Evaluation on the Essentiality Grades of Water Conserving in Tibet, China

Vol. 10 No.4 2005 628-634WUJNSWuhan University Journal of Natural SciencesArticle ID: 1007-1202(2005)04-0628 -07Evaluation on the Essentiality Grades ofWater Conserving in Tibet, China0 Introduction口HE Xiao-rong12，ZHONG Xiang-hao't,FAN Jian-rong' , FAN Ji-hui12，The ecological essentiality of the water resources conser-LI Hui-xia3ving of regional ecosystem lies in the degrees of total re-1. Institute of Mountain Hazards and Environment,gion depending on the water resources of evaluated areas.Chinese Academy of Sciences, Chengdu 610041， Sichuan,China;Firstly, we must make certain that whether or not the regions2. Graduated School of Chinese Academy of Sciences,have the function of water resources conserving according tcBejing 100039，China;3. Department of Resource and Environment， Foshanthe status of vegetation. And then, we appraise on the func-University, Foshan 528000, Guangdong, Chinational essentiality of the water resources conserving and makethe different grades standard, from which we analyze on sev-Abstract: Taking Tibet as an example, the functional es-eral aspects such as the abilities of water supply， water re-sentiality degrees of water resources conserving of regionsquirements and the demands for preventing natural hazardswere discussed in this paper. At first, based on the status ofand so on,regional vegetation, whether the region has the function ofwater conserving was made certain. And then, according toOn the basis of the practical situation and characters ofthe impacted objects of water resources conserving，taking in-Tibet，the regional location of the areas with the abilities ofto account the demands for water and regional supply capaci-water resources conserving were marked off according to theties of water and the requirement of environmental protection,requirements of water resources conserving of impacted objectsthe functional grades of regional water resources conserving ofTibet were evaluated in this paper.and the regional vegetation actuality. In accordance with theKey words: Tibet; function of water resources conserving;capacities of water supply and the requirements of water re-evaluationsources of impacted objects， the evaluations of essentialityCLC number: P 966; P 964grades of the water resources conserving were put forward. .1 Index System of the Essentiality Evalu-ation of Water Resources ConservingReceived date: 2004-12-28Foundation item: Supported by the *973' Project of Ministry of Sci-ence and Technology of China (2003CB415202)， the Research of theThe approach of the esentialty evaluation of water re-Alarm System in Advance on Eco envionmental Fragility and Eecolog-sources conserving in a rooinn is that_ based on the analyses ofical Security Strategy in Tibe(2004CCA( )3600) and Ecological Fourdation Division Research of Tibet Autonomous Region (2001-2002)regional中国煤化工ation on the essentialityBiography: HE Xiao -rong (1970-)， female, Ph. D candidate, re-of water resMYHIC N M H Grried out separately ac-search direction: environmental degradation and ecosystem rebuilding.E mail: hxr69707@ yahoo, com. cncording to the requirements of water consumption in producingt To whom correspondence should be addressed. E mail: xhzhong@and living of local regions, the requirements of moisture re-imde. ac. cn628Wuhan University Joumal of Natural Sciences Vol.10 No.4 205plenishment in lakes and wetlands, and the demands forOn the basis of the characters of Tibet, owing to thepreventing natural hazards. The regional precipitation in-big evaporation, it is not enough only taking the precipita-dicates the status of water supply. The water require-tion into account for evaluation. The evaporation is also anments can be ascertained by the level of cities and towns,important factor. Actually, using the types of moisture tothe degrees of wetness of the farmlands and grassland.replace the index of precipitation has good effects on evalu-Natural hazards should be considered by its kinds. Difation. Taking the impacted object as standard, the evalua-ferent kinds of hazards have different demands for watertion results of the essentiality grades on functional areas ofresources conserving.water resources conserving are shown in Table 1.Table 1 The essentiality grades of water resources conserving of the eco-system in TibetEvaluation indexUnimportantImportantModerately importantExtremely importantsemi -moistureTypes of wet and aridmoisture zonesemi-arid z2onearid zonezoneWater consumption incities and towns ofcity of provincial capitalcounty towncities and townsdistrict capital locatedlocateWater consumption offarmlands in the moisturefarmlands in thefarmlands in zonefarmlandzone and