The influence of natural and human factors in the shrinkingof the Ebinur Lake, Xinjiang, China, during the 1972–2013period

Fei Zhang & Tashpolat Tiyip & Verner Carl Johnson & Hsiang-te Kung & Jian-li Ding &

Qian Sun & Mei Zhou & Ardak Kelimu & Ilyas Nurmuhammat & Ngai Weng Chan

Received: 30 June 2014 /Accepted: 28 October 2014# Springer International Publishing Switzerland 2014

Abstract The Ebinur Lake is a closed inland lake lo-catedwithin the arid region of the XinjiangAutonomousRegion in the northwestern part of China, near theKazakhstan border. The shrinkage of the lake area isbelieved to be caused by ecological environmental de-terioration and has become an important restrainingfactor for the social development of the local population.Of all the lakes in the Xinjiang Autonomous Region, theEbinur Lake is the most severely impacted water body.The lake has undergone change in size naturally for overthousands of years due to natural causes. However, theauthors observed the dramatic changes in the freshwaterresources of this region from the aerial images from1972 to 2013. Thus, this paper traces and analyzes thechange in the Ebinur Lake surface area in the past41 years. A set of six satellite images acquired between

1972 and 2013 was employed to map the change in thesurface area of the Ebinur Lake using the water indexapproach. The authors applied the traditional normal-ized difference water index (NDWI) and the modifiednormalized difference water index (MNDWI) to quan-tify the change in the water body area of the Ebinur Lakeduring the study period. The results indicate that the lakearea has experienced a dramatic decrease of 31.4% from1972 to 2013. The paper also examines the naturalprocesses and human activities that may have contrib-uted to the decrease in the lake area. The results showthat the decrease in total lake area appears to coincidewith periods of rapid land reclamation in the study area.Moreover, the uncontrolled land reclamation activities,such as irrigation, can increase the sedimentation in theEbinur Lake thereby reducing the lake size. Reductionof the lake area has a negative ecological impact on theenvironment and on human life and property. The lakearea is the most important factor to ensure the environ-ment of the watershed and the key index to measure theenvironment balance.

Keywords Human impacts . Ebinur Lake . Remotesensing . Geographic information system

Introduction

Lakes are not only valuable economic resources forhuman beings but also play an important role in regionalecological and environmental issues, such as hydrolog-ical cycle and natural flood control function (Beeton

Environ Monit Assess (2015) 187:4128DOI 10.1007/s10661-014-4128-4

F. Zhang (*) : T. Tiyip : J.<l. Ding :Q. Sun :M. Zhou :A. Kelimu : I. NurmuhammatCollege of Resources and Environment Science/KeyLaboratory of Oasis Ecology, Xinjiang University,Urumqi 830046 Xinjiang, Chinae-mail: zhangfei3s@163.com

V. C. JohnsonDepartment of Physical and Environmental Sciences,Colorado Mesa University,Grand Junction, CO 81501, USA

H.<t. KungDepartment of Earth Sciences, The University of Memphis,Memphis, TN 38152, USA

N. W. ChanSchool of Humanities, Universiti Sains Malaysia,11800 George Town, Penang, Malaysia

2002; Bronmark and Hansson 2002; Williamson et al.2009). However, in recent years, many lakes around theworld are changing rapidly mainly caused by the cli-matic changes and human activities (Coe and Foley2001; Schindler 2001; Hampton et al. 2008; Arizteguiet al. 2010; Cui et al. 2013). In China, Fang et al. (2005)used five decades of historical land cover informationand remote sensing data to estimate changes in the sizeand number of the lakes in the Jianghan Plain from the1950s to 1998 and explore the causes of these changesand their ecological consequences. Yun et al. (2007)have studied the historical changes of the well-knownfreshwater lakes in the Jianghan Plain and DongtingLake area in the middle reaches of the Yangtze Riverand witnessed the shrinkage lakes that do havesignificant negative impacts on the hydrology of theareas. Teh et al. (2006) have modeled lakes as floodretention ponds and shown that the human activityencroachment can significantly reduce the size of thelakes. Moreover, the environmental changes of lakescan greatly affect the available freshwater resources,lead to the consequential evolution of regional ecologi-cal environment, and have a critical influence factor forregional sustainable development. Determination ofcauses and consequences of the changes of lakes is thusthe precondition of solutions for their protection andrestoration, which is one of the main challenges in thepresent research.

