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1 This article was downloaded by: [Jia, Shaofeng] On: 2 March 2010 Access details: Access Details: [subscription number ] Publisher Routledge Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Water International Publication details, including instructions for authors and subscription information: Will China's water shortage shake the world's food security? Jia Shaofeng a ; Lin Shijun a ; Lv Aifeng a a Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, People's Republic of China Online publication date: 29 January 2010 To cite this Article Shaofeng, Jia, Shijun, Lin and Aifeng, Lv(2010) 'Will China's water shortage shake the world's food security?', Water International, 35: 1, 6 17 To link to this Article: DOI: / URL: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Water International Vol. 35, No. 1, January 2010, 6 17 RWIN Water International, Vol. 35, No. 1, December 2009: pp. 0 0 Will China s water shortage shake the world s food security? Water Jia. International S et al. Jia Shaofeng*, Lin Shijun and Lv Aifeng Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, People s Republic of China (Received 10 February 2009; revised 16 November 2009; accepted 16 November 2009) This paper presents a detailed analysis of the long-term relationship between China s grain output and its use of irrigation water. It shows that over the last 30 years, China has maintained an increase in grain output while irrigation water withdrawal has been decreasing. Irrigation water use was not significantly correlated with grain output due to the greater offsetting effect of prices and cropping area. Although China s agricultural water use will continue to dwindle, there is no reason to expect that water productivity increases cannot continue to keep pace. This is no excuse for complacency, however. Keywords: Irrigation water use; water productivity; food security; grain output; China Introduction China uses only 9% of the world s cultivated land to feed 22% of the world s population. At present, food supply is seemingly secure in China because per capita grain production has been above 350 kg/person for most years since 1980 (Table 1), which is close to the world average (Halweil 2007). But a decade and a half ago some researchers, led by Lester Brown s question Who will feed China? (1995) posited that China cannot produce enough food for a huge, continuously growing population that continues to become more prosperous because almost all suitable land has been developed. Brown raised the spectre that the consequent ballooning in China s grain imports would affect global food security by driving up prices. In later elaborations, Brown and Halweil (1998) and Brown (2004) further suggested that water shortage would be the ultimate driver of this global impact. While some scholars such as Nickum (1998) have argued that water quantity is not a binding constraint on grain production in China, theirs has not been the dominant view. For example, the 2009 World Economic Forum alleged that water bubbles are now bursting in parts of China, affecting agriculture as well as the larger economy (World Economic Forum 2009). Some of China s own leading analysts see cause for concern. Liu (2007) used a GISbased EPIC model to study the relationship of water and wheat output of north China, and found that lower irrigation water use will cause a decrease of wheat output in north China. Liu et al. (2008) analyzed the impact of food consumption patterns on agricultural water demand and reached the conclusion that an additional amount of water ranging between 407 and 515 km 3 /yr will be required in 2030 over the 1127 km 3 /yr of total water used to *Corresponding author. jiasf@igsnrr.ac.cn ISSN print/issn online 2010 International Water Resources Association DOI: /

3 Water International 7 Table 1. Year China s per capita grain production. Grain production (m. t) Population (m. people) Per capita grain production (kg/person) , , , , , , , , , , , , , , , , , , , , Data source: Statistical yearbook of China (2008) and Statistical bulletin of socio-economic development of China (2008). Note: For China, grain includes rice, wheat, corn and other cereal crops, beans and tubers. Five kg of tubers is counted as 1 kg of grain. Cereal takes up about 90% of total grain. produce food in If this huge increment is really required, it will be impossible for China to supply. Even if green water and virtual water strategies were adopted, China s and the world s food security would indeed be shaken by water shortage. No one would deny that grain production in China faces a difficult future. The greatest potential for enlarging the area of cultivated land is northern China, where water resources are already overdeveloped with higher than 80% water use intensity in most large basins. Even more disturbing, the situation there is deteriorating because rapid industrialization and urbanization have been appropriating water from the agricultural sector. Nonetheless, it is argued in this study that water shortage is unlikely to threaten the grain output of China, much less the food security of the world. Previous studies that foretold the water bankruptcy of China s agriculture focused on the pressure of population growth and rising living standards to the clear neglect of the great potential to reduce water demand through greater water use efficiency. The empirical record bears this out. Using aggregate water use data now available continuously from 1997, the authors show here that China has successfully maintained an increasing grain output with decreasing irrigation water withdrawals. This study then analyzes the reasons for this phenomenon. Finally, the study predicts that water shortage will not hinder the rise of grain output or endanger food security provided the growth rate of irrigation water crop productivity in the next years maintains a growth rate averaging only one-fifth that of the past 30 years.

