Ecological Economics

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1 Ecologcal Economcs 70 (2011) Contents lsts avalable at ScVerse ScenceDrect Ecologcal Economcs journal homepage: Analyss Analyses of water footprnt of Bejng n an nterregonal nput output framework Zhuoyng Zhang a,c, Hong Yang b,, Mnjun Sh a,c a Graduate Unversty of Chnese Academy of Scences, , Bejng, Chna b Swss Federal Insttute of Aquatc Scence and Technology (Eawag), 8600, Dübendorf, Swtzerland c Research Centre on Fcttous Economy & Data Scence, Chnese Academy of Scences, , Bejng, Chna artcle nfo abstract Artcle hstory: Receved 4 August 2010 Receved n revsed form 16 August 2011 Accepted 16 August 2011 Avalable onlne 6 September 2011 Keywords: Vrtual water Input output analyss Interregonal nput output model Chna Bejng s under severe water resource pressure due to the rapd economc development and growng populaton. Ths study quanttatvely evaluates the water footprnt of Bejng n an nterregonal nput output framework wth a focus on blue water resources and uses. The nter-connectons of water resources between Bejng and other provnces are analyzed wth a sectoral specfcaton. The results show that the total water footprnt of Bejng s m 3 /year, of whch 51% s from the external water footprnt acqured through vrtual water mport. Agrculture has the hghest water footprnt of m 3 /year wth 56% comng from external sources. The man vrtual water provder for Bejng s Hebe, another water scarce regon, from whch Bejng receves vrtual water of m 3 /year wth 40% from agrculture. The results of ths study suggest that the nterregonal trade coordnaton, especally for the man sectors wth hgh water use ntensty, s mportant for enhancng the effcency of regonal and natonal water resource utlzaton Elsever B.V. All rghts reserved. 1. Introducton Bejng, the captal of Chna, s under severe water resource pressure due to the rapd economc development and growng populaton. Durng the perod 1998 to 2008, the GDP of Bejng ncreased from bllon Yuan to bllon Yuan (Natonal Bureau of Statstcs of Chna, ) (1 Yuan 0.16 USD), whle the total populaton grew from 12.5 mllon to more than 16.9 mllon (ncludng regstered permanent resdents and floatng populaton) (Bejng Bureau of Statstcs, ). The average annual per capta water resources avalablty (referrng to surface and ground water resources n ths study) of Bejng s currently about 150 m 3 /capta, far below the nternatonally recognzed mnmum standard of 1000 m 3 /capta (Wang and Wang, 2005). To meet the ncreasng water demand of Bejng, there have been not only engneerng measures lke the South to North Water Dverson project whch drectly provdes water for Bejng but also hdden or vrtual water supports from other regons to Bejng n the form of nterregonal trade of goods and servces. The latter, however, has not been explctly announced as a conscous polcy acton. By defnton, vrtual water s the freshwater requred n the producton process (Allan, 1993). Importng goods and servces to a regon s vrtually equvalent to mportng water that would otherwse be requred for local consumpton (Chapagan et al., 2006; Yang et al., Correspondng author. Tel.: ; fax: E-mal addresses: zhangzy-b08@mals.gucas.ac.cn (Z. Zhang), hong.yang@eawag.ch (H. Yang), mjsh@gucas.ac.cn (M. Sh). 2006; Yang and Zehnder, 2007). Wth the contnuous ntensfcaton of water scarcty and the ncreasng nterregonal trade, t s expected that vrtual water mport wll become a more mportant addtonal water source to be taken nto consderaton n Bejng's water resources plannng. Ths rases a number of questons: How much water s used for the producton of fnal products consumed wthn Bejng? How much vrtual water s suppled from other regons to meet Bejng's consumpton through nterregonal trade? Whch provnces are the major vrtual water provders for Bejng's consumpton? Whch sectors n Bejng are the major recevers of vrtual water mported from other provnces? More generally, what s the nterregonal water resources relatonshp between Bejng and other provnces? Answerng these questons s of great sgnfcance for supportng regonal water polces to address water scarcty problems n Bejng. Therefore, t s worthwhle to conduct an nterregonal consumpton-based vrtual water analyss for Bejng to provde a scentfc reference for allevatng water resources pressure on the cty. Water footprnt s a concept closely lnked wth vrtual water (Hoekstra and Chapagan, 2007). By defnton, the water footprnt of a product s the volume of freshwater used to produce the product, measured over the full supply chan (Hoekstra et al., 2009). In the framework of vrtual water, the water footprnt of a product can also be defned as ts vrtual water content. Water footprnt has blue, green and grey components. The blue water footprnt refers to the consumpton of surface and ground water resources along the supply chan of a product; the green water footprnt refers to the consumpton of sol mosture; the grey water footprnt refers to the volume of freshwater requred to assmlate the load of pollutants based on natural background concentratons and exstng ambent water /$ see front matter 2011 Elsever B.V. All rghts reserved. do: /j.ecolecon

