multiple methods for calculating minimum ecological flux of the desiccated lower tarim river,...

ECOHYDROLOGYEcohydrol. (2012)Published online in Wiley Online Library(wileyonlinelibrary.com) DOI: 10.1002/eco.1337

Multiple methods for calculating minimum ecological flux ofthe desiccated Lower Tarim River, Western China

Ye Zhao-xia,1* Shen Yanjun2 and Chen Yapeng11 State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang,

China2 Lab of Hydrology and Agricultural Water Resources, Center for Agricultural Resources Research, Chinese Academy of Sciences, Shijiazhuang,

Heibei, China

*CEcoSciE-m

Co

ABSTRACT

We estimated the minimum ecological influx in the lower Tarim River via the wetted perimeter method using the curvaturetechnique. Calculations were based on river geomorphology data during the fifth and sixth ecological water conveyances. Resultsshowed that the minimum ecological influx of the three control sections of the river (Yinsu, Alagan, and Yiganbjima) were 2.85,3.76, and 1.76m3/s, which accounted for 9.7%, 14%, and 6.9% of the multi-year average annual discharges, respectively. Exceptfor the dry season, annual ecological water demand of the river was 0.79� 108m3, excluding evaporation and leakage. Multiplemethods were used to prove the rationality of the results. It is by using the Tennant method that the percentage of minimumecological influx accounting for multi-year average flux varied from 6.9% to 14% (average 10.2%), which is considered normalfor the maintenance of river habitat. It is by using the R2Cross method that the minimum ecological influx of the lower TarimRiver was 2.935m3/s. These calculation results mirror the actual situation and serve as the base of water-source distribution inlower Tarim River. Further research is required to validate and adjust the results according to long-term hydrographicobservations. Copyright © 2012 John Wiley & Sons, Ltd.

KEY WORDS minimum ecological flux; Tarim River; wetted perimeter; Tennant method; R2Cross method

Received 8 July 2011; Revised 7 February 2012; Accepted 23 September 2012

INTRODUCTION

With continuing exploitation of water resources andincreasing frequency of drought, serious environmentalissues, such as river blanking, lake desiccation, anddecreasing groundwater levels, have emerged in arid inlandriver basins to the detriment of local economies (Luo et al.,2005). Although ecological water demand (EWD) is animportant issue in water resource management, it is rarelyemphasized in research, especially for inland river basins ofwestern China. Eco-hydrology, a newly formed interdis-ciplinary field, has helped improve EWD studies fororganizations such as UNESCO/IHP (Zalewski et al.,1997; Zalewski, 2000). The calculation of EWD can clarifythe percentage of water demand consumed by people(Li et al., 2006), that constitutes the bases for understandingwater resource distribution and utilization.Tarim River, located in the south Xinjiang Uygur

Autonomous Region of western China, is the longest aridinland river in China. Human activities related to theexploitation of water resources during the past five decadeshave led to significant changes in its natural ecologicalprocesses, especially the lower reaches from the DaxihaiziReservoir to Taitema Lake between the Taklamakan andKuluke Deserts (Chen, 1999; Liu and Chen, 2002). Torestore the lower Tarim River ecosystem, a series of

orrespondence to: Ye Zhao-xia, State Key Laboratory of Desert and Oasislogy, Xinjiang Institute of Ecology and Geography, Chinese Academy ofences, 818 South Beijing Road, Urumqi 830011, Xinjiang, China.ail: [email protected]

pyright © 2012 John Wiley & Sons, Ltd.

environmental measures have been implemented, includingthe Ecological Water Conveyance Project. Numerousstudies have been conducted on the ecological effects(Chen et al., 2003a, 2003b, 2004a, 2010, 2012; Zhang andChen, 2004; Xu et al., 2007), rational water table (Chenet al., 2006a; Chen et al., 2008), and physiological varietyof vegetation in inland river basins (Chen et al., 2003a,2003b, 2004b, 2011). Although EWD research on ecologicalsecurity (Chen et al., 2006b; 2011) and vegetation (Ye et al.,2010) has been active, most studies have ignored the issue ofin-stream flow requirements. Generally, EWDof a river basincan be divided into demand inside and outside of theriver (Liu and Men, 2007). The aim of our study was tocalculate in-stream flow requirement.

