Interactive national virtual water-energy nexus networks
Graphical abstract
Introduction
Economic development and population growth substantially increase global resource demand (e.g., water and energy) (Liu et al., 2015a, Liu et al., 2015b, Steffen et al., 2015), resulting in resource scarcity that becomes a barrier for sustainability (Yergin, 2006; Mekonnen and Hoekstra, 2016). Virtual resources, such as water and energy, that are consumed in commodity production processes have gained global attention as a key mechanism for alleviating resource scarcity in a receiving system (e.g., a region, a city) through commodity trade (Novo et al., 2009; Wiedmann, 2009; Steinmann et al., 2017; Xu et al., 2018). Today, transfers of virtual resources such as water and energy have been intensified by globalization (Dalin et al., 2012; Chen et al., 2018). For example, the volume of global virtual water transfers embodied in international food trade has substantially increased over time (Dalin et al., 2012). The virtual energy flows embodied in international trade have also evolved into a highly interconnected network (Chen et al., 2018).
Many studies have evaluated trade within a single virtual resource trade network (e.g., water). These analyses focus on virtual resource trade's spatial pattern, structure, and impacts on sending and receiving systems (Hoekstra and Hung, 2002; Chapagain and Hoekstra, 2003; Chapagain et al., 2006; Dabrowski et al., 2009; Wiedmann, 2009; Konar et al., 2011; Zhang et al., 2011; Mubako et al., 2013; Zhang and Anadon, 2014; Zhao et al., 2015; Oita et al., 2016). However, based on the integrated framework of metacoupling (Liu, 2017), we found that little research has simultaneously explored the interactions between trading systems in two types of virtual resource transfer networks from a nexus perspective (von Braun and Mirzabaev, 2016), as different kinds of virtual resource transfer may influence each other and cross-sectoral impacts may happen. Cross-sectoral impacts occur when changes in one sector influence another sector. For example, while China constructed more hydropower stations to develop hydropower and satisfy energy demand, substantial water loss occurred when water evaporated from reservoirs, resulting in regional water scarcity (Liu et al., 2015a, Liu et al., 2015b). Current water-energy nexus studies mainly focus on one specific place instead of the relationship between multiple distant places (Liu et al., 2018a, Liu et al., 2018b). Also, there is little research comparing trade between distant systems with trade between geographically adjacent systems. Furthermore, little research has explored drivers of two types of virtual resource transfer simultaneously by using a gravity model (Duarte et al., 2018). Such information is urgently required as the world demand for various natural resources in different places may change at differing rates. A more holistic understanding of multiple types of virtual resource trade should be developed to improve resource management efficiency. Moreover, comparing the influences from adjacent and distant provinces can help reveal influential places in different geographical regions. This comparison can also help unveil socioeconomic and environmental impacts from trade with adjacent and distant provinces (e.g., distant trade often consumes more energy for transportation and therefore emits more CO2) (Liu et al., 2018a, Liu et al., 2018b).
To address these knowledge gaps, we studied China's interprovincial virtual water and energy transfer networks simultaneously. Water and energy are strongly interrelated in human activities and play significant roles in both environmental conservation and socioeconomic development (Liu et al., 2015a, Liu et al., 2015b). Therefore, analyzing virtual water and energy transfer networks together can help us better understand the interactions between provinces in different virtual resource transfer networks. China is facing a serious water crisis and energy shortage in the 21st century (Crompton and Wu, 2005; Zhao et al., 2015). Even though China ranks fourth in the world for freshwater resources, its high population makes its per capita renewable freshwater resources levels only one quarter of the world average (Liu and Yang, 2012). Furthermore, uneven water resource distribution within China is a barrier to development (Liu and Yang, 2012). China has also become the world's largest energy consumer after surpassing the United States (U.S.) in 2009 (Swartz and Oster, 2010; Chen et al., 2013). The distribution of coal, natural gas and electricity in China is largely uneven and has negative impacts on China's development (Ma and Oxley, 2012). Understanding the interactions between China's interprovincial virtual water and energy transfer networks and their impacts can provide useful information and lessons for enhancing water and energy security through virtual resource transfer in other developing countries.
Based on the most recently available multiregional input-output table for developing interprovincial energy and water trade networks simultaneously in China (Zhang et al., 2013; Zhao et al., 2015), we used network analysis to study interactions across virtual water and energy networks between provinces. We also constructed a “without trade” scenario to study the impact of trade on the nexus between water and energy consumption across provinces. Furthermore, we used the augmented gravity model to explore the drivers of China's virtual water/energy transfer.
Section snippets
Data sources
We used the most recently available multiregional input-output table for developing energy and water networks simultaneously in China (Zhang et al., 2013, Zhao et al., 2015). The Chinese 2007 interprovincial input-output table was constructed by the Chinese National Bureau of Statistics. Being consistent with the previous research (Zhao et al., 2015), water withdrawal data by sector at the provincial level were derived from Water Resource Bulletin and Chinese Economic Census Yearbook 2008 (
Interactions across water-energy nexus network
In interprovincial virtual water-energy flow network, more than 40% of the provinces gained in trading water at the expense of losing their own energy or gained in trading energy at the expense of losing their own water (Fig. 1). Almost a quarter (23%) of the provinces (Guangxi, Hunan, Jiangxi, Fujian, Anhui, Hebei, Heilongjiang) gained virtual energy but lost water, while 20% (Guizhou, Guangdong, Jiangsu, Shandong, Liaoning, Inner Mongolia) gained virtual water but lost energy. Twenty percent
Discussion
Our study finds that in this virtual water and energy network, more than 40% of provinces gained in trading water at the expense of losing their own energy or gained in trading energy at the expense of losing their own water. Twenty percent of provinces suffered a double loss of both their own internal water and energy, while the rest of provinces gained both water and energy through trade at no cost to their own internal water and energy. GDP is one important driver of virtual water and energy
Conclusions
Our paper investigated the interactions across two types of virtual resource transfer networks – energy and water at the national scale, using China as a case study. The results showed that more than 40% of provinces gained one type of resource (either water or energy) by trade at the expense of losing the other type of internal resource (energy or water), and 20% of the provinces suffered a double loss of both water and energy. The rest of provinces gained both water and energy. Moreover,
Acknowledgements
We acknowledge the insightful editorial comments from Sue Nichols.
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