Keywords

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

12.1 Distribution and Types of Lakes in Arid Regions of Northwest China

There are about more than 700 lakes in arid areas of northwest of China, and they are mainly distributed in Xinjiang (Tables 12.1 and 12.2). There are 29 lakes with size more than 10 km2, of which three lakes are distributed in both inside and outside the boundary of Inner Mongolia, and rest 26 lakes all located in Xinjiang (Table 12.2) (Abuduwaili 2012).

Table 12.1 Main lakes in arid and semi-arid areas of China
Full size table
Table 12.2 Lakes with a surface area larger than 10 km2 in the arid land of China
Full size table

The large lakes in arid areas are mainly supplied by rivers. They are the trails of rivers and are an important part of the water cycle in arid areas. As the last link in the system of natural and human economic activities in arid areas, its ecological system and environment was first to respond to the interference of human activities.

Bosten Lake is the largest inland freshwater lake, which is located in the south of Tian Shan mountain, made up of two large and small lakes. It is feeding by the Kaidu River, which is the Rump Lake of Kaidu River and source of Konqi River, and is the only throughput Lake in arid areas of China (Xia et al. 2003). The water level of the lake is 1047.5 m, with surface area of 974.5 km2, the volume of 7.59 billion m3, the largest depth is 16.8 m, and the average water depth is 7.5 m.

The small lake covers an area of 363.9 km2, with 16 lakes connected with the old river road of Konqi River, area of 44.5 km2 of water level. The area of Reed Lake is 802 km2; area is 39.3 km2 of pasture and beaches. Ecological detections are settled in the interval of Lake dike hose (brake, culvert), two-way penetration. It is needed to be emphasized that since 2000, the water environment of Bosten Lake has changed. The Bosten Lake sustains a healthy state. The fishery production of Lake was up to 6500 ton in 2005, while was 2620 ton (2.48 times) in 1990. The Bosten Lake owes special position in the local and national economy, ecology and environment in Xinjiang of northwest China.

It is well known that water resources in arid areas (including surface water and groundwater) are the result of mountainous runoff area, affected by the geological structure and hydrogeological condition, recharged by groundwater and formed many springs in the vast region outside of runoff zone; springs converge to a small lake, such as there are about 144 in less than 1–10 km2 freshwater and saltwater lakes and salt lakes, with the total area of 33.42 km2.

Influenced by the predatory exploitation of land and its rich, environment change of small lake is prominent in arid areas. Some freshwater lakes have disappeared, such as some Small Haizi of Tarim river basin in Xinjiang. Corksu lake, and Algol lake and other small lakes; Algol lake covers an area of about 70 km2 (water report of 1990), all dried up. Some lakes have disappeared, such as Eric lake and Manas lake in Karamay (Xinjiang).

Eric lake is the rump lake for poplar river. According to the satellite remote sensing image in 1989–2005 for Eric lake, the lake dried up in 2000, the area of lake was 59.6 km2 in 2003 (including reed area of water).

Salt lake is another type of lake in arid areas, and it is a type of lake which has an important value. Salt lake (also known as Lake brine) usually refers to the lake of which the salinity is equal to or greater than 50 g/l. Lopnor is the second largest salt lake in China, today, with area of about 5,350 km2. In historical period, the Lopnor was a big freshwater lake collected by runoff of south of Tian Shan, and the Kunlun and Altun. The lake dried up in 1962 due to interference of human activities and became a vast dry lake (about 600 km2). There are salt crust with crack shape about 10–15 cm and large dead reeds at the rim of lake in the dried bottom about 450 km2. After drying Lobnor lake, salt deposition of surface and bottom is rich in inter-crystal brine in and inter-layer brine, with relative density of 1.286, pH of 6.07, the content of KCl of 2.08%, and refers to sulfate magnesium and sulfate subtypes with hydrochemical type (Wang and Dong 2002).

According to the information of scientific expedition to Lobnor in the Qinghai Institute of Salt Lakes Chinese Academy of Sciences, there are utilized of resources, brine, and halide salts. Inter-crystalline brine occurs between the surface rock salt, gypsum and glauberite salt layer, rich brine potassium high mineralization, with the thickness of aquifer of more than 100 m, salinity of inter-layer brine of 372.08 g/l. In saline resources, rock salt owes an area of 700 km2, thickness of 0.5–2.5 m. The content of NaCl is 60–80%, the highest up to 94%, reserves of about hundreds of one hundred million tons, a very large rock salt deposit. There reserves about 250 million t of potassium magnesium salt deposit, 120,000 ton of potassium nitrate, huge amount of sodium calcium sulfate ore (Guo et al. 2003).