4 8 Jia S. et al. Method and data To study the relationship between irrigation water use and grain output and to examine the factors influencing China s grain output, correlation and regression analysis were the methods used in this paper. For future trends, this study focuses on grain demand when the population of China reaches a peak. Several scenarios of different predictions of peak population and per capita grain demand standards are analyzed to evaluate if water demand for those scenarios can be met. The historic data for the years (Table 1) and provincial distribution data of grain output are used in this paper. These data include grain output and possible influencing variables such as the number of rural agricultural labourers, the area of land under grain, the effectively irrigated area, the quantity of fertilizer consumed, the total power of agricultural machinery, crop-sown areas covered by natural disasters, crop-sown areas affected by natural disasters, grain production price index, the price index of means of agricultural production (including machinery, materials and power used for production) and agricultural water use. In this study agricultural water use is seen as crop irrigation water use because there were no detailed data for every year of non-crop-irrigation agricultural water use, which includes water use for forest irrigation, grass irrigation and fishery, and is estimated to amount to only 8% of total agricultural water use. The data sources are provided with Table 1 and Table 2. Data in addition to that for water use came from the Statistical Yearbook of China 2007 and the Statistical Bulletin of Socio-Economic Development of China 2007, 2008 (Statistical Bureau of China 2007, 2008, 2009). From 1997 onwards, statistical water use data have been published by the Ministry of Water Resources of China ( ) in the Water Resources Bulletin. For the earlier years of 1980 and 1993, water use data exist because water resource appraisals and water supply and demand planning projects respectively were done these two years. For the year 2008, the authors obtained only grain output data as all other data had not been published at the time of the revision of this paper. Changes to irrigation water and grain output over the last 30 years Table 2 and Figure 1 give the variation of irrigation water and grain output over the last 30 years. It can be seen that China s grain production increased from about 300 million metric tons in 1978 to 500 million tons in 2007, while agricultural water use decreased from about 370 billion tons to 360 billion tons. So, from these historic statistical data, a conclusion can be reached: China has successfully produced more grain with less water for the last 30 years, especially during the period when agricultural water use decreased from 392 billion tons in 1997 to 360 billion tons in 2007, while grain production remained about 500 million tons. In 2008, China s grain output hit a new historic record of million tons. Figure 2 further shows the distribution as well as the change in grain output from The top five producing provinces in 2006 were Henan, Shandong, Heilongjiang, Jiangsu and Sichuan. Only four of China s 31 province-level administrations showed a decline in grain output from , the two megacities of Shanghai and Beijing and two coastal provinces, Zhejiang and Fujian; the latter have the lowest amount of cultivated land in China per capita and are where rapid urbanization occupied an unusual proportion of cultivated land. Most main grain-producing provinces increased grain production while their use of irrigation water decreased. The top five provinces in grain output growth from were Henan, Heilongjiang, Jilin, Shandong and Hunan, with all but Hunan located in northern China

5 Water International 9 Table 2. China s grain output and possible influence variables. Year y x 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x ,587 44, ,790 24, ,234 44, ,526 29, , ,845 44, ,365 22, ,933 44, ,140 23, ,268 44, ,090 20, ,123 44, ,870 23, ,205 44, ,991 24, ,466 47, ,474 17, ,314 47, ,472 27, ,560 48, ,333 25, ,509 48, ,829 23, , ,544 48, ,043 31, ,060 49, ,821 22, ,548 50, ,989 21, ,912 51, ,429 30, , ,787 52, ,145 25, , ,161 53, ,981 26, , ,463 53, ,688 34, , ,080 54, ,215 31, , ,891 54, ,119 27, , ,410 54, ,506 32, , ,606 54, ,106 16, , ,278 55, ,818 19, , ,489 56, ,091 24, , ,530 56, , Data source: All data besides water use are from Statistical Bureau of China (2007, 2008). Water use data source: data of 1980 and 1993, Nanjing Hydrology and Water Resources Institute of the Ministry of Water Resources and the Institute of Hydropower and Water Conservancy of China (1999); data of , Ministry of Water Resources of China ( ). Symbols: Y: grain output (m t); x 1: number of rural agricultural labourers (m. people); x 2 : grain sown area (1000 hm 2 ); x 3 : effectively irrigated area (1000 hm 2 ); x 4 : quantity of fertilizer consumed (m. t); x 5 : the power of total agricultural machinery (m. kw); x 6 : area covered by natural disasters (1000 hm 2 ); x 7 : areas affected by natural disaster (1000 hm 2 ); x 8 : grain price index (%); x 9 : price index of means of agricultural production (%) ; x 10 : agricultural water use (0.1 billion t). Here water use means fresh water withdrawal. grain output (m.t) grain output agricultural water use 4,000 3,900 3,800 3,700 3,600 3,500 3,400 agricultural water use (100 million t) Figure 1. Grain output and agricultural water use in China.