Researchers started river flux research early in the 1940sand developed the hydrology-based Tennant method(Tennant, 1976) and hydraulics-based R2-Cross method(Mosely, 1982). Following the introduction of the RiverContinuum Concept, theories regarding in-stream flowrequirements have improved, and new methods have beendeveloped, including the holistic approach from Australia(Arthington et al., 1992) and the holistic building blockmethodology from South Africa, both of which are basedon the entire river ecosystem (King and Low, 1998).Recently, Liu et al. (2006) have put forward a number ofcalculation methods, with wetted perimeter deemed thesimplest on the basis of river geomorphology. This methodestablishes a wetted perimeter–flux relationship curve, onwhich the critical point is used to determine the minimumecological flux in a river. Most research in China has

https://www.researchgate.net/publication/245911682_Development_of_an_holistic_approach_for_assessing_environmental_flow_requirements_for_riverine_ecosy?el=1_x_8&enrichId=rgreq-998d86f2-1291-449f-91b7-3f5e16b21735&enrichSource=Y292ZXJQYWdlOzIzODg1NTg1NjtBUzoxMDIwMjQ1NTMxNzI5OTRAMTQwMTMzNTk1Nzc1Ng==

Y. ZHAO-XIA C. YA-NING AND L. WEI-HONG

mainly focused on the Yellow River, Liaohe River, andHaihe River (Shi and Wang, 2002; Wang et al., 2003;Jiang et al., 2004; Tang et al., 2004; Zheng et al., 2005; Suet al., 2006). Arid inland rivers have been neglected, andtherefore research on the in-stream flow requirements ofthe Tarim River is essential.The ecological flux of a river is the minimum flux that

can maintain system integrity and prevent an absence offlux. Its essential function is to maintain a river’s originalconformation and ensure its continuity. Rivers arefundamental aquatic ecosystems, which rely heavily onflux to maintain primary conditions; certainly, waterquality deteriorates if minimum ecological flux fails tomeet the critical needs of the river (Tang et al., 2004). Thein-stream flow requirement of a river is the amount of waterneeded for hydrophytic life-forms to survive, for theaquatic ecosystem to maintain stability, and for the river topreserve its original conformation (Ji et al., 2006). Flowrequirement and ecological flux are inextricably linked asthe cumulativeness of flux that influences total waterdemand. In addition, after the cross-section area of a river isdetermined, ecological velocity of flow can be calculated bythe minimum ecological flux. Therefore, the key to studies onin-stream flow requirements of rivers is the calculation of theminimum ecological flux of the river way.Minimum ecological flux can maintain the continuity

and geometrical shape of a river and assist hydrophytic life-forms adapt to adverse environments during low-waterseasons. Once flux is under minimum requirements, a riverway will face the risk of desiccation and will be unable toadjust (Su et al., 2006). Therefore, research on minimumecological flux is crucial for maintaining the integrity andfunction of a river and to ensure ecological safety.

MATERIALS AND METHODS

Study area

The Tarim River is a typical arid inland river supplied byheadstreams. The study area is located between theDaxihaizi Reservoir and the Taitema Lake in the lowerTarim River (39�380–41�450N, 85�420–89�170E) (Figure 1).The channel bed stretches from west to east on alluvial fansalong the Taklamakan and Kuluke Deserts. The region isone of the most arid zones in China, with an annual average

Figure 1. Distribution of the transects

Copyright © 2012 John Wiley & Sons, Ltd.

precipitation of less than 50mm and annual evaporationbetween 2500 and 3000mm.

With intensive human disturbance, especially thedevelopment of oasis agriculture, surface water at theQiala Hydrologic Station has been reduced from11.57� 108m3 in the 1950–1960s to only 2.7� 108m3

by the 1980–1990s. Construction of the DaxihaiziReservoir in 1972 disrupted much of the stream flow inthe Tarim River, which resulted in a total absence ofsurface water for a 321-km stretch and a significant drop ingroundwater levels at the river’s lower reaches.

Data and materials

The Ecological Water Conveyance Project encompassesBoston Lake to the lower reaches of the Tarim River. It wasinitiated by the Chinese and local Xinjiang Governments in2000, and there have been eight intermittent deliveries ofwater from Boston Lake to the lower reaches of the TarimRiver from 2000 to 2006. To monitor the changes ingroundwater during and after delivery, we established atotal of nine groundwater-monitoring transects along theQiwenkuer River, which supplies the water conveyances tothe lower Tarim River (Figure 1). These transects wereAkdun (A), Yahepu (B), Yinsu (C), Abudali (D), Kardayi(E), Tugmailai (F), Alagan (G), Yiganbjima (H), andKaogan (I), and were found downstream from theDaxihaizi Reservoir. Yinsu, Alagan, and Yiganbjima usedthe control transects and divided the river way into four parts.During the fifth and sixth water delivery, hydrographs andtachometers were equipped for monitoring water level, flux,velocity of flow, river width, depth, starting distance, andsection area.