The impacts of climatic change and human activitiesare considered to be the most important factors for therecent lake changes in world (Schindler 2001; Coe andFoley 2001; Bozelli et al. 2009; Russell et al. 2009;Waters et al. 2009; Ariztegui et al. 2010; Li et al.2014). The effects of human activity on lakes in a givenregion always have different local features and dependon many factors, such as geomorphic characteristics,hydrological cycling, and the types of local humanactivities including water conservancy project, agricul-tural irrigation, and domestic and industrial water usage.Analyzing both the regional lake changes and the im-pacts caused by human activities in recent years is a veryimportant factor for water resource management anddecision-making of the local government (Gupta andAsher 1998; Webb et al. 1999). In China, Cai et al.(2001) have shown that encroachment of human activ-ities has shrunk the sizes of lakes in the Jianghan Plain,resulting in a loss of natural flood control functions.

The delineation of the lake outlined from the remotesensing images is an ongoing research from the

availability of the satellite data in different spatial, tem-poral, and spectral resolutions and the diversity of imageprocessing tools and techniques. Satellite remote sens-ing can be appropriated for water body mapping andmonitoring in the developing countries where funds arelimited and information on lake areas, such as surround-ing land uses and lake area losses over time, are notavailable. Generally, the near-infrared (NIR) and themiddle-infrared (MIR) bands are high potential methodsfor detecting water bodies (Lillesand et al. 1994); there-fore, these two bands are used in lake detection andmonitoring. Beyond classical digitization of the waterbody’s boundaries, there are other techniques used todelineate the peripheries of a lake area. Image classifi-cation, principal component analysis (PCA), tasseledcap (TC) transformation, normalized difference waterindex (NDWI), and analysis of digital elevation models(DEM) are examples. An unsupervised classificationtechnique was applied to a series of Landsat imagesbetween 1973 and 2003 to explore changes in theManzala Lagoon area in Egypt (Ahmed et al. 2009).Guirguis et al. (1996) applied a standardized and a non-standardized principal component analysis to highlightchanges that occurred in the Burullus Lagoon usingmultispectral scanner (MSS) images covering the pe-riods 1983, 1985, and 1991. They observed that thestandardized PCA could emphasize the changes thatarose at this lagoon effectively. Ouma and Tateishi(2006) utilized the wetness component of the TC trans-formation compiled with water indices to map theboundaries of five African lakes in Kenya. EI-Asmarand Hereher (2011) were the first to introduce the waterindex approach for mapping the surface area change inthe coastal lakes of Egypt. They concluded that waterindices are much accurate for mapping shallow andturbid coastal lagoons.

The NDWI was introduced by McFeeters (1996) todelineate the surface water body depending on the nor-malized relationship between the reflection in the greenand the NIR portions of the spectrum. This index wasapplied successfully using Landsat data to mark out thechange in the surface area of Lake Manzala, Egypt (EI-Asmar and Hereher 2011). Xu (2006) substituted thereflectance in the near infrared by the reflectance in theMIR and suggested a modified NDWI termed as themodified normalized difference water index (MNDWI),and he observed that the MNDWI is more accurate indelineating water body boundary than the NDWI be-cause the former could eliminate the noise pixels

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representing the urban landscape occurring in the back-ground of wetlands. Kanwar et al. (2014) extractedwater features mixed with vegetation using NDWI andMNDWI.

