THE BALANCE BETWEEN SUPPLY AND DEMAND OF WATER RESOURCES AND THE WATER-SAVING POTENTIAL FOR AGRICULT

CHINESE GEOGRAPHICAL SCIENCEVolume 12. Number 1, pp. 23 - 29, 2002Science Press, Beijing, Chins一THE BALANCE BETWEEN SUPPLY AND DEMAND OFWATER RESOURCES AND THE WATER-SAVINGPOTENTIAL FOR AGRICULTURE IN THE HEXI CORRIDORGAO Qian-zhao，DU Hu-lin，ZU Rui-ping( Cold and Arid Regions Enrironmental and Engineering Ressearch Institute, the Chinese Academyof Sciences, Larzhou 730000, P. R. China)ABSTRACT: The Hexi Cormidor is an important base of agriculture development in Northwest China. Aecording to re-cent statistics, there are 65. 94 x 10'm' of waler resources available in the Hexi Corridor. Al present, net consumption indevelopment and uilization is 43. 33 x 10*m'. Water supply and demand reach a balance on the recent level of produc-tion, but loss of evaporation and evapotranspiration is as much as 25. 69 x 10*m'. So net use efciency of water resourcesis 59%。Based on analyzing balance belween water and land considering ecological environment at present, there existsthe serious waler shortage in the Shiyang River system where imigation lands have Ov erloaded. There is a comparative bal-ance between supply and demand of water resource in the Heihe River system; and the Sule River system has sume sur-plus water to extend imigation land. Use of agriculture water accounts for 83. 3% and ecological forest and gTass for6. 9% . The Hexi Corridor still has a great potential for water saving in agriculture production. w ater-saving eficiencey ofirrigation is about 10% by using such traditional technologies as furrow and border-dike irigation and small check iriga-tion, and water-saving with plastic flm cover and techniques of advanced sprinkler and drip/ micro imigation ete. cansave more than 60% of imigated water. Incremental imigation area for water-saving potential in the Hexi Corridor hasbeen estimated as 56% - 197% to original imigation area. So the second water sources can be developed from waler sav-ing agriculture in the Hexi Coridor under Development of the Westem Part of China in large scale. This potential can berealized step by step through developing the waler-saving measures, improving the euological condition of asis agmicul-ture, and optimizing allocation of water resources in three river systems.KEY WORDS: water resources; balance between supply and demand; water-saving potential of agriculture; Hexi Corri-lorCLC number: TV211Document code: AArticle ID: 1002-0063 (2002)01-0023-071 AVAILABLE WATER RESOURCESglacier and snow meled waler formed the river runoff.The inland river basins in the Hexi Corridor in-Situaled in Gansu Province,27. 1 x 10'km2 in area clude the Shiyang River system, the Heihe River systemor amount to 59. 7% of Gansu's total area(CHEN,and the Sule River syslem from east to west. There are1992). the Hexi Corridor is a main economic develop- 60 inland rivers in the Coridor and the lower reaches ofment region and an important marketable grain base the Heihe River runs into the Inner Mongolian Plateau.whose annual grain yield gains about 2.31 billion kgRunoff volume of rivers is from 0.01 x 10*m3 t(and therefore supplies the Gansu Province with over 16. 12x 10*m?. Among them, runoff volume of 2460% marketable grain,rivers in the hydrological observation accounts foLocaled in temperate anid zone in Northwest Chi- 91. 2% of the total surface water resources.na, the Hexi Corridor has scare rainfall ,dry elimate andstrong evaporation. So its agriculture completely de- 1. 1 Surface W ater Resourcespended on irrigation and most of water supply originatedfrom the southern Qilian Mountain where precipitation,中国煤化工Hexi Coridor consistRcceived date: 2001-03-19MHCNMHGFoundation item: Under the auspices of the Key innovation Project Engineering of Chinese Academy of Sciences(KZcx-1-10-03)Biography: GAO Qian-zhao(1942-), male, a native of Changzhou, Jiangsu, Professor and supervisor of Ph. D students. His researchinterestas include hydrology and rational utilization of water resources in the arid zone.24GAO Qian zhao, DU Hu-lin, ZU Rui-pingof surface and ground water. The surface water which system 36.83 x 10*m' and the Sule River system 17. 22mainly originated from the southem Qilian Mountain canx10*m', and the total add up to 69. 