certain policies are only applicable to a subset of provinces. Our detailed analysis of future water pollution scenarios and response options to reduce pollution loads can help to inform the protection of freshwater resources in China and quantitatively assess the effectiveness of policies in other fields.

Significant decline of water pollution associated with inland fishery across China

Water pollution seriously threatens the sustainable development of fisheries in China. To inform effective pollution control policies, a comprehensive understanding of the fishery environment status is needed. However, nationwide data on the temporal changes of major pollutants in the fishery waters of China are scarce. This study collected data on the major water pollutants, including total nitrogen, total phosphorus, heavy metals, and total petroleum hydrocarbons (TPHs), from 2003 to 2017 to evaluate dynamic changes in the inland fishery water environment across China. We discovered that the levels of four heavy metals (Cu, Zn, Pb, and Cd) and TPH decreased during the 15-year period, corresponding to the reduced national discharge of pollution sources from 2003 to 2015. However, nitrogen and phosphorus levels in the inland fishery waters showed no significant changes during this period. A comparative analysis of water quality in different periods indicated that these improvements were highly associated with effective measures for water pollution control in China. In addition, the decline in pollution was consistent among the three regions of China (north, west, and southeast) from 2003 to 2017, while southeast China exhibited the weakest pollution mitigation among the three regions. These findings suggest that the inland fishery water quality improved during 2003-2017, but still faced eutrophication risk.

Exploring the drivers of quantity- and quality-related water scarcity due to trade for each province in China

Previous studies have explored virtual water flows due to interprovincial trade within China as well as related impacts on both regional quantity- and quality-related water scarcity aspects. However, the driving forces behind changes in these impacts remain unknown, especially the quality-related water scarcity. Exploring these driving forces can provide targeted measures to mitigate the negative impact of trade on these two types of water scarcity issues. In this study, blue and grey water footprints have been calculated under the consideration of interregional trade between provinces within China and those attributed to international exports from 2007 to 2015. This calculation was based on multi-regional input output model (MRIO). Moreover, the drivers of changes in blue and grey water footprints due to trade have been explored through structural decomposition analysis. The results showed that blue and grey water footprint increased and then slightly decreased from 2007 to 2015 in China. At the same time, interregional trade made an increasing contribution to the blue and grey water footprint, and the proportion increased from 28.8% to 35.0% and from 22.4% to 28.6%, respectively, from 2007 to 2015. The roles of importers and exporters regarding the blue and grey water footprint driven by interprovincial trade within China have changed little, and the quantity- and quality-related water scarcity issues of the main exporters have been intensified by interprovincial trade. A reduction in the water footprint intensity yielded the largest contribution to curb the increase in blue and grey water footprint driven by interprovincial trade. Our study showed that an improvement in efficiency of water use from both quantity and quality perspectives is the key to accomplish sustainable water use in China, especially considering the impact of trade on regional quantity- and quality-related water scarcity issues.

Geographic patterns of microbial traits of river basins in China

River microbiotas contribute to critical geochemical processes and ecological functions of rivers but are sensitive to variations of environmental drivers. Understanding the geographic pattern of river microbial traits in biogeochemical processes can provide important insights into river health. Many studies have characterized river microbial traits in specific situations, but the geographic patterns of these traits and environmental drivers at a large scale are unknown. We reanalyzed 4505 raw 16S rRNA sequences samples for microbiota from river basins in China. The results indicated differences in the diversity, composition, and structure of microbiotas across diverse river basins. Microbial diversity and functional potential in the river basins decreased over time in northern China and increased in southern China due to niche differentiation, e.g., the Yangtze River basin was the healthiest ecosystem. River microbiotas were mainly involved in the cycling of carbon and nitrogen in the river ecosystems and participated in potential organic metabolic functions. Anthropogenic pollutants discharge was the most critical environmental driver for the microbial traits, e.g., antibiotic discharge, followed by climate change. The prediction by machine-learning models indicated that the continuous discharge of antibiotics and climate change led to high ecological risks for the rivers. Our study provides guidelines for improving the health of river ecosystems and for the formulation of strategies to restore the rivers.

Imbalance in the city-level crop water footprint aggravated regional inequality in China

Crop production is the main consumer of water resources. The heterogeneous water resource endowments and imbalanced crop water use exacerbate regional resource consumption inequality. In this study, we quantified the crop water footprint (CWF) of 356 cities in China from 2000 to 2020, measured the inequality between the city CWF and water resources, and identified different strategies to alleviate regional CWF inequality. We found that the average CWF from 2000 to 2020 varied widely across cities, ranging from 0.03 × 10⁸ m³ to 806.78 × 10⁸ m³, and the inequality between city CWF and local water resource endowment was increasing. China had a strong dependence on green water in crop production, and its proportion increased from 52.48 % to 67.17 %. The Gini coefficient of the green water footprint increased from 0.545 to 0.621, and the degree of inequality increased significantly. In addition, the blue water and gray water continuously showed great inequality, especially the blue water, the Gini coefficient of which was 0.724 in 2020. The results show significant disparities in CWF among cities, which have highly exacerbated regional inequality in China. Improving the utilization rate of green water is an important measure to balance the allocation between serving the natural ecosystem and meeting the basic human needs. This study revealed for the first time the inequality of city-level CWF and highlights the severe situation of inequality among regions in China. Balancing the inequality between CWF and water resource endowment at city-level is conducive to fundamentally solving the problem of unreasonable water resource allocation.