Lake Types. Arid area is vast in China, and lakes are in diverse species (Tables 12.1 and 12.2). According to incomplete statistical classification, there are about nine lake types.

  1. (1)

    Settling lake. Geological period had a descending basin or lowland in the depression, rivers into the retention of water into the lake. Such as the LopNor lake of the Tarim River, the Junggar Lake in the Junggar Basin, the Heihe River, the Shule river basin in the east, the West Jueyan Sea and the Hokkaido, and the Lindi Basin in the Turpan Basin, the Aidynkol—154.31 m, the lowlands in China. As well as there are many lakes such as Ake kuku in the southern slope of the Kunlun Mountains and the Altun Mountains, Qiangtang plateau.

  2. (2)

    Subsiding lake. Such as Bosten Lake, Ulungu Lake, Ebinur Lake, Barkol Lake and the Tian Shi Lake belong to this lake type. This type of lake is mainly distributed in the edge of the basin or mountains basin, with a certain catchment area, from the surface water and groundwater into.

  3. (3)

    Terminal moraine lake. Ancient glaciers or planing erosion in modern glaciers alpine zone, forming shades, ranging in size after the depression, Ice Age, the glaciers receded, moraines (terminal moraine dam) damming the river to form glacier lake. It is characterized by growing up along the river bar, such as Xinjiang famous Fukang Tianchi and Burjin Kanas Lake Scenic Area.

  4. (4)

    Glacier blocking lake. China arid areas with modern glaciers 21,568 strips are the world’s mountains glaciers latitudes subregion up to the cloth (Shi et al. 2002). There are most extensive mountain of Chinese glaciers–Kunlun Mountains (Glacier area is about 12,566 km2), accounting for 20.7% of the country’s glacier area; China’s glacier has the largest distribution of the river—Tarim water (glacier area of 19,889 km2), accounting for 33.5% of the glacier area; there is the largest basin of Chinese glaciers—Kunlun peak area. The total glacier area is 4346 km2. There are 15 large glaciers with more than 300 km 2 in area distributed in the low latitudes of the world and four of them are found in the arid region of China. (337.9 km2 in the territory of China, 567.2 km2 in the territory of China), the Tommel Glacier (337.9 km2), the Tiggyrizi glacier (313.7 km2), and the sound of the Karakoram Mountains Glacier (379.9 km2) (Hu et al. 2002). As in the process of glacier movement, some support glaciers blocked the main river, some of the main glaciers blocked the tributaries of the river, and the formation of glaciers blocked the lake. At the elevation of 4,900 m a.s.l, the lake is 9.48 km long and has an average width of 638 m. The lake area is 6.1 km2 and the average water depth is 52.6 m depth of 154.5 m, with water storage capacity of up to 318 million m3. The glacier lake is often caused by important floods in the lower reaches of the basin.

  5. (5)

    Interfluve lake. Mainly distributed in the middle and lower reaches of the river basin in the arid region, such as the Lauru Lake in the Tarim river basin, Lake Sutherland, Saite Lake, Dada Mukule (length 2 km, width is 1.1 km, area 2.2 km2). Yili River, Heihe River, and Kaidu River are also distributed.

  6. (6)

    Oxbow lake. Rivers into the plains or flat basin area, the ground slope is gentle, the flow rate is reduced, such as the Tarim River stream in the British Bazaar to the Chala section, river bed slope of 1/7 700, slow water, river bend). Yeer Qiang River, Hetian River downstream section also has a small amount of Oxbow lake.

  7. (7)

    Wind erosion lake. In the lower reaches of the Tarim river basin and the lower reaches of the Shule River, there are many low-lying depressions formed by strong directional wind erosion, forming rivers when floods are flooded. Such as the Tarim River mainstream famous Daxi Haizi and so on.

  8. (8)

    Submerge lake. Tian Shan Mountains, Qilian Mountains, Kunlun Mountains, Altun Mountains, Altai Mountains are the southern slope of the spill overflow zone, overflowing water retention in the depression to form lakes, such as Lake Aidynkol, mushroom lake (built reservoir) and the northern slope of the Kunlun Mountains, such as Berkeley Kul and so on. There are more than 460 large and small lakes in the Badan Jaran Desert and Tengger Desert, and they belong to this lake type.