The Ebinur Lake is located within the lowest eleva-tion of the Junggar Basin in the Xinjiang Province, anarid region in northwest China. It is also the largest saltlake in the Xinjiang Province. The lake is shallow withan average depth of only 1.3 m, and the area is verysensitive to the incoming water flows. As a result, thelake area always changes in size, likely from the extremeweather effects. The causes can be from heavy precipi-tation to dry seasons and strong sand–dust storms suchas the Alashankou, a famous desert wind storm with amaximum wind speed of up to 55 m/s. Usually, thesand–dust storms have their origin at the northwesternpart of the Ebinur Lake region where an average of164 days annually has strong winds at Beaufort 8 orhigher according to the wind scale, developed by Wuand Lin (2004). The Ebinur Lake is also one of theplaces in northwest China with the most serious sand–dust storms during the periods of the 1970s and 1980s(Zhou and Lei 2005). In our study region, the EbinurLake landscape photos are show in Fig. 1

The main objectives of the present study are (1) toestimate the surface area change in the Ebinur Lake overthe past four decades from Landsat satellite imagesusing water indices, (2) to explore the causes of thechange in the lake area, and (3) to offer a scientificbaseline in the Ebinur Lake region for future develop-ment management.

Materials and methods

Study area

The Ebinur Lake region (43° 38′ to 45° 52′ N and 79°53′ to 85° 02′ E) (Fig. 2) is located in the northwestern

part of the Xinjiang Province, just west of Boertalavalley, south of the Jinghe proluvial fan, and east ofthe Gobi Desert zone of the lower part of the KuitunRiver. The total area of the study area is 50,621 km2. It issurrounded by mountains to the north, west, and south.The mountainous area is 24,317 km2 and the plain areais 26,304 km2 (Wang et al. 2014a). The Ebinur Lake is aclosed saline lake with the water salinity from 80 to120 g/l; sodium sulfates and chlorides predominate inthe composition of dissolved salts (Fan and Zhang1992). The altitude of the lake is about 190 m. Itsaverage depth is only 1.4 m and the maximum depth isabout 4 m. In the Middle Holocene (about 5 ka BP), itwas a freshwater lake of about 3000 km2 in area and40 m in depth. The water was supplied from heavyprecipitation and abundant runoff. In the Late Holocene,the climate changed becomingmore arid and the surfacerunoff reduced; the lake area began to shrink. At thebeginning of the twentieth century, the area of the lakewas about 1300 km2. Since the early 1950s, the con-sumption of surface water for domestic use and irriga-tion has increased from 0.409 to 2.137×109 m3. Thedischarge of the rivers flowing into the lake has reducedand the desiccation of the surrounded area accelerated(Yang et al. 1996). At present time (late September2013), the area of the lake is only about 420 km2 asseen in the satellite image. Thus, the area of the dry lakebottom has reached 880 km2. The surface from the waterevaporation represents a vast bare solonchak with a highamount of salts (more than 40 % in the upper 2 cm and10–30 % in the lower layer of 2–5 cm) made up ofpredominantly sodium sulfates and chlorides(Abuduwaili and Mu 2006).

The climate of the area is temperate and arid. Themountain areas to the northwest of the study area aremostly oasis–desert systems, and the climate is mainlytemperate and arid with the mean annual precipitation of100 to 200 mm and the annual potential evaporation of1500 to 2000 mm. Maximum precipitation falls in

Fig. 1 Landscape photos of theEbinur Lake (photographed byFei Zhang)

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summer. In winter, the snow cover is shallow usuallyfrom 10 to 25 cm annually and persists up to lateFebruary or early March. The mean July temperatureis +27 °C; the mean January temperature is −17 °C.Strong winds are typical of this region. The number ofdays with the wind velocity above 8 m/s averages164 days per year (Mu et al. 2002).

Satellite data

Six satellite images are used in this study. Table 1 showsthe sensor type, resolution, and date of image acquisi-tion. The MSS image includes four bands in the blue,green, red, and near-infrared portions of the spectrum.The TM, ETM+, and OLI_TIRS images have additionalspectral bands in the middle and thermal infrared por-tions. All satellite images cover a ground area of 185 by185 km. Also, all the images have a minimum cloudcover.