Human health and ecosystem impacts of China's resource extraction

The throughput of materials fuels the economic process and underpins social well-being. These materials eventually return to the environment as waste or emissions. They can have significant environmental impacts throughout life cycle stages, such as biodiversity loss, adverse health effects, water stress, and climate change. China is the largest resource extractor globally, but the endpoint environmental impacts and the role of possible socioeconomic drivers associated with its resource extraction remain unclear. Here, we account for and analyze the two endpoint environmental impacts associated with China's resource extraction from 2000 to 2017 and quantify the relative contributions of various socioeconomic factors using structural decomposition analysis. The results show that the environmental impacts of China's resource extraction peaked in 2010. There was a significant decline from 2010 to 2017, in which human health damage decreased by 32.8 % and ecosystem quality damage decreased by 55.8 %. On the consumer side, the advancement in China's urbanization process led to an increase in the environmental impacts of urban residents' consumption, and the effect of investment on the environmental impacts decreased significantly after 2010. Decreases in the intensity of the environmental impacts in most sectors and improvements in production structure could reduce the impacts of resource extraction on human health and ecosystems.

Multiple accounting and driving factors of water resources use: A case study of Shanghai

Previous research papers on urban water resources accounting were confined to the perspectives of production and consumption, ignoring the perspective of income. This paper proposes a systems framework to analyze the income, production, and consumption-based water uses and underlying driving forces of a city based on the methods of multi-scale input-output analysis and structural decomposition analysis. A case study is performed for Shanghai as a megacity. The results show that the income, production and consumption-based water uses of Shanghai had decreased from 5.70 billion m³, 10.85 billion m³ and 28.45 billion m³ in 2007 to 2.80 billion m³, 6.20 billion m³ and 24.10 billion m³ in 2017, respectively. Domestic imported primary inputs had emerged as an important virtual water supplier of Shanghai and its share of total supply-side water use had increased from 23.92% in 2007 to 42.95% in 2017. Meanwhile, about 46% and 40% of Shanghai's total consumption-based water use had been imported from other Chinese regions and foreign countries in 2017, respectively. It is revealed that trade played an important role in relieving water use pressure in Shanghai. The factors that had increased the uses of water resources in Shanghai include population, per capita value-added, per capita output, final consumption structure, and per capita final consumption. The factors that had reduced the water uses in Shanghai include technology, value added mix, output structure, value added structure, domestic import, commodity mix, and foreign import. It is suggested that in addition to curbing urban water use from the production side, more targeted water-saving measures should be devised from the supply (e.g., restricting loan to heavy water-consuming enterprises) and consumption sides (e.g., encouraging residents to buy low-water products).

Local and non-local drivers of consumption-based water use in China during 2007-2015: Perspective of metacoupling

Increasingly growing consumption-based water use (WU) combined with climate change have exacerbated water stress globally and regionally, yet little is known about how the WU change is affected by metacoupled processes which involve human-nature interactions across space; within and across adjacent and distant places. This study aims to unveil the spatio-temporal pattern of China's WUs during 2007-2015 and its underlying local and non-local drivers. Results show that China's total WU exhibited an upward trend from 386.7 billion m³; in 2007 to 431.2 billion m³ in 2012 but dropped to 412.6 billion m³ by 2015. Widespread and continuous water use efficiency improvement contributed most to offsetting the increase in WU driven by the rising affluence and growing population in the context of rapid urbanization and industrialization. Economic structure drove a relatively large WU reduction (responsible for -23.7% of the WU change during 2007-2015), in line with China's ongoing transform from a capital investment-driven economy to a consumption-driven one and decoupling economic growth from environmental pressure. The population share representing the non-local factor of migration effect was large enough to be seen clearly in the changing WUs across China: the WUs of coastal areas ascended while inland areas descended, which was in accordance with migration patterns. Our findings could make a valuable contribution to decision-making in identifying hotspot areas, charting systematic courses for sustainable water use, and combining demand-oriented and supply-oriented measures.

Dynamic variations of cyanobacterial blooms and their response to urban development and climate change in Lake Chaohu based on Landsat observations

Recurring cyanobacterial blooms have seriously hindered the sustainable development of cities. In this study, the variation trend of cyanobacterial blooms was analyzed by taking Lake Chaohu in China as the study area, and the Normalized Difference Vegetation Index (NDVI) derived from Landsat observations combined with the development index of surrounding cities from 2009 to 2019 was used to quantitatively analyze the response of cyanobacterial blooms to urban development and climate change. The results showed that the NDVI of the Northwest Lake region was significantly higher than that of other regions. Summer and autumn were the main seasons for the outbreak of cyanobacterial blooms. The NDVI of Lake Chaohu and Baohe Lake region showed a significant correlation with the gross domestic product (GDP) growth rate of Hefei city (HF), the districts and counties around the lake (DCL), Baohe District (BH), and the population (P). As the economic regions gradually focused on BH rather than on HF and DCL, there was an increasing trend correlation between the NDVI of Baohe Lake region and the GDP growth rate. However, the elimination of GDP in BH did not affect the consistency relationship between the economic growth of other regions and the NDVI of Lake Chaohu on a large scale. In addition, the results of relative importance analysis indicated that the GDP growth rate of BH and the area of Hefei except DCL (HF-DCL) accounted for important contribution to the [Formula: see text] of the regression. This study has momentous reference value for understanding the coupling relationship between urban development and lake environment.

