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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle Reaches of the Heihe River Basin, Northwest China
Available online at www.sciencedirect.com Agricultural Sciences in China
2006, 5 ( 2 ) : 130-140
sciENcE@DiREcT*
February 2006
Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle Reaches of the Heihe River Basin, Northwest China JI Xi-bid, KANG Er-si1, CHEN Ren-shengl, ZHAO Wen-zhil.2,XIAO Sheng-chunl and JIN Bo-wed2 1
2
Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, P.R.China Linze Inland River Basin Comprehensive Research Station, Chinese Ecosystem Network Research, Linze 734200, P.R.China
Abstract Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year (2003), the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system. Key words: middle reaches of Heihe River, irrigation region, water resources supply and demand balance, evaluation of
the security of water resources
INTRODUCTION To keep within limits the degradation trends of ecological environment, and transact the conflicts arising from competitive uses of scarce water supplies and long running disputes over the water allocation of interprovinces, such as Gansu Province, located midstream
of Heihe River basin, and Inner Mongolia, downstream of the river, in Northwest China, an unified planning and allocation of water resources in the entire Heihe River basin was developed through an analysis of China government’s policy statements, and was carried out annually during the period 1999-2004 (Wang et al. 2004). As a consequence, for the Ejinaqi key oasis, downstream of the Heihe River basin, the degradation
This paper is translated from its Chinese version in Scientia Agriculrura Sinica. JI Xi-bin, Ph D, Tel: +86-93 1-4967156, E-mail: [email protected]
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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle -
of ecological environment has been mitigated to some extent, whereas, in the midstream of Heihe River basin, the performances of the unified development and planning of water with increasing over pumping on a large scale due to the reduced surface water extracted from the Heihe River, have been carried into execution, and complicated the problems of water allocation and ecological environment (Gao et al. 2004). Based on the historical runoff process, the planning of water resources allocation cannot be directly applied to the water resources management decision support system. Therefore, appropriate development and planning of water resources allocation must be taken into account to forecast information of water resources supply and demand balance at the present in the entire river basin, and the operation would be modified by the variable adjustment factors (Bormann et al. 1999). In addition, in view of the spatial distribution of the parameters of the operation, calculating and evaluating the water resources supply and demand balance will not resolve the regional problem of water resources utilization in a relatively large scale in the inland basin (Bormann et al. 1999). Thus, according to the system theory, with respect to the evolution mechanisms of the renewable water resources, the relationship between water and ecology evolution and the interaction mechanism for water-economy (Zhong et al. 2004; Andreu el al. 1996; Huang et al. 2004) are significant. Under such circumstances, taking the complications inherent in water resources planning for this region into account, the key measures to realize the sustainabledevelopment of agricultural economy in Heihe River basin is to improve efficiency in water use and allocation (Shan 2002).
Study site description The site selected for the present study is located in the middle of Hexi corridor, Northwest China, piedmont valley plain oases, located between Gao'ai and Pingchuan gauging station, including Pingchuan, Banqiao,Yanuan, and Liaoquan irrigated district (99"57'100'22' E, 39'08'-39'23' N), covering an area of about 399.1 km2,with 42.6 km along the Heihe River (Fig.1). Elevation changes from 1300 to 1800 m in this region; the main topographical feature is characterized by their relative elevations with high in the north, east, and south,
131
Fig. 1 A map of the schematic view of the study region.The arrow represents the direction of the Heihe River flow; dashed, solid, and black solid lines are the administrative division boundary, irrigated districts boundary between different irrigated districts, and the Heihe River, respectively.
low in the west, continental arid temperate climate. The mean annual precipitation is about 119.5 mm; about 60% of the total year precipitation with low rainfall intensity is received during July-September, and only 3% during winter. But the potential evaporation is 2 365.6 mm yr-I, about 20 times of gross annual precipitation; dryness index 15.9; annual mean air temperature is 7.6"C, the maximum and minimum are 39.1 and 27.3"C, respectively; the mean accumulated temperature of 3 10°C is 3 088°C. The fundamental features of society and economy in the study region can also be found in Table 1.
WATER RESOURCES SUPPLY AND DEMAND BALANCE ANALYSIS Available water resources quantity In this study regions, agriculture depends on irrigation from. underground water or from rivers (Heihe and Liyuan river) descending from mountains, in which available water resources quantity was calculated by water resources system model, and runoff volume at the Gao'ai gauging station was calculated by frequency analysis with the historical stage flow data during 1948-
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132
1999 (Huang et al. 2004). The analysis implicated that the mean runoff volume at the Gao'ai gauging station is 1 1 . 8 3 lo8, ~ 9 . 8 6 lo8, ~ 8 . 1 7 lo8, ~ and 6 . 3 2 lo8 ~ m3 yr-', corresponding to the different guaranteed efficiency P = 25%, P = 50%, P = 15%, and P = 95%, respectively. Moreover, it also can be found that there are the similar hydrology frequency features at Pingchuan and Gao'ai gauging station. The year 2003 represents the present year, in which the total runoff volume at Gaoai and Pingchuan gauging stations is 12.58 x lo8m3 and 10.12 x lo8m3, respectively. In addition, the flow volume is about 0.44x lo8m3in Liyuan River of the study area. The flow regimes of Heihe River and Liyuan River are characterized by annual and seasonal fluctuation (Figs.2 and 3), and approximately 43.86 and 64.85%of the annual runoff volume in Heihe River and Liyuan River occur in the period from July to September, respectively. However, during the plant growing season, they account only for 17.35 and 25.96%,respectively,
especially in a dry year, when there is insufficient water supply for irrigation of crops, there are also three reservoirs and ten main channel weirs fended by Heihe and Liyuan rivers, constructed to assist in providing water for agriculture, stock, and domestic purposes. The quantity of groundwater available was determined by the utilization capacity in the calculated unit, given permissible mining groundwater amount being its maximum. Thus, the permissible (the present year 2003) and planning (the future year 2010) groundwater resources are 657.7 x lo4 and 380.5 x lo4 m3 yr-I, 325.4 x lo4and 2 0 7 . 6 ~104 m3yr', 7 2 9 . 4 104 ~ and 4 6 3 . 3 104 ~ m3 yr-', and 1 050.8 x lo4and 670.3 x 104 m3 yr-I in the irrigated districts of Pingchuan, Banqiao, Yanuan, and Liaoquan, respectively.
Analysis of balance of water supply and demand The water requirements of the irrigated districts in the
Table 1 Fundamental features of society and economy in the study region Name of irrigated district
Year
Population
Pingchuan
1997 1999 2003 1997 1999 2003 1997 1999 2003 1997 1999 2003
21558 21634 21753 17410 17423 17466 11482 11497 11532 17921 17935 18046
Banqiao
Yanuan
Liaoquan
120
Agricultural area (ha) 3 000.0
3 000.0 3000.0 2666.7 2666.7 2666.1 1866.7 1866.7 1866.7 2 266.7 2266.7 2266.7
Irrigated area (ha) 2 800.0 2733.3 2600.0 2666.7 2666.7 2666.7 1466.7 1466.7 1466.7 1933.3 1933.3 1866.7
Livestock Output value of industry (Yuan RMB) 10360 329.7 10360 537.3 1 392.1 10260 10 005 532.3 10005 771.9 9 917 1614.0 5 426 321 .O 5 426 494.8 5 426 827.2 8990 27 1.6 8 990 369.4 8990 960.0
5
7
The areas of forest and grass land @a) 3 200.0 3 200.0 3 533.3 2 200.0 2 200.0 2 266.7 866.7 866.7 1133.3 1200.0 1200.0 1400.0
+ Yinluoxia statxon
- +Gao'ai station
-
- -W-
Zhengyixia station Liyuanhe station
h
v)
3
80 -
7
60
-
I
1
2
3
4
6
8
9
10
11
12
Months
Fig. 2 The average monthly runoff volume at different gauging stations in Heihe River basin.
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Analysis of Water Resources Supplv and Demand and Securitv of Water Resources Development in Irrigation Regions of the Middle
133
Pingchuan 2.00
. ..
I ." 0.00
---C
1984 10 00
1992
1994
1996
1998
2000
-C-
---*--- Dongwan
2002
Haowa I
1986
1988
1990
1992
1994
1996
1998
2000
2002
r
-
I
' 1984
6.00
1990
A-W 1984
1.50 100
1988
+Shanjiazhuang I
-i- Yigongcheng
Banqiao
4.00 2.00 0.00
4.00
1986
Huang'er
1986
Wanzi
--~t Shangzhuang
1988
1990
1992
1Y88
1990
1992
-
Xiazhuang I
1994
1996
1998
2000
2002
1994
1996
1998
2000
2002
r Liaoquan
3.00 2.00 1.oo
I
\I.""