Image processing

ENVI 5.0 and ArcGIS software were used to processand visualize satellite data in the present study. Thesatellite images were originally rectified to the UniversalTransverse Mercator (UTM) projection. The imageswere acquired in different seasons; thus, it was crucialto make an atmospheric correction and radiometric nor-malization to all images in order to eliminate effects ofdust, haze, and smoke as well as the solar angle varia-tions. Atmospheric correction was carried out to allimages by subtracting the minimum pixel value fromthe pixel matrix of each image (dark object subtraction)(Chavez 1996). The dark object was chosen to representthe clear deep water of the Ebinur Lake. As the solarangles are different in all images, it was crucial tonormalize these angle variations as if they all have beenacquired in the same season, i.e., summer. Thus, all theimages were subjected to radiometric normalization

Fig. 2 Location map of the study area

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taking into account the earth–sun distance, the solarelevation angle, and the dark object (minimum pixeldigital number). The radiometric correction was appliedusing the COST Model in ENVI 5.0 producing normal-ized images of reflectance values and ready for subse-quent processing.

Method of water body information extraction

In this paper, the authors used the NDWI and MNDWIto extract water body information. The NDWI isexpressed as follows (McFeeters 1996; Wang et al.2014b):

NDWI ¼ Green−NIRGreenþ NIR

ð1Þ

where Green is a green band such as TM band 2 andNIR is a near-infrared band such as TM band 4. Thisindex is designed to (1) maximize reflectance of waterby using green wavelengths, (2) minimize the low re-flectance of NIR by water features, and (3) take advan-tage of the high reflectance of NIR by vegetation andsoil features. As a result, water features have positivevalues and thus are enhanced, while vegetation and soilusually have 0 or negative values and therefore aresuppressed (McFeeters 1996). However, the applicationof the NDWI in water regions with a built-up landbackground does not achieve its goal as expected. Theextracted water information in those regions was oftenmixed with built-up land noise. This means that manybuilt-up land features also have positive values in theNDWI image. As a result, the computation of the NDWIalso produces a positive value for built-up land just asfor water. This is why the enhanced water presence inthe NDWI image is often mixed with built-up landnoise. However, a detailed examination of the signaturesof the figure reveals that the average digital number ofTM band 5, representing middle infrared (MIR)

radiation, is much greater than that of TM band 2 (greenband). Therefore, if a MIR band is used instead of theNIR band in the NDWI, the built-up land should havenegative values. Based on this assumption, the NDWI ismodified by substituting the MIR band for the NIRband. The MNDWI can be expressed as follows (Tebbset al. 2013):

MNDWI ¼ Green−MIR

GreenþMIRð2Þ

where MIR is a middle-infrared band such as TM band5. The computation of the MNDWI will produce threeresults: (1) water will have greater positive values thanin the NDWI as it absorbs more MIR light than NIRlight, (2) built-up land will have negative values asmentioned above, and (3) soil and vegetation will stillhave negative values as soil reflectsMIR light more thanNIR light (Jensen 2004) and the vegetation reflects MIRlight still more than green light. Consequently, com-pared with the NDWI, the contrast between water andbuilt-up land of the MNDWI will be considerably en-larged owing to increasing values of water feature anddecreasing values of built-up land from positive down tonegative. The greater enhancement of water in theMNDWI image will result in more accurate extractionof open water features as the built-up land, soil, andvegetation all have negative values and thus is notablysuppressed and even removed.