Methods

Curvature technique of the wetted perimeter method.Wetted perimeter refers to the perimeter of a riverbed soakedby the water current as determined bywater cross-section. Thepolygon method is introduced in this research as it has higherprecision than the rectangle method.

P ¼Xni¼1

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffixi � xi � 1ð Þ2 þ yi � yi � 1ð Þ2

q(1)

in the lower reaches of Tarim River.

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Figure 2. Cross-sections of control transects of lower reaches.

MINIMUM ECOLOGICAL FLUX CALCULATING

where, xi and yi are the initial distance and altitude,respectively, and n is the number of subsections.The wetted perimeter is used to estimate minimum

ecological flux and requires sufficient geometrical cross-section data of the river way, which was provided by theEcological Water Conveyance Project. The relationshipbetween the wetted perimeter and discharge was analysed.According to the breakpoint on the fitting curve, therecommended minimum ecological flux value wasestimated. As a rule, the wetted perimeter rises along withthe accretion of flux. However, when the wetted perimeter isabove a certain critical value, rapid increase of flux can bringlittle change in wetted perimeter. Accordingly, the elementaryrequirements that support hydrophytic environments can besatisfied if the critical wetted perimeter is maintained.Ji et al. (2006) determined the relationship between

discharge and wetted perimeter according to the Chezy andManning formulas on different river way cross-sectionsand simulated different fitting curves. They determined thattriangle, U, and parabola shaped cross-sections accordedwith power functions, whereas trapezium and rectanglecross-sections conformed to logarithms.The data, measured by monitoring and undertaking field

surveys in the Yinsu, Alagan, and Yiganbjima transects,showed that Yiganbjima was triangular, whereas Yinsu andAlagan were transitions between triangle and trapezium(Figure 2). The Alagan section was also wider andshallower than the other two. On the basis of the researchby Ji et al. (2006), the Yiganbjima transect was fitted withthe power function model, whereas the others weresimulated by the logarithm model. The critical positionswere fixed on the curves.There are three ways to fix critical positions on the

curve of wetted perimeter-discharge, specifically ocularestimation method, slope technique, and curvaturetechnique (Gippel and Stewardson, 1998). Ocular esti-mation is not commonly used; the slope technique takesthe discharge at the point of the curve where the slopeequals 1 as the critical value, whereas the curvaturetechnique chooses the critical point by calculating themaximum curvature of the curve. Research by Liu et al.(2006) on the South–North Water Transfer Project provedthat the curvature technique is the most reliable methodby reforming the mathematical expression of minimumecological in-stream flow requirement for rivers withtriangle transects and symmetrical fluxes. In addition, thecurvature technique was valid for the first-stage construc-tion of the South–North Water Transfer Project, in whichdepth and width data from 35 transects in six rivers werecalculated. Therefore, the curvature method was adoptedin this paper.

Kcurve ¼�� d2P=dQ2� �

= 1þ dP=dQð Þ��2

h i32=

(2)

where P is the wetted perimeter and Q is the flux.The point of maximum curvature lies where the

derivative of the curvature via flux is zero, therebyallowing minimum ecological flux of a river to be reached.


Tennant method. The Tennant or Montana method is astandard non-field measurement method and an indirectmeans to validating the results of other methods.Recommended flux can be based on the predefinedpercentage of annual average flux. For instance, 10% ofannual average flux is considered necessary to maintain aviable river ecosystem, 30% of annual average flux isconsidered the minimum threshold to maintain a healthyriver ecosystem, and 60–100% of annual average flux isconsidered the natural level of a thriving river ecosystem.

R2Cross method. The R2Cross method was first proposedby Nehring (1979) and has been successfully utilized instudies such as the habitat water demand programmesimplemented by the Colorado Water Conservation Board.The R2Cross method is based on the Manning Equationand has been applied to estimate stream flow requirementsfor habitat protection in riffles based on minimum flowsthat meet or exceed criteria for average depth, percentageof bankfull wetted perimeter, and average water velocity(Table I) (Parker et al., 2004). These hydraulic criteria

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Table I. R2Cross criteria for four hydraulic parameters forprotection of aquatic habitat (Parker et al., 2004).

