Utilization of water resources, ecological balance and land desertification in the Tarim Basin, Xinj Utilization of water resources, ecological balance and land desertification in the Tarim Basin, Xinj

Utilization of water resources, ecological balance and land desertification in the Tarim Basin, Xinj

  • 期刊名字:中国科学D辑
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  • 论文作者:樊自立,夏训诚,沈玉凌,艾里西尔·库尔班,王让会,李生宇,马
  • 作者单位:Xinjiang Institute of Ecology and Geography,Xinjiang Remote Sensing Center
  • 更新时间:2020-07-08
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Vol. 45 Supp.SCIENCE IN CHINA (Series D)December 2002Utilization of water resources, ecological balance and landdesertification in the Tarim Basin, XinjiangFAN Zili (樊自立)", XIA Xuncheng (夏训诚)', SHEN Yuling (沈玉凌)',Alishir Kurban' (艾里西尔●库尔班), WANG Ranghui (王让会)',LI Shengyu (李生宇)' & MA Yingjun (马映军}1. Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;2. Xinjiang Remote Sensing Center, Urumqi 830011, ChinaReceived September 15, 2002Abstract Because of the human exploitation and tiliation of water resources in the Tarim Basin,the water resources consumption has changed from mainly natural ecosystem to artificial oasisecosystem, and the environment has changed correspondingly. The basic changes are: desertification and oasis development coexist, both "the human being advance and the desert retreat" and"the desert advance and the human being retreat" coexist, but the ltter is dominant. In the upperreaches, water volume drawing to irigated agricultural areas has increased, artificial oases havebeen enlarging and moving from the deltas in the lower reaches of many rivers to the piedmontplains. In the middle and lower reaches of the Tarim River, the stream flow has decreased, old 0a-ses have declined, natural vegetations have been degenerating, deserification has been enlarging,and the environment has deteriorated. The transition regions, which consist of forestlands, grass-lands and waters between the desert and the oases, have been decreasing continuously, theirshelter function to the oases has been weakened, and the desert is threatening the oases seri-ously.Key words: Tarim Basin, water resources, ecological balance, desertification.The Tarim Basin is an extremely arid land in the world. Its natural environment is character-ized by the basin surrounded by high mountains and the oases in the basin surrounded by the de-sert, the rivers rising in the alpine zone, and water being the key factor in the desert oasis ecosys-tem. Therefore, it is important to prevent and control deserification.1 Evolution trend of the ecological environment caused by human exploitation and utiliza-tion of water resourcesIn the Tarim Basin, there would be no agriculture without irigation. Since the beginning ofdevelopment of plant farm, the artificial oases have been developed by undertaking continuouslynew water conservancy projects and diverting water for irrigation, the ecological balance has beenchanged and rebuilt. In the processes, the change trends of the ecological environment caused by .exploitation and uilization of water resources are: (1) The natural rivers are replaced by the artifi-cial canals. The total length of the canals of dfferent levels in south Xinjiang is about 164500 km,and the annual volume of water diverted into the irrigated areas is 25.81 billions m', the artificial中国煤化工MYHCNMHGSupp.WATER RESOURCES. ECOLOGICAL BALANCE & LAND DESERTIFICATION .03imigation networks have formed, and many rivers have been replaced by the artificial canals in theplain, the steam flow in the middle and lower reaches is reduced and even cut off. (2) The naturallakes are replaced by the artificial reservoirs. In order to regulate the runoff and solve the problemof shortage of water in spring season, there are 184 reservoirs of dfferent size have been built, thetotal storage capacity is up to 3.21 bllion m', which exceeds the total storage capacity (1.34 bil-lion m) of the Lop Nur Lake and the Taitema Lake. Streams cannot reach the lower reaches be-cause of the reservoirs in the upper reaches, and the lakes in the lower