Decreased levels and ecological risks of disinfection by-product chloroform in a field-scale artificial groundwater recharge project by colloid supplement

To bolster freshwater supply, artificial groundwater recharge with recycled water has increasingly attracted research attentions and interests. However, artificial groundwater recharge has potential risks to groundwater quality, as recharge water disinfection is frequently used for pathogen inactivation and causes the concerns of disinfection by-products (DBPs). Colloid supplement is a good approach solving this problem, but its roles in mitigating DBPs remains unclear. In this study, we collected 20 groundwater and soil samples from a field-scale groundwater recharge project, and explored the impacts of silica colloids on chloroform migration and groundwater bacterial communities during the recharge process. Water physicochemical variables changed along the recharge time, and colloid supplement significantly reduced chloroform formation and slowed its migration in groundwater. Bacterial communities in groundwater, river water and recharge water were significantly different. Gammaproteobacteria in recharge water (71.7%) was more abundant than in river water (30.5%) and groundwater (33.5%), while Actinobacteria dominated groundwater (40.6%). After recharge, Gammaproteobacteria increased more with colloid supplement (75.7%) than without (52.6%), attributing to its dominance in soils (74.6%). Our results suggested more bacterial lineages released from soils into aquifer by silica colloid supplement, owing to the competitive adsorption encouraging microbial transfer, especially Gram-negative bacteria. Our findings unraveled the effects of colloid supplement on chloroform formation and migration during artificial groundwater recharge, which consequently altered groundwater bacterial communities, and offered valuable suggestions for the safety management of DBPs in aquifer recharge.

Water lock-in within China's economic industry based on the input-output method and social network analysis

As one of the countries with the most severe water resource problems, China faces enormous challenges in the intensive use of water resources. Rapid economic development has led to serious waste of water resources in the industry, resulting in path dependence on water-consuming technologies, namely the concept of 'water lock-in'. This study aims to estimate the water lock-in effects in various industries in China from 1997 to 2017. To this end, a novel combination of the input-output analysis and social network analysis methods is used to calculate 'integrated, intra-sectorial and inter-sectorial' water lock-in, identify the complex water resource dependence relationship and explore the dynamic evolution process of the lock-in mechanism. The research results are as follows. (1) From 1997 to 2017, the integrated, intra-sectorial and inter-sectorial water lock-in coefficients decreased by 82.08%, 77.92% and 83.14%, respectively. (2) Non-metallic minerals and other mining products underwent the largest decline in water lock-in within the sectors, whereas coal, oil and gas extraction products underwent the most significant decline in water lock-in between the sectors. (3) Water lock-in conduction is most durable and obvious from S01 (agriculture, forestry, fishery products and services) to S06 (textiles). Policy recommendations are suggested to realise the water-unlocking path.

Exploring solutions to alleviate the regional water stress from virtual water flows in China

China has long faced an uneven distribution of physical water resources, which has been further exacerbated by the virtual water transfers embodied in the interregional trade. To alleviate such unfavorable influences of interregional virtual water flows on regional water scarcity, this paper first combined a multi-regional input-output model and a structural decomposition analysis to identify the major driving forces behind the changes in interregional virtual water flows from 2002 to 2012, and then conducted a scenario analysis to explore solutions for sustainable water resource management in China. Results indicated that the virtual water outflows from water-deficient developing regions (Northwest and Northeast) to water-abundant developed regions, such as East Coast and South Coast, have been increasingly intensified from 2002 to 2012. During the period, the final demand predominated the increase of virtual water transfers, while the improvement of water use efficiency dominated the decline in virtual water flows from 2002 to 2012. Results from the designed scenarios indicated that the negative impacts of interregional virtual water flows on the water stress can be effectively relieved, indicating the high priority of regional water use efficiency improvement, especially in water-starved regions.

Effect of virtual water trade on freshwater pollution in trading partners: a systematic literature review

Systematic reviews are a more complete, repeatable, and less biased form of literature reviews leading to evidence-based conclusions. A systematic review was conducted on articles that have investigated the trade of virtual gray water (VGW) and its effect on freshwater pollution in importer and exporter partners. Scopus and ScienceDirect databases were searched for journal articles covering VGW trade on global, international, and national scales. The relevant articles then were selected and using snowball approach led to more relevant articles. Then, the required data were extracted and recorded. A total of 34 articles met the inclusion criteria, of which 13 articles studied VGW trade on a national scale, 13 on an international scale, and the rest on a global scale. The present study developed a critical appraisal tool to evaluate the methodological quality of the included articles. The results of the critical appraisal showed that none of the included articles can undergo quantitative synthesis. Research gaps regarding VGW trade were observed in the water-scarce developing countries that need to be covered. One of the policy implications to reduce pollution impacts on water bodies would be agricultural and industrial reforms by VGW exporters. Besides, changes in economic structure in both sides of the trade, and goods or water consumption patterns, especially by VGW importers, can also play an important role in water resource conservation. Therefore, international and multi-stockholder cooperation should be taken to alleviate the environmental impacts of the VGW trade.

Identifying the driving factors of water consumption from water-energy-food nexus in the Yangtze River Delta region, China

The current water shortage in China is critical. Moreover, the water shortage has become the main bottleneck hindering sustainable economic growth. Against the background of China's dual control target of total water use and intensity, we choose the Yangtze River Delta (YRD) region as a research object, which encompasses Shanghai, Jiangsu, Zhejiang, and Anhui. Based on the perspective of water-energy-food nexus, we employ the generalized Divisia index method to decompose the change of water use into eight factors, regional economic scale effect, regional energy use scale effect, regional food production effect, regional water technology effect, regional energy technology effect, regional water-energy nexus effect, regional food-energy nexus effect, and regional water technology for food production effect, and analyze the contribution of each driver to identify the key drivers of total water use control. The results showed that the top four influencing factors are GDP, water intensity, energy consumption, and water-energy nexus in the YRD region. Regional economic scale is the first driving factor for increasing water use in the YRD region except for Zhejiang. Water intensity is the primary driving force of water-saving in Zhejiang. Energy consumption is the third driver of increasing water use in Jiangsu and Anhui. The effect of water-energy nexus is the third driving factor that affects the change of water use in Shanghai and Zhejiang. The authorities in the YRD region should vigorously develop water and energy utilization technologies to increase the water intensity and decrease energy consumption. The energy sector should decrease the water use to decrease the water-energy nexus which is also the main driving factor affecting the change of water use.