aridzone of semi- aridof semi- moistureW ater consumption ofgrassland in thegrassland in zonegrassland in semi- aridgrassland .zoneand aridlakes and wetlands in ar-Protetion of importantid zone， semi-arid anclakes and wetlandssemi- moistureGrades valueconserving in the head sites of water consumption of cities2 Evaluations on the Essentiality ofand towns should consider the impacts of such factors asWater Resources Conserving for Dif-the scale grades of cities and towns and the quantity offerent Impacted Objectswater consumption during the producing and living.Therefore，we can work out the essentiality grades, tak-2.1Evaluation on the Essentiality of Water Re-ing the demands for water as dominant factor and thesources Conserving of the Water Head Site of theprecipitation and vegetation as assistant factors. TheWater Consumption in Cities and Townsmain cities and towns of Tibet include the Lhasa city ofThe cities and towns in Tibet, with the smaller scaleprovincial capital and the cities and towns of district cap-than those in other provinces, have not big requirementsital such as Rikaze city， Bayi town, Cahngdu town,of water consumption. However, except the southeastNaqu town, Shiquanhe town and Zedang town. Thepart, most districts of Tibet is characterized of the smallevaluation results of essentiality grades of water resourcesprecipitation with the uneven seasonal distribution, sig-conserving function in the water head sites of main citiesnificant dry and wet seasons. Precipitations distributeand towns are shown in Table 2.mostly in rainy season, which often lead to water shorta-The evaluations of functional essentiality of waterges in dry seasons. At the same time, the precipitation isresources conserving on the water head sites of Countyfrequently in the form of solid, which aggravates the se-town in Tibet are decided in terms of the types of wet andrious water shortages-. On the other hand, with the re-arid.①The county towns in the moisture zone andgional economic development， the scale of cities andsemi-moisture characterized by abundant precipitation andtowns are extending gradually-J and the requirements ofenough moisture, which can supply enough water for the :water consumption are increasing. So the functions oneeds中国煤化rions of water resoureswater resources conserving in the water head sites of wa-conserve small influence on the:tYHCNMH Gter consumption of cities and towns have great influencecounty tuwr. bu Loouiiuiailly grade of water resourceson the inhabitant’s producing and living activities.conserving in those areas are unimportant. ②There areThe evaluation on essentiality of water resourcesmore county towns in the semi-arid zone than in otherWuhan Uniyergi数gnal of Natural Sciences Vol.10 No.4 2005629zones and most of them distribute along the Brahmaputrascale and mean populations of between 2000 to 3000 per-and its branches. The main water head sites are in thesons in each town, the needs of water of towns are rathermiddle and upper reaches of the Brahmaputra and itssmall. However, owing to such factors as the small pre-branches. Owing to the small scale of county towns, thecipitation with the uneven seasonal distribution, and sig-requirements of water is small too. Thus the essentialitynificant dry and wet seasons, the function of water re-grade of water resources conserving in those areas are un-sources conserving of the water head sites has vital effectsimportant. Those areas are the unimportant regions foron the residence' s daily producing and living activity.the water demands of county towns with their impacts onThe essentiality grades is moderately important. The re-the producing of agriculture and livestock.③Because ofsults of evaluations of water resources conserving onthe small number of the county towns, extremely smallcounty towns are shown in Table 3.Table 2 The evaluation results of essentiality grades ofwater resources conserving function in the main water head sites of main cities and townsEssentialityAnnualCities andTotalPopulationprecipitationTypes of wetWater headDominantgrades oftownsarea/ km2/10and aridsitesvegetationwater/ mmconservingthe upper reachesalpine scrubLhasa city49.640200-500semi- aridof Lhasa riverAlpinextremelyimportantand its branchesmeadowthe upper reaches needle and broadmoderatelyBayi town8.6semi- moistureof Niyang riverleaved forest,scrub and steppeChangdu town_ 4. 50.6470Angqu riverunimportantNaqu town3.81.1406Naqu riveralpine scrub extremely importantthe brahmaputra .and the smallsubalpine steppe,Rikaze city8. 929.1420branches besidedefoliate scrubof townthe middle andsubalpineShiquanhe town 1. 130. 6200aridupper reaches ofdesert steppeextremely importantShiquanbe riverZedang town31. 