reaches are dried up. (3)The natural soils are replaced by the artificial cultivated soils. The human beings change thephysical, chemical and biological properties of the natural soils by irigation, drainage, cultivation,fertilizing, and growing crops. For example, the peculiar irigation-deposited soil is formedthrough a long-term irmigation by the stream water with high silt content. (4) The natural vegeta-tions are replaced by the artificially planted plants. After reclamation, the natural desert vegeta-tions dominated by the desert species are replaced by artificial vegetations which include the ce-real, industrial and oil-bearing crops, green manure plants, herbage, melons, fruit trees, vegetablesand various artificial forests. The biomass of the artificial plants is ten or even hundred timeshigher than that of natural plants, however, their reversal resistance and adaptability to the envi-ronment are much lower than that of natural plants. (5) The natural ecosystem is replaced by theartificial oasis ecosystem. Through the human exploitation and utilization of water resources andagricultural development, the peculiar artificial oasis ecosystem has formed, which is supportedby the artificial water systems and coupled by the ecosystem of farmlands, artificial forests,breeding and aquiculture, rural and urban residential regions. Thus, some desert regions havechanged into the artificial oases that provide the bases for human existence and development inthe arid land.2 The relationship among the utilization of water resources, ecological balance anddesertification during the different periodsExploitation and utilization of water resources are historical processes, the distribution of theoases, ecological balance and desertification situation are different in the different historical peri-ods because of the different ways and degrees of exploitation and utilization. The history and thepresent situation of exploitation and utilization of water resources in the Tarim Basin can be clas-sified into the following periods:2.1 The period of natural river systemsAbout before the 6th century, the population was about 20000 in the Tarim Basin, more than20 small kingdoms, such as Loulan, Niya and Karadun, are ditributed on the deltas in the lowerreaches of the rivers' (fig. 1). Productive forces were very low, most of the production tools weremade by wood,“the farmers do not know how to use cattle to plouh"12. The irigation canalswere built simply, farming was undertaken wherever streams flowed to. The artificial imigatedoases were not formed yet in the plains at that time, a water volume of about 38.4 billions m'中国煤化工MYHCNMHG104SCIENCE IN CHINA (Series D)Vol. 45flowed into the Tarim Basin, about 90% were consumed by the natural vegetations, evaporation,and flowed into the lakes in the lower reaches. The area of the Lop Nur Lake was over 5000 km'.The vegetation consisted of phragmites communis, Tamarix chinensis, Popular diversifolia, Pen-nisetum flaccidum, etc., grew luxuriantly, and the nomads lived wherever there was water andgrass in Shanshan Kingdom in the lower reaches of the Tarim River and the Kongque River".Although the area of sand desert in the Tarim Basin was over 0.3 million km2 during the period,the desert formed under the impacts of climate and the natural changes of the river systems.,KuqAKorlaTarim River: River 1[ AlarTikanitLop NurLakeAlaganTarim BasinRuoqiangTaklimakan DesentShacheiemo三目OldoasisPaleo-oasis |Fig. 1. The sketch map of oases distributed in the Tarim Basin!"l. Paleo-oasis: 1. Loulan; 2. Miran; 3. Washixia; 4, AncientQiemo; 5, Tieying; 6, Dawuzilieke; 7. Andear; 8. Niya; 9, Kaladun: 10, Majianlike; I1, Dandanwulike; 12. Hihasi; I3, AncientDamagou: 14. Wurentati: I5, Kanaqin: 16, Mailikeawati; 17. Yuetegan: 18, Akesiper: 19. Rewake: 20. Mazatag: 21, Zanggui; 22,Ancient Pistan: 23. Layipu: 24, Daman City: 25, Tuhushalat: 26. Kalayuergun: 27. Dawangkumu; 28. Tongzibasi: 29,Qiongqing: 30, Heitaqig; 3I, Yushijati: 32, Pjak; 33, Heitaiker, 34, Zhuoguote; 35, Yeyungou; 36, Yingpan.2.2 The period of semi-natural and semi-artificial river