Water reservoir. According to incomplete statistics, there are about 500 water reservoirs in arid areas of China in different sizes and functions. They play an important supporting role in the economic development of the basin and has different positive and negative effects on the local environment.

12.2 Ebinur Is the Largest Salt Lake in the Northwest China

Ebinur Lake is located in the western part (43° 38ʹ–45° 52ʹN; 79° 53ʹ–85° 02ʹE) of the Junggar basin in Xinjiang in northwest China and is a typical rump lake in an arid region (Abuduwaili et al. 2007; Abuduwaili 2009). Ebinur Lake is a shallow, closed lake basin in arid region of northwest China (Fig. 12.1). The lake has a drainage area of 50,321 km2, including 24,317 km2 of mountainous terrain and lakes 542 km2. The Ebinur Lake is the largest lake in the basin as well as the largest salt lake in Xinjiang in northwest China (Abuduwaili et al. 2014). Ala Mountain borders the lake to the north and northwest, Borotala Valley is to the west, the Jing River pluvial fan is to the south, and sand dunes around the Kuitun River are to the east. The Borotala, Jinghe, and Kuitun Rivers are the main feeders into the lake that come from the west, south, and east, respectively. Due to the arid desert climate, there is little rainfall with the average annual rainfall of the basin around only 100–200 mm and a potential evaporation of up to 1500–2000 mm (Abuduwaili et al. 2014). Mean annual precipitation around the lake is about 95 mm, whereas annual evaporation is 1315 mm (Wu et al. 2009). Maximum precipitation falls in summer. In winter, the snow cover is shallow—10–25 cm—and persists up to the late February or early March. The mean July temperature is +27 °C; the mean January temperature is—17 °C.

Fig. 12.1
figure 1

Ebinur lake basin

Full size image

The lake has a maximum water depth of 3.5 m and an average depth of 1.2 m. The lake water has 85–124 g L−1 of total dissolved solids. The lake water salinity is about 120 g/l (Mahpir and Tursunov 1996). The lake has a sodium chloride–sulfate or sulfate–chloride composition of water (Table 12.3). Based on a field survey conducted in 2009, it was shown that the major ions in Lake Ebinur were chlorine and sodium, and the hydrochemical classification subsequently changed from sulfate-sodium-II type to chloride-sodium-II type (Wu et al. 2014a, b).

Table 12.3 Hydrochemical characteristics of water in the Ebinur lake (Fan and Zhang 1992)
Full size table

Ebinur Lake receives surface water inputs from the Borotala and Jing Rivers. The Ala Mountain pass, northwest of the lake, is a well-known wind corridor, with wind speeds exceeding 20 m s−1 on 164 days of the year and maximum wind speeds of up to 55 m s−1 (Wu et al. 2009; Ma et al. 2011b) and northwestern winds prevail in the region. Strong winds are frequent in this region.

The Lake basin is considered an important base for grain, cotton, animal husbandry, oil and chemical industries. In Xinjiang in northwest China, it is also an important open channel to the west, known as the “Euro-Asian Continental Bridge” that runs along the Ebinur Lake across the lake basin from the north to the southwest (Zhou and Lei 2005; Mi et al. 2008). Since the 1990s, both the implementation of the “Western Development Policy of China” and the developmental policy by the Xinjiang Uygur Autonomous Region in northwest China have led to prodigious economic development in the Ebinur Lake Basin. In this area, fertilizers and pesticides imprudently used in agricultural processing and large quantities of emissions by the townships have led to pollution of the main feeders, the Jing and Bortala Rivers. This has significantly and negatively influenced the water quality of the main water area of the Lake. This pollution will eventually seep into the sediment and become a threat against the aquatic organisms and the ecological environment (Liu et al. 2011). Over the last 50 years, a combination of the population and large-scale exploit of water and soil of Aibi Lake has led to a dramatic reduction in the amount of water flowing into the lake from rivers (Liu et al. 2011). In the Aibi Lake Basin, the flora is primarily that of Central Asia and Mongolia. There is a total of 385 plant species belonging to 53 families and 191 genera (Qian et al. 2004). The soil types are mainly Piedmont psephitic and Gypsum desert soil; the vegetative cover is mainly H. ammodendron desert and Ephedra desert; and plant growth is Populus euphratica forest, Phragmites australis, and lowland meadow. Since the 1950s, the driving forces of industrial and agricultural development have dramatically decreased the amount of water flowing into the lake, resulting in a reduction in the lake water area from 1000 to 500 km2. As the lake has dried up, the ecological environment of the lake basin has visibly deteriorated (Liu et al. 2014a, b).

