Water-energy-carbon nexus in China's intra and inter-regional trade

Dynamic simulation of the water-land-food nexus for the sustainable agricultural development in the North China Plain

Inter-regional trade of agricultural products based on the flow of agricultural virtual resources is of great importance for sustainable agricultural development. We focused on grain crops (rice, wheat and maize) in the North China Plain (NCP), and used the Penman-Monteith equation to simulate crop water requirements. We further analyzed the flow of virtual land and virtual water associated with the grain trade using an environmentally expanded multi-regional input-output model. The coupling coordination of land, water, and food was evaluated to assess the rationality of regional agricultural production resource allocation. Between 2007 and 2017, agricultural virtual land and virtual water embodied in the grain trade between the NCP and other areas increased by 48.10 % and 34.41 %, respectively, indicating that the NCP is gradually consolidating its position as the main production area and distribution center of crops in China. Agricultural virtual resources in the NCP were mainly transported to the southeast coastal region, with an overall trend of resource movement from north to south. The total supply of agricultural land and water resources markedly increased in the NCP, whereas the transfer of virtual resources across regions showed a decreasing trend. Because of the irrational structure of crop cultivation and unevenness of regional resource allocation, the coupling coordination of the water-land-food nexus in the NCP is much lower than the national average. This study provides important information on the trade flows and coupling relationships of virtual water and land resources of three major food crops, which will help to alleviate resource pressure in agricultural production and promote sustainable agricultural development in the NCP.

Physical and virtual water transfers in China and their implication for water planetary boundary

China is an extremely water-scarce country with an uneven distribution of regional water resources. We define two absolute sustainability indicators, using the multi-regional input‒output (MRIO) model to outline the contribution of China's physical and virtual water transfers in mitigating the problem of regional water boundary-exceeding. Although the overall use of freshwater resources is within the safe operation space, 55% of province's water resource development transgresses the local water planetary boundary. Physical and virtual water transfers effectively mitigate the stress of water supply to the water planetary boundary in China's water-scarce regions. Among them, the role of virtual water transfers occupies the main part. The cost of using physical water in water-receiving regions and the situation of virtual water flowing from water-scarce regions to developed water-rich regions cannot be ignored, and a small number of provinces are responsible for most of the virtual water net imports and exports. The obtained results are helpful for the redistribution of water planetary boundary transgressing responsibilities among provinces and the formulation of absolute sustainable water resources management policies.

Evaluation and prediction of water-energy-carbon nexus efficiency in China based on a new multiregional input-output perspective

Water, energy and carbon are three basic environmental factors that affect countries. An in-depth study of the water-energy-carbon (WEC) nexus is of great significance for realizing regional sustainable development. However, at present, research on the evaluation and prediction of large-scale WEC nexus based on multiple perspectives is not sufficiently mature, especially the prediction of WEC nexus efficiency. This study evaluates and predicts the WEC nexus efficiency in 30 regions of China based on a new comprehensive perspective. The WEC efficiency and the slack variables of 30 regions from 2006 to 2020 were calculated by using the slack-based measure model. The 30 regions were divided into 4 efficiency groups using hierarchical cluster analysis. Efficiency trends in 2006-2020 were analyzed for specific regions. The coupling interaction between the WEC nexus is studied based on the perspective of the coupling degree and coupling coordination degree. More importantly, this study is the first to quantitatively predict the WEC efficiency of 30 regions in China from 2021 to 2030, using the rank set pair analysis model. The following results were obtained in this paper. The WEC efficiency has a slow decreasing trend in 2006-2020. A total of 16.7% and 33.3% of the regions are in the extreme and high coupling coordination stages, respectively, and are mainly concentrated in the northern and southeastern parts of China. Fifty percent of the regions have moderate coupling coordination, mainly concentrated in the central and southern regions. From 2021 to 2030, the WEC efficiency of Beijing, Tianjin and Qinghai will remain at a high level; the WEC efficiency of Shandong and other regions will remain at a low level; and 70% of the regions' water efficiency will remain low. This paper has important guiding significance for promoting the regional WEC nexus balance and sustainable development of the economy, society and environment. According to the characteristics of the four efficiency groups, some valuable suggestions on regional sustainable development are proposed.