Because the MSS image lacks a MIR band, only theNDWI was applied using the Modeler Function inENVI. The resultant NDWI images highlight waterbodies present in the study area. This index ranges from−1 to +1 with water bodies of high values (close to +1).As TM, ETM+, and OLI_TIRS five images have spec-tral bands within the visible, near-, and middle-infraredspectra, thus, the MNDWI was applied using the Mod-eler Function in ENVI in order to eliminate any noisepixels (Xu 2006). The output MNDWI images which

Table 1 Satellite data used in the present study

Number Sensor_ID Path/row Acquisition date Resolution (m)

1 MSS 157/29,158/29 September 21, 1972 and September 25, 1972 60

2 TM 145/29,146/29 September 25, 1998 and September 2, 1998 30

3 ETM+ 145/29,146/29 September 28, 2002 and September 21, 2002 30

4 TM 145/29,146/29 September 18, 2007 and September 11, 2007 30

5 TM 145/29,146/29 September 13, 2011 and September 6, 2011 30

6 OLI_TIRS 145/29,146/29 August 26, 2013 and September 2, 2013 30

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range from −1 to +1 reveal the lake water in the images.Few authors (EI-Asmar et al. 2013; Wang and Yu 2014)reported that water indices are efficient to highlightturbid water bodies, which have submerged plants.The threshold was calculated in each NDWI andMNDWI map. The number of pixels above the thresh-old value was counted together to represent the waterbody. Finally, the surface area of lake was thencalculated.

Dynamic degree of the lake area

To determine the change rate of the lake area in differentstudy periods and to assess the influence of the westerndevelopment on the changing trend and speed of thelake area in the study area, the single lake area dynamicdegree was adopted. The single lake area indicator isused to analyze the change in the lake area in a particularperiod. It can be derived as follows (Zhao et al. 2013):

k ¼ Ub−Ua

Ua� 1

T� 100% ð3Þ

where K is the dynamic indicator for the lake area, Ua

and Ub are the areas of the lake area at the start date andat the end date, and T is the timescale underconsideration.

Gravity center transfer model

Temporal trends of the lake area can be depicted bythe gravity center transfer model. The equations forcalculating the center of gravity are given as follows(Wang et al. 2000; Zhang et al. 2013; Duan et al.2014): The movement of spatial distribution of thelake area was defined as the difference center ofgravity in different periods. This application of thegravity center allowed us to quantify the direction anddistance of change by representing the shifts as vec-tors linking the gravity center from different periods.

X t ¼X

i¼1

N

Cti � X ið Þ.X

i¼1

N

Cti ð4Þ

Y t ¼X

i¼1

N

Cti � Y ið Þ.X

i¼1

N

Cti ð5Þ

where Xt and Yt are the latitude and longitude coordi-nates of the gravity center of the lake in year t, respec-tively; Cti is the area of the lake in region i in year t; and

Xi and Yi are the latitude and longitude coordinates of thegravity center in region i, respectively. Comparing thegravity center at the start date and at the end date of themonitoring period, the temporal trends of the lake areacould be traced (Zhang et al. 2006). The technical flow-chart of this research is given in Fig. 3.

Results and discussion

Change in lake surface area

In this paper, the authors adopted the NDWI to extractwater body information in 1972, 2007, 2011, and 2013images. They also used the MNDWI to extract waterbody information in 1998 and 2002 images. As shownin Fig. 4, the water body areas have changed at theEbinur Lake region in each of the 6 years of images.Most of lake water body has shrunk mainly from thesiltation within the lake. Drying at the northern part ofthe lake is also observed in the raw images. Farmland,forestland, and unutilized land (including salinity land,gobi, desert, and sandy land) showed a lower indexvalue and are considered non-water body. The thresholdvalue of water as obtained from the NDWI image of1972 is 0.45, of 2007 is 0.33, of 2011 is 0.31, and of2013 is 0.13. On the other hand, the threshold values ofwater as obtained from the MNDWI are 0.41 and 0.45for the years 1998 and 2002, respectively. This largedifference in the threshold values between the NDWIand the MNDWI is attributed to the optical properties ofthe surface water in terms of its relationship with theelectromagnetic radiation. The near-infrared radiation isgenerally less absorbed by the water body than themiddle-infrared band at the time where the green bandabsorption is constant, giving this difference in thethreshold values.

