آنالیز ورودی و خروجی (IOA) سه معیاره آب مجازی برای اقتصاد شهری

ABSTRACT Embodied water for urban economy: A three-scale input–output analysis for Beijing 2010

With the fact that only a tiny fraction of water resources on our globe is available for human beings’ freshwater needs (Lambooy, 2011), fresh water is inevitably an critical natural resource. Movever, imbalanced distribution of fresh water aggravates the water crisis in many regions. Particularly with the fast-growing economy and increasing urban population, water shortage regions are facing increasingly severe water crisis. Under this circumstance, water grabbing through commodity trade has been deemed as an effective measure to meet the local fresh water requirements (Rulli et al., 2013).

The concept of virtual water was first put forward by Allan (1993), in the effort for water study to ease water shortage in the Middle East. After that, virtual water of different products, such as coffee, tea, rice, and meat, and virtual water in non-food products has been extensively analyzed (Chapagain and Hoekstra, 2003; Hoekstra and Chapagain, 2007; Hoekstra and Hung, 2002, 2005). Associated with virtual water, water footprint, defined as the volumes of water needed for the production of goods and services consumed by a country, region, sector/industry or individual, is deemed as an essential concept in the field of water resources accounting (Hoekstra et al., 2009). As ecosystem studies were extensively conducted, input–output analysis (IOA), a well-established top-down accounting method, was extensively employed for ecological elements accounting, stirring an accounting frenzy at various economic scales especially in the aspect of water resources accounting (Chen and Chen, 2012; Guan and Hubacek, 2007; Lenzen et al., 2013).

There are two distinctive IOA methods employed in water resources accounting. One is the environmentally-extended IOA method (Leontief, 1970, 1986) as an extension of the standard economic input–output table (Leontief, 1936). By assigning the sectorial direct water consumption to the final demand through the Leontief inverse, the environmentally-extended IOA has been applied to analyze water use on the global scale (Lenzen et al., 2013; Dalin et al., 2012), national scale (Dalin et al., 2014; Guan and Hubacek, 2007; Lenzen and Foran, 2001; Llop, 2008; Zhao et al., 2009), and urban scale in particular, by cases of Zhangye and Beijing, China (Wang et al., 2009; Wang et al., 2013; Zhang et al., 2011), Andalusia, Spain (Dietzenbacher and Velázquez, 2007; Velázquez, 2006) and Victoria, Australia (Lenzen, 2009).

Another is the systems IOA, as originally illustrated for energy study by Costanza (1980) and Odum (1983). Derived as a combination of Odum’s biophysical balance in systems ecology (Odum, 1983) and Leontief’s input–output model (Leontief, 1986), systems IOA has been rigorously developed to investigate various ecological elements at multiple economic scales, and furthermore was specifically applied to analyze water use on the global scale (Chen and Chen, 2012; Chen et al., 2012), national scale (Chen and Chen, 2010; Chen and Han, 2015; Chen et al., 2010), and urban scale (Han et al., 2014; Chen and Li, 2015; Zhou et al., 2010).

The urban economy in Beijing suffers a severe water crisis due to endogenous water shortage, population explosion and economy booming. According to Beijing Water Resources Bulletin 2010 (Beijing Water Authority, 2010), the direct water withdrawal throughout the whole year is 3.52 billion cubic meters (m3 hereafter), and the local water supply capability is 1.40 billion m3. In this study, all the direct water withdrawal is considered as local water withdrawal to avoid misunderstanding. Till now, this gap (2.38 million m3) is mainly filled by over-drafting groundwater and transferring water from surrounding water scarce provinces (e.g., Hebei and Shanxi). As a consequence, over-exploitation of ground water makes ground water depth decrease at a speed of 1.1 m/year and forms a subsidence area of 2.65 billion square meters (Beijing Water Authority, 2010). To solve this problem, the Middle Route of South-to-North Water Transfer Project has been put into service since 2008, and one billion m3/year of water is planned to be sent to Beijing since 2014 (Beijing Municipal Government, 2011).

IOA has been employed to investigate Beijing’s water use, especially for the year of 2002 and 2007 (Han et al., 2014; Zhou et al., 2010). Besides, an interregional input–output analysis was performed to investigate interregional water resources connections between Beijing and other regions in China (Dalin et al., 2014; Zhang et al., 2011). In addition to the static analysis, the decomposition analysis on the water use change in the period of 1997–2007 was performed (Zhang et al., 2012). Even though contributed significantly to in-depth analysis of water shortage in Beijing economy, the existing studies did not cast light on the impacts from domestic and foreign trade on local water use. To provide comprehensive policy recommendations, it is significant to identify water sources and destinations for water scare regions, in particular that embodied in booming global and domestic trade activities (Wang et al., 2013; Zhang et al., 2011).

The present work takes Beijing as a case to carry out a threescale systems analysis for urban scale water resources use in light of national and global water intensity databases. An elaborated assessment on intensity inventory, final demand, and trade of Beijing economy in the year of 2010 is conducted, and discussions on water imbalance embodied in trade and Beijing economy’s water balance are given as an empirical application to the systems IOA method for an urban economy.