Evaluation of Physical and Economic Water-Saving Efficiency for Virtual Water Flows Related to Inter-Regional Crop Trade in China

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1 sustanablty Artcle Evaluaton of Physcal and Economc Water-Savng Effcency for Vrtual Water Flows Related to Inter-Regonal Crop Trade n Chna Jng Lu 1,2,3, Yu Zhang 4 and Zhongbo Yu 1,2,3, * 1 State Key Laboratory of Hydrology-Water Resources and Hydraulc Engneerng, Hoha Unversty, Nanjng , Chna; lujng0027@hhu.edu.cn 2 Jont Internatonal Research Laboratory of Global Change and Water Cycle, Hoha Unversty, Nanjng , Chna 3 College of Hydrology and Water Resources, Hoha Unversty, Nanjng , Chna 4 Marketng Department of the Busness School, Hoha Unversty, Nanjng , Chna; yuyuzhang88@hhu.edu.cn * Correspondence: zyu@hhu.edu.cn; Tel.: Receved: 30 October 2018; Accepted: 18 November 2018; Publshed: 21 November 2018 Abstract: If products were traded from regons wth relatvely hgh water productvty to regons wth relatvely low water productvty, water savng could be acheved. In ths study, two ndces physcal water-savng effcency (volume of water savngs per cubc meter of vrtual water flows) and economc water-savng effcency (value of water savngs per cubc meter of vrtual water flows consderng water rght tradng) were proposed to analyze the effcency of nter-regonal vrtual water flows related to crop trade n Chna. Results ndcated that the volume of nter-regonal vrtual water flows was m 3, more than 90% of whch was occuped by ol-bearng crops, cereals, and beans. In terms of physcal effcency, only cereals and vegetables presented negatve values. All knds of crop trades were economcally effcent, whle most crops economc water-savng effcency was less than Yuan/m 3. The applcaton of advanced water-savng technologes, the cultvaton of new crop varetes, the adjustment of regonal croppng patterns, or consumpton and trade patterns, could contrbute to more water savngs and hgher physcal water-savng effcency, whle the possble socal, economc, and envronmental tradeoffs should be consdered smultaneously. Water rght tradng and vrtual water compensaton could contrbute to sustanable water consumpton, and full-cost prcng should be adapted n the future. Keywords: physcal water-savng effcency; economc water-savng effcency; water savng; vrtual water; crops; Chna 1. Introducton As water shortages have become more and more severe due to the ncreasng populaton, changng clmate, and other factors, the mprovement of water effcency has been promoted frequently and many dfferent water effcency ndcators/ndces have been ntroduced. In agrcultural producton systems, rrgaton effcency (classcal rrgaton effcency [1], net or effectve rrgaton effcency [2]) and water productvty (crop water productvty [3], water use effcency [4], generalzed water productvty [5], gross nflow water productvty [6], rrgaton water productvty [7], and ran-fed water productvty [8]) are currently used to evaluate water use effcency. In 2002, the concept of a water footprnt was proposed. The water footprnt of a product s the volume of freshwater used to produce the product, measured over the full supply chan, and the water footprnt per mass of product s used to show the effcency of water use for dfferent sectors [9]. People can obtan Sustanablty 2018, 10, 4308; do: /su

2 Sustanablty 2018, 10, of 10 products wth greater dversty and quantty than before wth the help of trades, and vrtual water embedded n traded products flows among regons [10 12]. To evaluate the water effcency assocated wth product trades, or the effcency of vrtual water flows, the concept of water savng was proposed. Water savng s calculated as the dfference between the actual water consumpton for mported products and the assumed water consumpton f these mported products were produced locally [13]. Vrtual water flows are effcent f products are traded from regons wth relatvely hgh water productvty to regons wth relatvely low water productvty, n whch case a postve water savng can be acheved; otherwse, vrtual water flows are neffcent and a negatve water savng,.e., a water loss, would result [9,13]. A large amount of research has been conducted on water savngs on dfferent scales, such as the global scale [14], nter-regonal scale [15,16], country scale [17 19], and rrgaton dstrct scale [20]. Besdes these studes, Zhao et al. assessed scarce water savng through nterprovncal trade wthn Chna, for whch water scarcty status was consdered [21]. The value of water savng s usually affected by trade volume and vrtual water effcency for dfferent scales, whch s dffcult to compare only wth the water savng ndex. Thus, a physcal water-savng effcency was proposed to show the volume of water savngs per cubc meter of vrtual water flow. Recently, the role of economc factors n determnng vrtual water flows has been explored by scholars, whle few studes have shown the economc effcency of vrtual water flows [22,23]. Only a combnaton of dfferent perspectves can provde a complete pcture of regonal water effcency evaluaton. In ths study, two ndces are proposed to analyze the physcal and economc effcency of water savngs due to vrtual water flows. Frstly, we estmated the vrtual water flows related to crop trades n Chna and the related water savngs. Then, the physcal water-savng effcency (the volume of water savngs for per cubc meter of a vrtual water flow) and economc water-savng effcency (the value of water savngs for per cubc meter of a vrtual water flow when consderng water rght tradng) were evaluated. Ths study could be benefcal for the analyss of regonal water savng and contrbute to the mprovement of regonal producton and trade patterns. 