The change in the Ebinur Lake surface area (Fig. 5)reveals a drastic shrinking in the past 41 years. In 1972,the Ebinur Lake surface area was 598.43 km2 and in1998 it was 536.78 km2. The Ebinur Lake, however, hadexpanded to 842.84 km2 in 2002, but continued toshrink to 455.81 km2 in 2007 and 450.48 km2 in 2011.The Ebinur Lake area approached to 410.58 km2 in2013, a total loss of 187.85 km2 (31.4 %) between1972 and 2013.

As seen in Table 2, during the 1972–1998 pe-riod, the lake area decreased by 61.65 km2 and thedynamic degree is −0.40 %; during the 1998–

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2002, the lake area increased by 306.06 km2 andthe dynamic degree is 14.25 %; during the 2002–2007, the lake area decreased by 387.03 km2 andthe dynamic degree is −9.18 %; during the 2007–2011, the lake area decreased by 5.33 km2 and thedynamic degree is −0.29 %; and during the 2011–2013, the lake area decreased by 39.90 km2 andthe dynamic degree is −4.43 %. It was indicatedthat the trend of the lake area shows the retreat→expand→ retreat processes from 1972 to 2013. Ac-cording to Fig. 5, the overall area of the lake hasshrunk from 1972 to 2013, but expanded only in2002. According to the weather record, 2002 wasa wet year and the precipitation was twice theannual average; thus, much water was flowing intothe lake. The runoff rate into the lake had in-creased to 12.11×108 m3, and therefore, the sizeof the lake area increased. The authors used theoverlay function of ArcGIS in order to delineatethe lake outlines with different years and analyzedthe lake area status efficiently. Figure 6 shows thelake dries mainly in the northwestern part of theEbinur Lake, except in 2002.

To further explore the shifts of spatial distribution ofthe lake area in the study area, the authors conducted themovements of the gravity center of the lake (see Fig. 7).During 1972 to 2013, the gravity center of the lake

surface area had occurred in varying degrees of migra-tion. In general, in 41 years, the gravity center of the lakehas a southeast migration trend, and the offset distancewas 0.98 km. The migration of the gravity center issignificant, and the direction is irregular. The changein lake area gravity center indicates that the lake area isretreating year by year, except in 2002 (see Fig. 5).

Reasons for lake area changes

Lake area retreat and climate

Of all the factors contributing to the lake areavariation, climate change may be the most impor-tant one. Lake area fluctuation on timescales thatare longer than a century is controlled mainly bytemperature and precipitation. The daily air tem-perature and precipitation data from five high-altitude meteorological stations in the Ebinur Lakeregion acquired from 1959 to 2005 are used in thestudy area (Table 3).

Annual mean temperature and total precipitation forthe 46-year period from 1959 to 2005 were recordedfrom the five closest weather stations in the study area(Fig. 8). Records from these five stations displayed agradual increase in the annual precipitation, at an aver-age rate of 7.12 mm/(10a). The linear trend analysis of

Fig. 3 Flowchart for the analysisof Ebinur Lake area changes from1972 to 2013

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mean temperature indicates that the average rate ofannual temperature had increased at 0.31 °C/(10a). Al-though the annual temperature increased gradually

between 1959 and 2005, the annual precipitation in-creased slightly that leads to a significant change in thelake area as seen in Fig. 9. This indicates that with the

Fig. 4 The left column shows the Ebinur Lake as it appears in sixrawMSS, TM, ETM+, and OLI_TIRS images.Blue color refers towater; red refers to vegetation; and pale refers to salinity land,

gobi, desert, and sandy land. The right column shows the waterbody (white color) in these four dates as estimated from the NDWIand the two dates as estimated from the MNDWI

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annual precipitation increase, the lake surface area alsoincreased during the 1998–2004 period, which appearsto be the most significant factor for recent lake shrinkagein the Ebinur Lake region. But the increasing amount ofprecipitation could not compensate for the lake massloss due to the temperature increase in the study area.