Evaluation of virtual water trade in the Yellow River Delta, China

Virtual water trade is a method to reallocate water resources among regions, implementing virtual water strategy can alleviate the shortage of water resources. In the context of ecological protection and high-quality development of the Yellow River Basin, the evaluation of virtual water trade between the Yellow River Delta and other regions can provide decision support for the formulation of virtual water strategies and the promotion of high-quality development of the Yellow River Basin. This study used the 2012 multi-regional input-output table to calculate the volume of virtual water in trade between the Yellow River Delta and other provinces, and assessed the degree of dependence of the Yellow River Delta on external water resources. Research results indicated that virtual water trade exacerbates the shortage of water resources in the Yellow River Delta because virtual water export was greater than import. Specifically, agriculture was the most important virtual water export sector with an export of 117.2 kilosteres and the largest direction of virtual water was to the Northwest Region (45.4%). We suggest several strategies for virtual water management and high-quality development of the Yellow River Delta: (1) Implement virtual water trade strategy; (2) Reducing water export and promoting the competitiveness of water consumption by emerging industries; (3) Setting up an effective policy of virtual water compensation.

Life Cycle Blue and Grey Water in the Supply Chain of China’s Apparel Manufacturing

Apparel manufacturing involves high water consumption and heavy water pollution in its supply chain, e.g., planting cotton, producing chemical fibers, and dyeing. This study employs a multi-regional input–output (MRIO) model to (1) assess the life cycle of blue and grey water (chemical oxygen demand (COD) specific) of China’s apparel manufacturing; (2) reveal the hidden linkage among sectors and regions in the whole supply chain; and (3) identify the key regions and upstream sectors with the most water consumption and heaviest water pollution. We found that the agricultural sector (i.e., planting fiber crops) is responsible for primary water consumption and water pollution. In addition, different provinces assume different production roles. Guangdong is a major output province in apparel manufacturing. However, its economic output is contributed to by other regions, such as blue water from Xinjiang and Jiangsu and grey water from Hebei and Shandong. Our research reveals the significance of taking an inter-regional perspective on water resource issues throughout the supply chain in apparel manufacturing. The sustainable development of China’s apparel manufacturing relies on improving water-use efficiency and reasonable industrial layout. The results are of significance and informative for policymakers to build a water-sustainable apparel industry.

Understanding the industrial NOx and SO2 pollutant emissions in China from sector linkage perspective

Since the most stringent-ever clean air policy was implemented in 2013 in China, main industrial air pollutant emissions have notably decreased. However, there are few studies on air pollutant emissions of industrial sectors driven by supply chain before and after implementing this policy. This paper attempts to provide a new perspective from industrial linkage to understand the emission of air pollutants. Based on Input-Output model framework, we revealed the linkages of SO₂ and NO_x emissions between sectors from 2012 to 2017 and the driving forces behind emission changes. Moreover, we simulated the possible impact of the key sector linkages on air pollutant emissions. Results show that the most noteworthy change during this period is that the metal melting sector has replaced the power sector, as the largest pollutant output emission sector associated with other sectors, especially the transport equipment sector. The main reason of this phenomena is that the emission intensity reduction rate of metal smelting sector (e.g., only 17% for NO_x) is far less than other sectors. In the future, the development of the equipment manufacturing may put pressure on the metal smelting sector to reduce emissions. For example, when the transport equipment sector increases total output by 20% ~ 40%, the metal smelting sector will be driven to emit 0.04Mt ~0.08Mt of NO_x. This paper provides a basis to quantitatively analyze the industrial sector linkages and identify the key sectors from 2012-2017, and helps decision makers better understand the impact of sector linkage on pollutant emissions.

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.

Unraveling the effect of inter-basin water transfer on reducing water scarcity and its inequality in China

Securing water supply in the face of increasing water scarcity is one important challenge faced by humanity in sustainable development. Inter-basin water transfer is widely applied to provide water supply security in regions where water demand exceeds water availability. However, the effect of inter-basin water transfer on alleviating water scarcity and its inequality is poorly understood especially at the national scale. Based on a newly compiled database of inter-basin water transfer projects in China, here we report a first national assessment of their effect on securing water supply in different basins. We developed a number of indices to facilitate quantifying the effect of water transfer on water scarcity and its inequality. The capacity of inter-basin transfer projects has been steadily increased, which achieved ~48.5 billion m³ yr^-1 by 2016 (equivalent to ~8% of the national water use). The results indicate that water transfer has impacted water supply of 43 sub-basins out of a total of 76 sub-basins, but it hardly changes a basin's water scarcity level (e.g., from water scarcity to low water scarcity). Approximately three quarters of people in China are affected by water transfer. More than a half of the national population (705 million) benefit from alleviated water scarcity, leading to the inequality coefficient reduced from 0.64 under natural water availability condition to 0.59 considering water transfer in 2016. However, 357 million people in water transfer source basins are subject to increased water scarcity, in which ~21% are from water stressed sub-basins. This study reveals for the first time water transfer induced water scarcity and inequality change across sub-basins in China, and highlights the challenges to secure water supply across basins.