Stream topwidth (m)

Averagedepth (m)

Bankfull wettedperimeter (%)

Averagevelocity (m/s)

0.3–6.3 0.06 50 0.30486.3–12.3 0.06–0.12 50 0.304812.3–18.3 0.12–0.18 50–60 0.304818.3–30.5 0.18–0.3 ≧70 0.3048


variables were developed to quantify the amount of streamflow required for ‘preserving the natural environment to areasonable degree’ (Espegren, 1996).

Figure 3. Relationship between wetted perimeters and flux in differenttransects.

ANALYSIS AND RESULTS

Curvature technique of the wetted perimeter method forcalculating minimum ecological flux

For the Yinsu and Alagan transects, an exponential modelwas adopted to simulate the curve, and a power functionmodel was adopted in Yiganbjima. The coefficients ofdetermination were all over 0.5 (P< 0.01) (Figure 3), withthe Yiganbjima transect less than that in Yinsu and Alaganbecause (1) Yiganbjima was farther away from DaxihaiziReservoir and (2) the duration was shorter than that ofother transects, resulting in more limited data and unstableconfiguration of the river course. According to Equation (2)and the definition of the maximum point of curvature,minimum ecological flux of the Yinsu, Alagan, andYiganbjima transect was 2.85, 3.76, and 1.76 m3/s,respectively.The relationship between the wetted perimeter and flux

can be measured from data on geometrical sizes and fluxfrom multi-transects or single transects. Previous researchhas indicated that certain hydraulic characteristics such asriver depth and width, and velocity of flow have a simpleexponential relationship with flux (Leopold and Maddoek,1957), with the following equations

w ¼ aQb (3)

d ¼ cQf (4)

v ¼ kQm (5)

bþ f þ m � 1 (6)

a� c� k � 1 (7)

where, w is the river width, d is the average river depth, v isthe average velocity of flow, Q is the flux; and a, c, b, f, andm are constants.Compared with existing methods from other countries,

this method is practical for studies in China as it can copewith disadvantages such as greater measurement error,fewer transects, and non-reflection from yearly variation(Zheng et al., 2005).According to Equations (3), (4), and (5), the relationship

between flux and river width, average river depth, andaverage velocity of flow was simulated, with the results all


showing significance (P< 0.01) (Table II). The minimumecological flux was then imported into each equation tocalculate river width, average river depth, and averagevelocity of flow (Table III).

For rivers with a complex network of intertwiningchannels and tributaries, minimum ecological flux of lowerreaches is larger than that of upper reaches (Tang et al.,2004; Zheng et al., 2005). The Tarim River showed theopposite, however, as minimum ecological flux of its lowerreaches was less than that of its upper reaches, despite theriver having no tributaries. Similarly, the minimumecological flux in the upper section of the lower reacheswas larger than that in the lower section of the lowerreaches. However, the Alagan section showed someabnormality as its minimum ecological flux was the largestamong the three sections. This result is likely due to thefact that two water conveyance rivers (Qiwenkuer Riverand Tarim River) converged in the Alagan section(Figure 1), which was also wider and received pressurefrom two rivers. Because the river in the study area hasbeen dried for more than 30 years and has suffered serious

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Table II. Relationship between flux and river width, average river depth, and average velocity of flow in the three control transects oflower reaches.

Transects River width and flux Average river depth and flux Average velocity of flow and flux

Yinsu w= 16.977Q0.0623 d= 0.6101Q0.3562 v= 0.0964Q0.5821

R2 = 0.6588 R2 = 0.8938 R2 = 0.9285Alagan w= 10.393Q0.3643 d= 0.5836Q0.2104 v= 0.1649Q0.4285

R2 = 0.9498 R2 = 0.4862 R2 = 0.8862Yiganbjima w= 15.751Q0.1639 d= 0.8104Q0.3669 v= 0.0441Q0.7154

R2 = 0.5451 R2 = 0.7777 R2 = 0.8576

Table III. Minimum ecological flux, river width, average river depth, and average velocity of flow.