2. Materals and Methods 2.1. Methods In ths study, seven knds of crops cereals, beans, tubers, ol-bearng crops, sugar crops, vegetables, and fruts were studed for the vrtual water flows, whch were the product of crop vrtual water content and trade volume. The vrtual water content refers to the water requred for the producton of commodtes per unt of mass (m 3 /kg), and was derved from the research of Mekonnen and Hoekstra [24]. The trade volume was calculated based on the surpluses and defcts method [25 27]: { E If P C, then = P C (1) I = 0 If P < C, then { E = 0 I = C P (2) where P and C are the producton and consumpton volumes for crop (kg), respectvely, and E and I are the export and mport volumes for crop (kg), respectvely. If crops are exported from a provnce wth relatvely low vrtual water content to a provnce wth relatvely hgh vrtual water content, a postve natonal water savng occurs, ndcatng that the trade was effcent from the perspectve of water consumpton. Otherwse, a negatve water savng would result, showng that the trade was neffcent. The value of water savng can be calculated as follows [9]: n WS = (VWC mp VWC exp ) T (3) =1

3 Sustanablty 2018, 10, of 10 where WS s the natonal water savng due to crop trade (m 3 ); VWC mp and VWC exp are vrtual water contents (n m 3 /kg) for crop n crop mportng and exportng regons, respectvely; T s the trade volume for crop (kg); and n s the number of crop types. To compare the water effcency for dfferent regons from physcal and economc perspectves, especally for those at dfferent scales, two ndces physcal water-savng effcency and economc water-savng effcency were proposed. Physcal water-savng effcency can demonstrate the volume of water savngs per cubc meter of a vrtual water flow, whch s smlar to the defnton of rrgaton effcency n agrcultural producton systems [1,28,29]. The physcal water-savng effcency was calculated as follows: PWSE = WS (4) VWF where PWSE s the physcal water-savng effcency and VWF s the volume of nter-regonal vrtual water flows (m 3 ). A regon wth a relatvely hgh physcal water-savng effcency can acheve more water savng than a regon wth a relatvely low physcal water-savng effcency when the volumes of vrtual water flows are the same. The economc value of water n the agrcultural sector was usually much lower than that of other sectors, especally the ndustral sector. We assumed that f the water consumed n the producton of traded crops was consumed by the ndustral sector, the obtaned economc value would be the deal value of these water resources. In Chna, water rght tradng has been tred by the Yellow Rver rural farmers, n whch case water saved from agrculture was used to meet ndustral producton demands; a smlar case can also be found n Australa [22,23]. Thus, the economc water-savng effcency was calculated as follows: EWSE = n (VWC mp T V mp VWC exp T V exp ) =1 VWF (5) where EWSE s the economcal water-savng effcency (Yuan/m 3 ) and V mp and V exp are the economc value n ndustral sectors per unt volume of water consumpton n crop mportng and exportng regons, respectvely (Yuan/m 3 ). The economc water-savng effcency could demonstrate the value of water savngs, consderng water rght tradng per cubc meter of vrtual water flow. A regon wth a relatvely hgh economc water-savng effcency could generate more economc value than a regon wth a relatvely low economc water-savng effcency when the volumes of vrtual water flows are the same. The economc value n ndustral sectors per unt volume of water consumpton (V, Yuan/m 3 ) was calculated as follows: V = V tot (6) WW α where V tot s the total economc value n the ndustral sector (Yuan), WW s the ndustral water wthdrawals (m 3 ), and α s the ndustral water consumpton rato (the proporton of ndustral water consumpton to ndustral water wthdrawal) [30 32], whch s manly nfluenced by ndustry structure and appled water-savng technologes [9,33] Data Sources Data on crop output and consumpton and total economc value n the ndustral sector were obtaned from the Statstcal Yearbook of Chna and the Agrcultural Statstcal Data of Chna [34,35]. Data on water wthdrawals and water consumpton ratos were obtaned from the Chna Water Resources Bulletn and the Water Resources Bulletn for provnces [36].