Income impacts on household consumption's grey water footprint in China

Urbanization is accompanied by growing household consumption and changing consumption patterns, with both having impacts on the life-cycle water pollution generated. This study uses the indicator of grey water footprint (GWF) within an Input-Output framework to examine the decadal change from 2002 to 2017 of the life-cycle water pollution change for household consumption in China, where rapid urbanization has particularly posed looming environmental challenges. Against the background of enlarging inequality, the results also shed light on the impacts of households within different income groups. From 2002 to 2017, GWF required by urban household consumption has increased significantly from 1586 to 2195 km³ while that for rural households have decreased slightly from 1139 to 964 km³ during the same period. Total Nitrogen required the largest GWF throughout the whole period and throughout all different income groups. Food consumption dominated the GWF for household consumption. However, the share of GWF for food consumption decreases with income increases, from 83% for extremely poor rural households to 71% for very rich urban households in 2012. Urbanites on average require higher GWF for their consumption than their rural counterparts. An average person from the highest income rural households required 2033 m³ GWF for household consumption, which is higher than a person from a very poor urban household (1685 m³) but lower than that of a person from poor urban household (2149 m³). While household consumption volume increase has been the primary driver for GWF increase, pollution intensity reduction has offset such impacts. Household consumption pattern change's impacts differ by household income and by pollutant considered.

Exploring consumption-based planetary boundary indicators: An absolute water footprinting assessment of Chinese provinces and cities

The water planetary boundary (PB) has attracted wide academic attention, but empirical water footprint research that accommodates local biophysical boundaries remains scarce. Here we develop two novel quantitative footprint indicators, the water exceedance footprint and the surplus water footprint. The first measures the amount of excessive water withdrawal (exceeded amount of water withdrawn against local water PBs) and the latter evaluates the potential of surplus water that can be sustainably utilised (amount of surplus water available within local water PBs). We quantify the extent to which demand for goods and services in Chinese provinces and cities are driving excessive withdrawal of local and global water resources. We investigate both territorial and consumption-based water withdrawal deficit and surplus against local water withdrawal PBs. We also trace how PB-exceeded water and surplus water are appropriated for producing certain commodities. In 2015, China's domestic water exceedance reaches 101 km³ while the total water exceedance footprint is 92 km³. We find that 47% of domestic excessive water withdrawal is associated with interprovincial trade. Exceeded water transfers were dominated by agricultural trade from the drier North to the wetter South. A revised virtual water trade network informed by exceedance and surplus water footprint metrics could help address sustainability concerns that arise from the trade of water-intensive commodities. Our findings highlight that policy targets need to accommodate PB exceedance of both direct and virtual water use.

Changes in agricultural land requirements for food provision in China 2003-2011: A comparison between urban and rural residents

Rapid income growth and urbanization have led to significant changes in food consumption patterns in China. The impact of dietary changes is likely to increase agricultural land demand for food provision. This study investigates the changes in three types of agricultural land requirements for urban and rural residents in China using embodied land use intensities. Our results indicate that total per capita cultivated land requirement of rural residents decreased by 24.3%, from 1984 to 1501 m² during the study period, while total per capita cultivated land requirement for urban residents decreased by 25.1%, from 2736 to 2049 m². Total per capita pasture land requirement of rural residents increased by 13.6%, from 543 to 617 m², while total per capita pasture land requirement of urban residents decreased by 31.4%, from 2991 to 2053 m². Total per capita forest land requirement of rural residents increased by 31.0%, from 45 to 59 m², while total per capita forest land requirement of urban residents decreased by 8.4%, from 164 to 150 m². Our study provides clear implications about the linkages between dietary change and agricultural land demand. Our results imply that without sufficient improvement in production efficiency, pressures posed by dietary change on land resources related to the provision of food will remain high in the future.

Managing the water-energy-food nexus in China by adjusting critical final demands and supply chains: An input-output analysis

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

Decrease of both river flow and quality aggravates water crisis in North China: a typical example of the upper Yongding River watershed

Due to unevenly distributed water resources, semi-arid regions are particularly prone to severe water shortage and quality degradation. In this study, based on long-term hydrological database (1935-2015), and the latest available water quality data sets (2011-2016), we analyzed the water crisis and its driving forces in the upper Yongding River watershed, a typical water shortage area in North China. The results showed that human induced excessive water consumption is responsible for the significantly decreased river flow over the past eight decades. Although the capacity of the watershed wastewater treatment has improved, current water quality does not meet the requirements of the national water management goals, because of the excessive nitrogen and COD_Cr (chemical oxygen demand), which mainly come from the wastewater and feedlots discharge. Due to the decreased river flow, current Yongding River is unable to dilute and assimilate pollutions. The analysis of river pollutant load illustrated that more than 60 % of the nitrogen in the river water system is diverted for reservoir storage, and more than 50 % of the COD_Cr and TP are diverted for irrigation, thereby, increasing the risk of reservoirs eutrophication and threatening food safety. Besides, the high Cl^- (388.2 ± 322.5 mg/L) and SO₄^2- (470.6 ± 357.7 mg/L) imply that the upper river water are not suitable for drinking and irrigation purposes, and a potential risk of salinization if the river flow continues to decrease. We conclude that water resources over extraction and quality degradation are the main driving factors of the Yongding River water crisis.