Transects Min. ecological flux (m3/s) River width (m) Average river depth (m) Ave. velocity of flow (m/s)

Yinsu 2.85 18.12 0.89 0.18Alagan 3.76 16.84 0.77 0.29Yiganbjima 1.76 17.32 1.00 0.05


environmental deterioration, its highest minimum ecologic-al flux value in the three transects (3.76m3/s) was actuallyless than the minimum ecological flux required to preventdesiccation of the entire lower reaches of the river.

Tennant method for calculating minimum ecological flux

Minimum ecological flux in the lower Tarim River wascalculated strictly by mathematical methodology, but multi-method verification was required to avoid the errors that arisefrom singlemethods. Zhong et al. (2006) discussed numerousmethods for calculating the ecological flux of river ways, withthe Tennant method deemed the best for verification.Because of the long-term lack of surface water, there

were no historical data on the annual average flux in thelower reaches of the river. However, the annual averageflux for the Yinsu, Alagan, and Yiganbjima transects wascalculated indirectly by hydraulic data obtained from theQiala Hydrologic Station, located 150 km from theDaxihaizi Reservoir. For the Tennant method, over10 years of continuous annual average flux data andminimal human activity are required. Hao et al. (2006)showed that main stream runoff was not influenced byhuman activities until Peacock River water was importedinto the Tarim River in 1970. Therefore, it is by using theannual average fluxes from 1957 to 1970 that the multi-year average runoff volume was 11.57� 108m3. Assumingthe volume had symmetrical distribution, the multi-yearaverage flux could be calculated. According to the datafrom the seven ecological water conveyances and the

Table IV. Percentage of minimum ecological

Reach

Length of reach (km)Recharge volume of unit river length (108m3/km)Computational multi-year average runoff (m3)Computational multi-year average flux (m3/s)Minimum ecological flux (m3/s)Minimum ecological flux accounting for multi-year average flux (%


distance between transects, water consumption of the riverlength in the lower reaches was obtained. In addition, themulti-year average runoff of the three transects wasdetermined to be 8.59� 108m3 (Table IV).

The percentage of minimum ecological flux accountingfor multi-year average flux varied from 6.9% to 14%(the average is 10.2%). Using the Tennant method, weconsidered 10% the minimum flux necessary to maintainthe ecosystem. This means that the stream flow require-ment should be 0.86� 108m3.

R2Cross method calculation of minimum ecological flux

The R2Cross method is a traditional empiric methodderived from the research of the aquatic ecosystem of therivers in the Colorado State, USA, and the criteria forhydraulic parameters in the method apply to the research ofthe coldwater fish species in high-altitude regions of theUSA. From Daxihaizi Reservoir to Kaogan in the lowerreaches of the Tarim River is 324-km long, with an averagegradient ratio of 2%. The velocity of flow was low, and themeasured data showed that the velocity of flow varied littlewith flux increase. Therefore, the requirements for velocityof flow were lower than the criteria listed in Table I.

The key to the R2Cross method is correct cross-sectionchoice in the studied reach, specifically at relatively wide andshallow shoals of the river. In Tarim River, however, only flatand straight riverbeds without evident shoals were found inthe lower reaches. As such, we selected two sections at Yinsuand Alagan in a relatively straight portion of the river way to

flux accounting for multi-year average flux.

Qiala–Yinsu Yinsu–Alagan Alagan–Yiganbjima

210 128 960.0111 0.0061 0.00419.24 8.46 8.0829.31 26.82 25.632.85 3.76 1.76

) 9.7 14.0 6.9

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Figure 4. Relationship between flux and width, average depth, bankfull wetted perimeter, and velocity of flow in low flux conditions (a: Yinsu transect;b: Alagan transect).


calculate various hydraulic parameters and obtain recom-mended values for habitat water demand. As the sectionschosen lacked shoals, the average depth of the river was higherthan the criteria listed in Table I. The bankfull wetted perimeterwas measured, and qualitative analysis was conducted todetermine velocity of flow and average river depth.Figure 4 shows that hydraulic parameters increased as