92 x 10*m'.be divided into the station- controlled river flow， theAccording to statistical data， the water volumenon-station-controlled streamflowand the flowing out from the Qilian Mountain area is 68. 5 x .front-mountains runoff , their surface runoffs respectively 108 m' because of consumption in the mountains (Tableamount to 91.2%，5.8% and 3. 0% of the surface 2)， of which the Shiyang River system is 15. 55 xwater resources in Hexi Corridor. Among three river 10*m'， the Heihe River syslem 36. 22 x 10*m' and thesystems(Table 1) in the Hexi Coridor, the Shiyang Sule River system 16. 73 x 10*m'.River system makes up 15. 87 x 10'm' , the Heihe RiverTable 1 The surface water resource in the Hexi CorridorShiyang RiverHeihe RiverSule RiverHexi CorridorRecord Survey Caleulete Total Record Survey Calculate Total Record Survey Calculate Total Record Survey Calculate TolalRunoft volume(I0*m")14.80.49 0.58 15.87 33.01 2.86 0.96 36.83 15.94 0.69 0.59 17.22 63.75 4.04 2.13 69. 92% of toltal93.3 3.1 3.6 100 89.6 7.8 2.6 10 92.6 4.0 3.4 100 91.2 s. 83 100Table 2 Surface water flowing oul from the mountains in the Hexi CororidorHexi CoridorSurface Consumption Total Surface Consumnption TotalSurface Consumption Totale Consumption Touarunoff in mountainsrunff in mountainsrunoff in mountsinsRunof volume(10'm') 15.550.32 15.87 36. 220.61 36.83 16.730.49 17.22 68.51.42 69.92呢o lotal98.02.0 100 98. 02.0 100 97. 22.81008.02.01. 2 Groundwater Resourcesable, which exclude the consumption in the QilianMountain area， are the surface water flowing out fromIn the Hexi Corridor, the natural groundwater re- the mountain area adding the non-repeated ground watersources mainly come from the leakage of the river (Table 4), of which, the Shiyang River system makescourses, the channels and fields. These belong to the up 16. 87x 10*m'，the Heihe River system 38. 71xsection of repeated with surface water. In addition, a 10*m'， which includes 7. 50 x 10*m' of water flowingpart of phreatic water of valleys in mountain mouths andinto the lower reaches of the Heihe River, and the Sulethe rainfall infiltration in the plain area also formed the River syslem 17. 86 x 10*m'. The total water resources .groundwaler that is not included in the surface water are 73. 44 x 10*m’and resources available for the Hexiresources. According to statistics of the hydrogeological Corridor are 65. 94x 10m'. The surface waler anddepartment of the Gansu province , the total groundwaler groundwater occupy 92. 5% and 7. 5% respectively.volume in the Hexi Corridor is about 4. 94 x 10*m’According to the present situation, in the Hexi(Table 3), of which the Shiyang River system occupies Corridor water volume per capila is about 1420m' and1.32x l0*m'，the Heihe River syslem 2. 49 x 10*m2 per ha is 11 235m'. For three river systems, thand the Sule River system 1. 13 x 10*m'.Shiyang River are 725m' per capita and 5580m' per ha,he Heihe River are 1665m3 per capital and 1 l010m’Table 3 Groundwater non-repeated with surfaceper ha and the Sule River are 4000m' per capita and 26water in the Hexi Corridor( 10'm2) .445m' per ha.Shiyang River Heihe River Sule River Hexi CorridorRainfall feeding0.481. 120. 822.422 ANALYSIS OF THE BALANCE BETWEEN DUPPLYSide feeding0.821.370.312.52AND DEMAND OF W ATER RESOURCESTotal1.322.491. 134.942. 1 The Balance Between Supply and Demand of W alter1. 3 Tolal Water Resources Available for the Hexi Cor- Resour中国煤化工ridorYHCNMH G; the mounlains isIn the Hexi Corridor, total water resources avail- channeled into canals and farmlands by reservoir regu-The Balance Between Supply and Demand of Water Resources and the w aler-Saving Polential for Agriculture in Hexi Corridor 25Table 4 Available Weter resources in the Hexi CoridorShiyang RiverHeibe RiverSule RiverHexi CorridorSurface GroundCroundSurduce GroId TotalWater volume 10*m)15. ss1.32 16.8736.22 2. 4938.71 16. 731. 1317. 8668.50 4. 9473. 44名of the total7.810093. 6.4 1006.7 100Water per capita(mn') 72516654000420Water per ha(m')558010102644511235lation and water conservancy works, about 30% of the agriculture, industry, municipal supply， drinking osurface runoff is transformed into groundwater from river human being and livestock in rural region and irigatedcourses, which accounts to 23. 