1984
1986
Year
Fig. 3 The variation curve of groundwater table at irrigation area during 1984-2003.
inland basin are composed of the ecological, domestic, industrial, and agricultural consumption. Note that agricultural consumption is mainly the water for agricultural irrigation to evaporation and transpiration, calculated by using the Penman-Montieth equation in this study (Ji et al. 2004; Xie et al. 2002). The actual field evapotranspiration is equal to the potential evapotranspiration multiplied by the crop coefficients of different crop plants, and as a consequence the crop's water requirements are defined by the sum of the crop consumption during the different growing stages. The industrial water requirements are determined from the water consumption for each industrial yield (m3R104), given as 237 m3,362 m3 and 398 m3R104by1997 (past year), 2003 (present year) and 2010 (future year), respectively. The domestic water requirements comprise water consumption for the urban and rural livelihood and public fundamental facilities purpose, and related to the other purposes. According to the local living standard, each person's water consumption is predicted to be about 198, 204, and 215 L d-I by 1997,
2003, and 2010, respectively; and the rural water consumption by people and their livestock to live fundamentally, evaluated by consumption quota in view of the local living standard, and given the unit water consumption, is about 50,55, and 83 L d-' for people, 40 L d-' for big livestock, and 6.7 L d-' for small livestock. The average net irrigating water quota of farm fields for crop plant growth is 7 020 m3ha-' yr-l, and the maximum ratio of water usage in farm fields is 0.62. The water requirement for ecology (some of the water is used along the way to support the various ecosystems and maintain their functioning) is estimated by the superposition analysis method based on the ecological and water resources zoning approaches. The water requirements corresponding to the ecological zoning units are determined with respect to the different ecological systems, from which the water requirements of the artificial and natural oasis ecological system were evaluated (Wang et al. 2002a, 2002b). The artificial oases comprise the shelter forest belt, e.g., sand for protect-
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134
ing planting arbor and shrub, forest for protection against soil denudation, and fire wood forest and timber for protecting the natural vegetation cover, etc. Whereas the water requirements of natural oases ecological system include the riparian forests, water is consumed to support the particular ecosystems and maintain their functioning. As a general rule, an ecological system’s water requirement is deduced from the water consumption per dry biomass, for example, the value of 243.6, 243.6, 128.9, 71.3, 306.5, and 14.3 g m-2is given for the ecological system of intensive cover degree, swamp land and bottomland, moderate cover degree grass, sparse grass land, forest and shrub land, desert and Gobi belt (cover degree less than 5%, too barren to utilize), respectively. Moreover, some studies showed that the efficiency of water production is 1.05-10.05 kg ha-’mm-*(Wang et al. 2002b; Hou et al. 2004) in the inland river basin. In the current arid desert zone context, given the total evapotranspiration in an expected ecological unit, its mean efficient value of water production for different vegetation was extrapolated. Otherwise, for the ecological systems with no evapotranspiration data, the efficiency of water production is substituted by that of similar adjacent systems. An unit with azonal vegetation depends on precipitation and runoff, and its controllable vegetation consumption was evaluated by the phreatic evapotranspiration of the ecological system with the specific vegetation community, however, assuming that the uncontrollable consumption is equivalent to the precipitation in the region. Other data derived from the Statistical Yearbook of Linze County, in Gansu Province, Northwest China, and from the farreaching plan of economy development in 2010, developed from an analysis of the local government policy statements. The balance of water demand and supply results in Table 2 show the annual water budget for different purposes froin 1997 to 2010, given the different guaranteed efficiency. By 1997, given the value P=50% of guaranteed efficiency, the water balance calculations show that the total supply amount was more than the total demand with positive water balance in every irrigated district; given P = 75%, the total water supply was less than the water demands in all irrigated districts except for in Banqiao irrigated districts; and given
JI Xi-bin et al
P=95%, a negative water balance occurred, from which it can be seen that balance of water supply and demand in the oasis irrigated districts of the midstream of Heihe River basin was controlled by runoff volume of the upstream of Heihe River. By 2000, the unified management and planning of water resources in the entire Heihe River basin resulted in a decrease in water diverted from Heihe River by 10%and an increase in extracted groundwater by 50%; as a result, the water balance calculations have been changed, for instance, given P= 50%, the amount of available water tightly meets the demand of this systems, given P=75%, water supply did not meet the demand to some extent for different irrigated districts, given P= 90%, the available water supply was far less than the demand on a large scale, and most of the farm land would be beyond irrigation. By 2003, the water balance calculations show results similar to that in 1997 (Table 2). However, the available water diverted from Heihe River for irrigation decreased by 13%, and extracted groundwater amount increased by 157.6%, compared to water balance calculations in 2003. Because the area of the land returned from farming to forest and grass will amount to 10% of the total area of present cultivated farmland, in 2010, water resources availability of cannel system will increase up to 0.62, the water-saving ratio of agricultural planting system will increase up to 20%, and water consumption for each industrial yield (m3N104)will increase up to 189 m3M04(RMB); based on above data, water resources balance of supply and demand was forecasted along with water-saving strategies for irrigation planting carried out in the midstream of the Heihe River basin (Table 3), and the results show that water supplies would equal or exceed the demands.
Assessing safety of regional balance of water supply and demand To assess the safety of balance of water supply and demand in the midstream of Heihe River basin, the ecological system’s consumption for purposes of maintaining its development and functions must be taken into account in the downstream of Heihe River. Based on the methods of water resources exploitation and utilization in the past 50 years, the present water utilization capacity, and the periodic variation of mountain
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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle
135
Table 2 Water resource supply and demand for irrigated districts in different years .year
Name of Available water supply (xl(rm3 yrl) Water resources demand (xlOd m3 yrl) irrigated district Warranted efficient (%) Surface water Well Agriculture Industry Domestic Ecological system 1997 Pingchuan 50 7384.1 58.7 6850.4 34.9 24.8 460.6 7091.6 160.9 15 6945.4 160.9 95 33.1 24.2 412.1 6615.7 57.3 6137.5 Banqiao 50 6563.8 51.3 15 6222.6 51.3 95 Yanuan 19.2 14.0 287.2 4604.9 33.2 4272.0 50 4422.6 58.3 75 4331.4 58.3 95 31.7 23.1 Liaoquan 5725.1 54.8 5311.3 357.2 50 5498.4 112.8 75 5385.0 112.8 95 2000 Pingchuan 39.5 28.8 491.5 6938.2 130.0 6389.4 50 75 6501.5 219.9 6193.3 322.5 95 38.6 28.1 430.1 6413.2 126.8 5890.7 Banqiao 50 6244.7 156.2 75 5144.8 235.1 95 22.2 Yanuan 4250.0 13.4 3916.2 16.1 340.5 50 3917.3 19.5 75 3787.1 111.6 95 36.6 Liaoquan 5653.9 121.3 5248.4 26.8 389.7 50 5317.7 154.5 75 4816.9 226.6 95 2003 Pingchuan 50.4 36.8 509.6 6586.0 141.1 6383.1 50 6161.9 238.5 15 5872.2 341.1 95 49.2 Banqiao 6391.6 137.6 5989.9 35.9 450.3 50 6235.9 211.2 75 5757.1 276.7 95 28.2 20.6 4430.4 79.6 3963.9 Yanuan 340.5 50 4 169.3 86.3 75 3986.8 123.3 95 47.1 34.2 Liaoquan 5380.9 131.5 4181.4 396.6 50 4859.0 167.6 15 95 4828.0 239.1
Water resources balance of demand and supply ( ~ 1 0m3 ' yrl) 72.1 -218.2 -264.4 65.5 13.6 -327.6 45.1 -111.5 -202.7 56.6 -112.1 -225.5 119.0 -227.8 -433.4 152.5 13.4 -407.5 28.4 -238.2 -396.3 73.7 -229.3 -398.0 -252.5 -513.2 -766.3 9.9 -18.2 -491.5 156.8 -197.6 -343.1 247.1 -138.7 -197.6
Total 7 370.7
6607.5
4592.4
5723.3
6949.2
6087.5
4 295.0
5701.5
6979.6
6025.3
4353.2
5 265.3
Table 3 Water resources sumlv and demand in the future (2010) ~
~~~~
Name of irrigated Available water supply (xlO4m3 yrl) Water resources demand (xlO4m3 yrl) Water resources balance of demand and supply (xlO4 m3 yr-I) district Warranted efficient (%) Surface water Well Agriculture Industry Domestic Ecological system Total Pingchuan 50 6261.8 155.1 5691.0 63.9 46.7 592.5 6 394.1 28.8 15 262.2 5 866.3 -265.6 5 582.2 95 364.9 -447.0 6012.4 111.3 Banqiao 50 5242.1 62.5 45.6 518.5 5867.7 256.0 5 856.7 75 183.8 172.8 5 397.2 204.9 95 -265.6 Yanuan 4031.9 50 187.5 3733.1 36.3 26.4 369.3 4165.1 54.3 3781.3 15 214.8 11.0 376.3 3 605.9 95 -182.9 5 134.2 Liaoquan 244.6 50 4643.0 59.8 43.6 459.2 5205.6 273.2 4 825. I 284.2 75 3.7
runoff data for the Heihe River, we conclude that the safety in water balance has a high degree of confidence, if the annual water consumption in the midstream of Heihe River basin is equal to or less or more than that regulated by the government; meanwhile, the effects of extracting groundwater on vegetation growth is slight in the oasis ecological system, or the vegetation impacted can be recovered in the regions. However, for
the midstream of Heihe River basin, the regional water supplies and ecological system is in critically alarming state. When the lack of water supply is offset by increasing in extracted groundwater, and the groundwater level is not in a trend of continuous drawdown in the midstream of Heihe River basin, or there is a temporary influence of decreasing of water table on vegetation growth because the groundwater table draw-
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136
down can recover itself. Thus, in this paper, the index of assessing safety in the regional water balance includes water balance calculations of supply and demand, available groundwater yield or potential groundwater yield, and the fluctuation of water table in the irrigated districts of the piedmont oasis.