2 Z. Zhang et al. / Ecologcal Economcs 70 (2011) qualty standards (Hoekstra et al., 2009). Ths study focuses on the blue water footprnt assessment of Bejng. The green water footprnt and grey footprnt are not consdered. The man reason for gnorng green water follows Zhao et al. (2010). In short, green water s only drectly relevant to the agrcultural sector. It cannot be a substtute for blue water use n other sectors consdered n ths study. Includng green water n the assessment would lead to content nconsstency between agrcultural (wth green and blue water) and all other sectors (wth almost only blue water). The gnorance of grey water footprnt s due to the lack of nformaton and the complex nature of pollutants from dfferent sectors. The water footprnt of a regon/naton refers to the water needed for the producton of the goods and servces consumed by the nhabtants of the regon/naton (Hoekstra and Chapagan, 2007). Snce the products consumed by a regon are not only produced locally usng local water resources, but also produced outsde of the regon usng the water resources of other regons, the water footprnt of a regon conssts of two parts: the nternal footprnt (the volume of water used from local water resources to produce locally consumed products) and the external footprnt (the volume of the vrtual water mported from other regons mnus any export of vrtual water assocated wth the re-export of any (part) of the mported products) (Hoekstra et al., 2009). For a gven regon, the nternal water footprnt s the real water use of the local resources. The external footprnt s the water used n other regons to produce goods and servces consumed by the nhabtants of the regon consdered. Due to the lmtaton of data avalablty and the complex systems n producton and nterregonal trade, t s generally dffcult to dstngush the nternal and external water footprnt of a product or an economc sector. The nput output table, ntally developed by Leontef (1941), represents the monetary transactons of goods and servces among dfferent sectors of an economc system. It provdes a technque to quanttatvely study the nterconnectons and nterdependences of economc unts. Snce t can specfy how the substances flow among sectors through supplyng nputs (ncludng water) for the outputs (where vrtual water s embedded) n the economc system, the nput output framework has been recently appled to the studes of vrtual water trade and water footprnt. Many of them have been lmted to regonal assessment, such as Detzenbacher and Velazquez (2007), Wang and Wang (2009), Wang, et al. (2009a, 2009b), Zhao et al. (2009), and Zhao et al. (2010). They are not able to specfy the orgns of the vrtual water, whch could be water scarce regons. In order to obtan a clearer understandng of regonal water resource nterdependence, t s mportant to nvestgate sources and destnatons of vrtual water flows n the nput output framework. The nterregonal nput output table was developed based on the general regonal (sngle-regon) nput output table (Isard et al., 1960). Compared wth the regonal nput output table, the nterregonal nput output table provdes a more comprehensve data foundaton of monetary transactons of goods and servces across not only dfferent sectors but also dfferent regons. Snce the nterregonal nput output table can systematcally quantfy the substance flows among dfferent regons, some studes have appled nterregonal nput output tables to assess vrtual water flows. Lenzen (2009) demonstrated the applcaton of an eght-regon nterregonal nput output model for quantfyng the vrtual water flows of Vctora (Australa) from the perspectves of producton and consumpton. The study revealed that the producer-perspectve analyss suggested Vctora a net vrtual water mporter, whereas the consumerperspectve analyss ndcated Vctora a sgnfcant net vrtual water exporter. However, ths study dd not further dstngush sectors where the external water footprnt orgnates. Yang et al. (2010) assessed and compared domestc and total water footprnts of the Southeast and Northeast of England and the UK by applyng a three-regon nterregonal nput output model. The study managed to dstngush the nternal and external water footprnt of the study areas and provded specfcaton of sectors n terms of the orgn of the external water footprnt. However, t dd provde complete nformaton on the water use nterconnecton among dfferent regons n the country. The study by Guan and Hubacek (2007) used an extended regonal nput output model for eght hydro-economc regons n Chna to account for vrtual water flows between North and South Chna. The fndngs revealed that the current trade structure n Chna was not favorable wth regards to effcent water resource allocaton. However, for a study area lke Chna, whch s vast n terrtory and uneven n spatal dstrbuton of water resources, the north south dvson s too coarse to obtan a comprehensve pcture of vrtual water flows. Snce the provnces are the most basc and actve unts n economc actvtes n Chna, t s mportant to apply a provncal-level nterregonal nput output table to nvestgate vrtual water flows across provnces. Ths paper ams to quanttatvely evaluate the water footprnt and vrtual water trade of Bejng by applyng a provncal-level nterregonal nput output model. The evaluaton dstngushes the local (from Bejng tself) water footprnt and the external water footprnt (from the rest of provnces). It determnes the man vrtual water provders for Bejng's consumpton, dentfes key water consumpton sectors, and specfes the nterregonal water resource connectons between Bejng and other provnces. The results of ths study provde new nsghts and a scentfc reference for allevatng water scarcty n Bejng. 