systemsDuring the long period from the 6th century to 1949, the population increased from 2200to 3 millions, the iron tools and the cattle plowing techniques were used universally, and peopledammed rivers, dug large canals and constructed the irigation systems day by day'3!. The abilityof local residents to regulate streams and watercourses strengthened, the stream water could bediverted from the debouchment of the rivers, the oases were enlarged towards the piedmont allu-vial-diluvial plains (fig. 1). In the old oases, the cultivated area was 0.6 millions hm2, and about 15一19 billions m' of water was consumed by irigation agriculture, which occupied 40%- -50% ofthe surface water resources in the basin. The increase of the volume of water diverted into thepiedmont artificial oases made the stream water flowing to the lower reaches decrease and led tothe decline and fall of the ancient oases in the lower reaches, and the primitive natural ecologicalbalance was destroyed. The ancient Loulan Kingdom became a“rugged and barrn"l41 area withYardan landforms in the 6th century; the Qiemo and Jingjue kingdoms had been uninhabited中国煤化工MYHCNMHGSupp.WATER RESOURCES. ECOLOGICAL BALANCE & LAND DESERTIFICATION10in the 7th century!S!. The drainage nets in the lower reaches of the Tarim River and theKongque River disintegrated, the vegetations degenerated, desertification developed in theregion, and the area with the“dense forests of Popular diversifolia"l evolved as the“vastsand desert"?.“Stream was separated day by day and the great might of the Tarim River waslostr"18l, and the area of the Lop Nur Lake was reduced to 1900 km2 in the 1830s9!. Except theimpact of natural factors, the desertification during this period was superposed by human im-pact, and the area of desertified land was 19700 km2 and was enlarged at a speed of 13.0 km2per yearl0!.2.3 The period of artificially controlled river systemsFrom 1949 to the present in the Tarim Basin, the population increases from 3 millions to 9millions, and the cultivated area is enlarged to 1.333 millions hm'. The surface water is controlledcompletely except the flood season by building diversion, storage water conservancy projects.Moreover, many plain reservoirs are built by using the depressions in the marginal zones of allu-vial fans and in the alluvial plains, thus most of the newly enlarged oases irigated by the reser-voirs are distributed in the peripheries or the marginal zones of the old oases (fig.1). The annualwater volume diverted into the imigated areas is about 25- 30 billions m', which occupies 70%-80% of the total annual runoff volume in the basin, this exceeds the generally recognized standardthat the diverted volume of surface water cannot exceed 50% of the total, whereas the waterconsumption for the ecological balance is reduced to less than 20%- -30%. For example, thefeeding stream water to the mainstream of the Tarim River is continuously reduced due to theincrease of the volume of diverted water from its source streams, the annual water volume of themainstream was reduced from 5 billions m' in the 1950s to 4.202 billions m' in the 1990s at Aralin the upper reaches, from 1.35 bllions m' to 0.27 bilion m' at Kara in the lower reaches, whichmade the stream flow downstream from Daxihaizi along a river section of 320 km in length cut offfor more than 20 years, the Lop Nur Lake and the Taitema Lake dry up. The groundwater table inthe lower reaches is lowered from2- 4 mto 8- -12 m, the vegetations withered, the area of de-sertification enlarged, the proportion of the area of desertified land occupied 63.5% in the 1950s,increased to 85.5% in the early 1980s and to 94.8% in the middle 1990s. The water resources andthe ecological environment are strongly disturbed by human activities, and the area of de-sertification is enlarged to 8600 km2 and increased at a speed of 170 km2 per year9!.3 Laws of the ecological environment change caused by exploitation and utilization of wa-ter resourcesHuman exploitation and utilization of water resources have changed the water resourcesconsumption dominated by the natural