flux increased. When the flux in Yinsu was 3.12m3/s, thevariation rates for river width (19m), wetted perimeter(83.5%), and average depth (1.03m) were largest, with thevelocity of flow measuring 0.16m/s. When the flux inAlagan was 2.75m3/s, the variation rates for river width(18.5m) and wetted perimeter (63.2%) were largest, withaverage river depth and velocity of flow measuring 0.48mand 0.31m/s, respectively. The double-section R2Crossmethod was used to average the results for these twosections, so that when Q = 2.935m3/s, river width was18.75m, wetted perimeter was 73.35%, average river depthwas 0.755m, and the velocity of flow was 0.235m/s.Comparison between the results from the R2Cross methodand the criteria for hydraulic parameters showed that wettedperimeter conformed to the criteria, average velocity of flowwas slightly smaller than the criteria but consistent in thepractical situation, and average river depth was not onlyhigher than the criteria but also consistent in the practicalsituation. Therefore, 2.935m3/s was taken as the minimumecological flux in the lower reaches of the Tarim River.We assumed constant water flow in the river from July to

the following February (243 days in total), and thecalculated minimum annual runoff at any lower reachsection of the Tarim River was 0.62� 108m3.

CONCLUSIONS AND DISCUSSION

We applied the curvature technique of the wetted perimetermethod to calculate minimum ecological flux and deter-mine annual in-stream flow requirements. The Tarim Riveris a seasonal river, and a water year includes three periods:flood period (from July to September), level period (fromOctober to next February), and low-water period (fromMarch to June). If the lower reaches of the Tarim River isnot drying up, it will still follow the same hydrological law.Stream flow requirement was 0.79� 108m3, which wasreally only an estimate for implementing emergency waterconveyance projects, not actual water demand. Through


analysis of previous water conveyances, we determined thatthe majority of water discharged from Daxihaizi Reservoirsupplied the groundwater of riversides, although some surfacewater was lost through evaporation. After seven waterdischarges, the total consumption rate (the percentage thatwater consumption accounted for discharges) of DaxihaiziReservoir to the Yinsu, Alagan, and Yiganbjima sections was42.5%, 79.5%, and 86.7%, respectively. Because riverblanking for more than 30 years has led to a significant fallin groundwater levels, river way leakage has had a muchgreater impact than it would have otherwise. With the step bystep introduction of the ecological water conveyance project,however, groundwater levels have increased continuouslyand, in the end, leakage will drop off and move tohomeostasis. During the initial stage of returning ground-water, therefore, water demand will vary with time.

Many-year average river width was calculated by introdu-cing many-year average flux into the flux and river widthmodel. The corresponding rate was the percentage of riverwidth accounting for average river width. As a result, thecorresponding percentages of the three transects were 86%,49%, and 64%, respectively, and the average was 66%. Theseresults accordwith similar other research (Zheng et al., 2005).

We selected three methods to calculate minimumecological flux and minimum EWD in the dry river ofthe lower reaches of the Tarim River. Minimum EWD was0.86� 108m3, which was determined using the Tennantmethod based on the maximum value principle. Our resultsshowed that the river had to maintain 0.86� 108m3 ofwater for itself in addition to the water demand byvegetation in the lower reaches. Of course, this calculatedresult requires further testing and adjustment based onlong-term hydrological and hydraulic observations.

Because of a lack in aquatic life information, modelsbased on the relationships between hydrographic river data,and ecosystem functions and species variation could not beestablished and therefore requires further investigation. Inaddition, as ecosystem health is related to water quality,temperature, and velocity of flow, research on therelationships between ecosystem health and river hydrauliccharacteristics must be studied to more accurately ascertainEWD, particularly for rivers that experience seasonal flow.

In view of the present situation, taking superfluous waterfrom Boston Lake during high water periods for waterconveyance is risky if water quantity of the lake

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diminishes. Such an occurrence increases the likelihood ofthe lower Tarim River blanking again. According to thedata from the Tiemenguan Reservoir, the Kaidu River (thesource flow of Boston Lake) blanked three times in 2007,which led to a 0.58-m fall in the lake and a 6� 108m3

decrease of the entering water. To solve the problem oflimited water in the lower reaches, upper and middle reachesof the TarimRiver must be restored to increase water quantityof the Qiala Hydrologic Station. Steps for meeting thedownstream water demand target should accord with theupstream and midstream renovation project.

ACKNOWLEDGEMENTS

This workwas supported by theWest Light Foundation of theChinese Academy of Sciences (XBBS200907), NationalNatural Science Foundation of China (91025025) and theKnowledge Innovation Project of the Chinese Academy ofSciences (KZCX2-YW-Q10-3-4). We would like to thankthose volunteers who assisted us with fieldwork.

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multiple methods for calculating minimum ecological flux of the desiccated lower tarim river,...

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