Analysis of actual water supply and consumption In the present year (2003), the surface water loss volume was 2 . 4 6 ~ 1 0 m3, ~ of which 2 . 0 1 ~ 1 m3 0 ~ was con0 ~from Liyuanhe tributed from Heihe River, and 0 . 4 4 ~ 1m3 River. The result of the water balance calculation of supply and demand shows that the total water consumption was 1.71x1O8m3,by deducting the volume of water m3 ~ and evaporation 0. 19x108m3for seepage 0 . 5 4 ~ 1 0 Heihe and Liyuan rivers, of which water consumption for irrigation and ecological system extracted from rivers is 1.65x10sm3and 492.4x104m3,respectively, and 0 ~and 273.9~104 its net water consumption is 0 . 9 6 ~ 1 m3 m3,respectively. The leakages in Pingchuan and Sanba reservoirs, located in Pingchuan and Banqiao irrigated 0 ~ and 1 . 4 ~ 1 m3, 0~ districts, were 6x104m3, 1 . 2 ~ 1 m3, respectively, and their pan evaporation was 18 x lo4,9 x lo4,and 20x lo4m3, respectively. The actual water supply and consumption results in the present year can be seen from Table 4, in which the results show that the consumption of industries, people, and live stock was satisfied by the current water supply systems, but there is extreme lack of water resources for agricultural and ecological purposes (Tables 2, 3, and 4); for instance, except for Pingchuan irrigated district, there is a lack of water supply for agricultural irrigation of 966.7 x lo4, 1 401.5 x lo4, and 839.2x lo4 m3,respectively, in Banqiao, Yanuan, and Liaoquan irrigated districts. Moreover, the lack of ecological supplies was 2 0 9 . 4 ~ lo4,3 9 9 . 4 lo4, ~ 3 1 3 . 0 lo4, ~ and 283.1 x lo4m3in Pingchuan, Banqiao, Yanuan, and Liaoquan district at present, respectively. Only in Pingchuan district, water supply meets the demand in cost of groundwater overdraft, for example, in Pingchuan district, the available utilization volume of groundwater is 380.5x lo4m3,but the actual amount of groundwater pumping was up to 1190.0x lo4m3. Under the condition of a unified management of water resources guaranteed in the Heihe River basin, in 2003, a high flow
JI Xi-bin et a1
year, the amount of water diverted from the Heihe River was 6 586.0 x lo4, 6 397.6 x lo4, 4430.4 x lo4, and 5 380.9 x lo4 m3in Pingchuan, Banqiao, Yanuan and Liaoquan district (Table 2), respectively, but actual diversion volume were 5 91 1.3 x lo4,5 004.1x lo4, 2548.9 x lo4 and 3 552.1x lo4 m3, respectively. Thus, one can conclude that the surface water resources utilization and development did not preponderate over the alarming line of safety by the wet year (2003).However, there is extreme lack of water resources to sustain the running of the agriculture and maintain ecology system functions of the oasis in the midstream of the Heihe River basin, of which the great negative effects on the development of agricultural, economic, and ecological systems is significant; taking the surface water and groundwater utilization into account, there are great deficits in water demand in these regions.
Analysis of the potential groundwater capacity In the irrigated districts of the piedmont oasis in the midstream of Heihe River basin, the degree and performance of groundwater utilization in a region can be represented by the index of potential groundwater capacity; its mathematical representation is given in the form:
I= QjQ, Where Z is the index of the available groundwater capacity, Q, and Q, are the potential available yield and actual groundwater mining amount (x lo4m3yr-I). Assuming that I> 3.3 represents the great potential capacity of utilizing groundwater, 1.7 C Z G3.3 represents moderate, 1.2c Z < 1.7 represents poor, 0.8 c I 6 1.2, represents critical with the balance between recharge and extraction, 0.6 C Z 6 0 . 8 represents slight shortage, 0.4 c Z G0.6 represents moderate shortage, and Z60.4 represents extreme shortage. In these irrigated districts, Yanuan and Liaoquan lie on the south bank of Heihe River, where there are main spring water belt developments, irrigating crops from the Heihe River, and drinkable water depends on groundwater drawn with hand-pumps or shallow wells. In the present year (2003), the indexes of available potential groundwater capacity were 1.12 and 1.27 (Table 5 ) and reach up to the maximum of the available ground-
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-4nalysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle
water mining, it occurs to water balance of mining and recharge, so much so that actual groundwater exploitation amount was almost equal to the planning allowable mining capacity. Water demand for irrigation will increase and the shortage of irrigation water will increase by a considerable percentage, due to the regression of spring water and increasing area of farmland. Moreover, Pingchuan lies on the north bank of the Heihe River, where the index of available potential groundwater capacity is 0.32, and groundwater overdraft is very serious and the water is depleting. In addition, Banqiao also lies to the north of Heihe River, where there are water enrichment zones distributed along both the banks of Heihe River, In present year, the index of available potential groundwater capacity was 1.79,being regarded as moderate with the reasonable groundwater utilization, but the belts of groundwater exploitation have shifted further far from the bank of Heihe River. The results from the analysis of the available potential groundwater capacity above show that groundwater exploitation amounts have exceeded the available potential capacities and are beyond the alarming value in Pingchuan. For other irrigated districts, the actual groundwater utilization volume is almost equal to the available potential capacities and approach alarming values. If reasonable planning and development of water is not carried out in this region, there would be more complex problems of the safety of water resource supply and demand.
Groundwater table fluctuation analysis According to the long-term measured data obtained during the period 1984-1999, the dynamics of groundwater table depth in this irrigated districts shows that the groundwater table depth varied in the range of -0.1 to 0.1 m yr-I. Such fluctuations are also the characteristics of the typical stable fluctuation in the study regions, However, during 2000-2003, the groundwater table was in a trend of continuous drawdown, for example, the annual average rates of groundwater drawdown were 0.23,0.38,0.25, and 0.41 m, respectively, in Pingchuan, Banqiao, Yanuan, and Liaoquan, from which one can conclude that water resources balance has alarmingly exceeded its value of safety. The analysis result shows that the main factor causing the drawdown of groundwater level is: first, setting high standards for adequate irrigation and water conservancy resulted in a decrease in the groundwater recharges, which is the determining factor in groundwater continuous drawdown; second, the excessive groundwater exploitation on a large scale is the major factor in groundwater table lowering, for example, extensive groundwater was exploited immoderately, resulting in the groundwater exploitation volume exceeding its natural recharge capacities; third, along with the unified management and allocation of water resources in the Heihe River basin put into practice, there were so
Table 4 Actual water supply and consumption at irrigated districts in the present year') Pingchuan G.W
s.w Available water supply (x 104 m3)
Agriculture Ecology Industry Drink
Water consumption (x I 0 4 m3)
5611.1
4953.2
70.0
Yanuan S.W G.W 2521.4
41.0
Liaoquan S.W G.W 3438.3
510.0
300.2
0
50.9
0
27.5
0
113.8
0
0
50.4
0
49.2
0
28.2
G
47.1
38.6
0
46.0
0
25.3
0
0
Agriculture Ecology Industry Drink
Balance (x 104 m3) I)
1101.0
Banqiao S.W G.W
51.6
6383.1
5 989.9
3 963.9
4787.4
509.6
450.3
340.5
396.6
50.4
49.2
28.2
47.1
36.8
35.9
20.6
34.2
27.4
-1356.0
-709.8
-1104.5
S.W and G.W indicate surface water and groundwater supplied.