4 Sustanablty 2018, 10, of Results 3.1. Vrtual Water Flows and Water Savngs Table 1 shows the vrtual water flows related to the trade of dfferent knds of crops. As Chna s an mportant cereal-producng country, only fve of ts provnces mported vrtual water due to cereal trade. The largest mporter, Shangha Provnce, accounted for 54.14% of the total vrtual water mports, whle the largest exporter, Helongjang Provnce, accounted for about 13.41% of vrtual water exports. For beans, about two thrds of the provnces had a vrtual water mport, and the value mported by the largest mporter, Guangdong Provnce, was tmes that mported by the smallest mporter (Nngxa). The vrtual water mports related to ol-bearng crops were manly domnated by Zhejang, Guangdong, and Helongjang Provnces, and the vrtual water exports were manly domnated by Inner Mongola, Henan, and Hube Provnces. The frut needs of nearly all regons could be met locally, excludng Shangha, Bejng, Tanjn, Qngha, and Tbet. Compared wth the abovementoned crops, the values of vrtual water flows related to tubers, sugar, and vegetables were much smaller. About two thrds of the provnces had a vrtual water mport related to nter-regonal sugar crops, whle Bejng was the only provnce wth vrtual water mports related to vegetables. Takng all knds of crops together, about 60% of vrtual water exports were due to the exports n Inner Mongola, Henan, Anhu, and Xnjang Provnces, whle the mports n Shangha, Bejng, and Guangdong Provnces accounted for 72.95% of the total vrtual water mports. Due to dfferences n crop water productvty, a postve or negatve water savng could result, as shown n Table 2. Ol-bearng crops were the crops wth the largest water savng, whle the values for fruts and tubers were much smaller, amountng to 2.04% and 1.13% of the value for ol-bearng crops, respectvely. Unlke other crops, the trades of cereals and vegetables resulted n a negatve water savng, ndcatng that the trades were neffcent from the perspectve of water productvty. Takng all knds of crops together, a postve water savng of m 3 was obtaned.

5 Sustanablty 2018, 10, of 10 Provnces Cereals Beans Tubers Table 1. Vrtual water flows related to crop trade n Chna. Ol-Bearng Crops Sugar Crops Fruts Vegetables Vrtual Water Exports Related to Crop Trade Vrtual Water Imports Related to Crop Trade Anhu Bejng Chongqng Fujan Gansu Guangdong Guangx Guzhou Hanan Hebe Helongjang Henan Hube Hunan Inner Mongola Jangsu Jangx Jln Laonng Nngxa Qngha Shaanx Shandong Shangha Shanx Schuan Tanjn Tbet Xnjang Yunnan Zhejang Natonal vrtual water exports Natonal vrtual water mports Note: the negatve values mean vrtual water mport, whle the postve values mean vrtual water export.

