Sustainable urban development in water-constrained Northwest China: A case study along the mid-section of Silk-Road – He-Xi Corridor

Journal of Arid Environments 74 (2010) 140–148

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Sustainable urban development in water-constrained Northwest China: A case study along the mid-section of Silk-Road – He-Xi Corridor C.-L. Fang a, Y. Xie b, * a b

Institute of Geographical Science and Natural Resource Research, Chinese Academy of Sciences, Beijing 100101, China Department of Geography and Geology, Eastern Michigan University, 125 King Hall, Ypsilanti, MI 48197, United States

a r t i c l e i n f o

a b s t r a c t

Article history: Received 29 March 2008 Received in revised form 26 April 2009 Accepted 26 July 2009 Available online 18 August 2009

The urbanization process in the middle section of Silk-Road (He-Xi Corridor) bears noticeable inscriptions of its fragile physical environment. This paper develops an integrated research approach to examine urban growth under severe water shortage and to quantify the dynamic relationship between sustainable urbanization and restricted water supplies. This new approach is synthesized from the field survey often adopted in regional studies of resource management, the policy study of sustainable urban development and rational water utilization, and the regional predictive analysis of economic and demographic growths based on the economic base theory. The total available water resources and the water quotas by major economic sectors at present were calculated from the field survey. The water quotas and their change rates by economic sectors over the period of 2000–2030 were estimated on the basis of policy study of regional development goals and future trends of water usages and changes. Finally the water quotas and their change rates were integrated with regional models of demographic and economic predictions to compute sustainable economic development by economic sectors, and then to derive total population and urban population. Therefore, a sustainable urban growth under the limitation of insufficient water supplies in He-Xi was determined. Ó 2009 Elsevier Ltd. All rights reserved.

Keywords: Arid China Regional development Semi-arid Sustainability Urbanization Water shortage

1. Introduction Growing population and rapid urbanization have worsened water shortage challenges in arid and semi-arid regions. The total population in He-Xi Corridor increased from 4.11 million in 1990 to 4.73 million in 2000 (Gansu Statistics Bureau, 2001). The urban population grew from 0.84 million in 1990 to 1.18 million in 2000. However, the annual urban water supply (including both production and domestic consumptions) increased from 190.92 million M3 in 1990 to 201.19 million M3 in 2000. The urban population during this period grew by 40.48%, but the urban water supply increased by 5.38%. Moreover, there was a 16.54% gap between the total volume of available water resources and the actual volume of total water demands in He-Xi since 1990 (Fang and Li, 2004). In addition, this area is located in the innermost center of the Eurasia continent, and is surrounded by Qilian Mountains, Tianshan Mountains, and the Mongolia Plateau. These high mountains and plateau block atmospheric circulation. Thus this area is dominated with a dry climate and is very vulnerable to climate changes. Recent

* Corresponding author. Tel.: þ1 734 487 0218; fax: þ1 734 487 6979. E-mail address: [email protected] (Y. Xie). 0140-1963/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2009.07.009

research confirms that the air temperature increased by 1.0  C in the past 140 years in the east Qilian Mountains (the southern border of He-Xi) (Wang, 1991). High air temperature was positively correlated with increased glacial melt water (Shi et al., 2007). Since glacial melt water is the most important water source in He-Xi, there is a serious concern about the receding glaciers due to the unbalance between the increased glacial melt and the precipitation input (Shi, 2001). The available water resources in Northwest China (and He-Xi) are bound to decrease in the end (Ye et al., 2001). Hence, both global warming and increased human activities have resulted in serious environmental problems in this area, the runoff courses of most rivers were shortened, the terminal lakes reduced or dried up, the water quality in the lower reaches became worsened, the soil salinity and desertification became more and more serious, and the vegetation was seriously degraded or destroyed (Lu et al., 2005). This paper describes a case study of water consumption by a rapidly urbanizing region (He-Xi Corridor) in Northwest China, where renewable water resources are insufficient to meet the growing demand. This case study develops a systematic approach to quantify the use of water resources while emphasizing the sustainability of water supply. This approach consists of three methods often deployed in socio-economic studies, field survey,