Table 5 The potential groundwater capacity in the midstream of Heihe River mainstream Irrigated district
Present mining (x104m3 yrl)
Planning allowable capacity (x10'mlyr-I)
Potential capacity index
Adjustable mining (xlO'm3 yr1)
Pingchuan Banqiao
1190.0
380.5
0.32
116.0
207.6
1.79
91.6
Yanuan Liaoauan
416.4
465.3
1.12
48.9
528.1
670.3
1.27
142.2
-809.5
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many disadvantages of the quota allocation system of water distribution and the water rights commerce under the conditions of the present agricultural and economical development; for instance, the running performance of the unified water management and allocation is characterized by the division channel closed in the midstream of Heihe River that supplies water to Ejina directly, downstreamof the Heihe River basin. However, the time of the closed diversion channel was related to that of the runoff volume that occurred upstream of Heihe River; furthermore, the time of incoming flow upstream is not synchronous with that of the water extracted from Heihe River for irrigation, and there is also insufficient water to irrigate farmland in the crop growth seasons in the irrigation districts in midstream of the Heihe River basin. Therefore, at the present, the most important strategy to realize sustainable development of agricultural, economic, and ecological systems midstream of the Heihe River basin is to take the scientific water management of long-established water resources systems and water resources optimal allocation system into account.
CONCLUSIONSAND DISCUSSION Balance of water resources supply and demand In the oasis irrigation districts midstream of the Heihe River basin, balance of water supply and demand was obviously controlled by the passing runoff of the Heihe River.in this region. In addition, since the unified management and allocation of water resources was conducted in the entire Heihe River basin, the components of the original sources of water supply have been changed with a decreasing in the annual water volume by 13.0 % diverted from Heihe River and increase in the groundwater extracted by 157.6%. There was still a great lack of water supply for agricultural and ecological systems, however, owing to the readjustment of agricultural set-up, and water-saving techniques lag behind in the unified management and planning of water resources in the entire Heihe River basin. Agriculture development in the oases depends on water resources supply, which has, and is expected to continue to have, significant impacts in the Heihe River
JI Xi-bin er al
basin as elsewhere in the inland basin, under the condition of the present standard level of economic and technological development. By present year (2003), in water supply terms, the volume of surface water diverted from Heihe River does not exceed the available maximum of the divertible water in every irrigated district; the shortage of water supply for irrigation is supplemented by extracting groundwater. Except for Pingchuan irrigated districts, the tight demands and supplies of water resources balance could be found with the groundwater over pumping (i.e., the volume of groundwater over pumping is up to 809.5x104m3); however, for other irrigated districts, the shortage of water supply has become one of the most serious problems. In the future, works must place emphasis on the water resources management, field water-saving techniques, and the readjustment of the agricultural set-up. The complex problems in the ecological, environmental,agricultural,and economic systems, etc. will be resolved in the midstream of Heihe River basin, even the entire Heihe River basin. At the present, there is a great lack of water supply in Pingchuan, Banqiao, Yanuan, and Liaoquan irrigated districts. But the volume of water diverted from the Heihe River is less than the alarming value of secure water balance; on the other hand, irrigation depends on the groundwater overdraft only, for instance, groundwater overdraft volume was about 8O9.5x1O4m3.In 2003, the balance of water supply and demand module was forecast in the typical irrigation district, oasis midstream of the Heihe River basin, from which the results show that water supply would suffice to meet the water consumption, taking the readjustment of the agricultural set-up, increasing rate of water resources utilization, and different water-saving techniques into account, along with the social with water-saving establishment supported by the government.
Countermeasures and suggestions for guaranteeing the securities of balance of water supply and demand The decisive methods for the development and planning of water resources are to maximize the water supply for agriculture and promote water conservation and efficienct usage, at the oasis irrigated districts midstream
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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle
of the Heihe River basin. The integrated model with particular, regional, and unique functions for agricultural water-saving that was established can be applied to sustainable development of agriculture, economy, and ecology. These projects can help establish reasonable management and planning of water resources and thereby contribute to improve the input-output ratio in agriculture and raise the living standards, so as to guarantee the safety of balance of water supply and demand and availability of the resources and efficiency in its use, and to provide the foundation for improving the quality of ecological environment system. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while establishing efficient agriculture-ecology system and maintaining or improving the quality of the natural ecosystems is one of the key challenges in the future. For instance, the proportional readjustments of water supply for livelihoods, industries, agriculture, and ecology purposes. An additional aspect is that the readjustment of agricultural set-up by reducing the cultivated land area, increasing the area of forest and grass land, cutting down the area of planting for food, increasing commercial crop planting area, reducing the planting area with high water-consumption, increasing low water-consumption planting area, and strengthening the complementaryrelationships between agriculture, forest, and livestock development. Surface and ground water comprise a whole system and affect each other owing to the complication inherent in the hydraulic relation between them. This relationship between surface and ground water is characterized by the multiple and frequent conversions and utilizations repetitively. Observing that the conversion law of surface and ground water is a must for the sustainable management of water resources, and the module of the optimum allocation, combined surface with ground water development should be carried out in practice. In the inland river basin, options for increasing water productivity include improving the capacity of water resources combined surface and ground water utilization with the help of regulation and management methods developed from an analysis of local government policy statements. A prerequisite of effective implementation of the reasonable utilization of water resources is to establish the module of reasonable and
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scientific development and utilization of surface and ground water, and the corresponding technology research in irrigation and drainage. Meantime, the researches on the effects of canal seepage control, seepage control by hard soil-cement for plain reservoirs, and others measures of the field water-saving in the hydrological process and ecological environment systems in the Heihe River basin are taken into account. Water resources management and allocation in' the different regions should emphasize on the possible maximum water consumption for the specific oasis system (including agricultural, industrial, livelihoods, and ecological systems consumption), or the potential water resources capacity to sustain the maximum scale of oasis. Especially, in the Heihe River basin, water scarcity has become a development constraint seriously impeding the economic and social development, giving rise to conflicts over water resources among agriculture, ecology, economy, and livestock. Thus, not only in the management and planning of water resources should we consider the balance of water supply and demand to secure in the whole watershed, but also attach importance to readjustment of the ratio of the artificial to natural oasis water consumption. Furthermore, the need for maintaining a reliable groundwater table depth to preserve the oases ecological functions and development requires further emphasis on increasing the water consumption for ecological purposes and decreasing the water consumption for agricultural purposes, so as to achieve a unified and sustainable development of economic, social, agricultural, and ecological systems.
Acknowledgements This work was supported by the Knowledge Innovation Program from the Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences (CACX2003 102), the Chinese Academy of Sciences (KZCX 1- 10-03-01), the National Natural Science Foundation of China (40401012).
References Andreu J, CapillaJ, Sanchis E. 1996.AQUATOOL, a generalized decision-support system for water-resources planning and operational management. Journal of Hydrology, 177,269291. Bormann H, Iekkruger B D, Renschler C, Richter 0. 1999.
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Regionalization scheme for the simulation of regional water balances using a physically based model system. Physics and Chemistryfo the Earth, 24,43-48. Gao Q Z, Wu Y Q, Liu F M, Hu X L. 2004. Unified management of water resources and enhance of carrying capacity in Heihe river basin. Journal of Desert Research, 24, 156-161. (in Chinese) Hou X Y, Wan L Q, Gao H W. 2004. Research on keystones of grassland science in western china. ScientiaAgricultura Sinica, 37,558-565. (in Chinese) Huang D Y, Hu K L, Chen G Q, Huang M, Peng T B. 2004. Soil and water resources and land sustainable productivity in the catchment area with intensive management in hilly red soil regions, China. Agricultural Sciences in China, 3,356-363. Ji X B, Kang E S, Zhao W Z, Chen R S, Jin B W, Zhang Z H. 2004. Simulation of the evapotranspiration from imgational farmlands in the oases of the Heihe river basin. Journal of Glaciology and Geocryology, 26,7 13-7 19. (in Chinese) Shan L. 2002. Development trend of dryland farming technologies.