ecosystems to that dominated by the artificial oasis eco-system, correspondingly the temporal and spatial distribution of water resources as well as theecological environment has been changed. The basic laws are: (1) Desertification and oasis de-中国煤化工MYHCNMHG06SCIENCE IN CHINA (Series D)Vol. 45velopment coexist, both“the human advance but the desert retreat" and“the desert advance andthe human retreat" coexist, but the latter is dominant. (2) The volume of diverted water is in-creased in the piedmont regions, the artificial oases move from the deltas in the lower reaches to-wards the debouchure of the rivers and their areas are enlarged, the ecological environment is im-proved there. (3) The stream flow was decreased in the middle and lower reaches, the decline andfall of the ancient oases occured, the natural vegetations degenerated, desertification developed,and the ecological environment deteriorated. (4) The volume of water diverted into the artificialoases is increased, which made the groundwater table rise in the oases and the secondary soilsalinization occurs and develops, in the regions out of the oases, the groundwater table is loweredand the area of the deserification is enlarged. (5) The transition regions between the desert and theoases are reduced, their shelter function to the oases is weakened, and the deserts are threateningthe oases seriously.Exploitation of water resources also causes the spatial change of landscape, which can besummarized as“two enlargements and four reductions". The“two enlargements" mean that boththe artificial oases and the deserts are enlarged simultaneously. The cultivated area was 16000 km',the area of the artificial oases was 34800 km2 ", the area of the desertified land was 24200 km2and the potential desertified land was 12700 km2 during the historical periodll2. According to thedata from the mapping with homo-phase remote sensing information sources, on the map of Aralin the upper reaches of the Tarim River, the cultivated area was enlarged from 22870.6 hm2 in1959 to 27691.7 hm2 in 1996, increased by 14821.1 hm2 (able 1). On the map of Aragan in thelower reaches the area of desertified land was enlarged from 137120 hm2 in 1959 to 149420 hm2in 1996, increased by 12307 hm2 (able 2)"3), in the Tiekanlik irmigated area in the lower reaches,the are a of abandoned cultivated and desertified land was 16600 hm2 due to the shortage of water.Table | Land use situation in Aral region in the upper reaches of the Tarim River (Unit: hm)Type1959198319921996Cultivated land22870.6 .29524.133792.837691.7Forestlands38690.3Grasslands49238.146330042078.6Saline and alkaline lands4119.04340.14267.4267.5Deserts32123.931314.131071.130967.5Table2 Desertification stuation in Aragan region in the lower reaches of the Tarim River (Unit: :hm)YearTotalSeriously desertifiedIntensively desertified Moderately deserified Slightly deserified_ land -land137120957839342405871983 14602049763965845495411131992 148720532241450438013720014942055541184004379131697The“four reductions" mean that the area of natural waters, forestlands, grasslands and habi-tats of wild animals between the deserts and the oases are reduced. (1) The redued areas of the中国煤化工MYHCNMHGWATER RESOURCES. ECOLOGICAL BALANCE & LAND DESERTIFICATION107lakes and the wetlands are 2100 km2 and 660000 hm2 respectively, the river courses in the lowerreaches of most rivers have dried up. (2) The area of the forestlands of Popular diversifolia hasreduced from 528600 hm2 before 1960 to 280500 hm2 at present, the area of the destroyed shrub-bery of Tamarix chinensis is 14000 km'. (3) The area of the degenerated grasslands in the main-stream area of the Tarim River is 455800 hm', and the area of grasslands is reduced by 1.633 mil-lions hm' in the whole Tarim Basin. (4) Xinjiang tigers inhabited in the forests, shrubbery and thegrasslands along the rivers were extinct for half a century, the alive wild camels are less than 1000due to the shortage of drinking water, and the Aspiorhychus laticeps, a local species in the TarimBasin, becomes as a species on the brink of extinction because of the