6 Sustanablty 2018, 10, of 10 Table 2. Water savngs related to crop trade n Chna, physcal water-savng effcency, and economc water-savng effcency. Crops Water Savngs Physcal Water-Savng Effcency (m 3 / m 3 ) Economc Water-Savng Effcency (10 3 Yuan/m 3 ) Cereals Beans Tubers Ol-bearng crops Sugar crops Fruts Vegetables All knds of crops Physcal Water-Savng Effcency As can be seen from Table 2, the physcal water-savng effcency of tubers was the hghest, wth a value of 9.48 m 3 /m 3, ndcatng that 9.48 m 3 of water resources could be saved per cubc meter due to the nter-regonal vrtual water flows related to the tuber trade. Sugar crops occuped second place. Compared wth these two knds of crops, the physcal water-savng effcency for beans, ol-bearng crops, and fruts was much lower, wth the value for fruts beng less than 10% of that for tubers. For cereals and vegetables, the stuatons were dfferent. Consderng that nter-regonal vrtual water flows occur due to all knds of crop trades, 0.85 m 3 of water resources could be saved per cubc meter Economc Water-Savng Effcency All knds of crops presented a postve economc water-savng effcency value, whch means that the water savng due to the nter-regonal vrtual water flows of Chna was effcent n terms of economc values (Table 2). As wth the physcal water-savng effcency, the value of the economc water-savng effcency for tubers was the largest, and sugar crops took second place. For the rest of the crops, no more than Yuan of economc value could be obtaned per cubc meter nter-regonal vrtual water flows. The economc water-savng effcency of cereals was the lowest, amountng to only 2% of the value for tubers. Consderng all knds of crops, the economc water-savng effcency was Yuan/ m Dscusson Vrtual water adds a new dmenson to product trade, whle the meanng of vrtual water flows s scale-dependent [20]. For a certan regon, more water consumpton and severe water scarcty can be seen when t exports vrtual water, whle less water consumpton occurs f t s a vrtual water mporter [13,25,27,37]. Wang et al. showed the role of vrtual water trades on Chna s water securty [38]. On a larger scale, ncludng both exportng and mportng regons, the concept of water savng can show the dfferences n water productvty among regons, ndcate whether water s used effcently, and gve a more comprehensve pcture for water management [13,25,39]. Physcal water effcency s the focus of many scholars, and economc values have played an ncreasngly sgnfcant role n water management [8,22,23]; thus, the water effcency for water savngs from both the physcal and economc perspectve were analyzed n ths study. The volume of nter-regonal vrtual water flows related to crop trade n Chna was m 3, more than 90% of whch was occuped by ol-bearng crops, cereals, and beans. The adjustment of crop-producng and crop-exportng provnces from regons wth relatvely low water productvty to those wth relatvely hgh water productvty, especally for the three knds of crop mentoned above, could provde a way to acheve hgher natonal water savngs and a hgher physcal water-savng effcency. Takng ol-bearng crops as an example, f all the ol-bearng crops exported from Henan (the largest producng and exportng regon) were suppled by Guzhou, where water productvty