2. Data and Methodology 2.1. Data Sources In Chna's admnstratve system, Bejng s a muncpalty wth a provncal status. The muncpalty conssts of Bejng cty (the core) and 5 countes/dstrcts Daxng, Huarou, Pnggu, Myun and Yanqng (manly rural areas wth most of the land used for agrculture and forest). The Bejng Water Authorty s the admnstrator governng the water allocaton and of the muncpalty. In ths study, the scope of Bejng covers the entre muncpalty. The man data foundaton of ths study s the Chna Interregonal Input Output Table 2002 (Chna-IRIO 2002), a 30-regon, 60-sector nterregonal nput output table compled based on Chna Regonal Input-Output tables 2002 (Natonal Bureau of Statstc of Chna, 2008) n the framework of the Chenery Moses model (Chenery et al., 1953). The 30 regons n ths model nclude 22 provnces, 4 muncpaltes and 4 autonomous regons n manland Chna. Hong Kong, Macao, Tawan and Tbet are not ncluded due to data unavalablty. The 60 sectors nclude 5 prmary sectors, 25 secondary sectors and 30 tertary sectors. In ths study, consderng the sector correspondence between the Chna-IRIO 2002 and Bejng Sectoral Water Requrement Quotas (Bejng Muncpal Water Conservaton Offce, 2001), the 60 sectors were aggregated nto 33 sectors, ncludng 4 prmary sectors, 19 secondary sectors and 10 tertary sectors. In ths study, the data of drect water consumpton n the 33 sectors were estmated prmarly based on Bejng Sectoral Water Requrement Quotas (Bejng Muncpal Water Conservaton Offce, 2001). In order to ensure data relablty, the data were further calbrated to keep the total amount of water consumpton of prmary sectors, secondary sectors and tertary sectors consstent wth the data from the Bejng Water Resource Bulletn (Bejng Water Authorty, 2003). In the ndustral sectors, the estmaton of drect water consumpton was adjusted wth the recyclng rates reported n the Sectoral Water Consumpton Quota. In dong so, the values of drect water consumpton n ths study concern only the freshwater ntakes, whle excludng the recycled and reused water wthn the systems. The wastewater dscharge was not deducted from the drect water

3 2496 Z. Zhang et al. / Ecologcal Economcs 70 (2011) consumpton because the polluted water may not be used agan wthout treatment. The same procedure s also taken n other studes, e.g., Hoekstra and Chapagan, 2007; Yu et al., 2010; Zhao et al., In the agrcultural sector, the return flow from agrculture (prmarly rrgaton) was deducted from the water footprnt calculaton. Accordng to Bejng Water Resources Bulletn (Bejng Water Authorty, 2003), the depleton rate of agrcultural water use amounts to 89%, suggestng a return flow rate of 11% n the agrcultural water use. The agrcultural water use n ths study s multpled by the percentage excludng ths return flow rate. We are aware of the potental effect of sectoral aggregaton on the results, as elaborated by Su et al. (2010) n ther analyss of sectoral CO 2 emsson assessment n Chna. However, t s dffcult to fnd proper references and feasble approaches to estmate the water consumpton quotas for all 60 sectors presented n the Chna-IRIO Strong assumptons have to be made for the estmaton, whch may lead to larger errors n the system. Therefore, although a fne level sectoral classfcaton can provde more detaled nformaton, we consder the sectoral aggregaton to be a more approprate opton than estmatng water requrement quotas for all the 60 sectors n ths study. It s worth notng that IO tables for 2007 for sngle provnces have become avalable progressvely n recent years. However, untl now not all sngle provncal IO tables for 2007 are avalable or offcally publshed. Even f all the sngle provncal IO tables for 2007 become avalable, t would stll need to go through rather complcated processes to derve Chna-IRIO 2007, whch could take a couple of years to accomplsh. Hence, Chna-IRIO 2002 s htherto the latest avalable data we can use for ths analyss. The Chna-IRIO 2002 s characterzed as an mport-compettve table. The underlyng assumpton s that the mports are compettve wth domestc supples and hence the mports can be ncorporated wth domestc supples n each row (Table 1). A further assumpton s that the mports from foregn countres are compettve wth the local part of domestc supples, whch means that the mports (from abroad) of a regon meet only the ntermedate consumpton and fnal consumpton of the regon tself rather than other regons. Therefore, the nternal water footprnt calculated n ths study actually ncludes the consumed vrtual water suppled by the local regon and foregn countres Water Footprnt Based on Interregonal Input Output Table The nterregonal nput output table s a top-down economc model. It uses nterregonal and nter-sectoral monetary transacton data to account for the nterconnectons of dfferent ndustres n dfferent regons. Assumng the number of regons s n, and for each regon there are m sectors, then the mathematcal structure of an nterregonal nput output system conssts of (m n) lnear equatons. They show the contrbuton