Lake area retreat and river runoff

Currently, the Ebinur Lake is seriously water-deficient.Runoff to the lake in this region plays a significant rolein the economic development of Xinjiang. Thus, deter-mination on the shirking lake that affects the economypotential of the lowland areas is important.Water supplyflowing into the lake from the rivers relies on input fromglacier-melt, snow-melt, and precipitation. The totalsurface river runoff in the Ebinur Lake region is42.19×108 m3. In the study area, the rivers with annualrunoff greater than 1×108 m3 are the Kuitun, Sikeshu,Jinghe, Daheyanzi, and Bortala. However, due to large-scale water conservancy construction since 1949, andespecially since the 1980s, the Kuitun River surfacerunoff has been exhausted and the rivers Bortala and

Jinghe have become the main supply of water for theEbinur Lake. Based on the annual runoff records at therivers Bortala and Jinghe as well as the sum of the tworivers as seen in Fig. 10, the authors found that annualrunoff of the Bortala River shows a decreasing trend and

598.43536.78

842.84

455.81 450.48410.58

0

100

200

300

400

500

600

700

800

900

1972 1998 2002 2007 2011 2013

Year

Su

rface a

rea/k

m2

Fig. 5 Surface area change of the Ebinur Lake between 1972 and2013

Fig. 6 The overlay outlines of the Ebinur Lake delineated from1972 to 2013

Table 2 Change in lake area from 1972 to 1998, 1998 to 2002,2002 to 2007, 2007 to 2011, and 2011 to 2013

Period Lake area increase amount/km2

Dynamic degree (K)/%

1972–1998 −61.65 −0.401998–2002 306.06 14.25

2002–2007 −387.03 −9.182007–2011 −5.33 −0.292011–2013 −39.90 −4.431972–2013 −187.85 −0.77 Fig. 7 The change of the lake area gravity center in the study area

from 1972 to 2013

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the Jinghe River shows an increasing trend, but theoverall annual runoff of the two rivers is decreasing. Inthe Ebinur Lake region, runoff variation was observed tobe closely related to precipitation and air temperature.Clearly, glaciers in the upper reaches of a river have animportant role in stabilizing runoff. For a lake without aglacier supply, the coefficient of variation for runoff isvariable. The rivers are the main sources of water for theEbinur Lake and flow into the lake is varied. The rela-tionship between the lake surface area and the amount ofwater flowing into the Ebinur Lake (Fig. 11) has indi-cated that the lake surface area has increased from theincreasing water flow into the lake.

Lake area retreat and human activities

Although perhaps less important than natural forces,human forces have also imposed upon the evolution ofthe lake area. In the present study, the human activitiesare three proxies: the human population, the number oflivestock, and the farmland. The results illustrated thatthere had been significant variations in these three prox-ies throughout the study period in the Ebinur Lakeregion (Fig. 12).

In the study area, the population growth and intensi-fication of agriculture in the twentieth and twenty-firstcenturies have led to considerable change in the land use

pattern. Thus, the areas of inhabited and irrigated landshave expanded significantly, which led to in-creased water consumption for domestic, industrial,and agricultural purposes. The population of thestudy area increased by 17.3×104 from 32.3×104

to 49.6×104 during the 1990–2010 period, whichincreased the need for farmland, by convertinggrasslands and woodlands to agricultural uses.These led to lake area variance of the study area.During the 1990–2010 period, the populationshowed obvious changes, which greatly enhancedthe pressure on the land use for growing crops andraising livestock. According to the statistical year-book of the study area, from 1990 to 2010, thenumber of livestock increased by 20.3×104 from89.3×104 to 119.6×104, of which about 70 % oflivestock was free-herding. According to the inves-tigation, the number density of sheep grazing wasgreater than the bearing capacity of grassland.With the increasing of farmland and livestock inthe study area, water resource became moreexhausted.

Overall, the northern portion of the Tien Shan is avital ribbon of economic development in the Xinjiangregion (Tang et al. 2013). The people of the Ebinur Lakeregion rely on glacier-melt water for domestic water,irrigation, industry, and hydropower (Liu et al. 2002).