7 Sustanablty 2018, 10, of 10 was 1.70 tmes hgher than n Henan, then the water savngs related to the ol-bearng crop trade and physcal water-savng effcency would be m 3 and 1.43 m 3 /m 3, respectvely, ndcatng an ncrease of 7.64% and 18.08% compared wth the actual stuaton. However, water consumpton n Guzhou could result n more envronmental mpacts compared wth Henan [40]. For nstance, the mpact of water consumpton on human health and on ecosystem qualty n Guzhou would be 2.17 tmes and 2.91 tmes the current values, respectvely, consderng the adjustment for the producng regons of ol-bearng crops mentoned above. Furthermore, the applcaton of advanced water-savng technologes, the cultvaton of new crop varetes whch requre less water for ther growth, and the adjustment of regonal croppng patterns or consumpton patterns from water-ntensve crops to less water-ntensve ones could contrbute to more water savngs and a hgher physcal water-savng effcency. However, the possble socal, economc, and envronmental tradeoffs should be consdered smultaneously before adjustment measures are taken [41 44]. Vrtual water flows related to product trade were not only nfluenced by regonal water resources but also affected by other factors, especally economc factors, due to the fact that the vrtual water flows were the result of regonal product trade [45 47]. Thus not only the physcal perspectve but also the economc perspectve should be ncluded for the analyss of regonal water resource use. Tradable water rghts help farmers n water-scarce regons to act flexbly when facng hgh fluctuatons n water avalablty and to use water n a sustanable and envronmentally frendly manner [22,23]. Compensaton for vrtual water exports related to crop trade was also promoted for sustanable water consumpton [23,44,48]. Accordng to the results of ths study, crop trade was economcally effcent, whle most crops economc water-savng effcency was less than Yuan/m 3. In the future, more efforts to reflect water value, such as full-cost prcng (ncludng operaton and mantenance costs, captal costs, opportunty costs, scarcty rents, and external costs of water use), whch has receved worldwde acknowledgment, and the adjustment of regonal producton, consumpton, and trade patterns mentoned above, should be encouraged [49 51]. Clmate change could nfluence regonal vrtual water flows and water savngs. For example, Konar et al. found that the staple food trade s projected to save more water across most clmate change scenaros for the year 2030, largely because the wheat trade reorganzes nto a structure where large quanttes of wheat are traded from relatvely water-effcent exporters to less effcent mporters [52]. Konar et al. evaluated the drect mpacts of clmate change and trade lberalzaton together and n solaton [53]. In our future research, the mpacts of clmate change should be ncluded. Only crops were consdered n ths study, whch was manly due to the data avalablty; however, more knds of products should be studed n the future to obtan a more complete pcture for regonal water management. Addtonally, the effcency of vrtual water flows should be measured from many dfferent perspectves n the future, and not restrcted to the physcal and economc felds we mentoned. 5. Conclusons In ths study, two ndces (physcal water-savng effcency and economc water-savng effcency) were proposed to analyze the effcency of water savngs due to nter-regonal vrtual water flows related to crop trade n Chna. The followng conclusons could be drawn: The volume of nter-regonal vrtual water flows related to crop trade n Chna was m 3, more than 90% of whch was occuped by ol-bearng crops, cereals, and beans. Only the nter-regonal trades for cereals and vegetables resulted n negatve water savngs, ndcatng that ther trade pattern s neffcent n terms of water productvty. The applcaton of advanced water-savng technologes, the cultvaton of new crop varetes, the adjustment of regonal croppng patterns, or consumpton and trade patterns could contrbute to more water savngs and a hgher physcal water-savng effcency; however, the possble socal, economc, and envronmental tradeoffs should be consdered smultaneously.