C.-L. Fang, Y. Xie / Journal of Arid Environments 74 (2010) 140–148

policy study, and regional predictive analysis of economic and demographic growth. A main focus is placed on the quantitative analysis of the relationship between sustainable urban development and water shortages in arid and semi-arid regions. There is an abundant literature concerning complex interactions between urban growth and sustainable water utilization. It is commonly agreed that urban land expansion has noticeable impacts on regional hydrology and water environment (Atef and Rakad, 2003; Carter et al., 2005; Klocking and Haberlandt, 2002). The United Nations Educational, Scientific, and Cultural Organization (UNESCO) has started a long-term research project since 1974 to examine the relationship between urbanization and water resources utilization, including, The Hydrological Impacts of Urbanization (UNESCO, 1974), Urbanization and Industrialization on the Impact of Hydrology and Water Situation (UNESCO, 1977), Urbanization and Industrialization on the Impact of Water Resources Planning and Management (UNESCO, 1979), Urbanized Areas Drainage Manual (UNESCO, 1987), Integrated Water Resources Management – To Meet the Challenge of Sustainability (UNESCO, 1993), Urban Development and Fresh Water Resources: Actions and Suggestions of Small Coastal Towns (UNESCO, 1998a), Water, City and City Planning (UNESCO, 1998b), and The Frontier of Urban Water Resources Management: Deadlock or Hope (UNESCO, 2002). These publications presented many cases studies of sustainable urban development from the perspectives of hydroengineering, water resource management, technical innovations, impacts to and from industries, and policy implications. An increasing number of studies are also reported on sustainable economic development and urban growth in water-constrained Northwest China. Regional water resource utilization potential and strategy were always affected by the natural conditions, the socio-economic levels, and the technical advances of the region (Gao and Liu, 1997). The lack of water resources in Northwest China showed a damping impact on regional economic development and urban growth (Cai, 2008). Fang and Huang (2004) analyzed the spatial characteristics of urban land expansion in Northwest China and discussed the economic and ecological impacts resulted from the rapid urbanization and the restriction of water resources. The primary driving forces of urban development in He-Xi Corridor were the over-dependency on the exploitation of natural resources and the excessive reliance on the transportation network (Fang and Sun, 2005). The most noticeable hindering factors of urbanization in He-Xi Corridor were not the water shortage alone though its impact was significant and hard to overcome, but the weak industrial infrastructure and the low efficiency of water usage. From the perspective of policy study and sustainable development, a consensus is that there is no single solution to the problems of urban water management in the developing world. Workable solutions must have site-specific characteristics with respect to the climatic, economic, social, environmental, and cultural conditions of the areas concerned (Nawaz and Adeloye, 2002). Based on an integrated analysis of economic, environmental, fiscal, and social implications, Cai recommended that decisions of water allocation under water stress should be shared by stakeholders concerned at all levels. Varis and Fraboulet-Jussila (2002) developed a Bayesian network model to study the conflicting interests among various stakeholders and between the environmental and the social concerns in the Senegal River, Africa. Thus, there is a critical need to develop an operational water management system that integrates an important element of rigorous policy studies (Brandes and Maas, 2004). Various quantitative methods are employed in the studies of the relationship between urban development and sustainable utilization of water resources (Gao, 1998). An index system is developed

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to evaluate urbanization process and water resources utilization conditions (Gao et al., 2002). The social welfare maximization theory has been used to quantify urbanization in Xi’an, China and to simulate the water environment’s response to urbanization (He et al., 2008). Moreover, system dynamics modeling is another new approach employed in recent years to analyze water-related sustainability quantitatively (Passell et al., 2003). An objectoriented system dynamics model was applied in the Yellow River Basin of China to simulate a water resource system and capture the dynamic characteristics of the main elements that affect water demand and supply (Xu et al., 2002).

2. The study area and the research methods He-Xi (Yellow River – West) in Gansu Province is taken as the case study in this paper. He-Xi is located in the semi-arid and arid areas of Northwest China. The annual rainfall decreases from 158 mm at the east to 35 mm at the west (Gansu Statistics Bureau, 2004). The importance of geologic events is attributed to the tectonic activity during the Silurian period of the Paleozoic era (444–416 million years ago) which molded the Qilian Mountains (Zhao, 1997). Millions of years of glacial activities on the Qilian Mountains created a huge solid reservoir of gravels and sands. The result is a 1120 km level area referred to as the present day He-Xi Corridor. Melt water from the mountain glaciers is the primary source of water in addition to the limited rainfall. Being confined by the physical conditions of geology, physiognomy, and water resources, cities and towns were developed at the foot of the mountain on the diluvian fans and alluvial plains, and along the rivers supplied with the glacier melt water. There are 85 towns and 7 cities in He-Xi, including 5 districtlevel cities (Jiayuguan, Jinchang, Zhangye, Wuwei and Jiuquan), and 2 county-level cities (Dunhuang and Yumen) (Fig. 1). These cities are the most important economic and demographic centers (Gayl and Low, 2000), and also the centers of industries, domestic and foreign investment, urban construction, transportation, communication, information technology, culture, and education (Hu et al., 2000; Scott, 2001). These cities are the dragon-heads in the urbanization process because they serve as the spring-boards to advance regional socio-economic development in the He-Xi Corridor region (Takabito et al., 2002). However, urban growth of these cities is restricted because of severe shortage of water resources and irrational water utilization structure (Niu and Song, 2002). The population sizes of these cities are small; their urbanization levels are low; and there are no primate cities on the basis of urban non-agriculture population. For example, in Wuwei, the largest city in terms of population (close to 2 million) in He-Xi, only 15% of its population comprises urban residents who are engaged in non-agricultural activities (Xie et al., 2007). Moreover, there exist obvious disparities among the five district cities, Jiayuguan, Jinchang, Jiuquan, Wuwei and Zhangye (see Appendix 1: Regional Disparities of Five District Cities in He-Xi). The research design and methodology is depicted in Fig. 2. This new approach is synthesized from three research methods often deployed in regional studies. The first one is the field survey. We conducted the field surveys during the period of 2002–2004 by visiting the statistics bureaus of the five district cities in the He-Xi Corridor region. The data of the total water resources, the utilized water amount by major economic sectors, and the water utilization coefficients by major economic sectors between 1985 and 2000 were compiled from the governmental tabulations archived in these city bureaus (Fang, 2003; Huang and Fang, 2003). Based on the field survey, the computational formulas for structural analyses of water resource and water supply in He-Xi Corridor are as follows.