Evaluating water resource sustainability from the perspective of water resource carrying capacity, a case study of the Yongding River watershed in Beijing-Tianjin-Hebei region, China

China is facing great challenges to balance its natural water resource use and eco-environment protection, especially in the north semi-arid region with large water consumption due to the rapid economic growth. This highlights the urgency to use water resource carrying capacity (WRCC) as a measure to maintain the sustainable development of the human and natural water system. Here, we used a coupled model based on the system dynamics and cellular automaton models to assess the WRCC under the critical value of water resource withdrawal ratio (40%) and its sustainability in the Yongding River watershed in Beijing-Tianjin-Hebei region, where the water use highly depends on river flow and nonrenewable groundwater resources. The analytical results showed that the current regional WRCC is severely overloaded due to strong human activities. The predicted results based on four scenarios, i.e., existing development, water saving, industrial restructuring, and integrated development schemes, showed that although the improvement of water saving and water use efficiency has mitigated the regional water shortage, evidenced by the increased WRCC, the water shortage would continue due to the increased water demand. Under the integrated development scenario, it will need at least additional 7.1 × 10⁸ m³ water per year (Beijing: 2.5 × 10⁸ m³, Tianjin: 0.8 × 10⁸ m³, Hebei: 3.8 × 10⁸ m³) via the water transfer project to maintain the sustainability in the next decades. Our research provides recommendations for reasonable water utilization and supplementation under the severe water crisis.

Tension of Agricultural Land and Water Use in China's Trade: Tele-Connections, Hidden Drivers and Potential Solutions

Interregional trade can potentially extend the management of scarce resources beyond a region's territory along supply chains. Here we combined the multiregional input-output model with structural decomposition analysis to reveal the distant connections of agricultural land and water use as well as the drivers behind their variations in China. Our results show that trade-embodied agricultural land use increase by 2.3-fold and 2.5-fold for virtual agricultural water use flows from 2002 to 2012. The water-starved northern China with abundant agricultural land is the main exporter of virtual (also called trade-embodied) agricultural land and water. Moreover, the role of the virtual water use importers and exporters were determined by the availability of land, rather than water resources. Based on scenario analysis, we found that if agricultural water use efficiency of north China reached the world's top-level but agricultural land use efficiency remained unchanged, the virtual water flows would be reduced by 32% and only water resources, not agricultural land, would be able to sustain future economic development. Our findings may provide significant information for potential solutions to China's regional water shortage from a land-water nexus perspective.

Deceleration of China's human water use and its key drivers

Increased human water use combined with climate change have aggravated water scarcity from the regional to global scales. However, the lack of spatially detailed datasets limits our understanding of the historical water use trend and its key drivers. Here, we present a survey-based reconstruction of China's sectoral water use in 341 prefectures during 1965 to 2013. The data indicate that water use has doubled during the entire study period, yet with a widespread slowdown of the growth rates from 10.66 km³⋅y^-2 before 1975 to 6.23 km³⋅y^-2 in 1975 to 1992, and further down to 3.59 km³⋅y^-2 afterward. These decelerations were attributed to reduced water use intensities of irrigation and industry, which partly offset the increase driven by pronounced socioeconomic development (i.e., economic growth, population growth, and structural transitions) by 55% in 1975 to 1992 and 83% after 1992. Adoptions for highly efficient irrigation and industrial water recycling technologies explained most of the observed reduction of water use intensities across China. These findings challenge conventional views about an acceleration in water use in China and highlight the opposing roles of different drivers for water use projections.

Hydrologic and Pollutant Removal Performance of Media Layers in Bioretention

The current study was aimed to investigate the filler layer structure in modified bioretention systems. Three different structural layers in bioretention were proposed to evaluate their hydrologic performance and pollutant removal efficiency under different rainfall intensities. These layers were as follows: all three layers (filter, transition, and drainage layers), without transition layer, and without drainage layer. Synthetic stormwater was used for experimental purpose in current work. Results revealed that compared with “all three layers”, runoff control rate of “without transition layer” and “without drainage layer” was reduced by 0 to 7.4%, 0 to 10.1%, and outflow start time was advanced by 6 to 8 min and 1.5 to 4.5 min, respectively. Moreover, CODcr (chemical oxygen demand), NH4+-N (ammonium nitrogen), TN (total nitrogen) and TP (total phosphorus) removal rates were 86.0%, 85.4%, 71.8%, and 68.0%, respectively. Particle size distribution of the fillers revealed that during operation, particle moved downward were mainly within 0.16–0.63 mm size. Findings showed that transition and drainage layer played an important role in runoff control, and total height of the filler layer should not be less than 800 mm. Filter layer effectively reduce runoff pollution but the thickness of the filter layer should not be less than 500 mm. Whereas, transition layer has the function of preventing the filler loss of the filter layer; therefore, proper measures must be taken into consideration during structural optimization.

Pollution exacerbates China's water scarcity and its regional inequality

Inadequate water quality can mean that water is unsuitable for a variety of human uses, thus exacerbating freshwater scarcity. Previous large-scale water scarcity assessments mostly focused on the availability of sufficient freshwater quantity for providing supplies, but neglected the quality constraints on water usability. Here we report a comprehensive nationwide water scarcity assessment in China, which explicitly includes quality requirements for human water uses. We highlight the necessity of incorporating water scarcity assessment at multiple temporal and geographic scales. Our results show that inadequate water quality exacerbates China's water scarcity, which is unevenly distributed across the country. North China often suffers water scarcity throughout the year, whereas South China, despite sufficient quantities, experiences seasonal water scarcity due to inadequate quality. Over half of the population are affected by water scarcity, pointing to an urgent need for improving freshwater quantity and quality management to cope with water scarcity.