The surface area of this lake was about 1070 km2 in 1950 and then experienced a rapid contraction. In 1972, the lake area decreased to 589 km2. In the late 1990s, Ebinur Lake started to expand; however, the lake area shrank sharply from 2004. The variation of Lake Ebinur area is jointly controlled by human activities and climate change. However, the human activity was mainly responsible for Ebinur Lake shrinking quickly over the past half century (Ma et al. 2014).

12.3 Hydrograhical Characteristics of the Sayram Lake and Environmental Issues in the Region

Sayram Lake is located in the western part of the Tian Shan Mountains, northwest China (Fig. 12.2). It is a closed-basin lake in the western Tian Shan. The lake surface area fluctuated between 458.6 and 462.2 km2 over the decade from 2001 to 2011 (Wu et al. 2014a, b). The water body is surrounded by high mountains and has a catchment area of 1408 km2 (Wang and Dou 1998). The vegetation of Sayram Lake Basin has relatively simple composition and obviously vertical bands. Above the 3800 m above sea level (asl), the surface is snow-covered region. From 3800 m to 2800 m asl, the vegetation changes from alpine sparse vegetation to alpine meadows.

Fig. 12.2
figure 2

a, b Geographic location and bathymetry of Sayram Lake. c Sites of dustfall samples. d Sites of riverine samples collection (Ma et al. 2015)

Full size image

The surface is covered with subalpine steppe meadows (2800–2400 m asl). Then, the vegetation changes to forest meadows and mountain meadows (2400–2150 m asl). Around the lakeside belts, the vegetation varies to steppe and desert–steppe (Jin 1995). Lake Sayram has a maximum water depth of 99 m and an average water depth of 46.4 m (Wu et al. 2014a, b). The lake is located in the hinterland of the Eurasian continent where Northern Hemisphere westerly winds are characteristic of the semi-arid climate. So the climate of the region is dominated by Northern Hemisphere westerly winds.

Water in Sayram Lake comes mainly from glacial snowmelt and phreatic water (Jin 1995). There are 39 inflows around the lake. Among these, 7 rivers are perennial, 13 ones are spring-fed, and 19 ones are seasonal (Jin 1995). The region receives annual total precipitation of 350 mm, and mean annual temperature is about 0.5 °C (Wang and Dou 1998). Regional grasslands constitute a rich resource that is exploited by traditional Kazak herders. There are no residential villages, and there is no agricultural cultivation around the lake. Nomadic grazing of livestock is the most important activity in the drainage basin.

Given its basin structure and location, Sayram Lake possesses a high-quality sediment archive that can be utilized to increase our understanding of past climate and environmental change. The Sayram Lake sediment record was used to evaluate anthropogenic metal accumulations and quantify the human contribution to heavy metal pollution in the water body (Zeng et al. 2014). Liu et al. (2014a, b) used multiple sediment variables, including geochemical composition, carbonate content, magnetic susceptibility, and δ13C and δ18O of bulk carbonate, to infer regional environmental change.

Regional climate was generally dry, but experienced strong oscillations from ca. 1910 to the 1930s in agreement with Chaiwopu Lake region inferred from organic matter and its stable isotope (13 °C) in the lacustrine records (Ma et al. 2013a, b). These conditions provided enhanced source material for aeolian transport. Meteorological data indicates increased temperature and precipitation during the past 50 years in the Sayram Lake region (Shi et al. 2007), but human activities reduced the influence of wetter climate on surface soils. Magnetic minerals in lake sediment come mainly from surface material in the watershed. Higher values of magnetic susceptibility over the past few decades (Fig. 12.3) indicate greater erosion in the lake drainage basin, caused by human activity (Hu 2002). Widespread deforestation in the 1970s also opened the landscape and induced greater soil erosion. Similarly, overgrazing during the 1980s (Jin 1995) increased land surface erosion. According to the Eco-environment Protection Program in Lake Sayram Basin (2012–2016) (http://www.xjboz.gov.cn), raised by the government of Boertala Mongolia Autonomous Region, Xinjiang, China, inside the summer pasture area of 1.11 million mu (China unit of area; 15 mu = 1 ha), 62.8% of pasture area are destroyed and underwent degeneration. The phenomena of vegetation degradation, surface exposed and desertification occurred in lakeside belts, and the desertification area has reached 250 ha.