6 10 Jia S. et al. Figure 2. Distribution of grain output and its change by province. where water resources are scarcer than in the Yangtze or Zhujiang (Pearl) basins in south China. These southern basins, plus Hainan Island and some parts of Tibet, have abundant water resources with per capita water normally available at more than 2000 m 3 /person. Northern China (including the Huaihe, Huanghe, Haihe Liaohe and Heilongjiang basins as well as northwest arid and semiarid closed basins), has much scarcer water resources with a per capita availability normally lower than 1000 m 3 /person, and below 500 m 3 /person in several provinces. But the centre of gravity of grain production in China has nonetheless moved from the south to north. In 1978, north China, including Shandong, Henan, Hebei, Tianjin, Beijing, Shanxi, Neimenggu, Shaanxi Ningxia, Qinghai, Gansu, Xinjiang, Liaoning, Jilin and Heilongjiang produced only 43.4% of the total grain produced. By 2006, it produced 51.8%. Between 1978 and 2006, 64% of the growth in grain output occurred in water-stressed north China. It also should be noted that northern China experienced an agricultural water use decrease because urban and industrial development needed to use water formerly used by agriculture under the background of water shortage. The main factors influencing grain output in China Correlation analysis For water use, there are 13 years of data, for the years 1980, 1993 and By doing a direct correlation analysis, it can be found that the correlation between grain output and agricultural water use was very weak with R 2 = In fact, the grain output and agricultural water use of China are not correlated at all after There are 24 years (1978, 1980, ) of data for all other variables in Table 1. To analyze water use data together with those data, the authors interpolated and extrapolated

7 Water International 11 Table 3. Correlation matrix of variables concerning China s grain production. X 1 X 2 X 3 X 4 X 5 X 6 X 7 X 8 X 9 X 10 y X X X X X X X X X X y Table 4. Partial correlation coefficient. X 1 X 2 X 3 X 4 X 5 X 6 X 7 X 8 X 9 X 10 y linearly agricultural water use data for the years 1978 and The correlation matrix is shown in Table 3. For 24 observations, the threshold of coefficient of correlation for significant correlation is (α = 0.05). According to this threshold, China s grain output is correlated to rural agricultural labourers, crop-sown area, effectively irrigated area, fertilizer used and agricultural machinery power, while other variables including agricultural water use are found not to be correlated to grain production. But for partial correlation (see Table 4), not only are agricultural labour and machinery correlated to grain production, but also crop-sown area affected by natural disaster and the price index of means of agricultural production. Regression analysis The stepwise multi-variable regression analysis also rejected water use variable as well as area affected by natural disaster and grain price from the regression equation because they were not able to meet the statistical test requirements. If the final regression function obtained from stepwise regression analysis meets all statistical test requirements, such as t-tests, it should exclude multicollinearity problems. The final regression function is as follows: Y = X X 1.36 X X X 91.3X 9 (1) where Y = grain output; x 1 = number of rural agricultural labourers; x 2 = grain sown area; x 3 = effectively irrigated area (1000 hm 2 ); x 4 = quantity of fertilizer consumed; x 7 = areas affected by natural disaster; and x 9 = price index of means of agricultural production (%). The compounded correlation coefficient was R = , R 2 was , and F value was The significance level is , the adjusted correlation coefficient R a = , and adjusted R a 2 = Every variable in function (1) meets the requirements of statistical tests such as the fact that t-test values are greater than two (see Table 5). The Durbin-Watson statistic was d =