23x 10*m'. A part of forest and grass. Based on present imigated farmlandsfarmland irigation, industry and municipal use of water and net consumption quota of irrigation, water use sur-were still supplied by channeling spring water ancvey for industry, population of towns and villages andpumping groundwater in the Hexi Corridor. Up to the each drinking standard, livestock number and drinkingmiddle of the 1990s， there had been 120 large, middle water quota, imigated areas of forest and grass lands,and small reservoirs with total water storage of 10. 02x evaporation from surface area of water bodies and10*m3 and 11 868km of main and branch canals with groundwater, tbe present consumption volume of waterpavement of 70%， The water delivery efficiency of is calculated. Among these, water consumption for acanal systems reaches to 55% - 60%，and the wa- griculture accounts for 88. 3%，for industry for 6. 8%ter-use efficiency within farmlands is 83%. There were (DU， 1997)， for municipal supply and for drinkingabout 21 300 tub wells with electricity power of273 700 water in the rural region for 2. 9% and for irrigatedkW and 18 891 pumping stations for irigation with forest and grass for 6. 9%，For calculating and analyz-power 235 700Kw. Therefore water supply completelying the balance between supply and demand of waterdepends on the water resources available for the Corri- resources, the paper lakes water resources available fordor. .the Corridor as supply items and the net utilization asThe main users of water in the Hexi Corridor are consumption ones (Table 5).Table 5 W ater balance calculation( l0*m')ResourecesEvaporationNet consumptionBalanceRiver systemSurface Groundwater Water body Groundwater Agriculture Industry Ecological Municipal Drinking Shortage or surplus15. s51. 320. 332. 3314.96. 260. 640.320. 28-3: 25HeiheRiver36. 222.2111. 3416. 31.51s. 52(-1.98) .16. 739.04.46 0.78 0.850.07 0.072.15sum68. 52. 982.9822. 7135.72 3. 353.00 0.66 0. 66.4.42Total73. 4425. 6943. 33%10035. 059. 0Note: (1) The nuaber within brackets is the waler shorage for gupply of Ejina oases according to water llcaiono scheme between GansuProvince and Inner Mongolia Autononous Region.(2) Net consumption water is delernined on existing imgation areas and net inigtion quota for agriculture. irigated forest andgasland BrCas and nel quota for ecological forest and gass lands, survey for indutry. The municipal net consumption water iscalculated by the divirion standards of cities and towns, such a 50L/(p° d) for Wuwei, 60L/(p. d) for Zhangye. 50L/(p●d)for Jiuquan and 100L/(P●d) for Jinchang, and runicipel census in 1994, Countryide drinking water is calulaled by cenous andthe division standerds of 30L/(p●d) for Wuwei, 50L/(p●d) for Zhangyc, 35L/(p . d) for Jiuquan and 3SL/(p. d) for Jin-chang. Livestock drinking water is calculated by the division siandeards of a big stock 50L/p●d and smoall one 15L/p ●d forWuwei, big 50L/(p. d) and amall 10L/(p* d) for Zhangye. big 40L/(p. d) and small 17L/(p* d) for Jiuquan and big 35L/(p. d) and small 10L/(p●d) and the nrumbers of livestock satistias in the end of 1993.The results show that the net consumption of water supply and demand is evident, the ratio between supplyresources is 17. 46 x 10*m3 in the Shiyang River system，and中国煤化工eially，, in its lowerbut loss of lower effective evaporation as much as reacl-resources is seriously2. 66x 10*m'. The water shortage is 3. 25x 10'm’shorHC N M H Gs overexploited. The(Table 5) if not consider rehabilitating ecological envi- results also showed thal ine net use of the Heihe Riverronment of the Minqin region. So the contradictory of system is 19. 64 x 10*m’, the lower effective loss of e:6GA0 Qian-shao, DU: Hu-lin, ZU Rui-pingvaporation amounts l0 13. 6x 10*m', the surplus which velopment has great potential of land resources in themainly supply to Ejina oases of the lower reaches is Hexi corridor.5.5 x 10*m’. Although there is a balance stage betweenBased on the present level of agriculture produc-supply and demand in the Heihe River system(GAO，tion, adopting the theory of water balance, the balance1991) , but it still has litle water shortage and the ratio equations between land and water in every river systemis 1: 1. It can be found that the net water use in the are set up in the Corridor. In the equations in Table 6,Sule River system is 6. 