7410Xionqu riverTable 3 The evaluation results of essentiality grades ofwater resources conserving in the main water head sites of county townsNumbers andPopula-Precipita- Main waterStatus ofscale of countygrades of waterand droughttiontion/ mmhead sitesArid zonelow number2 000-<200Kongque River, Xiangquanalpine steppe, .small scale3 000River, the riverhead ofalpine desertGeer River and the aroundsteppeareas of Bangong LakeSemi-arid zonehigh number<8 000200- 400 the brahmaputra and itsalpine steppebranchesand meadowSemi- moisture< <10000400-600 the riverhead of Lujiangalpine scrub andzoneRiver, Jinshajiang Riverand Lancangjiang River,Lhasa River an中国煤化工:TYHCNMHGMoisture zone<15 000 > 600The brahmaputrm wwadits branchesHE Xiao rong et al : Evaluation on the Esentialityt Grades of ..2.2 Evaluation on the Essentiality of Water Re-tural and livestock production in the Qignhai- Tibet plat-sources Conserving of the Main Lakes and Wetlandseau. The function of water resources conserving in thoseMost lakes and wetlands in Tibet distribute in theregions has vital impacts on inhabitant’s surviving.semi moisture zone，semi-arid and arid zonel-3), in whichThe evaluations on functional essentiality of waterthe big acreage lakes are beneficial in solving the contra-resources conserving in lakes and wetlands of Tibet werediction of abundant moisture in summertime with the lackcarried out in terms of the types of wetness and arid, asof water in winter and spring. So the zones of lakes arewell as the status of vegetation and the impacted objects.the areas with frequent human activities and the agricul-The results of evaluations are shown in Table 4.Table 4 The evaluation results of essentiality grades of water resoures conserving in lakes and wetlandsTypes of wetStatus ofEssentialitygradesMain lakesImpacted objectsand aridvegetationwater conservingthe small grouped lakes in Bangong Subalpineinhabitant's producing and liv-extremelyArid z2onelake and its neighbouring areasdeserting activities, biodiversity main-importantsteppetainingMapangyong lake- lang lake,Alpineinhabitant' s producing and livPeigu lake, Duoqing lake, Yang-Semi aridzhuoyong lake Pupoyong lake,taining，protecting of regionalzoneNamu lake, Selin lake, Zharinan-meadowenvironmentmu lakeBagong lake, Ranwu lake,Alpine scrubthe lack of water in winter andSemi- moistureYigong lake, Ben lakeand meadowspring. producing and living ac-tivities2.3 Essentiality Evaluation of Water Resourcesculture of Tibet. The farmlands distribute in the middle-Conserving in the Water Head Sites of Farmland Irri-southern valley and basin, especially taking on the dis-gationtributed character of strip shape along the Brahmapu-In the moisture zone, owing to the centralized distri-tra-4l. Due to the wide ranges of farmlands, the require-bution of the alp and canyon， the farmlands distributement for water is rather great, especially in spring sea-separately and have small production scale. So the watersons. Because the spring flood usually occurs in spring-resources are abundant for agriculture production, whichtime, the water of spring flood can be reasonably used formeans that the impacts of the function of regional wateragricultural rrigation according to its evolution rules. Butconserving on agriculture production are rather small. Atthe precipitation of semi-arid ranges from 200 to 499the same time, most of farmlands distribute on the ter-mm, which is less than the quantity of the water needs ofraces along two sides of rivers-4.51 where there are enoughagriculture. And there exists the significant dry and wetwater resources for irrigation. Therefore, most part ofseasons, thus the water head has great impact on irriga-those zones are the areas with the small influences of wa-tion and the essentiality grade is extremely important.ter resources conserving on agricultural irrigation.The areas with the extremely important grade are at theIn the semi- moisture zone, the farmlands distributeriver head of Brahmaputra and its branches together within the eastern part of the three rivers ( Lujiang river ，the alpine zone of the Brahmaputra. The dominant vege-Jinshajiang river and Nancangjiang river) basin and alongtation of alpine steppe is beneficial in adjusting the uneventwo sides of valley located in the middle reaches of theprecipitation in season and conserving the water of theBrahmaputra-4]. Those areas have enough watermelted snows and ices.resources for irrigation, and the agricultural productions中国煤化工. farmlands distribute intake place nearly at the same time with the rainfall.the terr:the Bangong Lake withTherefore the impact of water resources is rather small onTHCNMHGof moisture. Thegvwu wusmtonsthe agriculture and the essentiality grade is unimportant.farmland scale