8 Sustanablty 2018, 10, of 10 In terms of physcal effcency, only cereals and vegetables presented negatve values, whch were consstent wth the stuaton for water savngs. The trade of all knds of crops was economcally effcent, whle most crops economc water-savng effcency was less than Yuan/m 3. Water rght tradng and compensaton for vrtual water exports could contrbute to sustanable water consumpton. In the future, more efforts to reflect water value, such as full-cost prcng and the adjustment of regonal producton, consumpton, and trade patterns, should be adapted. Author Contrbutons: Conceptualzaton, J.L.; methodology, J.L.; formal analyss, J.L. and Y.Z.; wrtng orgnal draft preparaton, J.L.; wrtng revew and edtng, Z.Y. Fundng: Ths work was jontly supported by the Natonal Natural Scence Foundaton of Chna (No ), the Fundamental Research Funds for the Central Unverstes (No. 2018B10614), the Natonal Natural Scence Foundaton of Chna (No ; ), the Natonal Key R&D Program of Chna (Nos. 2018YFF ; 2016YFC ; 2016YFC ), the Natonal Scence Funds for Creatve Research Groups of Chna (No ), and the Specal Fund of State Key Laboratory of Hydrology-Water Resources and Hydraulc Engneerng (No ). Conflcts of Interest: The authors declare no conflct of nterest. References 1. Bruce, L. Fctons, fractons, factorals and fractures; on the framng of rrgaton effcency. Agrc. Water Manag. 2012, 108, Wallender, W.W.; Grmmer, M.E. Irrgaton hydrology: Crossng scales. J. Irrg. Dran. Eng. 2002, 128, [CrossRef] 3. Yang, X.; Chen, Y.; Pacenka, S.; Gao, W.; Ma, L.; Wang, G.; Steenhus, T.S. Effect of dversfed crop rotatons on groundwater levels and crop water productvty n the North Chna Plan. J. Hydrol. 2015, 522, [CrossRef] 4. Sngh, R.; Garg, K.K.; Wan, S.P.; Tewar, R.K.; Dhyan, S.K. Impact of water management nterventons on hydrology and ecosystem servces n GarhkundarDabar watershed of Bundelkhand regon Central Inda. J. Hydrol. 2014, 509, [CrossRef] 5. Cao, X.; Wang, Y.; Wu, P.; Zhao, X. Water productvty evaluaton for gran crops n rrgated regons of Chna. Ecol. Indc. 2015, 55, [CrossRef] 6. Cao, X.; Ren, J.; Wu, M.; Guo, X.; Wang, Z.; Wang, W. Effectve use rate of generalzed water resources assessment and to mprove agrcultural water use effcency evaluaton ndex system. Ecol. Indc. 2018, 86, [CrossRef] 7. Wokker, C.; Santos, P.; Bansok, R. Irrgaton water productvty n Cambodan rce systems. Agrc. Econ. 2014, 45, [CrossRef] 8. Owes, T.; Hachum, A. Water harvestng and supplemental rrgaton for mproved water productvty of dry farmng systems n West Asa and North Afrca. Agrc. Water Manag. 2006, 80, [CrossRef] 9. Hoekstra, A.Y.; Chapagan, A.K.; Aldaya, M.M.; Mekonnen, M.M. The Water Footprnt Assessment Manual: Settng the Global Standard; Earthscan: London, UK, D Odorco, P.; Carr, J.; Lao, F.; Rdolf, L.; Vandon, S. Feedng humanty through global food trade. Earth s Future 2014, 2, [CrossRef] 11. Daln, C.; Rodríguez-Iturbe, I. Envronmental mpacts of food trade va resource use and greenhouse gas emssons. Envron. Res. Lett. 2016, 11, [CrossRef] 12. Porkka, M.; Kummu, M.; Sebert, S.; Vars, O. From food nsuffcency towards trade dependency: A hstorcal analyss of global food avalablty. PLoS ONE 2013, 8, e [CrossRef] [PubMed] 13. Chapagan, A.K.; Hoekstra, A.Y.; Savenje, H.H.G. Water savng through nternatonal trade of agrcultural products. Hydrol. Earth Syst. Sc. Dscuss. 2006, 10, [CrossRef] 14. Mekonnen, M.M.; Hoekstra, A.Y. A global and hgh-resoluton assessment of the green, blue and grey water footprnt of wheat. Hydrol. Earth Syst. Sc. 2010, 14, [CrossRef] 15. De Leo, F.; Mgletta, P.P. Water footprnt and vrtual water trade of olve ol. In Proceedngs of the 18th IGWT Symposum of Technology and Innovaton for a Sustanable Future: A Commodty Scence Perspectve, Roma, Italy, September 2012; pp