23 x 10*m2 and the lower efee- when the water volume W> 0, it means that imigationtive loss is 9. 48 x 10*m'. There is surplus water of land have overloaded, when W =0, waler and land are2.15x10*m' and the ratio of supply and demand is on a balance stage and when W <0 there is surplus1.3: 1.water to increase irigation land. These are respeetivelyAt present , the net water consuroption in the whole represented in the Shiyang River，the Heihe River andcorridor is 43. 33x 10*m', supply and demand of waler the Sule River systems.reach a weak balance on the recent level of production,Table 6 The interrelationship of water and land balancethe ratio is 0.96: 1. Based on above analysis, althoughin the Hexi Comridorit has physical water shortage. but the lower efectiveShiyang RiverHeihe RiverSule Riverloss amounts to 35. 0% of total water resources in theEquation W=3. 25+0.4955 W= 0. 15-0.57755 W=-2. 15+0. 66Hexi Corridor and the net utilization efficiency of walerresources is 59% under the economic development andW: Ralance waler volume of agriculure imigation (10" m');environment conditions al present.S: Vaniable of imigation ara (10'ha)Al present, the calculated results and existing2.2 The Balance Between Water and Land in the Hexibalance between water and land (Table 7) show thatCorridorirrigaled lands have overloaded by 6.5x l0*ha in theAccording to detailed survey of land use status inShiyang River system, a basically balance if no con-Gansu Province in 1992, the Hexi Corridor has 65. 38sidering a water deficit to the down stream in the Heihex 10*ha of cultivaled land(LI，1998)， of which theRiver system, and some surplus water in the Sule RiverShiyang River system is 30. 27 x 10^ha , the Heihe Riversystem which could extend 3. 33 X 10ha of irrigationsystem 28. 36x l0ha and the Sule River systemarea. That means the irigation areas could not be ex-6.75x 10* ha. In addition, the Hexi Corridor has alsotended in large scale according to traditional agriculturerain-f£ed farmland of 23. 01 x 10*ha, wasteland suitableand the carrying capacity of waler resources has reachedfor agriculture amounts to 31. I5 x 10*ha. So like othercritical limit in the coridor under the present productioninland river regions of northwest China, the land de-level of water use.Table 7 The balance of water and land in the Hexi CorridorImigation for farmalndIrigaion for forel and glassPresent belanceFresent belanceRiver systemImigated areaNet consunplionNet consumptionWater volume Area( x 10'ba)(m' per ha)( x 10*ha)(10*m')( x 10"ha)Shiyeng River30. 2749501.454425-3. 25-6.5328. 3657753. 1947250.150.266.7566001. 8945003.33To65. 3855056. 524575-0.95-2.943 THE POTENTIALOF WATER SAVING FOR AGRI- using new techniques and controlling the ineffective lossCULTUREof evapotraspiration so as to enhance the efficiency ofwater resources utilization.Going to the road of waler-saving agriculture is oneAccording to the analysis on actual crop irrigatedof effective ways of increasing the efficiency of water quota"中国煤化910193,eresources utilization and alleviating the shorlage of waler averagRiver system isresources (XIA0, 1996). Its main measures can be 5850 rCN M H Gem is 6975m2 peradopted such as decreasing the loss of leakage in canals ha and the Sule Kiver system is 7950m' per ha. Iri-by paverment, reducing the imigating water quola by gation experiment result shows that the net consumptionThe Balance Between Supply and Demand of Water Resoures and the Waler-Saving Potential for Agriculture in Hexi Corridor 27quota is 3750m2 per ha for wheat and 4500m' per ha forAccording to irrigation experiments of wheat andmaize and much less than present quota (Table 8).maize , net consumptive water in the wheat field are 33%According to practice of traditional irigation, it can befor soil evapotranspiration and 67% for leaf transpira-concluded that water-saving efficiency of normal irriga-tion, in the maize field are 39% for soil and 61% fortion technique is about 10% and water-saving by usingleaf (LI, 1992). Based on experiments on site of theadvanced techniques with plastic firm cover to wheatwheat fields of Wuwei, Zhangye and Jiuquan, net con-and maize can save more than 30% of irigation water,sumptive water