change of ecosystems.4 Countermeasures for rational utilization of water resources and desertification controlDesertification is mainly caused by irational utilization of water resources, that is to say thewater consumption is too much in the upper reaches for agricultural production but less in thelower reaches for the ecosystems. Therefore, to control the desertification, we must regulate theutiliaion of water resources from two aspects. (1) The infficient and extensive utilization ofwater resources should be changed towards the rational one in the irigated regions in the upperreaches. Lining the canals and water-economizing irmigation should be mainly undertaken, the ef-fective utiliation ratio of water resources should be increased. (2) For the economic development,the increase of the volume of diverted surface water should be turned to appropriately exploitinggroundwater. The volume of exploitable groundwater calculated by an exploitable cofficient of0.6 is 8 bllions m' in the basin, and at present a volume of 0.2- 0.3 bllionis m' is exploited only.If groundwater in a volume of 3- -4 bllions m' is exploited and utilized, the water consumptionfor the social and economic development in the future will be ensured, and the economized sur-face water will be able to flow to the lower reaches. (3) The construction stress of water conser-vancy projects should be shifted from the plains to the mountainous regions. It is suggested to .build the large-size mountain reservoirs in the upper reaches of the large rivers, such as atDashixia of the Aksu River, Xiabandi of the Yarkant River, Bulongkou of the Gez River andShanhentuohai of the Kaidu River. The reservoirs will have the functions of multi-year runoffregulation, flood control and irigation. The evaporation and seepage will be reduced comparedwith the plain reservoirs, the proportion of water consumption for the ecosystems will be in-creased, and the generated electricity will be used for pumping groundwater. (4) The water con-sumption for the ecological environment will be ensured. The depth of groundwater table shouldbe maintained at2- 4 m in the areas covered by natural vegetations. It is estimated that it needs awater volume of about 13 bilions m' to maintain the existing natural vegetations in the Tarim Ba-ReferencesI. Ban Gu, Westerm Han Dynasty. The Books in the Former Han: The Commentaries of the Westerm Regions, Vol. 2. Fascicle中国煤化工MYHCNMHG108SCIENCE IN CHINA (Series D)Vol. 45No.69 (in Chinese). about 100A.D.. Yang Xuanzhi. Norhern Wei Dynasly. Travels of Jiaian. Luoyang, Vol. 5 (in Chinese), about 530A.D.3. Li Daoyuan, Norhern Wei Dynasty. The Commentaries of Water Resources: The Part of the Rivers Vol, 2 (in Chinese),from the end of 5th centary to the beginning of 6th century.. Fa Xian. Norhermn Wei Dynasty. Travels in the Buddha Kingdoms (in Chinese), about 420 A.D.5. Xuan Zang. Bian Ji. Tang Dynasly. Travels in the Western Regions Tang Dynasly, Vol. 12 (in Chinese), 640 A.D.6. Xu Song. The Commentaries of waters in the Western Regions: The Lop Nur Lake, Vol. 2 (in Chinese).1823 A.D.7. Tao Baoian, Travels in Xinmao Year (1891). Fascicle No. 6 (in Chinese), 1891.8. Wang Shunan. Yuan Dahua, Map Records of Xinjiang: The water course, Fascicle No. 70, (in Chinese), 1910.9. Fan Zili, Formation and evolution of the oases in the Tarim Basin, Journal of Geography (in Chinese), 1993, 485): 421-427.10. Fan Zili. Research on the Impats of L.and Uilization to Ecology and Environment in Xinjiang and the CorrespondenceCountermeasures (in Chinese), Beiing: Meteorological Press. 1996, 159- -172.11. Li Lixian, The biomass in Xinjiang, in The Land crrying Capacity Xinjang (ed. Shi Yulin) (in Chinese), Bejing: SciencePress, 1989, 54- 63; 89- 91.12. Zhu Zhenda, Desetification and Its Control in China (in Chinese). Bejing: Science Pess. 1989.9- -17.13. Wang Ranghui, Fan Zili, Study on land deserifcation in the Aragan region at the lower reaches of Tarim River with remote sensing and GIS. Journal of Remote Sensing (in Chinese), 1998, 2(2): 137-142.中国煤化工MYHCNMHG

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