of the producton of one sector of one regon to the ntermedate and fnal consumpton of all the sectors of all the regons n the form of monetary transactons of goods and servces. The standard nterregonal nput output model s represented by Eq. (1) x R m ¼ n S¼1 j¼1 x RS j m þ y RS S¼1 where x R represents the total output of sector n regon R; x j RS represents the ntermedate consumpton of sector j n regon S suppled by sector n regon R. y RS represents the fnal consumpton of regon S suppled by sector n regon R. The drect nput refers to the nput provded by a sector for the producton of another sector n the last step of the producton chan and t s numercally equal to the elements of the ntermedate consumpton matrx (.e., x j RS s the drect nput from sector n regon R to sector j n regon S). The drect nput coeffcent a j RS ndcates the amount of nput from sector n regon R requred to ncrease one monetary unt output of sector j n regon S. a j RS can be obtaned by dvdng the nter-sectoral and nterregonal flow x j RS by total output x j S : a RS j x R ¼ x RS j =x S j Therefore, Eq. (1) can be rewrtten as: m ¼ n a RS S¼1 j¼1 j x S m j þ S¼1 y RS Eq. (3) can be shown as follows n matrx notaton: X ¼ A X þ Y h h h X ¼ x R ;A ¼ a RS j ;Y ¼ y RS where X*, A* and Y* are respectvely the matrxes of output, drect nput coeffcents and fnal consumpton. Assumng the matrx A* of drect nput coeffcents s constant, t s possble to change Eq. (4) nto a consumpton-drven format: X ¼ I A 1 Y ; B ¼ I A h 1 ¼ b RS j where (I A*) 1 s known as the Leontef nverse matrx; b j RS denotes how much output of sector n regon R s requred to meet one monetary unt of the fnal consumpton of sector j n regon S. The above equatons calculate how much the changes n fnal consumpton determne the sectoral output n monetary term. In order to lnk the monetary output wth water resources consumpton, the essental step s to determne the drect water consumptons coeffcent, whch s defned as the amount of drect water used to produce one ð1þ ð2þ ð3þ ð4þ ð5þ Table 1 The standard format of Chna-IRIO Intermedate consumpton Fnal consumpton Export Import Error Total output R 1 R 30 R 1 R 30 S 1 S 60 S 1 S 60 Intermedate nput R 1 S 1 x j RS f t RS E R M R ERR R X R R 30 S 1 S 60 Added value Total nput S v hj S X j S 60

4 Z. Zhang et al. / Ecologcal Economcs 70 (2011) Table 2 Sectoral drect water consumpton n Bejng (2002). Sector types Sectors Output x j b (10 6 Yuan) Drect water consumpton w j b (10 6 m 3 ) The prmary sectors 1. Agrculture Forestry Anmal Husbandry 11, Fshery Sub-total 22, The secondary sectors 5. Mnng Food processng 27, Manufacture of textle Manufacture of textle wearng apparel and leather Processng of tmber and manufacture of furnture Manufacture of paper and paper products 11, Processng of petroleum and cokng 31, Manufacture of raw chemcal materals 48, and chemcal products 13. Manufacture of non-metallc mneral products 14, Smeltng, pressng and manufacture of metals 28, Manufacture of specal purpose machnery 26, Manufacture of transport equpment 26, Manufacture of electrcal machnery and equpment 13, Manufacture of communcaton equpment, 108, computers and other electronc equpment 19. Manufacture of measurng nstruments and 10, machnery for cultural actvty and offce work 20. Other manufacturng sectors Producton and supply of electrc power 11, and heat power 22. Producton and supply of water Constructon 110, Sub-total 498, The tertary sectors 24. Freght transport and storage 43, Informaton transmsson, computer 71, servces and software 26. Wholesale and retal trades 199, Hotels and caterng servces 24, Toursm Scentfc research 20, Educaton, culture and entertanment 49, Health, sports and socal welfare 10, Servce to households Other techncal servces 98, Sub-total 528, Total 1,049, Drect water consumpton coeffcent e j b (m 3 /10 4 Yuan) monetary unt of output. It represents the drect water ntensty of a sector. The drect water consumpton coeffcent can be expressed as Eq. (6). h E B ¼ e B j ;e B j ¼ w B j =x B j ð6þ where E B s the matrx of drect water consumpton coeffcents of Bejng (measured n m 3 /10 4 Yuan n ths study); e j B s the drect water consumpton coeffcent of sector j n Bejng; w j B s the drect water consumpton of sector j n Bejng and x j B s the output (n monetary terms) of sector j n Bejng. For Bejng, the total water consumpton coeffcent δ j B can be acheved by multplyng drect water consumpton coeffcent [e j B ] by the Leontef nverse matrx [b j RB ] (the Bejng related part of the [b j RS ] shown n Eq. (5), whch represents the total water consumpton of sector n regon R to meet one monetary fnal consumpton of sector j n Bejng throughout the whole producton chan: h D ¼ δ B j ; δ B j ¼ e B b RB j j j where D s the total water consumpton coeffcent, whch lnks the monetary fnal demand wth ts correspondng total amount of water consumpton. ð7þ The water footprnt of Bejng can be derved by multplyng the total water consumpton coeffcent δ j B wth fnal demand [y RB ] (the Bejng related part of the [y RS ] shown n Eq. (4)): h T B ¼ t B j ;t B j ¼ δ B j y RB where T B s the matrx of the water footprnt of Bejng whch ndcates the total amount of water resources used n meetng the fnal consumpton of the nhabtants n Bejng. In ths study, t s measured n 10 6 m 