Table 3 Meteorological stations used in this study

District station number Meteorological station Latitude (N) Longitude (E) Altitude (m)

51,232 Alashankou 45° 11′ 82° 35′ 284.8

51,238 Bole 44° 54′ 82° 04′ 531.9

51,330 Wenquan 44° 58′ 81° 01′ 1354.6

51,334 Jinghe 44° 37′ 82° 54′ 320.1

51,346 Wusu 44° 26′ 84° 40′ 478.8

Fig. 8 Annual average temperature (a) and annual average precipitation (b) for 1959–2005 at the five meteorological stations in the studyarea

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As economic activities and population increase, thewater shortage in the Ebinur Lake region and in thelowland cities limits economic development and domes-tic water use. If climate warming and runoff decrease,the lake area loss will continue at rates like those report-ed in the present study. In addition, the shrinking of thelake area would result in eco-environmental deteriora-tion, such as acceleration of desertification which in-creases floating dust and sandstorm and decreases thenumber of wild animals. Therefore, the downstreamwater sources will also be depleted. This phenomenoncould endanger local economic development and peo-ple’s safety.

Conclusions

(1) In the Ebinur Lake region, Xinjiang, China, asignificant decrease in the lake area has been notedsince the 1970s. This is related to natural andhuman factors. From the authors’ point of view,the lake desiccation has resulted from the de-creased surface and ground water discharge to thelake due to the intensive water withdrawal forirrigation and domestic use.

(2) Surface area of the Ebinur Lake has decreasedsignificantly during the 1972–2013 period. Overthese 41 years, the lake area has decreased by

y = -0.00001684 x3 + 0.033x

2 - 20.5x + 4291.28

R2 = 0.845

0

50

100

150

200

250

300

350

200 400 600 800 1000

Annual Average lake area/km2

An

nual

pre

cip

itat

ion

/mm

Fig. 9 The relationship between annual precipitation and annualaverage lake area during the 1998–2004 period

Fig. 10 Annual runoff records at the rivers Bortala (a) and Jinghe (b) as well as the sum of the two rivers (c)

y = 285.35Ln(x) + 115.43

R2 = 0.7049

0

200

400

600

800

1000

3 5 7 9 11 13

Water flow into the lake/108m

3

Su

rface l

ak

e a

rea/k

m2

Fig. 11 The relationship between the lake surface area and theamount of water flow into Ebinur Lake (water flow into the lakeincluding rain drainage, Bortala River, and Jinghe River)

Environ Monit Assess (2015) 187:4128 Page 11 of 14, 4128

187.85 km2. These changes mainly resulted fromincreasing temperatures and population. Runoffhas played a significant role in the economic de-velopment in this region. More detailed researchusing reliable lake field data is needed to confirmthe calculations made here. Simulating future run-off trends is also needed to ascertain the relation-ship between changes in lake properties and runoffvariability.

(3) In general, during the 41 years, the gravity centerof the lake has the trend of a southeast migration,and the offset distance was 0.98 km. The migrationof the gravity center is significant and the directionis irregular.

(4) The Ebinur Lake is under the direct threat of envi-ronmental degradation due to the continuous lakearea shrinking. Another threat arises from the re-moval of the sand dunes bordering its lake face.This delicate arid lake ecosystem requires appro-priate management and protection. This is neces-sary because the country is moving toward sustain-able use of its natural recourses.

Acknowledgments We are grateful for the financial supportprovided by the National Natural Science Foundation of China(Grant No. 41361045), the National International Scientific andTechnological Cooperation Projects (Grant No. 2010DFA92720-12), the State Key Program of the National Natural Science ofChina (Grant No. 41130531), the Young Technology-InnovationTraining Program Foundation for Talents from the Xinjiang UygurAutonomous Region (Grant No. 2013731002), the Foundation forInnovative Research Groups of theMinistry of Education of China

(Grant No. IRT1180), the Key Laboratory of Oasis Ecology inXinjiang University (No. XJDX0201-2012-01), and the PhDGraduates in the Scientific Research Foundation (No.BS110125). The authors wish to thank the referees for providinghelpful suggestions to improve this manuscript.

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