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Scientia Agricultua Sinica, 35,848-855. (in Chinese) Wang F, Liang R J, Yang X L, Chen M J. 2002a. A study of ecological water requirements in Northwest China I : theoretical analysis. Journal of Natural Resources, 17, 1-8. (in Chinese) Wang F, Wang H, Chen M J,Wang Y, Tang K W. 2002b. A study of ecological water requirements in Northwest China, Part 11 : Application of remote sensing and GIS. Journal of Natural Resources, 17, 129-137. (in Chinese) Wang H, Chang B Y, Qin D Y. 2004. Research of rearrangement of water resources in Heihe river basin. China Water Resources and Conservation, 9, 18-21. (in Chinese) Xie Y, Kiniry J R, Williams J R, Chen Y M, Lin E D. 2002. Sensitivity analysis of the Almanac model’s input variables. Scientia Agricultura Sinica, 35, 1208-1214. (in Chinese) Zhong L P, Shao M A, LI Y S. 2004. Changes of ecosystem productivity responding to driving forces in semiarid region. Scientia Agricultua Sinica, 37,510-515. (in Chinese)
(Edited by ZHAO Qi)
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sciENcE@DiREcT*
February 2006
Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle Reaches of the Heihe River Basin, Northwest China JI Xi-bid, KANG Er-si1, CHEN Ren-shengl, ZHAO Wen-zhil.2,XIAO Sheng-chunl and JIN Bo-wed2 1
2
Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, P.R.China Linze Inland River Basin Comprehensive Research Station, Chinese Ecosystem Network Research, Linze 734200, P.R.China
Abstract Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year (2003), the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system. Key words: middle reaches of Heihe River, irrigation region, water resources supply and demand balance, evaluation of
the security of water resources
INTRODUCTION To keep within limits the degradation trends of ecological environment, and transact the conflicts arising from competitive uses of scarce water supplies and long running disputes over the water allocation of interprovinces, such as Gansu Province, located midstream
of Heihe River basin, and Inner Mongolia, downstream of the river, in Northwest China, an unified planning and allocation of water resources in the entire Heihe River basin was developed through an analysis of China government’s policy statements, and was carried out annually during the period 1999-2004 (Wang et al. 2004). As a consequence, for the Ejinaqi key oasis, downstream of the Heihe River basin, the degradation
This paper is translated from its Chinese version in Scientia Agriculrura Sinica. JI Xi-bin, Ph D, Tel: +86-93 1-4967156, E-mail: [email protected]
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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle -
of ecological environment has been mitigated to some extent, whereas, in the midstream of Heihe River basin, the performances of the unified development and planning of water with increasing over pumping on a large scale due to the reduced surface water extracted from the Heihe River, have been carried into execution, and complicated the problems of water allocation and ecological environment (Gao et al. 2004). Based on the historical runoff process, the planning of water resources allocation cannot be directly applied to the water resources management decision support system. Therefore, appropriate development and planning of water resources allocation must be taken into account to forecast information of water resources supply and demand balance at the present in the entire river basin, and the operation would be modified by the variable adjustment factors (Bormann et al. 1999). In addition, in view of the spatial distribution of the parameters of the operation, calculating and evaluating the water resources supply and demand balance will not resolve the regional problem of water resources utilization in a relatively large scale in the inland basin (Bormann et al. 1999). Thus, according to the system theory, with respect to the evolution mechanisms of the renewable water resources, the relationship between water and ecology evolution and the interaction mechanism for water-economy (Zhong et al. 2004; Andreu el al. 1996; Huang et al. 2004) are significant. Under such circumstances, taking the complications inherent in water resources planning for this region into account, the key measures to realize the sustainabledevelopment of agricultural economy in Heihe River basin is to improve efficiency in water use and allocation (Shan 2002).
Study site description The site selected for the present study is located in the middle of Hexi corridor, Northwest China, piedmont valley plain oases, located between Gao'ai and Pingchuan gauging station, including Pingchuan, Banqiao,Yanuan, and Liaoquan irrigated district (99"57'100'22' E, 39'08'-39'23' N), covering an area of about 399.1 km2,with 42.6 km along the Heihe River (Fig.1). Elevation changes from 1300 to 1800 m in this region; the main topographical feature is characterized by their relative elevations with high in the north, east, and south,
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Fig. 1 A map of the schematic view of the study region.The arrow represents the direction of the Heihe River flow; dashed, solid, and black solid lines are the administrative division boundary, irrigated districts boundary between different irrigated districts, and the Heihe River, respectively.
low in the west, continental arid temperate climate. The mean annual precipitation is about 119.5 mm; about 60% of the total year precipitation with low rainfall intensity is received during July-September, and only 3% during winter. But the potential evaporation is 2 365.6 mm yr-I, about 20 times of gross annual precipitation; dryness index 15.9; annual mean air temperature is 7.6"C, the maximum and minimum are 39.1 and 27.3"C, respectively; the mean accumulated temperature of 3 10°C is 3 088°C. The fundamental features of society and economy in the study region can also be found in Table 1.
WATER RESOURCES SUPPLY AND DEMAND BALANCE ANALYSIS Available water resources quantity In this study regions, agriculture depends on irrigation from. underground water or from rivers (Heihe and Liyuan river) descending from mountains, in which available water resources quantity was calculated by water resources system model, and runoff volume at the Gao'ai gauging station was calculated by frequency analysis with the historical stage flow data during 1948-
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1999 (Huang et al. 2004). The analysis implicated that the mean runoff volume at the Gao'ai gauging station is 1 1 . 8 3 lo8, ~ 9 . 8 6 lo8, ~ 8 . 1 7 lo8, ~ and 6 . 3 2 lo8 ~ m3 yr-', corresponding to the different guaranteed efficiency P = 25%, P = 50%, P = 15%, and P = 95%, respectively. Moreover, it also can be found that there are the similar hydrology frequency features at Pingchuan and Gao'ai gauging station. The year 2003 represents the present year, in which the total runoff volume at Gaoai and Pingchuan gauging stations is 12.58 x lo8m3 and 10.12 x lo8m3, respectively. In addition, the flow volume is about 0.44x lo8m3in Liyuan River of the study area. The flow regimes of Heihe River and Liyuan River are characterized by annual and seasonal fluctuation (Figs.2 and 3), and approximately 43.86 and 64.85%of the annual runoff volume in Heihe River and Liyuan River occur in the period from July to September, respectively. However, during the plant growing season, they account only for 17.35 and 25.96%,respectively,
especially in a dry year, when there is insufficient water supply for irrigation of crops, there are also three reservoirs and ten main channel weirs fended by Heihe and Liyuan rivers, constructed to assist in providing water for agriculture, stock, and domestic purposes. The quantity of groundwater available was determined by the utilization capacity in the calculated unit, given permissible mining groundwater amount being its maximum. Thus, the permissible (the present year 2003) and planning (the future year 2010) groundwater resources are 657.7 x lo4 and 380.5 x lo4 m3 yr-I, 325.4 x lo4and 2 0 7 . 6 ~104 m3yr', 7 2 9 . 4 104 ~ and 4 6 3 . 3 104 ~ m3 yr-', and 1 050.8 x lo4and 670.3 x 104 m3 yr-I in the irrigated districts of Pingchuan, Banqiao, Yanuan, and Liaoquan, respectively.
Analysis of balance of water supply and demand The water requirements of the irrigated districts in the
Table 1 Fundamental features of society and economy in the study region Name of irrigated district
Year
Population
Pingchuan
1997 1999 2003 1997 1999 2003 1997 1999 2003 1997 1999 2003
21558 21634 21753 17410 17423 17466 11482 11497 11532 17921 17935 18046
Banqiao
Yanuan
Liaoquan
120
Agricultural area (ha) 3 000.0
3 000.0 3000.0 2666.7 2666.7 2666.1 1866.7 1866.7 1866.7 2 266.7 2266.7 2266.7
Irrigated area (ha) 2 800.0 2733.3 2600.0 2666.7 2666.7 2666.7 1466.7 1466.7 1466.7 1933.3 1933.3 1866.7
Livestock Output value of industry (Yuan RMB) 10360 329.7 10360 537.3 1 392.1 10260 10 005 532.3 10005 771.9 9 917 1614.0 5 426 321 .O 5 426 494.8 5 426 827.2 8990 27 1.6 8 990 369.4 8990 960.0
5
7
The areas of forest and grass land @a) 3 200.0 3 200.0 3 533.3 2 200.0 2 200.0 2 266.7 866.7 866.7 1133.3 1200.0 1200.0 1400.0
+ Yinluoxia statxon
- +Gao'ai station
-
- -W-
Zhengyixia station Liyuanhe station
h
v)
3
80 -
7
60
-
I
1
2
3
4
6
8
9
10
11
12
Months
Fig. 2 The average monthly runoff volume at different gauging stations in Heihe River basin.
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Analysis of Water Resources Supplv and Demand and Securitv of Water Resources Development in Irrigation Regions of the Middle
133
Pingchuan 2.00
. ..
I ." 0.00
---C
1984 10 00
1992
1994
1996
1998
2000
-C-
---*--- Dongwan
2002
Haowa I
1986
1988
1990
1992
1994
1996
1998
2000
2002
r
-
I
' 1984
6.00
1990
A-W 1984
1.50 100
1988
+Shanjiazhuang I
-i- Yigongcheng
Banqiao
4.00 2.00 0.00
4.00
1986
Huang'er
1986
Wanzi
--~t Shangzhuang
1988
1990
1992
1Y88
1990
1992
-
Xiazhuang I
1994
1996
1998
2000
2002
1994
1996
1998
2000
2002
r Liaoquan
3.00 2.00 1.oo
I
\I.""