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China Heihe River Gansu province

Shulehe River Jiayuguan Dunhuang

Yumen

Jiuquan Shiyanghe River Zhangye Jinchang

He-Xi Corridor Wuwei 0

Gansu province

50

100 Km

Fig. 1. The study area.

QZt ¼

m X

QiZt ¼ Q1Zt þ Q2Zt þ Q3Zt þ Q4Zt þ Q5Zt  QKt

(1)

i¼1

QKt ¼ ¼

m X i¼1 m X

QiKt ¼ Q1Kt þ Q2Kt þ Q3Kt þ Q4Kt þ Q5Kt n X

atij btij Qtij

(2)

i¼1 j¼1

QZt is the total water resource volume at Year t, and QKt is the utilized water (supply) amount in He-Xi Corridor at Year t. QiZt and QiKt represent the total water volume and the utilized water amount at Year t and in City i, respectively. Qtij indicates the water supply amount at Year t, in City i, and in (Economic-) Sector j. btij is

the water supply coefficient at Year t, in City i, and in Sector j. atij is the water utilization change rate at Year t, in City i, and in Sector j. i ¼ 1, 2, 3, 4, 5 represents the city of Jiayuguan, Jinchang, Wuwei, Zhangye, and Jiuquan respectively; j ¼ 1, 2, 3, 4, 5, 6, 7 indicates the usage of irrigation-water, forestry-water, grassland-water, livestock-water, industry-water, urban domestic-water, and rural domestic-water, respectively. The values of these parameters for the years between 1985 and 2000 are obtained through the field survey. The future values of these parameters over the period of 2001 and 2030 are derived from policy studies. The policy study was deployed to find out balances between future water demands and supplies aiming at promoting rational urban growth and protecting decreasing water resources. The policy study was primarily conducted through the following sources. The first one is the comprehensive city master

Total Volume of Water Resource

Water Utilization Coefficient

Utilized Water Amount by Economic Sectors

Water Utilization Change Rate

Water Quota Coefficient

Sustained Economic Growth by Sectors

Water Quota Change Rate

Growth Rate of Urban Economy

Total Population

Water Utilization Efficiency Rate

Sustainable Urbanization (Urban Growth) Fig. 2. The design diagram of the water-constrained sustainable urban growth model.

C.-L. Fang, Y. Xie / Journal of Arid Environments 74 (2010) 140–148

plans from the five district cities (e.g., Jiayuguan Construction Committee, 1999; Jinchang Construction Committee, 2001; Jiuquan Municipal Government, 2000; Wuwei Construction Committee, 2002; Zhangye Construction Committee, 2001). The second source is the comprehensive regional plans from the provincial committees or agencies (e.g., Gansu Development and Planning Committee, 2002; Institute of Gansu Urban and Rural Planning & Designing Research, 2001). These master and comprehensive regional plans were usually developed using the rational planning process (Fang and Xie, 2008; Yeh and Wu, 1999), including the following components: survey and analysis of data, making projections into future, analyzing constrains to future development, developing goals for future growth, and establishing planning policies based on the goals. Because this region was increasingly facing water shortage, the governments gradually became aware of the importance of sustainable development and global climate change. Therefore, these documents usually included analyses of available water resources, current usage and shortage, and future expectation of water usage change in the context of policy recommendations. Four policy recommendations are extracted through the policy study: 1) to take gross-control and quota adjustment; 2) to give priority to reducing water consumption; 3) to shift the water quota from the primary industry to the secondary industry, and to give preference to the economic sectors with high water utilization efficiency over the economic sectors with high water consumption; and 4) to give priority to ecologywater consumption, and preference to production-water and domestic-water consumptions (see the details in Appendix 2: Four Policy Recommendations). The final analytical component is the predictive regional analysis of economic and demographic growth based on the economic base theory that is commonly applied in urban and regional planning to predict economic and demographic changes at regional scale (Klosterman, 1990; Klosterman and Xie, 1993). The economic base technique was revised in this research to integrate the quantities of water quotas and water quota changes into regional economic and demographic predictions. Examination of economic development and urban growth with consideration of available water supplies and their changes will reveal a sustainable level of urban development under water limitation. The sustainable urbanization in arid Northwest China refers to the utmost proportion of the agricultural population transformed to the nonagricultural population. The determination of this sustainability depends on many factors, including the basic guarantee of environmental construction in terms of water demand and supply, the speed and the scale of economic development, and the socioeconomic infrastructures to accommodate the transformed nonagricultural population. The main purpose for deriving this sustainable urbanization is to establish the quantitative relationship between the restriction of limited water resources and the objective function of urbanization in a dynamic and systematic manner. This sustainable urbanization threshold explains the environmental tolerance in terms of water shortage to the urbanization level in a water deficient area. The computation formulas are given below.