A factorial-based dynamic distributive model for virtual-water management in multi-urban agglomerations - A case study of Yangtze River Economic Belt

The economic development, population growth and rapid urbanization in the Yangtze River Economic Belt (YREB) have resulted in an imbalance between socio-economic development and available water resources of adjacent urban agglomerations. Exploring the virtual water flow (VWF) of adjacent urban agglomerations in YREB is crucial for the collaborative management of water resources. In this study, a factorial-based dynamic distributive model (FDDM) is first developed to analyze the variations in virtual water transfers and inter/inner-sectoral relationships within multi-urban agglomerations, and expound the spatiotemporal diffusion effects of multiple water policy alternatives (and their combinations) for virtual water. The FDDM is applied in YREB's urban agglomerations covering Yangtze River Delta (YRDA), Middle Reach of Yangtze River (MRA) and Chengyu Urban Agglomeration (CYA). The FDDM is capable of i) quantifying the dynamic evolution of direct/indirect virtual water volume and virtual water transfer direction/path between and within urban agglomerations; ii) demonstrating the spatiotemporal changes of the control/dependent relationship within sectors in sub-urban agglomerations, as well as the evolution of utility relationship within the system; iii) evaluating the interactions of different water policies (and their combinations) within each sub-urban agglomeration/key sectors on the direct and indirect virtual water consumption of the system. Our major findings are: (i) YRDA always has the largest direct and indirect water consumption as well as the water consumption intensities from 2007 to 2017; (ii) The three national urban agglomerations have evolved in the direction of benign development; (iii) the interactions between YRDA and MRA, YRDA_FLF (sector of farming, forest, livestock, and fishery in YRDA) and MRA_FTO (sector of food and tobacco processing in MRA) on VWF are obvious. These results will provide a new insight for balancing urban agglomeration development and water resource utilization in YREB.

How far are we from possible ideal virtual water transfer? Evidence from assessing vulnerability of global virtual water trade

With the increasing contradiction between water demand and supply in a telecoupled society where nature and human interplay intensively over distance, virtual water trade (VWT) plays an indispensable role in global water use sustainability. There has been little quantitative analysis of global water use sustainability depicting both overall system characteristics and flows between subsystems. In such a context, the extent to which virtual water transfer deviates from possible ideal expectations (i.e., virtual water flows from water-abundant regions to water-scarce ones), and its impact on global water use sustainability, are not well evaluated. Therefore, the global VWT vulnerability framework is proposed to delineate the gap between the real VWT and the possible optimal scenario, providing potential space for future optimization and regulation. Represented by the ratio of weighted total virtual water volume to the original one, the vulnerability is assessed from 2005 to 2015 based on the Eora input-output database and Virtual Water Transfer Multiplier which assigns differentiated weights to per unit volume of virtual water transfer based on the water stress levels of importers and those of exporters. Results show that the global VWT vulnerability has increased by 18.9% during the study period, with Africa and Southern and Central Asia making the biggest contribution. Developed countries contributed around 80% of the increased global VWT vulnerability. However, the proportion has fallen a bit, in terms of the conventional view of developed countries taking the approach of transferring responsibility to developing countries. Instead, the proportions of transferring responsibility between developing countries have rose by 10% to 30% during 2005-2015, partially due to stronger trade ties among developing countries. Our findings support policy decisions on tracing environmental responsibility for water scarcity and call for action to prevent water ecological downsides due to international trade.