1984
1986
Year
Fig. 3 The variation curve of groundwater table at irrigation area during 1984-2003.
inland basin are composed of the ecological, domestic, industrial, and agricultural consumption. Note that agricultural consumption is mainly the water for agricultural irrigation to evaporation and transpiration, calculated by using the Penman-Montieth equation in this study (Ji et al. 2004; Xie et al. 2002). The actual field evapotranspiration is equal to the potential evapotranspiration multiplied by the crop coefficients of different crop plants, and as a consequence the crop's water requirements are defined by the sum of the crop consumption during the different growing stages. The industrial water requirements are determined from the water consumption for each industrial yield (m3R104), given as 237 m3,362 m3 and 398 m3R104by1997 (past year), 2003 (present year) and 2010 (future year), respectively. The domestic water requirements comprise water consumption for the urban and rural livelihood and public fundamental facilities purpose, and related to the other purposes. According to the local living standard, each person's water consumption is predicted to be about 198, 204, and 215 L d-I by 1997,
2003, and 2010, respectively; and the rural water consumption by people and their livestock to live fundamentally, evaluated by consumption quota in view of the local living standard, and given the unit water consumption, is about 50,55, and 83 L d-' for people, 40 L d-' for big livestock, and 6.7 L d-' for small livestock. The average net irrigating water quota of farm fields for crop plant growth is 7 020 m3ha-' yr-l, and the maximum ratio of water usage in farm fields is 0.62. The water requirement for ecology (some of the water is used along the way to support the various ecosystems and maintain their functioning) is estimated by the superposition analysis method based on the ecological and water resources zoning approaches. The water requirements corresponding to the ecological zoning units are determined with respect to the different ecological systems, from which the water requirements of the artificial and natural oasis ecological system were evaluated (Wang et al. 2002a, 2002b). The artificial oases comprise the shelter forest belt, e.g., sand for protect-
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ing planting arbor and shrub, forest for protection against soil denudation, and fire wood forest and timber for protecting the natural vegetation cover, etc. Whereas the water requirements of natural oases ecological system include the riparian forests, water is consumed to support the particular ecosystems and maintain their functioning. As a general rule, an ecological system’s water requirement is deduced from the water consumption per dry biomass, for example, the value of 243.6, 243.6, 128.9, 71.3, 306.5, and 14.3 g m-2is given for the ecological system of intensive cover degree, swamp land and bottomland, moderate cover degree grass, sparse grass land, forest and shrub land, desert and Gobi belt (cover degree less than 5%, too barren to utilize), respectively. Moreover, some studies showed that the efficiency of water production is 1.05-10.05 kg ha-’mm-*(Wang et al. 2002b; Hou et al. 2004) in the inland river basin. In the current arid desert zone context, given the total evapotranspiration in an expected ecological unit, its mean efficient value of water production for different vegetation was extrapolated. Otherwise, for the ecological systems with no evapotranspiration data, the efficiency of water production is substituted by that of similar adjacent systems. An unit with azonal vegetation depends on precipitation and runoff, and its controllable vegetation consumption was evaluated by the phreatic evapotranspiration of the ecological system with the specific vegetation community, however, assuming that the uncontrollable consumption is equivalent to the precipitation in the region. Other data derived from the Statistical Yearbook of Linze County, in Gansu Province, Northwest China, and from the farreaching plan of economy development in 2010, developed from an analysis of the local government policy statements. The balance of water demand and supply results in Table 2 show the annual water budget for different purposes froin 1997 to 2010, given the different guaranteed efficiency. By 1997, given the value P=50% of guaranteed efficiency, the water balance calculations show that the total supply amount was more than the total demand with positive water balance in every irrigated district; given P = 75%, the total water supply was less than the water demands in all irrigated districts except for in Banqiao irrigated districts; and given
JI Xi-bin et al
P=95%, a negative water balance occurred, from which it can be seen that balance of water supply and demand in the oasis irrigated districts of the midstream of Heihe River basin was controlled by runoff volume of the upstream of Heihe River. By 2000, the unified management and planning of water resources in the entire Heihe River basin resulted in a decrease in water diverted from Heihe River by 10%and an increase in extracted groundwater by 50%; as a result, the water balance calculations have been changed, for instance, given P= 50%, the amount of available water tightly meets the demand of this systems, given P=75%, water supply did not meet the demand to some extent for different irrigated districts, given P= 90%, the available water supply was far less than the demand on a large scale, and most of the farm land would be beyond irrigation. By 2003, the water balance calculations show results similar to that in 1997 (Table 2). However, the available water diverted from Heihe River for irrigation decreased by 13%, and extracted groundwater amount increased by 157.6%, compared to water balance calculations in 2003. Because the area of the land returned from farming to forest and grass will amount to 10% of the total area of present cultivated farmland, in 2010, water resources availability of cannel system will increase up to 0.62, the water-saving ratio of agricultural planting system will increase up to 20%, and water consumption for each industrial yield (m3N104)will increase up to 189 m3M04(RMB); based on above data, water resources balance of supply and demand was forecasted along with water-saving strategies for irrigation planting carried out in the midstream of the Heihe River basin (Table 3), and the results show that water supplies would equal or exceed the demands.
Assessing safety of regional balance of water supply and demand To assess the safety of balance of water supply and demand in the midstream of Heihe River basin, the ecological system’s consumption for purposes of maintaining its development and functions must be taken into account in the downstream of Heihe River. Based on the methods of water resources exploitation and utilization in the past 50 years, the present water utilization capacity, and the periodic variation of mountain
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Table 2 Water resource supply and demand for irrigated districts in different years .year
Name of Available water supply (xl(rm3 yrl) Water resources demand (xlOd m3 yrl) irrigated district Warranted efficient (%) Surface water Well Agriculture Industry Domestic Ecological system 1997 Pingchuan 50 7384.1 58.7 6850.4 34.9 24.8 460.6 7091.6 160.9 15 6945.4 160.9 95 33.1 24.2 412.1 6615.7 57.3 6137.5 Banqiao 50 6563.8 51.3 15 6222.6 51.3 95 Yanuan 19.2 14.0 287.2 4604.9 33.2 4272.0 50 4422.6 58.3 75 4331.4 58.3 95 31.7 23.1 Liaoquan 5725.1 54.8 5311.3 357.2 50 5498.4 112.8 75 5385.0 112.8 95 2000 Pingchuan 39.5 28.8 491.5 6938.2 130.0 6389.4 50 75 6501.5 219.9 6193.3 322.5 95 38.6 28.1 430.1 6413.2 126.8 5890.7 Banqiao 50 6244.7 156.2 75 5144.8 235.1 95 22.2 Yanuan 4250.0 13.4 3916.2 16.1 340.5 50 3917.3 19.5 75 3787.1 111.6 95 36.6 Liaoquan 5653.9 121.3 5248.4 26.8 389.7 50 5317.7 154.5 75 4816.9 226.6 95 2003 Pingchuan 50.4 36.8 509.6 6586.0 141.1 6383.1 50 6161.9 238.5 15 5872.2 341.1 95 49.2 Banqiao 6391.6 137.6 5989.9 35.9 450.3 50 6235.9 211.2 75 5757.1 276.7 95 28.2 20.6 4430.4 79.6 3963.9 Yanuan 340.5 50 4 169.3 86.3 75 3986.8 123.3 95 47.1 34.2 Liaoquan 5380.9 131.5 4181.4 396.6 50 4859.0 167.6 15 95 4828.0 239.1
Water resources balance of demand and supply ( ~ 1 0m3 ' yrl) 72.1 -218.2 -264.4 65.5 13.6 -327.6 45.1 -111.5 -202.7 56.6 -112.1 -225.5 119.0 -227.8 -433.4 152.5 13.4 -407.5 28.4 -238.2 -396.3 73.7 -229.3 -398.0 -252.5 -513.2 -766.3 9.9 -18.2 -491.5 156.8 -197.6 -343.1 247.1 -138.7 -197.6
Total 7 370.7
6607.5
4592.4
5723.3
6949.2
6087.5
4 295.0
5701.5
6979.6
6025.3
4353.2
5 265.3
Table 3 Water resources sumlv and demand in the future (2010) ~
~~~~
Name of irrigated Available water supply (xlO4m3 yrl) Water resources demand (xlO4m3 yrl) Water resources balance of demand and supply (xlO4 m3 yr-I) district Warranted efficient (%) Surface water Well Agriculture Industry Domestic Ecological system Total Pingchuan 50 6261.8 155.1 5691.0 63.9 46.7 592.5 6 394.1 28.8 15 262.2 5 866.3 -265.6 5 582.2 95 364.9 -447.0 6012.4 111.3 Banqiao 50 5242.1 62.5 45.6 518.5 5867.7 256.0 5 856.7 75 183.8 172.8 5 397.2 204.9 95 -265.6 Yanuan 4031.9 50 187.5 3733.1 36.3 26.4 369.3 4165.1 54.3 3781.3 15 214.8 11.0 376.3 3 605.9 95 -182.9 5 134.2 Liaoquan 244.6 50 4643.0 59.8 43.6 459.2 5205.6 273.2 4 825. I 284.2 75 3.7
runoff data for the Heihe River, we conclude that the safety in water balance has a high degree of confidence, if the annual water consumption in the midstream of Heihe River basin is equal to or less or more than that regulated by the government; meanwhile, the effects of extracting groundwater on vegetation growth is slight in the oasis ecological system, or the vegetation impacted can be recovered in the regions. However, for
the midstream of Heihe River basin, the regional water supplies and ecological system is in critically alarming state. When the lack of water supply is offset by increasing in extracted groundwater, and the groundwater level is not in a trend of continuous drawdown in the midstream of Heihe River basin, or there is a temporary influence of decreasing of water table on vegetation growth because the groundwater table draw-
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down can recover itself. Thus, in this paper, the index of assessing safety in the regional water balance includes water balance calculations of supply and demand, available groundwater yield or potential groundwater yield, and the fluctuation of water table in the irrigated districts of the piedmont oasis.