is rather small and has low requirementsIn the semi arid zone, there is the yield base of agri-for water. So that the water conserving has small impactsWuhan Uniyergi数gnal of Natural Sciences Vol.10 No.4 2005631on agricultural production and the essentiality grade isacreage grasslands distribute mostly along lakes and riv-unimportant.ers. The areas of the wide ranges inner lakes and the high2.4 Essentiality Evaluation of Water Resourcescoverage vegetation around lakes have extremely impor-Conserving in the Water Head Sites of Grassland Ir-tant impacts of water conserving on livestock production.rigationIn those zones, the functions of water conserving serve asMost grasslands of Tibet distribute in the Naqu andthe basic guarantees for inhabitation' s living and produ-Ali district(6], namely in the northern part of the semi-cing activities.moisture zone and semi-arid and all of the arid zone.Owing to the small precipitations and great needs ofIn the northern part of the semir moisture zone namelywater, the essentiality grade of water resources conser-in the eastern part of Naqu district, the precipitation rangesving is extremely important.between 200 nm to 499 mm that can provide enough waterIn the arid zone， the grasslands distribute mainlyfor agriculture and livestock. However, in the low rainfallalong lakes and rivers and have the characters of wideseasons, the functions of water resources conserving haveranges distributing. The water resources conserving irvital impacts on the agriculture and livestock.the areas of water sources have some impacts on the agri-With the wide ranges of grasslands, big scale ofcultural production and the essentiality grade of water re-livestock production and great supporting capacities ofsources conserving is moderately important.livestock, those areas are the important production bases2.5 Essentiality Evaluation of Water Resourcesof livestock in Tibet. The alpine scrub and meadow is theConserving on the Areas of Being Propitious to Eco-dominant vegetation of grasslands and has good functionsenvironment Protectedof water conserving that can provide good conditions forThe main eco-environmental problem in Tibet is thethe growth of grass, enhancement of the supporting ca-water and soil erosion. According to the characters ofpacities of livestock and guarantees of the drink water fornatural exogenetic forces-7J ，mostly water forces andinhabitant and livestock.wind forces, the evaluation on essentiality grades of wa-Therefore, the functions of water conserving of al-ter and soil conserving is carried out in terms of the typespine scrub and meadow have moderately important imof wet and dry.pacts on the regional economic development and the sta-The details of results are shown in Table 5.bility of ecosystems. The essentiality grade is moderatelyimportant, and the essentiality grade of alpine scrub is3 Analyses on the Integrated Evalua-extremely important.tion of Water Resources ConservingThe northern part of semi-arid zone，namely thewestern and northern part of Naqu district and easternBased on the above evaluation results of water re-part of Ali district， have smaller rainfall than that ofsources conserving and reference to the distributing mapssemi-moisture. The dominant vegetation is alpine steppeof water system and vegetation system-81，the first step isthat has strong functions of water conserving. The bigto make the maps of essentiality grades of water resourcesTable 5 The essentiality evaluation of the functions of water resources conserving on the eco-environmentEssentialityTypes of wet Main eco-environmentalStatus ofImpacted objectsgrades ofand aridproblemsvegetationwater conservingArid zoneSerious of water and soil losssubalpinemaintaining of the biodiversity, extremely( wind erosion)desert steppeprotecting of regional environmentimportantSemi-arid zone water and soil loss caused byalpine steppemaintaining the biodiversity， pro-moderatelywind erosion and water erosionalpine meadowteting of regional environmentSemi- moisture degradation of grasslandalpine scrub and protecting of regional vegetationzonemeadow中国煤化工alpine needle andCHCNMHGde-Moisture zonewater erosion, hazards of flood,broad leaved for-culeieu opecus anlandslide and mud and rock flowest alpine scrub reducing the possibilities of moun-and meadowtain hazards632HE Xiao rong et al : Evaluation on the Esentialityt Grades of ...conserving impacted by each single factor. And then,the number j essentiality grades, a; refers to the weigh-using ARC/INFO software，weight stack the maps ofted value of the number i index, X; is the evaluated val-single factor.ue of the number i index and the number j grades. Ac-The formula to calculate the index of integratedcording to the index of