3 /year and composed of nternal water use and 29 external water uses (provnces); t j B s the water footprnt of sector j n Bejng. In the evaluaton of the external water footprnt from other regons to Bejng, the sectoral water requrement quotas of Bejng are used. Ths s because the assessment of the water footprnt and vrtual water flows s made from the perspectve of Bejng. Under ths settng, the orgns of the mported vrtual water to Bejng and the sectoral water requrement quotas n the source regons are rrelevant n the assessment. Ths s consstent wth the concept of mported vrtual water defned by Renault (2003). The vrtual water emboded n the mported products s not the real amount of water consumed n the producton of products n the source regon, but the water the recpent regon would consume f t had to produce by tself nstead of mportng. Thus, the external footprnt of Bejng ð8þ

5 2498 Z. Zhang et al. / Ecologcal Economcs 70 (2011) s the water beng saved through mportng goods and servces from other provnces. 3. Results 3.1. Drect Water Consumpton and Coeffcents Table 2 presents the drect water consumpton and drect water consumpton coeffcents of the 33 sectors n Bejng. The results show that the prmary sectors have the hghest absolute amounts of drect water consumpton as well as drect water consumpton coeffcents. The drect water consumpton of the prmary sectors amounts to m 3, whch s 40% of the total. The average drect water consumpton coeffcent of the prmary sectors s m 3 /10 4 Yuan, compared wth the secondary sectors and tertary sectors of 23.3 m 3 /10 4 Yuan and 11.2 m 3 /10 4 Yuan, respectvely. Agrculture s the hghest drect water-ntensve sector wth a drect water coeffcent of m 3 /10 4 Yuan. Besdes, ts absolute amount of drect water consumpton s also the hghest among all the sectors, accountng for 31% of the total. Fshery and forestry sectors are of hgh drect water ntensty, but the absolute amount of drect water consumpton s much lower due to the relatvely small outputs. The secondary sectors are also an mportant drect water consumpton component n Bejng. The total absolute amount of drect water consumpton of the secondary sectors s m 3, accountng for 40% of the total. Among the secondary sectors, sector 22 (Producton and Supply of Water) and sector 21 (Producton and Supply of Electrc Power and Heat Power) have hgh drect water consumpton coeffcents and absolute amounts of drect water consumpton. Although some secondary sectors lke sector 12 (Manufacture of Raw Chemcal Materals and Chemcal Products) and sector 6 (Food Processng) are relatvely low n drect water consumpton coeffcents, ther absolute amounts of drect water consumpton are hgh because of the large outputs. There are also manufacturng sectors whch are low n both drect water consumpton coeffcents and absolute amounts. For nstance, sector 19 (Manufacture of Measurng Instruments and Machnery for Cultural Actvty and Offce Work) requres only 4.8 m 3 drect water nput to produce an output of 10 thousand Yuan and ts absolute amount of drect water consumpton s as low as m 3. The tertary sectors have a drect water consumpton of m 3 whch s the lowest among the three sector types. Ther drect water consumpton coeffcents are low as well, mostly below 20 m 3 /10 4 Yuan. It s notceable that sector 27 (Hotels and Caterng Servces) has a relatvely hgh drect water coeffcent, 76.5 m 3 /10 4 Yuan. Its total drect water consumpton s also relatvely large. Sector 26 (Wholesale and Retal Trades) has a low drect water consumpton coeffcent. However, ts absolute amount of drect water consumpton s hgh due to the large output Water Footprnt at Sectoral Level The water footprnt of Bejng s calculated wth Eq. (8), whch s composed of Bejng's nternal water uses and external water uses from 29 provnces n the form of vrtual water mports. Table 3 provdes the quanttes of the total, nternal and external water footprnt of the 33 sectors n Bejng. The total water footprnt of Bejng n 2002 s estmated at m 3 /year, of whch m 3 /year s the nternal water footprnt, and m 3 s the external water footprnt. The external footprnt accounts for 51% of the total water footprnt of Bejng, suggestng that the vrtual water mported from other provnces has been a substantal component to meet the fnal consumpton of Bejng. The total water footprnt of sector 1 (agrculture) s the hghest among all the sectors, wth an amount of m 3 /year and makng up 34% of the total. The external water footprnt of agrculture Table 3 The sectoral water footprnt of Bejng (10 6 m 3 ). Sectors Total water footprnt Local water footprnt External water footprnt 1. Agrculture Forestry Anmal husbandry Fshery Mnng Food processng Manufacture of textle Manufacture of textle wearng apparel and leather 9. Processng of tmber and manufacture of furnture 10. Manufacture of paper and paper products 11. Processng of petroleum and cokng Manufacture of raw chemcal materals and chemcal products 13. Manufacture of non-metallc mneral products 14. Smeltng, pressng and manufacture of metals 15. Manufacture of specal purpose machnery 16. Manufacture of transport equpment 17. Manufacture of electrcal machnery and equpment 18. Manufacture of communcaton equpment, computers and other electronc equpment 19. Manufacture of measurng nstruments and