8 12 Jia S. et al. Table 5. Statistical test value for variables in function (1). Partial correlation coefficient T-value Significance level r(y,x 1 ) = r(y,x 2 ) = r(y,x 3 ) = r(y,x 4 ) = r(y,x 7 ) = r(y,x 9 ) = All these statistics indicate that function (1) is a good regression function with the exception of the negative regression coefficient of effectively irrigated area (x 3 ). The negative symbol of this coefficient means the greater the effectively irrigated area the lower the grain output, which is not true. This apparent contradiction may be explained as follows: effectively irrigated area indicates only the infrastructure capacity, not the area actually irrigated (Nickum 2003), so while the effectively irrigated area statistic maintained a continuous increase, grain output decreased in some years. Although function (1) cannot be used for grain output prediction because of the negative coefficient of effectively irrigated area, it can be used to model the historic data of China s grain output. From function (1), we can see the change in China s grain output is explained by agricultural labour (x 1 ), crop-sown area (x 2 ), effectively irrigated area (x 3 ), quantity of fertilizer consumed (x 4 ), area affected by natural disaster (x 7 ) and price index of means of agricultural production (x 9 ), but not by agricultural water use. The study also analyzed the relationship of the annual increment of grain output to other influential factors. The results are similar: that water use variable is not included in the final regression function. Figure 3 shows the fluctuation of annual grain output and grain price. The direction of change in grain output always followed that of grain price, sometimes with a one-year lag. The correlation coefficient of increment of grain output with grain index and one-year lagged grain index were and respectively. In Figure 1 and Table 2, we can see that grain output, sown-area bottomed out in 2003, together with agricultural water use. The main reason for this was a continuous decline in grain price from , which then stayed at a very low level in 2002 and Quite naturally, farmers cut back grain-sown area. Specifically, in , the prices annual grain growth (10,000t) annual grain price change (%) grain grain price Figure 3. Year-to-year change of grain output and grain price.

9 Water International 13 of wheat, rice and corn decreased by 29.6%, 27.1% and 23.1% respectively. In 2004, grain prices rose by 28.1% and the downward movement in grain output stopped, then bounced up. In fact, the rise of the price of grain induced several instances of mailiangnan (difficulty of selling grain). In early 1984, the government raised its purchase prices for grain and wheat from yuan/kg to yuan/kg and rice from yuan/kg to yuan/kg. Farmers planted more grain in response. The result was that at the end of 1984, the grain output of China increased by million tons to reach million tons, all granaries were unexpectedly full, and farmers could not find buyers. The problem of mailiangnan followed grain price rises in and 1996 (Wen 2001). When the grain price jumped, the grain output immediately responded and flooded the market, causing grain prices to fall and farmers to cut back on grain output. The above suggests strongly that the decrease of agricultural water supply of China did not influence grain output or food security over the past 30 years. Crop-sown area and grain prices, not agricultural water use, explain most of the changes in grain production. The main reason for this is the extension of better water-saving practices, including the development of water-saving crop varieties. For example, in north China the average irrigation quota has decreased from 5600 m 3 /hm 2 in the 1980s to the present 3750 m 3 /hm 2 while the crop yield per hectare has doubled. For the years 1980 and 2007, irrigation water productivity was kg/t and kg/t respectively, yielding an average annual growth rate of irrigation water productivity of 2.67%. What makes the authors of this study more confident in the universality of the secular increase in water productivity offsetting the decline in water availability is that this trend appears in the regions of the most serious water shortages in China, such as Hebei province in the Hai river basin, where the per capita annual available water resource is less than 300 m 3. Future trends Food security depends mainly on whether grain supply can meet grain demand. Grain demand is decided by total population and per capita grain demand. The demand side can be considered first. In the 1990s, many researchers predicted that the population of China would peak at 1.6 billion in the 2030s (Ma et al. 2000). More recently, this figure has slid to 1.45 billion (Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat 2004), or even to 1.40 billion (Men et al., 2005). The official prediction of the National Population and Family Planning Commission of China was 1.5 billion (Administrative Office of the National Population and Family Planning Commission of China 2005). The main reason for this downshift is that the fifth census of China in the year 2000 showed the total fertility rate (TFR) had dropped below 1.8 while the peak figure of 1.6 billion was obtained by using a TFR of 2.1. As for per capita grain demand, the present level is about 360 kg/person. As living standards rise, per capita grain demand includes both increasing and decreasing sectors. On the one hand, the increase of meat and subsidiary food consumption often causes grain demand to rise because the production of meat and subsidiary food consumes grain. On the other hand, greater consumption of vegetables, fruit and aquacultural foods replaces grain as food. In this study, the projections adopted are 350 kg/person as the lower standard and 400 kg/person as the higher. The combination of a lower peak population figure and per capita grain demand gives rise to lower total grain demand (Table 6). The lowest estimate is 490 billion kg, when the