for leaf transpiration during the cropso these techniques of water-saving are potential forgrowth period is only 2820 to 3555m' per ha. In com-popularizing perspective in crop imigation and suitable parison with the net quota of present irigation, the lossfor nalional conditions.of evapostranspiration in the field occupies 52% - 55%Table 8 The potential of saving-walter agriculture in the Hexi Corridor (m' per ha)Shiyang RiverHeihe RiverSule RiverAverage water volume55801101026445Net imigtion quota585069757950at presentNornal technique quota51907425afer 2000Plastic firm cover quota2700 - 3000 for wheat; 4665 - 4845 for maizeafier 2000Net quota in future450054006750Imigation experiment quoua3750 for wheat; 4500 - 5295 for maixeof the irigation water , the efficiency of waler use in the (including in border check or ditch) can save 10% -:rop field is about 45% -48%， At present, the nel30% of water than normal watering, irigation on filncoefficient of water delivery from canal to field is 0.48 can also decrease 30% of water volume than groundand the effective use rate of water resources from canal)ne, the spring irigation can save 30% of water thanto crop absorption is only 0. 23. It is obvious that there flooding and waler saving eficiency of trip/ micro imi-is big potential in the water-saving agriculture of the gation can get as high as 50% - 70% .Corridor.On the basis of water balance calculation above,According to traditional saving waler technologies raising the water-saving fficiency and increasing thein the Hexi Coridor from 1990 to 1993 , if substitutingcarrying potential of water are analyzed and the relationsfurrow irigation, border-dike irigation( <0. 033ha) or of water and land balance(Table 9) were set up in or~small check imigation( <0. 1ha) for flood irigation,the der to utilize water more eficiently. From these rela-water-saving ffciency can get to 10%，and if farmingtions , we can see that the potential of saving water in thewith plastic firm cover, the water-saving eficiency can Hexi Coridor is great and this can take .as a main di-reach as high as 60% . Advanced imigation techniques reetion of water rational utilization in future. So thetaken, such as spring imigation, surge irigation on second water sources can be developed from water sav-film, trip irigation and micro-irrigation by infiltrationing of agriculture.etc., still have great potential for water saving and per-After taking the water-saving imigation measuresspective for popularizing (WU, 2000)， but the more the development potential of water resources is indicatedinvests are needed. In general, surge imigationby the percentage( X) of the ratio of incremental imi-Table 9 The potential of water- saving imigation in the Hexi CoridorShiyang River .Water-savingeficiencyWater balanceIneremenbal areaIncremental areaIneremental areaequalof farmlandequationw=3. 27 +0. 495 s-6.61w=-0. 15+0.4575S 0. 26W= -2. 16+0. 60S3.2710%w=1.77 +0. 44555-3.97w= -1.75 +0.5205S 3. 36w= -2.61 +0. 59454.3920%w=0. 28 +0. 3968-0. 71w= -3.35 +05.7730%w= -1.22 +0.3465S3.5w= -4.95 +0中国煤化工0.4625”干+0.528S7.5740%W= -2. 72 +0.29789. 16w= -6. s6 +0.TYHCN M H Gt0. 3965+0. 396S9. 97S0%w= -4.22 +0. 2475S17. os .w=-8.16+0.开= -.对+0.33513. 30Note: w- -balance waler volume of inmgtion agriculrure (10*m?); S- -increment of igaion area (10"ha)28GAO Qian-hao, DU Hu-lin ZU Rui-pinggation area to original imigation area. The relationshipFrom the above non-linear models, we can deter-between saving-water efficiency ( Y) and the potential of mine the potential( X) of the carrying capacity of waterwater resources ( X) is non-linear (Fig. 1). Its mathe- resources according to achieving the water-saving de-matics models are arranged in Table 10. The correlative grees( Y)，or can determine the needful water-savingcefficient betweenX and Yis 0.98 (a=0. 01).degrees based on the developing the scale of imigationrea for safeguarding the balance between supply andTable 10 The relations between saving-waler eficiencydemand of water resources and coordinating develop-and potential of water resources in the Hexi Coridorment of water and land resources. Incremental irrigationRiver systemNon-linear models of efriency and potentialarea for water-saving potential can be estimated as 56%Shiyang River X= -21. 