Gt ¼ ¼

p X h¼1 p X

Ght ¼

m X i¼1

Vt ¼

m X i¼1

m X n a X ptij bptij QiKt

h¼1 i¼1 j¼1

sffiffiffiffiffiffiffi Gt 1 Gt0

tt 0

G1ti þ

uptij Wptij

G2ti þ

m X

G3ti

i¼1

(3)

(4)

dt ¼ Gt =QKt Pti ¼ PUti þ PRti ¼

Uti ¼

143

(5) Qti6 Q þ ti7 WPti6 Wpti7

PUti Pti

(6)

(7)

Gt is the total GDP at Year t over the study area, He-Xi Corridor. G1ti, G2ti, andG3ti represent the GDP in the primary industry, the secondary industry, and the tertiary industry at Year t and in City i, respectively. uptij is the water quota change rate, while Wptij is the water quota coefficient at Year t, in City i, and in Sector j. Vt is the growth rate of urban economy. dt is the coefficient of water utilization efficiency in He-Xi Corridor at year t. Pti is the total population at Year t and in City i. PUti is the (urban) non-agricultural population at Year t and in City i, which equals to the ratio between the urban domestic-water supply (Qti6) and the urban domestic-water quota (Wp). Qti6 is calculated through Equation (2) and the samples are given in Appendix 4. Wp is obtained through the surveys and the samples will be seen in Table 2. PRti is the agricultural population at Year t and in City i, which equals to the ratio between the rural domestic-water demand (Qti7) and the rural domestic-water quota (Wp). Qti7 is calculated through Equation (2), while Wp is obtained through the surveys. Uti is the sustainable urbanization level.

3. The analyses of water utilization structure and sustainable urbanization 3.1. The states and changes of water utilization structures

atij is interpreted as the annual increase rate of the proportion of water supply in City i and in economic Sector j. atij is the most important parameter in describing the water utilization structure. We collected the observed average values of atij in the past 15 years (1985–2000). Taking into consideration of the afore-mentioned policy guidelines (reducing the consumptions of irrigation-water, and increasing industry-water, urban domestic-water, forestrywater, and grassland-water), we worked out the values of atij during the period of 2001–2030 in the five district cities through our discussions with the colleagues in the statistical bureaus of these cities (Appendix 3). On the basis of atij, we derived the water supply coefficients of water utilization structure, btij (Table 1). Very useful information can be drawn from the water supply coefficients and the focus here is placed on the entire He-Xi Corridor region instead of the disparities between the cities. We first look at the water utilization structure by major economic sectors. The proportion of irrigation-water drops dramatically, while the allocations of forestry-water and grassland-water increase steadily. Irrigation-water clearly consumes a large chunk of water resource, but generates the lowest production value per unit water consumption compared with the water utilization efficiencies in other economic sectors. Thus the consumption of irrigation-water must be reduced by adopting water-saving techniques, such as pipe-irrigation, spray-irrigation, and drip-irrigation. The proportion of irrigation-water consumption in He-Xi will decrease from 86.71% in 1985 to 66.50% by 2030. The saved amount of water will be largely used to increase industry-water and urban domesticwater consumptions, and the rest will be diverted to forestry-water and grassland-water consumptions. By 2030, the forestry-water consumption in He-Xi will increase from 3.34% in 1985 to 6.11% in 2030, and the grassland-water consumption will increase from 4.02% in 1985 to 7.11% in 2030. The increase of industry-water

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Table 1 The supply coefficient of water utilization structures under the constraint of water resources in He-Xi. City