10 14 Jia S. et al. Table 6. China s grain and agricultural water demand when the population reaches a peak in Year P (b.) Per capita grain (kg/p) Total grain demand (b. kg) Ratio of grain from irrigated area Grain from irrigated area (b. kg) Irrigated water productivity (kg/t) Annual growth rate of water productivity (%) Water use or demand (b. t) (1) (2) (3) (4) (5) (6) (7) (8) (9) When population reaches a peak in population peak is 1.40 billion and per capita grain demand is 350 kg/person. The highest total grain demand is 640 billion kg, when the population peak is 1.6 billion and the per capita grain demand standard is 400 kg/person. Some predictions of more than 700 billion kg of peak grain demand of China (e.g. Liu 2006) appear to be unrealistically high. Can China supply enough water to produce this amount of grain in future? Assume that the ratio of grain produced in the irrigated area to total grain output is 0.83, slightly above the present level of Multiplying this ratio by total grain demand gives a figure of grain output from irrigated fields (column 6 of Table 6). Agricultural water demand (column 9) then equals grain from irrigated fields multiplied by irrigation water productivity (column 8). The highest water demand of the different scenarios obtained is 340 billion tons in 2030, which is not only much lower than the past peak of 392 billion tons in 1997, but also well below the more recent average agricultural water use of 360 billion tons. Some may question whether that amount of irrigation water can be supplied in the face of competition for water from cities and industries. The answer is yes. The authors previous studies have indicated that water demand will probably even decrease because of the Kuznets Curve effect on industrial water use (where such use declines as economies mature) and the enhancement of agricultural water use efficiency (Jia and Kang 2000, Jia et al. 2006). At the same time, water supply capacity is growing because of new water supply projects being constructed, such as the famous South to North Water Transfer Projects, and the development of new water supply technologies in areas such as waste water reuse and sea water desalinization. So the sense is that from the point of view of water quantity, China will have the ability to meet her agricultural water demand for grain production. One question that needs to be considered is whether irrigation water productivity can be raised as shown in Table 6. From 1980 to 2007, the average annual growth rate of irrigation water productivity was 2.67%. For the period , the authors suggest this rate will be 0.5%, less than one-fifth of the previous 28 years. Under this assumption, irrigation water productivity of China in 2030 should reach 1.56 kg/t. If we add effective precipitation used for crop growth (about 400 mm or 4000 t/hm 2 ), total water productivity will be about 0.9 kg/t. This is relatively modest compared to the best-practice dunliangtian

11 Water International 15 (land producing more than 15 t/hm 2 of grain) throughout China, where water use efficiency already exceeds 1.67 kg/t. At present, less than 1% of China s total irrigated area is under drip and micro-irrigation. As water-saving irrigation technologies become more widespread, water productivity will rise greatly. Rosegrant et al (2005) used an IMPACT- Water model to study the impact of the rising price of water on agricultural water use and food production and concluded that significant but reasonable water price increases lead to considerable water savings for environmental uses, especially in dry basins in north and northwest China, while there is little impact on irrigated food production if water prices induce irrigation water use efficiency improvements. Another question is whether there is enough land that can be irrigated, even if there is enough water. Irrigated land is increasingly occupied by rapid urbanization, and it is becoming progressively more difficult to expand the irrigated area. Yet the irrigated area of China in 2004 reached 54,478 khm 2 and has expanded modestly since. The authors predict that the irrigated area will continue to inch up over the next 30 years to reach 55,000 khm 2. With this irrigated area and grain output from the irrigated area (column 3), grain yield per unit of irrigated area (column 6 of Table 4) should increase by 5% 30% over the present level. While the irrigation quota (column 7and 8) seems easy to guarantee, the promotion of grain yield of unit irrigation area will be a very hard task. World grain land productivity rose from 1.1 tons per hectare in 1950 to 2.9 tons in 2004 (Brown 2004). China has higher grain land productivity than the world average but still lags behind advanced countries, so there is considerable potential in this area through the application of more advanced management techniques and the development of high production crop species such as super rice. Summary and discussion (1) Historically, water shortage has not hindered China s grain production and food supply. The experience of China after 1978 is one of maintaining growth in grain output while fresh water withdrawal has been decreasing. The historical data show that the fluctuation of grain output mainly depended on grain crop area and grain price, while the change of agricultural water use was not significantly correlated with grain output. (2) The main reason it was possible to produce more grain with less water was the rapid improvement in irrigation water productivity. In 1980, only kg were produced per ton of water. By 2007, it had risen to kg/t, an average annual growth rate of 2.67%. (3) Looking to the future, China s agricultural water use will continue to dwindle, but by relying on further increases in water use efficiency, China s grain output will maintain an upward trend. From the point of view of water resources, per capita grain production can be maintained at above a safe level of kg/person even when the population of China reaches a peak of about 1.5 billion in (4) Climate conditions were not considered directly in this paper. There are two reasons for this. Firstly, to a large degree the land area of China is large enough to temper and smooth droughts and floods that occur every year in one place or the other. Second, variables of land area covered or affected by natural disasters indirectly reflect the impact of weather. The impact of future climate change on grain output and water use is still full of uncertainty. Liu (2007) et al. proposed that temperature rises will make crop water demand increase, and reduce grain output