Improving water ecosystem sustainability of urban water system by management strategies optimization

Water management strategies play an important role in water shortage alleviation. This study evaluates the cost and water ecosystem benefit of 14 water management strategies in Beijing in the future scenarios for 2020 and 2035. In addition, optimal implements of abatement strategies are obtained within the context of legislated targets, with the consideration of interaction among strategies. The result shows that Beijing can meet its commitments for total water use and pollution control by the water management strategies implementation in both 2020 and 2035. For 14 water management strategies analyzed in this study, 5 options with negative abatement cost value achieve 12.2-24.1% of the total water ecosystem benefit in 2020 and 2035. Wastewater reclamation is the most efficient strategy in water ecosystem impact (WEI) reduction, which contributes 38.4% of the total WEI reduction with an abatement cost of 1.6 Yuan/m³ H₂O -eq. However, the sequence of optimal strategy implementation rate is not in accordance with the abatement cost of the strategies. The most cost-effective option is the water-efficient shower head, while the highest implementation rate is found for promotion of production technologies. A comparison between water management optimization with and without the consideration of interactions among strategies shows that taking the interaction among strategies into account imposes almost no influence on the total WEI reduction. But it has impacts on optimal implementation rate of each water management option and the cost estimation (+10.8%) of water management implementation. Such a systematic analysis of water management strategies provides general recommendations on sustainable water resource management in water scarce regions.

Inequality of household consumption and air pollution-related deaths in China

Substantial quantities of air pollution and related health impacts are ultimately attributable to household consumption. However, how consumption pattern affects air pollution impacts remains unclear. Here we show, of the 1.08 (0.74-1.42) million premature deaths due to anthropogenic PM2.5 exposure in China in 2012, 20% are related to household direct emissions through fuel use and 24% are related to household indirect emissions embodied in consumption of goods and services. Income is strongly associated with air pollution-related deaths for urban residents in which health impacts are dominated by indirect emissions. Despite a larger and wealthier urban population, the number of deaths related to rural consumption is higher than that related to urban consumption, largely due to direct emissions from solid fuel combustion in rural China. Our results provide quantitative insight to consumption-based accounting of air pollution and related deaths and may inform more effective and equitable clean air policies in China.

Water Degradation by China’s Fossil Fuels Production: A Life Cycle Assessment Based on an Input–Output Model

Fossil energy production not only aggravates water depletion but also severely contaminates water resources. This study employed a mixed-unit input–output model to give a life cycle assessment of national average water degradation in production of common types of fossil fuels in China. The results show that the amount of grey water generated is much more than that of consumptive and withdrawn water in all cases. Although there is a high discharge amount of chemical oxygen demand (COD) in fossil fuel production, the pollutants of petroleum (PE) and volatile phenols (VP) require more dilution water than COD. PE is the greatest contributor to water degradation caused by primary fossil fuels, while VP pollution is prominent in production of upgraded fossil fuels. Basically, the main causes of water degradation, PE and VP discharge, occurs at coal mines, oil fields, refinery plants, and coking factories, rather than in the upstream sectors. A scenario analysis showed that water pollution can be significantly reduced if VP discharge in the coking process is controlled to be at the standard concentration. PE requires a standard withalower discharge concentration in order to further mitigate water pollution in production of fossil fuels. The coal production industry has a much lower pollutant removal rate but spends more on wastewater treatment, up to 12% of its profit. The other fossil fuel industries have high removal rates of PE and VP (97%–99%) and thus demand technological renovation to further remove those pollutants at a low concentration.

Depicting Flows of Embodied Water Pollutant Discharge within Production System: Case of an Undeveloped Region

Water pollution is still an obstacle on the way towards sustainable development, especially for some undeveloped regions in China. To formulate policies for water pollution control from multiple perspectives, it is significant to holistically investigate how final demand purchases trigger water pollutant discharge in the production process. With Jilin Province as an empirical study area, the final production and consumption attributions of chemical oxygen demand (COD) discharge within the input–output framework are measured. By employing structural pass analysis and mapping approaches, the supply chain linkages between the two attributions of COD discharge are illustrated. The embodied flows of COD discharge across sectors through the supply chains are exhaustively revealed. The results show that the exports drive 70.23% of the total COD discharge. Animal production (S2) is the dominant contributor to COD discharge from both production and consumption perspectives. Final demand on the products of Foods & tobacco products (S8), Sawmills & furniture, and Construction largely induces COD discharge at higher production layers. In contrast, final demand on S2’s products mainly drives direct COD discharge (96.04%). S2 and S8 are the two key sectors in the supply chains, which provide other sectors with pollution-intensive products as intermediate inputs. The findings indicate that the export of S2’s products should be largely cut down, along with adjustment of the export structure. Innovations of production technologies and improvement of end-of-pipe abatement abilities for S2 and S8 should be facilitated. Besides, cutting capacity or reducing investment on these two sectors should be propelled.

Factors governing variations of provincial consumption-based water footprints in China: An analysis based on comparison with national average

Although several studies have revealed that the consumption-based water footprint (WF) is unequal in space, the contributing factors to this spatial inequality have rarely been quantified. This study addresses this need by quantifying the effects that determine the difference of one region's WF per capita and a benchmark average value. A decomposition framework is developed. Using provincial water uses in China as a case study, this framework breaks down the deviation of one province's per capita WF from the national average value into effects of five key factors, namely, the actual-requisite WF difference, direct water use intensity, economic production structure, consumption level and consumption structure. The structural decomposition analysis is adapted to investigate differences between the provincial WFs and national average value, in contrast to its conventional use for examining changes of an environmental variable over time. The results indicate that the drivers of a high or low WF level in different provinces are diverse. The dominant factors are most often the direct water use intensity and consumption level, which may contribute over 1000 and 400 m³ of per capita WFs per year, respectively. The results assist in the diagnosis of per capita WF for each province. Policy suggestions highlighting feasible institutional or technological arrangements are made for each province, which have the potential to reduce consumption-based WF inequality without compromising living standards of inhabitants.