8531 +86. 7437Y-5.0764￥+287.9630 - 197% to original irigation area if achieving the wa-Y=0.2187 +7. 9728x10-'X -8.2066x10 . xter-saving degree of 50% on the present base in the+5. 1910x 10-7只Hexi Coridor. The water saving degree of above 20%Heihe River x=0. 8294 111.1257Y+0. 91271 + 359.2593ris needed by taking some measures if water resourcesY= -7. 9583 x 10->+9.6385 x 10-'x-7. 0358utilization can reach the relative balance between waterx10 'X+2.4323x10-7Xand land in the Shiyang River system. And afterSule RiverX=48. 4270 + 163.3916Y+1.0315Y*+531. 481810 adopting water saving measures of irigalion to saveY= -0. 3987 +0.0102X-4. 3608 x 10-*X +7.7091water of 12%，the surplus water of the Corridor cansupply and meet the requirement of the Ejina oases of200of0叶80140212010080|。f 0104 0ot 05rEoT o.z0.30405r°二0丫σ203σ405￥Shiyang RiverHeibe River-Average-- P= 50%------P= 75%Fig. 1 The relationship between raising the saving water of imigation (% )and the carryingceapacity potential of increasing imigation areas of water supplythe lower reaches in the Heihe River system. There isa 4 CONCLUSIONSltte surplus water for extending imigation and adoptingwater-saving measures also is very important for im-Based on above analysis, we concluded that walerprovement environment and future development in the resources in the Hexi Coridor, which are not exploitedSule River system.fully, has great potential by adopting advanced wa-This potential can be realized step by step through ter-saving technologies. This potential can be carriedcarrying out various water-saving measures, inprovingout step by step under the following conditions: devel-the ecological condition by constructing concentraled oping the field irrigation technologies and ensure. thetype of oases, combining utilization of surface water and stable water-saving measures, improving the ecologicalgroundwater. decreasing and restraining evaporation of agricul，and optimizingwater surface and evapotranspration of groundwater and allocat中国煤化工y also showed thatoptimizing allocation of water resources to agriculture,at presHC N M H Gwater resources inforestry, livestock breeding and ecological environment the Hexi Corridor mainly caused by the low efficiencyconstruction in three river systems.and waste of water use. According to the water-savingThe Balance Between Supply and Demand of Water Resources and the Water Saving Potential for Agriculture in Hexi Coridor 29degrees，such as plastic firm cover in wheat the wa-tween supply and demand of water resources and the potentialter-saving efficiency can gain 60%，then water-savingof its carrying capacity of agricultural development in the HexiCoridor[J]。Jounal of Natural Resources, 12(3): 225 -potential can be estimated for the Corridor agriculture.The potential of water resources can be increased byCAO Qian-zhuo, LI Fu-xing, 1991. Case Study on Rational De232. (in Chinese)56% of imigation area in the Shiyang River system.velopment and Uiliation of Water Sources in the Heihe River112% in the Heihe River system,197% in the SuleBasin[M]. Lanzhou: Gansu Science and Technology Pres.River system for agriculture when reaching water saving23 - 105. (in Chinese)degree of 50% according to long-term average of water I Fu-xing, YAO Jian-hua, 1998. Economic Derelopment andresources. So it is very important to popularize the ad-Environment Construction in the Hexi Comidorl M]. Beijing:vanced water-saving technologies, such as drip/ microChina Environment Science Press, 3- 38. (in Chinese)irrigation, irigation by infiltration and plastic firm coverLI Shou-qian, LAN Nian-jun, 1992. The Study on Water Re-quirement of Crop and Water-Sazing lmigation in Arid Regionsetc，80 as to enhance the efficiency of water resources|MI. Lanzhou; Gansu Science and Technology Press, 1 - 25.utilization. Therefore we can exploit the second water(in Chinese)source from saving water of agriculture in the Hexi WU Pule, FENG Hao, FAN Xing-ke et al, 2000. Inquire intoCorridor.some questions of water saving irgation[A]. The High-ly-fFficient Use of Water in Agriculture and the Protection ofREFERENCESSoil- Water Entironment[C]. Xi'an: Shaanxi Science andTechnology Press, 31 - 38. (in Chinese)CHEN Long-heng, QU Yao-gang et al. 1992. 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