9 Sustanablty 2018, 10, of Mgletta, P.P.; Morrone, D. Managng Water Sustanablty: Vrtual Water Flows and Economc Water Productvty Assessment of the Wne Trade between Italy and the Balkans. Sustanablty 2018, 10, 543. [CrossRef] 17. Hoekstra, A.Y.; Chapagan, A.K. The water footprnts of Morocco and the Netherlands: Global water use as a result of domestc consumpton of agrcultural commodtes. Ecol. Econ. 2007, 64, [CrossRef] 18. Lamastra, L.; Mgletta, P.P.; Toma, P.; De Leo, F.; Massar, S. Vrtual water trade of agr-food products: Evdence from Italan-Chnese relatons. Sc. Total Envron. 2017, 599, [CrossRef] [PubMed] 19. Karandsh, F.; Hoekstra, A.Y. Informng natonal food and water securty polcy through water footprnt assessment: The case of Iran. Water 2017, 9, 831. [CrossRef] 20. Lu, J.; Sun, S.; Wu, P.; Wang, Y.; Zhao, X. Inter-county vrtual water flows of the Hetao rrgaton dstrct, Chna: A new perspectve for water scarcty. J. Ard Envron. 2015, 119, [CrossRef] 21. Zhao, X.; L, Y.P.; Yang, H.; Lu, W.F.; Tllotson, M.R.; Guan, D.; Y, Y.; Wang, H. Measurng scarce water savng from nterregonal vrtual water flows n Chna. Envron. Res. Lett. 2018, 13, [CrossRef] 22. Burdack, D.; Bewald, A.; Lotze-Campen, H. Cap-and-trade of water rghts: A sustanable way out of Australa s rural water problems? GAIA-Ecol. Perspect. Sc. Soc. 2014, 23, [CrossRef] 23. Wang, Y.B.; Lu, D.; Cao, X.C.; Yang, Z.Y.; Song, J.F.; Chen, D.Y.; Sun, S.K. Agrcultural water rghts tradng and vrtual water export compensaton couplng model: A case study of an rrgaton dstrct n Chna. Agrc. Water Manag. 2017, 180, [CrossRef] 24. Mekonnen, M.M.; Hoekstra, A.Y. The Green, Blue and Grey Water Footprnt of Crops and Derved Crop Products; Value of Water Research Report Seres No. 47; UNESCO-IHE: Delft, The Netherlands, Bulsnk, F.; Hoekstra, A.Y.; Booj, M.J. The water footprnt of Indonesan provnces related to the consumpton of crop products. Hydrol. Earth Syst. Sc. 2010, 14, [CrossRef] 26. Lu, J.; Wu, P.; Wang, Y.; Zhao, X.; Sun, S.; Cao, X. Impacts of changng croppng pattern on vrtual water flows related to crops transfer: A case study for the Hetao rrgaton dstrct, Chna. J. Sc. Food Agrc. 2014, 94, [CrossRef] [PubMed] 27. Lu, J.; Cao, X.; L, B.; Yu, Z. Analyss of Blue and Green Water Consumpton at the Irrgaton Dstrct Scale. Sustanablty 2018, 10, 305. [CrossRef] 28. Bos, M.G. Irrgaton effcences at the crop producton level. ICID Bull. 1980, 29, Ylmaz, B.; Yurdusev, M.A.; Harmancoglu, N.B. The assessment of rrgaton effcency n Buyuk Menderes Basn. Water Resour. Manag. 2009, 23, [CrossRef] 30. Ca, X.; Rosegrant, M.W.; Rngler, C. Physcal and economc effcency of water use n the rver basn: Implcatons for effcent water management. Water Resour. Res. 2003, 39. [CrossRef] 31. Hoekstra, A.Y.; Mekonnen, M.M.; Chapagan, A.K.; Mathews, R.E.; Rchter, B.D. Global monthly water scarcty: Blue water footprnts versus blue water avalablty. PLoS ONE 2012, 7, e [CrossRef] [PubMed] 32. Lu, J.G.; Lu, Q.Y.; Yang, H. Assessng water scarcty by smultaneously consderng envronmental flow requrements, water quantty, and water qualty. Ecol. Indc. 2016, 60, [CrossRef] 