Fig. 12.3
figure 3

Regional proxies for fluvial and aeolian environments. a Relative content of aeolian transported material (EM2 + EM3) in Sayram Lake sediments (dashed line) with the three-point running average (solid line). b Relative content of fluvial transported material (EM4 + EM5) in Sayram Lake sediments (dashed line) comparing with annual streamflow of Jinghe River (Shang et al. 2014) (solid line). c Ratio of aeolian to fluvial transport fractions in the Sayram Lake core. d Content of aeolian particle size populations recovered from the Chaiwopu Lake core (Ma et al. 2013a, b). e Magnetic susceptibility (MS) of Sayram Lake sediments

Full size image

Human activity in the lake ecosystem over the past 50 years provided large-scale environmental issues. Such as vegetation degradation, deforestation, desertification processes, and consequently dust and sand deflation and transport. Anthropogenic factor contributed to the increased dust storm activity in the region and an abundant material for dust storm generation, resulting in coarser particle size fractions being deposited in the lake.

12.4 Climate and Environmental Changes Over the Past 150 Years in the Chaiwopu Lake

Chaiwopu Basin is a small, inter-montane structural basin in the central Tian Shan Mountain area, northwest China. Yilianhabierga Mountain lies south of the basin and has an elevation of 4483 m above sea level (a.s.l.), and to the north is Bogeda Mountain (5445 m a.s.l.). Chaiwopu Basin is connected with the Junggar Basin to the west, and the Baiyanggou River links it with the Turpan Basin to the southeast. Chaiwopu Lake is situated in Dabancheng District, approximately 45 km southeast of Urumqi, Xinjiang, northwest China (Fig. 12.4a). The lake is fairly round in shape and approximately 5–6 km in diameter. The lake water level was 1903.86 m a.s.l. with a lake area of 30 km2 in 1971, but fell to 1901.66 m a.s.l. with an area of 27 km2 in 2008. The average water depth is ~2 m with a maximum depth of ~4 m (Fig. 12.4b). The lake is brackish, with a salinity of 6.8 g/l. It has a transparency of 18 cm, a pH of 9.04, and an average conductivity of 0.867 s/m (Ma et al. 2013a, b). Chaiwopu Lake is covered with ice from mid-November to late March or early April. It is a natural cold-water lake that receives water from several streams running from Bogeda Mountain. The lake and its surroundings have been officially protected since 2009, when Urumqi Chaiwopu Lake National Wetland Park was created by the State Forestry Administration of China.

Fig. 12.4
figure 4

Study site (a) and bathymetry of Chaiwopu Lake with core location (b)

Full size image

The meteorological stations of Dabancheng (43.3627°N, 88.3116°E; 918.7 m a.s.l.) and Urumqi (43.8259°N, 87.6174°E; 1105.3 m a.s.l.) have recorded the mean annual temperature and the annual total precipitation during the past 50 years (Fig. 12.5). Mean annual temperature rose gradually since the late 1950s, and stable higher temperatures have been maintained in recent years. Annual total precipitation increased since 1980 AD, whereas it has decreased over the last 10 years.

Fig. 12.5
figure 5

Curves of mean annual temperature and annual total precipitation with 5-year moving average (solid lines) in the region of Chaiwopu Lake (Ma et al. 2013a, b)