Determinants of Greenhouse Gas Emissions from Interconnected Grids in China

While direct greenhouse gas (GHG) emissions by China's power sector from the generation side have been widely investigated, driving forces from the electricity consumption perspective and inter-regional electricity transmission have been overlooked to a large extent. This study quantified relative contributions of six factors to changes in GHG emissions from interconnected grids in China during 2008-2015. These six factors include three generation-side factors (i.e., fuel mix of thermal power generation, energy efficiency of thermal power generation, and electricity structure), two consumption-side factors (i.e., electricity efficiency of GDP and GDP), and electricity transmission structure. GDP growth and changes in fuel mix of thermal power generation are two major drivers of increased GHG emission during 2008-2015, especially for the North China Grid. In contrast, changes in electricity transmission structure (especially in East China Grid and Southern China Grid), the increase in electricity efficiency of GDP (except for Northwest China Grid), improvements in energy efficiency of thermal power generation (especially in North China Grid and Central China Grid), and changes in electricity structure (especially in Southern Power Grid) are major factors offsetting GHG emission increments. Findings of this study can provide multiple-perspective policy implications for GHG mitigation in China's power sector.

Worse than imagined: Unidentified virtual water flows in China

The impact of virtual water flows on regional water scarcity in China had been deeply discussed in previous research. However, these studies only focused on water quantity, the impact of virtual water flows on water quality has been largely neglected. In this study, we incorporate the blue water footprint related with water quantity and grey water footprint related with water quality into virtual water flow analysis based on the multiregional input-output model of 2007. The results find that the interprovincial virtual flows accounts for 23.4% of China's water footprint. The virtual grey water flows are 8.65 times greater than the virtual blue water flows; the virtual blue water and grey water flows are 91.8 and 794.6 Gm³/y, respectively. The use of the indicators related with water quantity to represent virtual water flows in previous studies will underestimate their impact on water resources. In addition, the virtual water flows are mainly derived from agriculture, chemical industry and petroleum processing and the coking industry, which account for 66.8%, 7.1% and 6.2% of the total virtual water flows, respectively. Virtual water flows have intensified both quantity- and quality-induced water scarcity of export regions, where low-value-added but water-intensive and high-pollution goods are produced. Our study on virtual water flows can inform effective water use policy for both water resources and water pollution in China. Our methodology about virtual water flows also can be used in global scale or other countries if data available.

Socioeconomic Drivers of Greenhouse Gas Emissions in the United States

Existing studies examined the U.S.'s direct GHG emitters and final consumers driving upstream GHG emissions, but overlooked the U.S.'s primary suppliers enabling downstream GHG emissions and relative contributions of socioeconomic factors to GHG emission changes from the supply side. This study investigates GHG emissions of sectors in the U.S. from production-based (direct emissions), consumption-based (upstream emissions driven by final consumption of products), and income-based (downstream emissions enabled by primary inputs of sectors) viewpoints. We also quantify relative contributions of socioeconomic factors to the US's GHG emission changes during 1995-2009 from both the consumption and supply sides, using structural decomposition analysis (SDA). Results show that income-based method can identify new critical sectors leading to GHG emissions (e.g., Renting of Machinery & Equipment and Other Business Activities and Financial Intermediation sectors) which are unidentifiable by production-based and consumption-based methods. Moreover, the supply side SDA reveals new factors for GHG emission changes: mainly production output structure representing product allocation pattern and primary input structure indicating sectoral shares in primary inputs. In addition to production-side and consumption-side GHG reduction measures, the U.S. should also pay attention to supply side measures such as influencing the behaviors of product allocation and primary inputs.

Ecological network analysis for a virtual water network

The notions of virtual water flows provide important indicators to manifest the water consumption and allocation between different sectors via product transactions. However, the configuration of virtual water network (VWN) still needs further investigation to identify the water interdependency among different sectors as well as the network efficiency and stability in a socio-economic system. Ecological network analysis is chosen as a useful tool to examine the structure and function of VWN and the interactions among its sectors. A balance analysis of efficiency and redundancy is also conducted to describe the robustness (RVWN) of VWN. Then, network control analysis and network utility analysis are performed to investigate the dominant sectors and pathways for virtual water circulation and the mutual relationships between pairwise sectors. A case study of the Heihe River Basin in China shows that the balance between efficiency and redundancy is situated on the left side of the robustness curve with less efficiency and higher redundancy. The forestation, herding and fishing sectors and industrial sectors are found to be the main controllers. The network tends to be more mutualistic and synergic, though some competitive relationships that weaken the virtual water circulation still exist.

Physical and virtual water transfers for regional water stress alleviation in China

Water can be redistributed through, in physical terms, water transfer projects and virtually, embodied water for the production of traded products. Here, we explore whether such water redistributions can help mitigate water stress in China. This study, for the first time to our knowledge, both compiles a full inventory for physical water transfers at a provincial level and maps virtual water flows between Chinese provinces in 2007 and 2030. Our results show that, at the national level, physical water flows because of the major water transfer projects amounted to 4.5% of national water supply, whereas virtual water flows accounted for 35% (varies between 11% and 65% at the provincial level) in 2007. Furthermore, our analysis shows that both physical and virtual water flows do not play a major role in mitigating water stress in the water-receiving regions but exacerbate water stress for the water-exporting regions of China. Future water stress in the main water-exporting provinces is likely to increase further based on our analysis of the historical trajectory of the major governing socioeconomic and technical factors and the full implementation of policy initiatives relating to water use and economic development. Improving water use efficiency is key to mitigating water stress, but the efficiency gains will be largely offset by the water demand increase caused by continued economic development. We conclude that much greater attention needs to be paid to water demand management rather than the current focus on supply-oriented management.