12 16 Jia S. et al. decrease under the condition of lower irrigation water supply. But historically, some of China s most prosperous dynasties, such as the Han and Tang, flourished during periods of high temperature (Zhu 1972). (5) Although for the period agricultural water use is not correlated with grain production, and the fluctuation of grain output is sensitive to the change of crop-sown area, grain price and other factors, it cannot be said that grain production has nothing to do with water. Water is still one of the important conditions for grain production. The precondition of producing more grain with less water is the promotion of water productivity. So the conclusion of water not being correlated with grain output by no means implies that water can be neglected when considering grain production and food security. On the contrary, more attention should be paid to increasing water productivity and ensuring a sustainable supply of water, both in terms of quantity and quality. Acknowledgements This study was supported by the National Natural Sciences Fund of China ( , ) and the Chinese Academy of Sciences (KZCXZOYWO126O04). Dr. Xing Fang, Associate Professor at Auburn University, Dr. Junguo Liu, Professor at Beijing Forest University, the corresponding author s colleague Prof. Heqing Huang and several other experts are greatly appreciated for providing valuable suggestions for revising this paper. References Administrative Office of the National Population and Family Planning Commission of China, Population of China. Available from: htm [Accessed on 15 November 2006, in Chinese]. Brown, L.R., Who Will Feed China? New York: W.W. Norton. Brown, L.R., Outgrowing the earth: the food security challenge in an age of falling water tables and rising temperatures. New York: W.W. Norton. Brown L.R. and Halweil, B., China s water shortage could shake world food security. World Watch, 11 (4), Halweil, B., Grain harvest sets record, but supplies still tight. Available from: [Accessed 31 December 2009]. Jia S. and Kang D., How much will be the water use climax of China? Advance of Water Sciences, 21 (4), (In Chinese) Jia S., et al., Industrial water use Kuznets Curve: evidence from industrialized countries and implications for developing countries. Journal of Water Resources Planning and Management, 132 (3), Liu J., Modelling global water and food relations-development and application of a GISbased EPIC model. Dissertation. ETH No , Swiss Federal Institute of Technology Zurich. Liu J. and Savenije, H.H.G., Food consumption patterns and their effect on water requirements in China. Hydrology and Earth System Sciences, 12 (3), Liu Y., Some problems of grain and food demand and supply of China. Grain Science and Technology and Economy, 31 (5), 2 6. (In Chinese) Ma, Y., Feng L., and Leng M., Population and Economics, 2, 3 9. (In Chinese) Men, K., Guan L., and Jia L., China s Future Population: Predictions and Prospects. Population Review, 44 (1), Ministry of Water Resources of China, Water Resources Bulletin of China (Beijing: China WaterPower Press). (In Chinese) Nanjing Hydrology and Water Resources Institute of the Ministry of Water Resources, Institute of Hydropower and Water Conservancy of China, Water Supply and Demand of China in the 21 st Century. Beijing: China Waterpower Press. (In Chinese) Nickum, J. E., Is China living on the water margin? China Quarterly, 156,

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