Year

bti1

bti3

bti4

bti5

bti6

bti7

btic

btin

Jiayuguan

2000 2010 2015 2020 2030

33.12 27.58 25.05 22.99 20.12

6.00 5.29 5.43 5.77 6.26

2.57 5.88 5.69 5.33 6.26

1.57 1.43 1.37 1.31 1.25

50.96 54.74 57.56 59.91 61.41

5.40 4.66 4.44 4.26 4.27

0.38 0.42 0.46 0.43 0.44

56.36 59.40 62.00 64.17 65.68

43.64 40.60 38.00 35.83 34.32

Jinchang

2000 2010 2015 2020 2030

76.74 73.61 70.63 62.55 57.13

2.96 3.05 3.33 3.77 4.27

4.17 4.69 5.00 5.23 5.86

0.95 1.02 1.04 1.09 1.02

12.69 15.06 17.39 24.63 29.11

1.68 1.71 1.73 1.83 1.74

0.81 0.85 0.88 0.90 0.87

14.37 16.76 19.12 26.46 30.85

85.63 83.24 80.88 73.54 69.15

Wuwei

2000 2010 2015 2020 2030

86.82 83.73 82.32 78.58 74.89

2.42 2.82 2.89 3.17 3.47

6.02 6.22 6.33 7.04 7.30

1.10 1.29 1.36 1.49 1.70

1.29 3.48 4.54 6.89 9.53

0.98 1.06 1.10 1.25 1.40

1.38 2.27 1.41 4.54 1.46 5.65 1.59 8.14 1.72 10.93

97.73 95.46 94.35 91.86 89.07

Zhangye

2000 2010 2015 2020 2030

81.24 8.02 74.97 9.02 73.11 9.17 69.34 9.56 65.43 10.08

5.36 6.24 6.61 7.54 8.70

1.14 2.50 0.69 1.22 6.68 0.78 1.24 7.87 0.89 1.25 10.11 1.06 1.26 12.12 1.24

2000 2010 2015 2020 2030

84.55 79.59 76.58 73.56 68.43

3.52 4.21 4.56 4.96 5.12

3.31 4.44 4.80 4.99 5.86

1.07 6.22 0.75 0.58 1.10 9.22 0.82 0.62 1.12 11.42 0.86 0.66 1.15 13.71 0.91 0.72 1.17 17.67 1.00 0.75

He-Xi Corridor 2000 2010 2015 2020 2030

82.26 77.39 75.07 70.98 66.50

4.57 5.20 5.40 5.78 6.11

4.74 5.53 5.81 6.35 7.11

1.10 5.38 0.99 0.96 6.37 93.63 1.19 8.64 1.06 0.99 9.70 90.30 1.22 10.36 1.12 1.03 11.48 88.52 1.27 13.29 1.24 1.09 14.53 85.47 1.33 16.46 1.36 1.14 17.82 82.18

Jiuquan

bti2

1.06 3.18 96.82 1.09 7.46 92.54 1.11 8.75 91.25 1.14 11.17 88.83 1.17 13.36 86.64 6.97 10.04 12.28 14.61 18.68

93.03 89.96 87.72 85.39 81.32

Note: btic represents the supply coefficient of urban water utilization. btin represents the supply coefficient of rural water utilization. j ¼ 1, 2, 3, 4, 5, 6, 7 indicates the usage of irrigation-water, forestry-water, grassland-water, livestock-water, industry-water, urban domestic-water, and rural domestic-water, respectively.

consumption will have a very significant impact in He-Xi. Current industrial infrastructure in He-Xi is weak. Its water use efficiency is also low. Because the industrialization is the primary driving force for sustainable urbanization in He-Xi (Ning, 1998), the increase of industry-water supply will help industrial modernization process and accelerate healthy urban development. The industry-water supply will increase from 4.43% in 1985 to 5.38 in 2000 and 16.46% in 2030 (Table 1). Secondly, we compare the aggregated allocation of urban water consumption against the aggregated rural water consumption. We find out that the proportion of urban water supply increases notably, but the proportion of rural water supply reduces. In the coming 30 years, the allocation of urban water supply in He-Xi will increase from 4.44% in 1985 to 6.37% in 2000 and to 17.82% by 2030. The proportion of rural water utilization will decrease from 95.56% in 1985 to 93.63% in 2000, and to 82.18% by 2030 accordingly. This policy-driven transition of water utilization structure for urban and rural areas makes it feasible to improve water use efficiency and to accelerate healthy urbanization process in He-Xi Corridor. Finally we look at the water utilization structural changes from the perspectives of ecology-water (including forestry-water and grassland-water), production-water (irrigation-water and industry-water) and domestic-water (urban domestic-water, rural domestic-water, and livestock-water). The ratios of the ecologywater, production-water, and domestic-water consumptions in HeXi were 8.01:89.55:2.44 in 1985 and 10.72:86.03:3.24 in 2000, but will change to 13.22:82.96:3.83 by 2030. This trend of change leads to a better water utilization structure (Fang, 2001; Huang and Fang, 2003). With a growing awareness of ecological and environmental