Analysis of actual water supply and consumption In the present year (2003), the surface water loss volume was 2 . 4 6 ~ 1 0 m3, ~ of which 2 . 0 1 ~ 1 m3 0 ~ was con0 ~from Liyuanhe tributed from Heihe River, and 0 . 4 4 ~ 1m3 River. The result of the water balance calculation of supply and demand shows that the total water consumption was 1.71x1O8m3,by deducting the volume of water m3 ~ and evaporation 0. 19x108m3for seepage 0 . 5 4 ~ 1 0 Heihe and Liyuan rivers, of which water consumption for irrigation and ecological system extracted from rivers is 1.65x10sm3and 492.4x104m3,respectively, and 0 ~and 273.9~104 its net water consumption is 0 . 9 6 ~ 1 m3 m3,respectively. The leakages in Pingchuan and Sanba reservoirs, located in Pingchuan and Banqiao irrigated 0 ~ and 1 . 4 ~ 1 m3, 0~ districts, were 6x104m3, 1 . 2 ~ 1 m3, respectively, and their pan evaporation was 18 x lo4,9 x lo4,and 20x lo4m3, respectively. The actual water supply and consumption results in the present year can be seen from Table 4, in which the results show that the consumption of industries, people, and live stock was satisfied by the current water supply systems, but there is extreme lack of water resources for agricultural and ecological purposes (Tables 2, 3, and 4); for instance, except for Pingchuan irrigated district, there is a lack of water supply for agricultural irrigation of 966.7 x lo4, 1 401.5 x lo4, and 839.2x lo4 m3,respectively, in Banqiao, Yanuan, and Liaoquan irrigated districts. Moreover, the lack of ecological supplies was 2 0 9 . 4 ~ lo4,3 9 9 . 4 lo4, ~ 3 1 3 . 0 lo4, ~ and 283.1 x lo4m3in Pingchuan, Banqiao, Yanuan, and Liaoquan district at present, respectively. Only in Pingchuan district, water supply meets the demand in cost of groundwater overdraft, for example, in Pingchuan district, the available utilization volume of groundwater is 380.5x lo4m3,but the actual amount of groundwater pumping was up to 1190.0x lo4m3. Under the condition of a unified management of water resources guaranteed in the Heihe River basin, in 2003, a high flow
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year, the amount of water diverted from the Heihe River was 6 586.0 x lo4, 6 397.6 x lo4, 4430.4 x lo4, and 5 380.9 x lo4 m3in Pingchuan, Banqiao, Yanuan and Liaoquan district (Table 2), respectively, but actual diversion volume were 5 91 1.3 x lo4,5 004.1x lo4, 2548.9 x lo4 and 3 552.1x lo4 m3, respectively. Thus, one can conclude that the surface water resources utilization and development did not preponderate over the alarming line of safety by the wet year (2003).However, there is extreme lack of water resources to sustain the running of the agriculture and maintain ecology system functions of the oasis in the midstream of the Heihe River basin, of which the great negative effects on the development of agricultural, economic, and ecological systems is significant; taking the surface water and groundwater utilization into account, there are great deficits in water demand in these regions.
Analysis of the potential groundwater capacity In the irrigated districts of the piedmont oasis in the midstream of Heihe River basin, the degree and performance of groundwater utilization in a region can be represented by the index of potential groundwater capacity; its mathematical representation is given in the form:
I= QjQ, Where Z is the index of the available groundwater capacity, Q, and Q, are the potential available yield and actual groundwater mining amount (x lo4m3yr-I). Assuming that I> 3.3 represents the great potential capacity of utilizing groundwater, 1.7 C Z G3.3 represents moderate, 1.2c Z < 1.7 represents poor, 0.8 c I 6 1.2, represents critical with the balance between recharge and extraction, 0.6 C Z 6 0 . 8 represents slight shortage, 0.4 c Z G0.6 represents moderate shortage, and Z60.4 represents extreme shortage. In these irrigated districts, Yanuan and Liaoquan lie on the south bank of Heihe River, where there are main spring water belt developments, irrigating crops from the Heihe River, and drinkable water depends on groundwater drawn with hand-pumps or shallow wells. In the present year (2003), the indexes of available potential groundwater capacity were 1.12 and 1.27 (Table 5 ) and reach up to the maximum of the available ground-
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137
-4nalysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle
water mining, it occurs to water balance of mining and recharge, so much so that actual groundwater exploitation amount was almost equal to the planning allowable mining capacity. Water demand for irrigation will increase and the shortage of irrigation water will increase by a considerable percentage, due to the regression of spring water and increasing area of farmland. Moreover, Pingchuan lies on the north bank of the Heihe River, where the index of available potential groundwater capacity is 0.32, and groundwater overdraft is very serious and the water is depleting. In addition, Banqiao also lies to the north of Heihe River, where there are water enrichment zones distributed along both the banks of Heihe River, In present year, the index of available potential groundwater capacity was 1.79,being regarded as moderate with the reasonable groundwater utilization, but the belts of groundwater exploitation have shifted further far from the bank of Heihe River. The results from the analysis of the available potential groundwater capacity above show that groundwater exploitation amounts have exceeded the available potential capacities and are beyond the alarming value in Pingchuan. For other irrigated districts, the actual groundwater utilization volume is almost equal to the available potential capacities and approach alarming values. If reasonable planning and development of water is not carried out in this region, there would be more complex problems of the safety of water resource supply and demand.
Groundwater table fluctuation analysis According to the long-term measured data obtained during the period 1984-1999, the dynamics of groundwater table depth in this irrigated districts shows that the groundwater table depth varied in the range of -0.1 to 0.1 m yr-I. Such fluctuations are also the characteristics of the typical stable fluctuation in the study regions, However, during 2000-2003, the groundwater table was in a trend of continuous drawdown, for example, the annual average rates of groundwater drawdown were 0.23,0.38,0.25, and 0.41 m, respectively, in Pingchuan, Banqiao, Yanuan, and Liaoquan, from which one can conclude that water resources balance has alarmingly exceeded its value of safety. The analysis result shows that the main factor causing the drawdown of groundwater level is: first, setting high standards for adequate irrigation and water conservancy resulted in a decrease in the groundwater recharges, which is the determining factor in groundwater continuous drawdown; second, the excessive groundwater exploitation on a large scale is the major factor in groundwater table lowering, for example, extensive groundwater was exploited immoderately, resulting in the groundwater exploitation volume exceeding its natural recharge capacities; third, along with the unified management and allocation of water resources in the Heihe River basin put into practice, there were so
Table 4 Actual water supply and consumption at irrigated districts in the present year') Pingchuan G.W
s.w Available water supply (x 104 m3)
Agriculture Ecology Industry Drink
Water consumption (x I 0 4 m3)
5611.1
4953.2
70.0
Yanuan S.W G.W 2521.4
41.0
Liaoquan S.W G.W 3438.3
510.0
300.2
0
50.9
0
27.5
0
113.8
0
0
50.4
0
49.2
0
28.2
G
47.1
38.6
0
46.0
0
25.3
0
0
Agriculture Ecology Industry Drink
Balance (x 104 m3) I)
1101.0
Banqiao S.W G.W
51.6
6383.1
5 989.9
3 963.9
4787.4
509.6
450.3
340.5
396.6
50.4
49.2
28.2
47.1
36.8
35.9
20.6
34.2
27.4
-1356.0
-709.8
-1104.5
S.W and G.W indicate surface water and groundwater supplied.