integrated evaluation on essentiali-evaluation on essentiality grades of water resources con-ty grades of water resources conserving, the grades areserving is as follows:divided into such four levels as unimportant， important,D= 2aX,moderately important and extremely important. At last, .Where D is the essentiality grades index of regionalbased on the distribution of the essentiality grades indexwater resources conserving for all of the impacted ob-of regional water resources conserving, make the map ofjects，i stands for the number i evaluation index, j foressentiality evaluation of water resources conserving ofTibet，which is shown in Fig. 1.1: The exlremely important areas of waterresources conservingII: The middlinglyimportant areas of waterII: The important arcas of water resourcesconservingIV: The unimportant areas of water resourcesIITibeti I[m1Fig.1 The evaluation on essentiality grades ofwater resources conserving in TibetIn the moisture zone: with big precipitations and itssmall influence of water resources conserving on local ar-even allocation in seasons， relatively small number ofeas and the vital impacts on the lower reaches of three :populations-91，small acreages of farmlands and the lttlerivers. The essentiality grade of those areas is moderatelyrequirements of water-10， the essentiality grade of re-important. The Naqu district, located in the southerngional water resources conserving impacted on local areaspart of the semi-moisture zone and characterized by com-is unimportant. Those zones are the water head sites ofparatively less precipitations than that in the eastern part,several rivers in India. Therefore, considering the influ-is the main livestock production base which has the greatences of the regional water resources conserving on thosescale of livestock and great requirements of water. At therivers, the essentiality grade of regional water resourcesseam time, the dominant vegetation of alpine scrub andconserving raises to the moderately important.meadow in those areas has strong functions of water con-In the semi-moisture zone: The three river basinserving中国煤化ility grade of water redistricts, located in the eastern part of the semir moisturesourcesdistricts is extremely:THC NMH G'zone and characterized by the big precipitations, highimportan anlu"ulal UI apjiie ladow scrub districts isdrainage density, small scale of agricultural and livestockmoderately important.production and the lttle requirements of water， haveIn the semi arid zone: because of the centralized dis-Wuhan Uniyergi数gnal of Natural Sciences Vol.10 No.4 2005633tributing of cities and towns in this zone, where distrib-ute the merely two organic city of Lhasa city and RikazeReferencescity, there appear great requirements of water consump-tion. But its precipitations are rather small and allocate[1] The Integrated Survey Team of the Qinghai- Tibet Plateau ofChinese Academy of Sciences. The Climate of Tibet. Bei-unevenly in seasons. Thus the essentiality grade of waterjing: Science Press, 1984. 18-67(Ch).resources conserving in water head sites is extremely im-[2] Niu Feng ru. Focus of Western Great Development on Citesportant. The water heads sites distribute mainly alongnd Torwns. Beijing: Social Science Literature Publishingthe two sides of upper reaches of Lhasa River and itsCompany, 2002 ,81 :297-299.306(Ch).branches, and the headwaters of the Brahmaputra and its[3] The Integrated Survey Team of the Qinghair Tibet Plateau ofChinese Academy of Sciences. The Rirvers and Lakes in Ti-two sides. The southern parts of those areas are also im-bet. Bejing: Science Press, 1984. 51-110 (Ch).portant agricultural production bases in Tibet, in which[4] The Bureau of Land Management in Tibet. 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So the essentiality grade of those areas[8] The Integrated Survey Team of the Qinghai Tibet Plateau ofChinese Aceademy of Sciences. The Vegetation in Tibet. Bei-is extremely important too.In the arid zone: With very small precipitations, the[9] The Statistics Bureau of Tibet Autonomic Region. Statisticslittle requirements of water and poor vegetation condi-Anmual of Tibet Autonomic Region in 2002. Bejing: Statis-tics Publishing Company of China. 2003.tions, except for a few rivers, lakes and wetlands, most[10] Han Yur-sheng， Zhang Ming tao. Integrated Programmingarea belong to unimportant regions of essentiality of wa-of Resources Exploitation and Economic Development ofter resources conserving. The extremely important areasNiyanghe Basin in Tibet. Beiing: Science Press, 1993: 73-of that are Baangong Lake basin and the alpine desert74 (Ch).steppe areas in Shiquanhe basin.中国煤化工MHCNMHG634HE Xiao rong et al : Evaluation on the Esentialit Grades of ..