concerns, over 13% of the water resource will be used for ecoenvironmental productions and protections by 2030, which will definitely contribute to eco-environmental improvement in He-Xi. When the supply coefficients and the supply change rates are known, the water allocation by each economic sector can be calculated according to Equations (1) and (2) (Appendix 4). Although only the totals for the He-Xi Corridor region are listed, the water allocations for the district cities could be easily derived from Table 1 and Appendix 3. If no interregional water transferring is considered, the total amount of usable water resource in He-Xi is 7.98  109 m3. Among them, the usable water resources for Jiayuguan, Jinchang, Wuwei, Zhangye and Jiuquan are 2.40  108 m3, 8.76  108 m3, 2.09  109 m3, 2.35  109 m3 and 2.23  109 m3, respectively. By comparing the available water resources with the water supplies (or demands) by economic sectors, we can conduct a detailed analysis of water demand and supply for the cities in He-Xi. 3.2. The water quota and the water quota change rate The quantitative relationships between the productivity of economic sectors, the water quote coefficient and the water quota change rate are established in Equation (3). The water supplies and their future changes are different quantities from the water quotas and their future changes. The former are more tied with the development priorities and the policy interventions (as discussed in the previous section) while the later are closely related to available water-saving technologies in each economic sector. Moreover, the former impose macro-level controls over the later. We worked out the average water quotas by each economic sector over the past 15 years (1985–2000) based on currently available water-saving technologies in these economic sectors, and the water allocations and their changes in these economic sectors (Table 2). We estimated the water quotas and their future changes over the following 30 years (2001–2030) according to the future possible water-saving technologies that we obtained through our field surveys and the future changes of water allocations that we predicted through the policy studies. In 2000, the irrigation-water quota was 1.24  104 m3/ha, the forestry-water quota was 3.8  103 m3/ha, the grassland-water quota was 5.1 103 m3/ha, the livestock-water quota was 30.03 l/ head$day, the industry-water quota was 397.97 m3/10,000-yuan, the urban domestic-water quota was 170.39 l/person$day, and the rural domestic-water quota was 57.16 l/person$day. These water quotas were usually higher compared with the national averages. Thus, the water utilization efficiencies were low even though the water resources were deficient in He-Xi. In order to maintain steady economic growth without increasing the total water demand, the water quotas must be adjusted according to the thresholds of water

Table 2 The water quotas by economic sectors under the constraint of water resources in He-Xi.a Year

W1

W2

W3

W4

W5

W6

W7

1985 1990 1995 2000 2010 2015 2020 2030

1.32 1.34 1.29 1.24 1.21 1.19 1.16 1.13

0.67 0.62 0.39 0.38 0.38 0.39 0.40 0.41

0.53 0.47 0.55 0.51 0.51 0.50 0.49 0.48

0.05 0.05 0.04 0.05 0.05 0.05 0.05 0.05

2.03 1.51 0.84 0.60 0.30 0.28 0.26 0.23

0.22 0.28 0.26 0.26 0.24 0.23 0.22 0.21

0.05 0.06 0.08 0.09 0.09 0.09 0.09 0.10

a j ¼ 1, 2, 3, 4, 5, 6, 7 indicates irrigation-water, forestry-water, grassland-water, livestock-water, industry-water, urban domestic-water, and rural domestic-water, respectively. The unit of W1 is 104 m3/ha, while the unit of W2, or W3 is 103 m3/ha. The unit of W4 is l/head$day, the unit of W5 is m3/10,000-yuan, and the unit of W6 or W7 is l/person$day.

28.7 23.0 23.8 29.6 27.0 29.6 30.6 33.8 43.8 44.8 42.9 42.2 52.0 49.5 49.9 47.2 27.5 32.2 33.3 28.3 21.1 20.9 19.6 19.0 13.4 16.5 35.3 72.0 170.8 251.2 357.5 611.2 582.5 636.4 715.3 760.3 815.2 838.8 866.1 909.1 3.53 4.26 7.44 9.12 10.43 10.66 11.03 11.53 46.68 46.71 49.34 50.44 48.77 48.42 46.83 45.78 1985 1990 1995 2000 2010 2015 2020 2030

5.41 6.90 6.27 7.06 8.31 8.90 9.91 11.64

108.3 115.3 126.6 122.9 130.3 135.4 139.0 144.8

474.2 521.2 588.7 637.4 685.0 703.4 727.1 764.3

380.5 413.2 440.8 468.0 500.6 526.2 552.5 582.5

311.1 335.4 342.2 350.3 364.1 371.3 375.9 377.8

69.5 77.9 98.6 117.7 136.5 154.9 176.7 204.7

46.8 72.0 148.4 243.6 633.7 848.6 1169.3 1807.5

12.9 23.2 49.4 68.9 133.5 177.0 229.0 343.2

20.5 32.3 63.7 102.7 329.4 420.3 582.9 853.1

Secondary industry % Primary industry % Non-agricultural population Agriculturepopulation Total population Small livestock Large livestock Total livestock Grassland Forest and orchards Irrigation area (crop) Year

Table 3 Total economic growth and structure under the constraint of water resource in He-Xi (104 ha, 104 head, 104 people, 108 yuan, %).

GDP

Primary industry output

Secondary industry output

Tertiary industry output

Tertiary industry %

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supply by economic sectors and cities in the future. The quotas of the irrigation-water, the forestry-water, the grassland-water, the industry-water and the urban domestic-water have to be reduced. On the other hand, the quotas of the livestock-water and the rural domestic-water will be increased gradually. The water quota changes can be also worked out according to Table 2, which is omitted here due to the paper’s focus on the methodology and main findings.