Toward a Carbon-Neutral State: A Carbon–Energy–Water Nexus Perspective of China’s Coal Power Industry

Carbon neutrality is one of the most important goals for the Chinese government to mitigate climate change. Coal has long been China’s dominant energy source and accounts for more than 70–80% of its carbon emissions. Reducing the share of coal power supply and increasing carbon capture, utilization, and storage (CCUS) in coal power plants are the two primary efforts to reduce carbon emissions in China. However, even as energy and water consumed in CCUS are offset by reduced energy consumption from green energy transitions, there may be tradeoffs from the carbon–energy–water (CEW) nexus perspective. This paper developed a metric and tool known as the “Assessment Tool for Portfolios of Coal power production under Carbon neutral goals” (ATPCC) to evaluate the tradeoffs in China’s coal power industry from both the CEW nexus and financial profits perspectives. While most CEW nexus frameworks and practical tools focus on the CEW nexus perturbation from either an external factor or one sector from CEW, ATPCC considers the coupling effect from C(Carbon) and E(Energy) in the CEW nexus when integrating two main carbon mitigation policies. ATPCC also provides an essential systematic life cycle CEW nexus assessment tool for China’s coal power industry under carbon-neutral constraints. By applying ATPCC across different Chinese coal industry development portfolios, we illustrated potential strategies to reach a zero-emission electricity industry fueled by coal. When considering the sustainability of China’s coal industry in the future, we further demonstrate that reduced water and energy consumption results from the energy transition are not enough to offset the extra water and energy consumption in the rapid adoption of CCUS efforts. However, we acknowledge that the increased energy and water consumption is not a direct correlation to CCUS application growth nor a direct negative correlation to carbon emissions. The dual effort to implement CCUS and reduce electricity generation from coal needs a thorough understanding and concise strategy. We found that economic loss resulting from coal reduction can be compensated by the carbon market. Carbon trading has the potential to be the dominant profit-making source for China’s coal power industry. Additionally, the financial profits in China’s coal power industry are not negatively correlated to carbon emissions. Balance between the carbon market and the coal industry would lead to more economic revenues. The scenario with the most rapid reduction in coal power production combined with CCUS would be more sustainable from the CEW nexus perspective. However, when economic revenues are considered, the scenario with a moderately paced energy transition and CCUS effort would be more sustainable. Nevertheless, the ATPCC allows one to customize coal production scenarios according to the desired electricity production and emission reduction, thus making it appropriate not only for use in China but also in other coal-powered regions that face high-energy demands and carbon neutrality goals.

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

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

Assessment of the Sustainable Utilization Level of Water Resources in the Wuhan Metropolitan Area Based on a Three-Dimensional Water Ecological Footprint Model

The shortage and overexploitation of water resources restrict the sustainable development of metropolitan areas. To evaluate the sustainable utilization level of water resources, we identified the occupancy of natural capital stock and the consumption of natural capital flow by water resources consumption and analyzed the factors influencing water resources consumption in metropolitan area development. We took the Wuhan Metropolitan Area in China from 2010 to 2019 as the research object and introduced footprint depth and size, the water ecological footprint (WEF) model was expanded into the three-dimensional WEF model. Based on this model, an evaluation system for the sustainable utilization level of water resources was constructed with five indices—water ecological deficit, water ecological surplus, water ecological pressure, WEF depth, and WEF size. Finally, the driving factors of WEF change were analyzed using the Logarithmic Mean Divisia Index. The evaluation of the sustainable utilization level of water resources showed that the Wuhan Metropolitan Area as a whole experienced water ecological surplus from 2010 to 2019, but there were different degrees of water ecological deficit in its inner urban areas, and the most serious cumulative deficit was 5.02 ha/cap in Ezhou. In 2011 and 2019, the sustainable utilization level of water resources in the metropolitan area reached a relatively unsustainable state. Xianning was the urban area with the most sustainable utilization level of water resources. During the study period, the metropolitan area did not occupy the natural capital stock of water resources, and the natural capital flow of water resources in the inner urban areas could meet the demand of the current consumption of the region in 2010 and 2016. The analysis of the driving factors of WEF change showed that economic development effect and population pressure effect had a positive driving effect on WEF change, while WEF intensity effect and water resources carrying capacity effect had the opposite effect. Finally, according to the research results, it can be seen that improving the efficiency of water resources utilization, protecting the natural capital stock of water resources, realizing differentiated regional development through the market economy and developing water policy can be helpful to improve the level of sustainable water resources utilization.