Full size image

Organic matter in the lake sediment is a mix of aquatic and terrestrial plant debris, the latter resulting from watershed erosion (Meyers and Teranes 2001). The organic matter content can thus be used to reconstruct paleoenvironments of lakes and their watersheds and to infer past regional climate change (Brenner et al. 1999). In arid/semi-arid areas, regional moisture is the main factor influencing plant growth (Ma et al. 2011a). In humid climates, plants grow vigorously, leading to a higher content of organic matter in lake sediments, whereas under arid conditions, plant growth is limited and organic matter content in lake sediments is lower. The lower OM-LOI content indicates drier climate period, while the higher reflects wetter climate interval (Liu et al. 2002; Wu et al. 2009; Oldfield et al. 2010; Zhong et al. 2010). The OM-LOI variations are consistent with Palmer Drought Severity Index (PDSI) of the central Tian Shan Mountain area in northwest China (Li et al. 2006). The OM-LOI indirectly reflects humidity variation in Chaiwopu Lake region. OM-LOI analysis showed values between 3.7 and 6.3%. The OM-LOI below 35 cm is relatively low, with an average of 4.3%, whereas above 35 cm, it increases to an average of ~5.4%. The carbon isotope of bulk organic matter depends on several factors, such as sources of organic matter, biological productivity, intensity of photosynthesis, hydrological conditions, sediment environment, reservation of lake sediment, and so on (Hayes 1993; Kump and Arthur 1999; Wu et al. 2007). Chaiwopu Lake is a natural cold-water body, so the aquatic biological activities are more closely related to the water temperature. It was revealed that organic carbon isotopes reflected the regional temperature change in accordance with the sediment records for Xingcuo Lake, located on the Tibet Plateau (Wu et al. 2007). The δ13Corg correlated with the mean annual temperature in Urumqi. It is also positively correlated with the Northern Hemisphere temperature (Jones and Moberg 2003). In the Chaiwopu Lake sediment, δ13Corg ranges from −24.2 to −26.5%, with a mean value of −25.5%. There are three large negative shifts occurring at 1890 AD, 1910 AD, and 1960 AD. The δ13Corg curve shows a gradual increase to −24.2% at the top of the core. The implied climate and environmental changes were proved using instrumental data, which indicates that environmental information was effectively preserved in the lake sediment.

CONISS analysis of element and other sediment data enabled division of the Chaiwopu Lake core into three zones, which reflect three distinct climate and environmental periods:

  1. 1.

    The first period was from about 1880 to 1910 AD. The average particle size, element content, OM-LOI, and MS were relatively constant, which reflects a relatively stable sediment environment. The δ13Corg values were relatively low, indicating that the climate was quite cold at this time. During this period, the lake sediment consisted mainly of fine-grained particles. There is no significant variation in the median grain size, which reflects the stable hydrodynamic conditions. Values of the C index were relatively low and Sr/Ca was relatively high, suggesting that regional climate was dry and lake water salinity was high. The data indicates a relatively stable aquatic environment, with high salinity, under cold and dry climate conditions, after the Little Ice Age.

  2. 2.

    The period from 1910 to 1950 was the second stage. In this period, geochemical indicators OM-LOI and grain size fluctuated significantly. δ13 Corg increased. In this period, values of the C index were low and Sr/Ca remained high, suggesting that lake water was shallow and the regional climate was unstable, with generally higher temperature and humidity. Contents of mobile elements (Mg, Ca, and Sr) are lower (Fig. 12.7), which suggests that the chemical weathering intensity was still weak.

  3. 3.

    In the last 50 years, which correspond to the upper 25 cm in the core, and the 50-year instrumental data from the Urumqi meteorological station, the MAT displays a warming trend, and the lowest temperature was observed in the 1950s. The δ13Corg also decreased. Variations in annual total precipitation were more complex, and there was a significant increase in ATP since the 1990s. According to satellite images collected at different times, along with respective topographic maps, Chaiwopu Lake has remained stable, with fluctuations in total area of ˂2 km2 (Ma et al. 2011b). The grain size remained relatively constant, so the water body was relatively stable. MS is very different from that measured in previous periods, indicating greater erosion of the Chaiwopu Basin, perhaps caused by human activity. The high value of the C index suggests a high moisture condition in the watershed during this period, a better soil–vegetation environment, and more surface runoff. The low molar Sr/Ca supports this interpretation. Increases in heavy metal and total phosphorus (TP) concentrations were likely influenced by enhanced human activity.

Global warming will have a large impact around the globe, causing differences in precipitation distribution, hydrological cycles, and effective moisture changes. In the Chaiwopu region, the climate became warmer and moister beginning about 1950 AD. Shi et al. (2007) considered that a warm–moist transition may occur in northwest China, based on the instrumental data and glacier and lake changes over the last 50 years.

Global and Northern Hemisphere temperature experienced a significant change about 1910 (Jones and Moberg 2003; Brohan et al. 2006), and in the arid region of northwest China, PDSI also showed the central Tian Shan Mountain area was dry at this time (Li et al. 2006), consistent with the hypothesis that dry climate provides abundant material basis for sandstorms, and explaining how the aeolian sands increased the sediment grain size in Chaiwopu Lake.