3.3. Analysis of sustainable economic growth with the constraint of water resource Total economic amount, the economic structure, the growth rate and the water utilization efficiency can be computed according to Equations (3)–(5). Table 3 shows the current states and future changes of the economic structure in He-Xi. Gross Domestic Product in He-Xi Corridor will reach 1807.5  108 yuan by 2030 and witness an increase 1563.9  108 yuan from 2000. The primary industry will increase by 274.3  108 yuan, the secondary industry 750.4  108 yuan, and the tertiary industry 539.2  108 yuan. Over the 30 years (2000–2030), according to the structural changes we predicted, the percentage of primary industrial production shall decrease from 28.3% in 2000 to 19.0% by 2030, the percentage of secondary industry shall increase from 42.2% in 2000 to 47.2% by 2030, and the percentage of tertiary industry shall increase from 29.6% in 2000 to 33.8% by 2030. The industrial structure will adjust toward a more sustainable direction, because the constraints of water resource and sustainable water supply were taken into consideration when projecting the industrial growth (Table 3). There are obvious intraregional variations in the GDP growth rates and the industrial production values (Appendix 5). Jiuquan has a fastest growing economy among the five cities, Zhangye is the second fastest, Jiayuguan is the third, Jinchang is the next, and Wuwei is the lowest. Wuwei, which has the worst water deficiency, witnesses the slowest economic growth (Yang and Wu, 2001). So it is important to analyze urban economic development from the viewpoint of water utilization efficiency. Water utilization efficiency refers to the ratio of GDP to the utilized water amount (Equation (5)). The economic efficiencies of water utilization demonstrate a clear regional disparity (Appendix 6). The water utilization efficiency of He-Xi Corridor shows a trend of increase as a whole over the 45 years from 1985 to 2030. It was 0.66 yuan/m3 in 1985, rose to 3.21 yuan/m3 in 2000, and will increase to 8.29 yuan/ m3 by 2010, to 15.27 yuan/m3 by 2020, and to 23.14 yuan/m3 by 2030. The average annual increase rate is 8.23%. Secondly, four out of the five cities (except Jiayuguan) display a similar trend as that for the entire He-Xi Corridor area. Third, Jiayuguan has the highest water utilization efficiency. The explanation primarily relates to its economic advantage, because Jiayuguan is the largest and most advanced industrial city in He-Xi. The success of Jiayuguan suggests that the strategies of modernizing industries and adopting watersaving technologies are important measures to improve industrial

Table 4 Total population and sustainable urbanization in He-Xi over 2000–2030. Year

Urbanization Urban domestic- Urban domestic- NonTotal water quota population water supply agricultural level % (107 m3) (l/person$day) (106) population (106)

2000 2010 2020 2030

4.68 5.01 5.53 5.82

7.3 8.1 9.5 10.7

170.39 162.93 147.45 142.59

1.18 1.37 1.77 2.05

25.21 27.35 32.01 35.22

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10000 yuan/person

8 7

Added value of primary industry per agriculture capita

6

Added value of secondary and tertiary industry per nonagricultural capita GDP per capita

5 4 3 2 1

year

0 1985

1990

1995

2000

2010

2015

2020

2030

Fig. 3. The annual increases of three economic indicators in He-Xi.

production value per stere water (i.e., the water utilization efficiency) and thus to promote sustainable urbanization process. 3.4. Analysis of sustainable urbanization under the constraint of water resource We assume that the total water supply in He-Xi Corridor fully depends on its natural supplies without interregional water transferring, and that the economic growth rate is kept at less than 7.0% annually. Moreover, as we analyzed before, the policy changes in the coming years will reduce 10.54  108 m3 from the crop irrigation-water consumption between 2000 and 2030 (or at a speed 0.92% per year), and increase the proportion of ecology-water supply to 13% of the total water allocation (He et al., 2002). Under these postulations, we calculated the total population and the sustainable urbanization level according to Equations (6) and (7) (Table 4). Total population in He-Xi will be up to 5.01 106 by 2010, 5.53  106 by 2020, and 5.82  106 by 2030. Urban (non-agricultural) population will reach 1.37  106 in 2010, 1.77  106 in 2020, and 2.05  106 in 2030. Corresponding to the urban population growth, the urbanization level will rise from 25.21 in 2000 to 27.35 in 2010, 32.01 in 2020, and 35.22 in 2030. Although the urbanization level will only increase by 10.01% compared with that in 2000, this urbanization level is regarded as the upper sustainable threshold in He-Xi Corridor over 30 years, when considering the constraint of water resources. Can the economic infrastructures and employment opportunities in He-Xi Corridor support the migration of agriculture population to cities and the population growth? Three economic indexes, GDP per capita, the added value of secondary and tertiary industries per non-agricultural capita, and the added value of primary industry per agricultural capita, are analyzed in Fig. 3 and Appendix 7 (Fang, 2001). The GDP per capita was only 1230.04 yuan/person in 1985 and 5204.98 yuan/person in 2000, but will increase to 12,658.46 yuan/person by 2010, 21,163.04 yuan/ person by 2020, and 31,032.69 yuan/person by 2030. The GDP per capita in 2030 will be 25.75 times as much as that in 1985, and 5.96 times as much as that in 2000. The annual growth rate of GDP per capita will be 7.44% over the period of 1985–2030. Moreover, the increase of the GDP per capita is accelerated along the time (Fig. 3). Thus, from the viewpoint of GDP per capita, the economic aggregate in He-Xi Corridor can support 5.82  106 people with an improving living standard over the upcoming 30 years (Li and Yao, 1998). The added value of secondary and tertiary industries per nonagricultural capita provides a similar supporting argument. This