machnery for cultural actvty and offce work 20. Other manufacturng sectors Producton and supply of electrc power and heat power 22. Producton and supply of water Constructon Freght transport and storage Informaton transmsson, computer servces and software 26. Wholesale and retal trades Hotels and caterng servces Toursm Scentfc research Educaton, culture and entertanment 31. Health, sports and socal welfare Servce to households Other techncal servces Total s m 3 /year, whch makes up 56% of the total water footprnt. Other prmary sectors lke sector 2 (Forestry) and sector 4 (Fshery) also have a hgh total water footprnt and ther amount are m 3 /year and m 3 /year, respectvely. For the secondary sectors, sector 21 (Producton and Supply of Electrc Power and Heat Power), sector 12 (Manufacture of Raw Chemcal Materals and Chemcal Products), sector 14 (Smeltng, Pressng and Manufacture of Metals) and sector 10 (Manufacture of Paper and Paper Products) also have relatvely a hgh total water footprnt. The proportons of the nternal and external water footprnts of eleven man water consumpton sectors n Bejng are shown n Fg. 1. These sectors account for 84%, 78% and 90% of the total water footprnt, nternal water footprnt and external water footprnt of Bejng, respectvely. It can be observed that the proporton of external water footprnts of the man water consumpton sectors s generally hgh n the total water footprnt. For nstance, the external water footprnt proporton of the three sectors of the hghest total water footprnt, sector 1 (Agrculture), sector 21 (Producton and Supply of

6 Z. Zhang et al. / Ecologcal Economcs 70 (2011) proportons n total 100% 80% 60% 40% 20% 0% Sector Local water footprnt External water footprnt Fg. 1. Water footprnt composton of man water consumpton sectors n Bejng. Electrc Power and Heat Power) and sector 4 (Fshery), are 56%, 52%, and 65%, respectvely. For sector 27 (Hotels and Caterng Servces), the proporton of external water footprnt s as hgh as 98%, suggestng that the water used n hotels and caterng servces consumed by the nhabtants of Bejng s mostly from external provnces. Ths ncludes Bejng resdents' consumpton wthn Bejng and outsde of Bejng when they travel to other provnces. The agrcultural products whch are water ntensve are one of the most essental nputs for Hotels and Caterng Servces. Snce Bejng has lmted agrculture producton capacty, t depends greatly on the agrcultural product support from other provnces. The fnal consumpton and the correspondng water footprnt of the three ndustres n Bejng are presented n Table 4. The total fnal consumpton of the prmary sectors s Yuan/year, accountng for only 2% of the total fnal consumpton. However, the correspondng water footprnt of the prmary sectors s m 3 /year, accountng for 45% of the total water footprnt of all ndustres. Bejng tself s the man provder for ts fnal consumpton of prmary sectors wth Yuan/year, whle the external water footprnt amounts to m 3 /year, whch s larger than the nternal amount of m 3 /year. Most prmary sectors n Bejng, wth hgh waterntensty but relatvely low monetary value, depend heavly on the external water from other provnces. Hence, the monetary amount of fnal consumpton for prmary products from external provnces s not large, but the correspondng vrtual water emboded n the external supply s hgh. The proportons of the secondary sectors n the fnal consumpton and the water footprnt are 53% and 44%, respectvely, ndcatng ther hgh sgnfcance n both the local lvelhood and water savng. 38% of the total water footprnt of Bejng s suppled by other provnces to ts secondary ndustres. The total fnal consumpton of tertary sectors s Yuan/ year, accountng for 45% of all ndustres. The correspondng water footprnt s m 3 /year, a proporton of only 11% of the total water footprnt of all ndustres. The nhabtants of Bejng consume Table 5 The regonal dstrbuton of Bejng external water footprnt (10 6 m 3 /year). Provnce code Provnce name External water footprnt of Bejng Provnce code Provnce name 2 Tanjn Hube Hebe Hunan Shanx Guangdong Inner Guangx 25.1 Mongola 6 Laonng Hanan Jln Chongqng Helongjang Schuan Shangha Guzhou Jangsu Yunnan Zhejang Shaanx Anhu Gansu Fujan Qngha Jangx Nngxa Shandong Xnjang Henan a large amount of vrtual water embedded n tertary sectors mported from other provnces. The external water footprnt of the tertary sectors s m 3 /year, compared wth the nternal water footprnt of m 3 /year Sources of the External Water Footprnt of Bejng External water footprnt of Bejng In order to analyze the vrtual water supply demand relatonshp between Bejng and other provnces, the external water footprnt of Bejng from ndvdual provnces s nvestgated and the results are shown n Table 5. Table 4 Fnal consumpton and the correspondng water footprnt of the three Industres n Bejng. Fnal consumpton Amount(10 9 Yuan/year) Proportons (%) The three ndustres Total Local External Total Local External The prmary sectors The secondary sectors The tertary sectors Water footprnt Amount(10 6 m 3 /year) Proportons (%) The three ndustres Total Local External Total Local External The prmary sectors The secondary sectors The tertary sectors Fg. 2. The orgn of the Bejng external water footprnt (106 m 3 /year) (see Table 5 for the lst of the provnces).