Table 5 The potential groundwater capacity in the midstream of Heihe River mainstream Irrigated district
Present mining (x104m3 yrl)
Planning allowable capacity (x10'mlyr-I)
Potential capacity index
Adjustable mining (xlO'm3 yr1)
Pingchuan Banqiao
1190.0
380.5
0.32
116.0
207.6
1.79
91.6
Yanuan Liaoauan
416.4
465.3
1.12
48.9
528.1
670.3
1.27
142.2
-809.5
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138
many disadvantages of the quota allocation system of water distribution and the water rights commerce under the conditions of the present agricultural and economical development; for instance, the running performance of the unified water management and allocation is characterized by the division channel closed in the midstream of Heihe River that supplies water to Ejina directly, downstreamof the Heihe River basin. However, the time of the closed diversion channel was related to that of the runoff volume that occurred upstream of Heihe River; furthermore, the time of incoming flow upstream is not synchronous with that of the water extracted from Heihe River for irrigation, and there is also insufficient water to irrigate farmland in the crop growth seasons in the irrigation districts in midstream of the Heihe River basin. Therefore, at the present, the most important strategy to realize sustainable development of agricultural, economic, and ecological systems midstream of the Heihe River basin is to take the scientific water management of long-established water resources systems and water resources optimal allocation system into account.
CONCLUSIONSAND DISCUSSION Balance of water resources supply and demand In the oasis irrigation districts midstream of the Heihe River basin, balance of water supply and demand was obviously controlled by the passing runoff of the Heihe River.in this region. In addition, since the unified management and allocation of water resources was conducted in the entire Heihe River basin, the components of the original sources of water supply have been changed with a decreasing in the annual water volume by 13.0 % diverted from Heihe River and increase in the groundwater extracted by 157.6%. There was still a great lack of water supply for agricultural and ecological systems, however, owing to the readjustment of agricultural set-up, and water-saving techniques lag behind in the unified management and planning of water resources in the entire Heihe River basin. Agriculture development in the oases depends on water resources supply, which has, and is expected to continue to have, significant impacts in the Heihe River
JI Xi-bin er al
basin as elsewhere in the inland basin, under the condition of the present standard level of economic and technological development. By present year (2003), in water supply terms, the volume of surface water diverted from Heihe River does not exceed the available maximum of the divertible water in every irrigated district; the shortage of water supply for irrigation is supplemented by extracting groundwater. Except for Pingchuan irrigated districts, the tight demands and supplies of water resources balance could be found with the groundwater over pumping (i.e., the volume of groundwater over pumping is up to 809.5x104m3); however, for other irrigated districts, the shortage of water supply has become one of the most serious problems. In the future, works must place emphasis on the water resources management, field water-saving techniques, and the readjustment of the agricultural set-up. The complex problems in the ecological, environmental,agricultural,and economic systems, etc. will be resolved in the midstream of Heihe River basin, even the entire Heihe River basin. At the present, there is a great lack of water supply in Pingchuan, Banqiao, Yanuan, and Liaoquan irrigated districts. But the volume of water diverted from the Heihe River is less than the alarming value of secure water balance; on the other hand, irrigation depends on the groundwater overdraft only, for instance, groundwater overdraft volume was about 8O9.5x1O4m3.In 2003, the balance of water supply and demand module was forecast in the typical irrigation district, oasis midstream of the Heihe River basin, from which the results show that water supply would suffice to meet the water consumption, taking the readjustment of the agricultural set-up, increasing rate of water resources utilization, and different water-saving techniques into account, along with the social with water-saving establishment supported by the government.
Countermeasures and suggestions for guaranteeing the securities of balance of water supply and demand The decisive methods for the development and planning of water resources are to maximize the water supply for agriculture and promote water conservation and efficienct usage, at the oasis irrigated districts midstream
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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle
of the Heihe River basin. The integrated model with particular, regional, and unique functions for agricultural water-saving that was established can be applied to sustainable development of agriculture, economy, and ecology. These projects can help establish reasonable management and planning of water resources and thereby contribute to improve the input-output ratio in agriculture and raise the living standards, so as to guarantee the safety of balance of water supply and demand and availability of the resources and efficiency in its use, and to provide the foundation for improving the quality of ecological environment system. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while establishing efficient agriculture-ecology system and maintaining or improving the quality of the natural ecosystems is one of the key challenges in the future. For instance, the proportional readjustments of water supply for livelihoods, industries, agriculture, and ecology purposes. An additional aspect is that the readjustment of agricultural set-up by reducing the cultivated land area, increasing the area of forest and grass land, cutting down the area of planting for food, increasing commercial crop planting area, reducing the planting area with high water-consumption, increasing low water-consumption planting area, and strengthening the complementaryrelationships between agriculture, forest, and livestock development. Surface and ground water comprise a whole system and affect each other owing to the complication inherent in the hydraulic relation between them. This relationship between surface and ground water is characterized by the multiple and frequent conversions and utilizations repetitively. Observing that the conversion law of surface and ground water is a must for the sustainable management of water resources, and the module of the optimum allocation, combined surface with ground water development should be carried out in practice. In the inland river basin, options for increasing water productivity include improving the capacity of water resources combined surface and ground water utilization with the help of regulation and management methods developed from an analysis of local government policy statements. A prerequisite of effective implementation of the reasonable utilization of water resources is to establish the module of reasonable and
139
scientific development and utilization of surface and ground water, and the corresponding technology research in irrigation and drainage. Meantime, the researches on the effects of canal seepage control, seepage control by hard soil-cement for plain reservoirs, and others measures of the field water-saving in the hydrological process and ecological environment systems in the Heihe River basin are taken into account. Water resources management and allocation in' the different regions should emphasize on the possible maximum water consumption for the specific oasis system (including agricultural, industrial, livelihoods, and ecological systems consumption), or the potential water resources capacity to sustain the maximum scale of oasis. Especially, in the Heihe River basin, water scarcity has become a development constraint seriously impeding the economic and social development, giving rise to conflicts over water resources among agriculture, ecology, economy, and livestock. Thus, not only in the management and planning of water resources should we consider the balance of water supply and demand to secure in the whole watershed, but also attach importance to readjustment of the ratio of the artificial to natural oasis water consumption. Furthermore, the need for maintaining a reliable groundwater table depth to preserve the oases ecological functions and development requires further emphasis on increasing the water consumption for ecological purposes and decreasing the water consumption for agricultural purposes, so as to achieve a unified and sustainable development of economic, social, agricultural, and ecological systems.
Acknowledgements This work was supported by the Knowledge Innovation Program from the Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences (CACX2003 102), the Chinese Academy of Sciences (KZCX 1- 10-03-01), the National Natural Science Foundation of China (40401012).
References Andreu J, CapillaJ, Sanchis E. 1996.AQUATOOL, a generalized decision-support system for water-resources planning and operational management. Journal of Hydrology, 177,269291. Bormann H, Iekkruger B D, Renschler C, Richter 0. 1999.
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140
Regionalization scheme for the simulation of regional water balances using a physically based model system. Physics and Chemistryfo the Earth, 24,43-48. Gao Q Z, Wu Y Q, Liu F M, Hu X L. 2004. Unified management of water resources and enhance of carrying capacity in Heihe river basin. Journal of Desert Research, 24, 156-161. (in Chinese) Hou X Y, Wan L Q, Gao H W. 2004. Research on keystones of grassland science in western china. ScientiaAgricultura Sinica, 37,558-565. (in Chinese) Huang D Y, Hu K L, Chen G Q, Huang M, Peng T B. 2004. Soil and water resources and land sustainable productivity in the catchment area with intensive management in hilly red soil regions, China. Agricultural Sciences in China, 3,356-363. Ji X B, Kang E S, Zhao W Z, Chen R S, Jin B W, Zhang Z H. 2004. Simulation of the evapotranspiration from imgational farmlands in the oases of the Heihe river basin. Journal of Glaciology and Geocryology, 26,7 13-7 19. (in Chinese) Shan L. 2002. Development trend of dryland farming technologies.
T . I Xi-bin et a1
Scientia Agricultua Sinica, 35,848-855. (in Chinese) Wang F, Liang R J, Yang X L, Chen M J. 2002a. A study of ecological water requirements in Northwest China I : theoretical analysis. Journal of Natural Resources, 17, 1-8. (in Chinese) Wang F, Wang H, Chen M J,Wang Y, Tang K W. 2002b. A study of ecological water requirements in Northwest China, Part 11 : Application of remote sensing and GIS. Journal of Natural Resources, 17, 129-137. (in Chinese) Wang H, Chang B Y, Qin D Y. 2004. Research of rearrangement of water resources in Heihe river basin. China Water Resources and Conservation, 9, 18-21. (in Chinese) Xie Y, Kiniry J R, Williams J R, Chen Y M, Lin E D. 2002. Sensitivity analysis of the Almanac model’s input variables. Scientia Agricultura Sinica, 35, 1208-1214. (in Chinese) Zhong L P, Shao M A, LI Y S. 2004. Changes of ecosystem productivity responding to driving forces in semiarid region. Scientia Agricultua Sinica, 37,510-515. (in Chinese)
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