value in He-Xi Corridor was 4883.73 yuan/person in 1985, and 14,842.63 yuan/person in 2000, but will rise up to 36,642.68 yuan/ person by 2010, 53,233.27 yuan/person by 2020, and 71,532.99 yuan/person by 2030. This value will increase by 14.64 times compared with the 1985 value and by 4.83 times compared with the 2000 value. The annual growth rate of the added value of secondary and tertiary industries per non-agricultural capita will be 6.15% during 1985–2030. Actually its increase rate will climb up quickly (Fig. 3). Therefore, the 2.05  106 urban non-agricultural population in He-Xi Corridor should be able to enjoy the opportunities brought to them by rapid growth in the secondary and tertiary industries. A similar conclusion can be drawn for the 3.78  106 agricultural population from the analysis of the primary industry. The increase scales and rates of agricultural production value over the next 30 years clearly indicate that the agricultural growth in He-Xi Corridor can support its people in the rural areas with an improve living standard.

4. Conclusions The significance of this research is the analysis of water use by multiple sectors in multiple cities in a region of rapidly growing urbanization but with a severe shortage of water. This research has broader policy implications, extracting knowledge from the He-Xi case study for a more robust understanding of urban-hydrologic interactions in arid and semi-arid regions globally. First, this paper develops a new approach to quantify water use by economic sectors and individual cities and to maximize the use of water resources while emphasizing the sustainability of water supply. This new approach is synthesized from three regional study methods: the field survey, the policy study, and the regional predictive analysis of economic and demographic growth. Seven equations were formularized to describe the dynamic and quantitative relations between the key water utilization related parameters, such as, total water resource, utilized water amount, water supply coefficient, water supply change rate, water quota, water quota change rate, GDP, and urbanization. For instance, if no interregional water transferring takes place, the upper threshold of gross water supply in He-Xi is estimated as 7.81 109 m3 per year in the coming 30 years (2000–2030). The GDP corresponding to this gross water supply will be 1.81 1011 Chinese Yuan in 2030. The fastest average annual growth rate can reach 6.91%, and the optimal ratios of the primary industry, secondary industry, and tertiary industry will be 18.99:47.20:33.81. The total population will reach 5.82  106 persons in 2030, the non-agricultural population will be 2.05  106

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persons, and the urbanization level will rise to 35.14% by 2030, which is just at the average urbanization level of China in 2001. Second, in addition to linear extrapolations of current water use, this research suggests sustainable quotas for each sector to both prevent large increases in water use and to maximize the social value of water on the basis of policy recommendations. The introduction of the sustainable quotas enables the integration of policy analyses and the consideration of global climate changes into quantitative regional studies of sustainable development. This concept couples natural sciences, socio-economic studies and policy interventions into an operational decision support system. From example, the proportions of ecology-water, productionwater, and domestic-water in He-Xi are recommended to be adjusted to 13.20:83.50:3.30 by 2030 from the perspective of sustainable regional development. A reduction of 10.54  108 m3 crop irrigation-water is required between 2000 and 2030 with an annual deduction speed of 0.92%, while an increase of 3.25  108 m3 ecology-water is suggested by 2030 with an annual increase 1.87% from 2000. Third, this research also demonstrates that there exist obvious local variations (for instance, among five district cities in this case study) in terms of gross water supply, aggregate economic development, and sustainable urbanization level due to the varied levels of water shortage, water-saving technology, physical and ecological environment, development history, economic infrastructure and function, and demographic characteristics among these cities. Sufficient attentions need to be given to localities when this research approach is applied to a different region or country. Furthermore, it is an important task to validate the findings of such a research. This paper has made references to the publications and studies of other researchers, and the field surveys conducted by the authors. One future research is to revisit the study area to see how well the model performs in terms of the changes of water supply and water quota by economic sectors that are happening in He-Xi Corridor in the recent eight years. This post-model verification will help confirm whether this integrated model capture the essence of the nonlinear coupling relationship between the water utilization structural changes, economic development and urbanization. Another closely related research is to survey currently available water-saving technologies and procedures in agriculture, animal husbandry, industry and domestic-water use, and to explore sustainable models and policies of developing water-saving cities. Finally, as this paper iterated, rigorous efforts have to be made to assess how policies and policy changes impact sustainable usages of limited water resources and how these policies are adjusted to reflect new challenges (such as global climate changes and socioeconomic transformations), new ideals and new technologies to enforce healthy practices of water conservation and to guide rational regional development planning. Acknowledgements The authors wish to thank The National Natural Science Foundation of China (Foundation Item No. 40335049), and Chinese Academy of Sciences (Knowledge Innovation Projects: No. KZCX2YW-307-02, and No. KZCX2-YW-321-05) for supporting this research, and Dr. Qiao Biao at Institute of Geographic Science and Natural Resource Research for preparing the figures. Appendix. Supplementary information Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jaridenv.2009.07.009.

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