7 2500 Z. Zhang et al. / Ecologcal Economcs 70 (2011) Hebe, a water scarce provnce n Chna, s the most mportant water-savng helper for Bejng. Through the trade wth Hebe, Bejng receved m 3 /year of vrtual water, accountng for 16% of the total external water footprnt of Bejng. It should be ponted out that ths vrtual water amount does not equal the real water loss of Hebe snce the external water footprnt of Bejng s evaluated based on the water requrement quotas of Bejng, not Hebe. Consderng that the water use effcency of Hebe s generally lower than Bejng, the real water loss of Hebe from nterregonal trade wth Bejng could be hgher than m 3 /year. Except for vrtual water support n the form of product trade, Hebe also provdes Bejng wth real water resources through water transfer. Durng the perod from September 2008 to July 2009, for example, m 3 of water was transferred from Hebe to Bejng (Xaoxang Mornng Herald, 2010). The vrtual water transfer and real water support greatly allevated the water resource pressure n Bejng but further exacerbated the water resource crss n Hebe. Moreover, the vrtual water mports from Jln, Henan, Guangdong and Shandong are also mportant components of the external water footprnt of Bejng. The man water-savng helpers for Bejng can be roughly categorzed nto three groups: short-dstance provnces, economcally developed provnces and provnces wth both short dstance and developed economy (Fg. 2). For nstance, Hebe, Jln, Henan, Inner Mongola, Laonng and Shanx, are adjacent to or relatvely short dstances from Bejng; Guangdong, Shangha and Jangsu are provnces wth the hghest economc development levels as well as large economc scales n spte of long dstances; and Shandong s relatvely proxmate as well as economcally developed. Ths s consstent wth the Gravty Model (Poyhonen, 1963; Tnbergen, 1966) whch clams the negatve correlaton of geographc dstances and postve correlaton of economc scale to blateral trade volumes. The components of the external water footprnt to Bejng vary among ts helpers partly because of ther dfferent economc Hebe structures and natural endowments. Hebe, Guangdong and Shandong are selected as representatve provnces of the three groups to compare ther sectoral structure dfferences n meetng the fnal consumpton of Bejng (Fg. 3). The results show that the man sectors of Bejng whch obtan vrtual water for fnal consumpton from Hebe, Guangdong, and Shandong are sector 12 (Manufacture of Raw Chemcal Materals and Chemcal Products) and sector 21 (Producton and Supply of Electrc Power and Heat Power). Hebe and Guangdong are the major supplers for Bejng's fnal consumpton of sector 1 (Agrculture), wth proportons of 40% and 26%, respectvely. The agrcultural product varetes provded by Hebe and Guangdong are dfferent due to ther dfferent agrcultural structures. Hebe s one of the man producers of temperate agrcultural products such as wheat, corn, cotton and peanuts, whereas Guangdong s an mportant producer of sub-tropcal fruts and rce. Hence, the agrcultural mport from Hebe s manly for meetng Bejng's demand for temperate agrcultural products, whereas the agrcultural mport from Guangdong s manly for meetng the demand for sub-tropcal agrcultural products. As the man agrcultural producton base close to Bejng, Shandong plays an mportant role n meetng Bejng's demand for agrcultural products especally vegetables. In 2008, over 30% of the vegetable consumed n Bejng were provded by Shandong (Zhao and Ge, 2009). Therefore, a large proporton of agrcultural products consumed by the caterng servces n Bejng are from Shandong. 4. Dscusson The results show that the total water footprnt of Bejng was m 3 /year n the year 2002, slghtly hgher than the result of m 3 /year n the same year from the study by Wang and Wang (2009). The reason for the dfference between the two studes les prmarly n two aspects. Frstly, the dfferent sectoral dvsons. Wang and Wang (2009) s a three-sector level (prmary, secondary Guangdong Sector6 3% Sector5 6% Sector12 7% Sector21 12% Others 16% Sector14 16% Sector1 40% Sector12 5% Sector21 7% Sector10 8% Others 19% Sector27 13% Sector1 26% Sector4 22% Shandong Others 25% Sector27 19% Sector10 5% Sector21 10% Sector12 10% Sector5 18% Sector14 13% Fg. 3. A sectoral structure comparson of the external water footprnt of Bejng.