33. Wang, Y.; Wang, H.; Ca, Y. Calculaton and analyss of water footprnt n Bejng Cty. Chn. J. Eco-Agrc. 2011, 19, [CrossRef] 34. Natonal Bureau of Statstcs of the People s Republc of Chna. Statstcal Yearbook of Chna; Chna Statstcal Press: Bejng, Chna, Mnstry of Agrculture of the People s Republc of Chna. Agrcultural Statstcal Data of Chna; Chnese Agrcultural Press: Bejng, Chna, Mnstry of Water Resources of the People s Republc of Chna. Chna Water Resources Bulletn; Water Resources and Electrcty Press: Bejng, Chna, Zhang, Z.Y.; Yang, H.; Sh, M.J.; Zehnder, A.J.B.; Abbaspour, K.C. Analyses of mpacts of Chna s nternatonal trade on ts water resources and uses. Hydrol. Earth Syst. Sc. 2011, 15, [CrossRef] 38. Wang, H.R.; Lu, X.H.; Dong, Y.Y.; Wang, J.H. Analyss of Chna s Water Securty and Vrtual Water Trade. Chn. J. Popul. Resour. Envron. 2006, 4, Yang, H.; Pfster, S.; Bhadur, A. Accountng for a scarce resource: Vrtual water and water footprnt n the global water system. Curr. Opn. Envron. Sustan. 2013, 5, [CrossRef] 40. Pfster, S.; Koehler, A.; Hellweg, S. Assessng the envronmental mpacts of freshwater consumpton n LCA. Envron. Sc. Technol. 2009, 43, [CrossRef] [PubMed]

10 Sustanablty 2018, 10, of Konar, M.; Caylor, K.K. Vrtual water trade and development n Afrca. Hydrol. Earth Syst. Sc. 2013, 17, [CrossRef] 42. Zhang, C.; Anadon, L.D. A mult-regonal nput-output analyss of domestc vrtual water trade and provncal water footprnt n Chna. Ecol. Econ. 2014, 100, [CrossRef] 43. Zoumdes, C.; Bruggeman, A.; Hadjkakou, M.; Zacharads, T. Polcy-relevant ndcators for sem-ard natons: The water footprnt of crop producton and supply utlzaton of Cyprus. Ecol. Indc. 2014, 43, [CrossRef] 44. Lu, J.; Wang, Y.; Yu, Z.; Cao, X.; Tan, L.; Sun, S.; Wu, P. A comprehensve analyss of blue water scarcty from the producton, consumpton, and water transfer perspectves. Ecol. Indc. 2017, 72, [CrossRef] 45. Daln, C.; Suwes, S.; Konar, M.; Hanasak, N.; Rodrguez-Iturbe, I. Modelng past and future structure of the global vrtual water trade network. Geophys. Res. Lett. 2012, 39. [CrossRef] 46. Suwes, S.; Konar, M.; Daln, C.; Hanasak, N.; Rnaldo, A.; Rodrguez-Iturbe, I. Structure and controls of the global vrtual water trade network. Geophys. Res. Lett. 2011, 38. [CrossRef] 47. Tamea, S.; Carr, J.A.; Lao, F.; Rdolf, L. Drvers of the vrtual water trade. Water Resour. Res. 2014, 50, [CrossRef] 48. Jang, Y.; Ca, W.; Du, P.; Pan, W.; Wang, C. Vrtual water n nterprovncal trade wth mplcatons for Chna s water polcy. J. Clean. Prod. 2015, 87, [CrossRef] 49. Rogers, P.; De Slva, R.; Bhata, R. Water s an economc good: How to use prces to promote equty, effcency, and sustanablty. Water Polcy 2002, 4, [CrossRef] 50. Mekonnen, M.M.; Hoekstra, A.Y.; Becht, R. Mtgatng the Water Footprnt of Export Cut Flowers from the Lake Navasha Basn, Kenya. Water Resour. Manag. 2012, 26, [CrossRef] 51. Cho, I.-C.; Shn, H.-J.; Nguyen, T.T.; Tenhunen, J. Water Polcy Reforms n South Korea: A Hstorcal Revew and Ongong Challenges for Sustanable Water Governance and Management. Water 2017, 9, 717. [CrossRef] 52. Konar, M.; Hussen, Z.; Hanasak, N.; Mauzerall, D.L.; Rodrguez-Iturbe, I. Vrtual water trade flows and savngs under clmate change. Hydrol. Earth Syst. Sc. 2013, 17, [CrossRef] 53. Konar, M.; Remer, J.J.; Hussen, Z.; Hanasak, N. The water footprnt of staple crop trade under clmate and polcy scenaros. Envron. Res. Lett. 2016, 11, [CrossRef] 2018 by the authors. Lcensee MDPI, Basel, Swtzerland. Ths artcle s an open access artcle dstrbuted under the terms and condtons of the Creatve Commons Attrbuton (CC BY) lcense (