8 Z. Zhang et al. / Ecologcal Economcs 70 (2011) and tertary sectors) assessment, whereas ths study has 33-sectors. Secondly, the dfferent approaches used n determnng the sectoral drect water consumpton. In the study of Wang and Wang (2009), the data on the three-sectoral drect water consumpton s from Bejng Water Resources Bulletn (Bejng Water Authorty, 2003). Ths study referenced the Bejng Sectoral Water Requrement Quotas (Bejng Muncpal Water Conservaton Offce, 2001) to obtan sectoral drect water consumpton for the 33 sectors. The fndngs of ths study reveal the water resource challenges faced by Bejng. The total water resources of Bejng s about m 3 (Natonal Bureau of Statstcs of Chna, 2003). The gap between total water resources and total water footprnt amounts to m 3 /year. Subtractng the water saved through nterregonal trade of m 3 /year, there s stll a water resource gap of m 3 /year. Ths gap has been flled prmarly by drect water transfers from other regons and over-explotaton of non-renewable groundwater n the regon. Furthermore, the man water-savng helpers for Bejng, such as Hebe, Jln and Henan, are water scarce provnces as well. They are not sustanable vrtual water sources whch can allevate the water resources stress of Bejng. In vew of varyng values of fnal consumpton and water use ntensty among dfferent economc sectors, one possble approach for Bejng to amelorate ts water stress s to nternally adjust ts ndustral structure and externally coordnate the nterregonal trade wth other provnces. The prmary sectors have a low fnal consumpton but a hgh water footprnt. To address water shortage problems n Bejng, reducng the consumpton proporton of the prmary sectors, especally agrculture, should receve partcular attenton. Besdes, agrculture water savng measures should be encouraged to enhance the effectveness of local water consumpton. Importng prmary products from other provnces s also an effectve way to allevate the water resources pressure of Bejng. The secondary sectors are of promnent sgnfcance n the local economy. Water savng should focus on technology mprovement, manufacturng process adjustments, raw materal mport modfcaton, etc. The tertary sectors consume relatvely small amounts of water resources to meet the fnal consumpton. Ths should be consdered the drecton of future water-savng orented ndustral development. Externally, gven the great sgnfcance of the man water-savng helpers and the man sectors to meet water consumpton of Bejng, the water resources stuaton of the man helpers should be ncorporated n the strategc water and trade plannng of Bejng. Some shortcomngs n ths study should be noted. Due to the data constrant, agrcultural sectors are consdered as a whole wthout dstngushng specfc agrcultural products n ths study. Moreover, ths study dd not specfy the relatonshp between water footprnt and the potental socal and envronmental mpacts (beyond the scope of the gray water footprnt). It would be meanngful to conduct comparsons among products and producton systems n terms of ther contrbuton to water scarcty because a product wth a lower water footprnt could probably be more damagng to the envronment than one wth a hgher water footprnt dependng on where the water s sourced (Rdoutt and Pfster, 2010). In ths study, sector aggregaton can lead to nformaton loss n the nterregonal nput output table and thus have effect on the results. The tertary sectors are expected to be mostly affected because they have the hghest level of aggregaton, from 30 sectors to 10 sectors. However, as the water footprnt n these sectors s relatvely small n the total water footprnt of Bejng, the effect of the aggregaton n the tertary sectors on the total water footprnt s expected to be small. As for the extent of the effect of sectoral aggregaton on the water footprnt n other sectors, the avalable nformaton s not suffcent to make a relable estmaton. 5. Concludng Remarks Ths paper quanttatvely evaluates the water footprnt of Bejng n an nterregonal nput output framework. It dstngushes the nternal water footprnt and the external water footprnt for dfferent economc sectors n Bejng. The study demonstrates that the nterregonal nput output model s an effectve analytcal tool n quantfyng nterregonal vrtual water flows. The analyss of the sectoral and regonal structure of the water footprnt provdes a better understandng of the nterregonal supply demand relatonshp of water resources between Bejng and other provnces. The sectoral level results ndcate that the prmary sectors of Bejng, especally agrculture, have the hghest water footprnt; the secondary sectors' mportance n both local lvelhood and water savng s reflected by ther proportons of 53% and 44% n fnal consumpton and the water footprnt of all ndustres; the tertary sectors use 11% of the total water consumpton to meet 45% of the total fnal consumpton, showng ther superorty n water-savng strategy. At the provncal level, the results suggest that the vrtual water support from other provnces s a substantal component n meetng the fnal consumpton of Bejng. The analyss found that some major water-savng helpers for Bejng are water scarce provnces as well. Hence, nterregonal trade restructure and coordnaton need to be ncorporated nto Bejng's economc development strategy to ensure a sustanable use of regonal and natonal water resources. Fnally, ths study s an ntal attempt to nvestgate nterregonal water resources connectons through the trade of goods and servces. One mprovement for future study would be to apply an agrculture sector-subdvded nput output table, and to ncorporate the potental socal/envronmental mpact of water consumpton nto water footprnt assessment. Wth the gradual avalablty of ndvdual provncal IO 2007 tables, a further step to advance study would be to establsh the IRIO 2007 model. It would not only provde more recent nformaton of the vrtual water flows across economc sectors and regons, but also enable an examnaton of the dynamc changes of Bejng's water footprnt over tme, especally as results of rapd economc structural changes, technologcal advances and mprovements n sectoral water use effcency. Acknowledgments We are grateful to the 4 anonymous revewers for ther nsghtful and constructve comments and suggestons on the earler verson of the manuscrpt. 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