water

Article Linkage of Climatic Factors and Human Activities with Water Level Fluctuations in Lake in the Northeastern Tibetan Plateau,

Bo Chang 1, Kang-Ning He 1,2,*, Run-Jie Li 3, Zhu-Ping Sheng 4 and Hui Wang 1

1 College of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; [email protected] (B.C.); [email protected] (H.W.) 2 Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China 3 Institute of Water Resources and Hydropower of Qinghai Province, 810001, China; [email protected] 4 Texas A&M AgriLife Research Center, El Paso, TX 79927, USA; [email protected] * Correspondence: [email protected]; Tel.: +86-10-6233-8356

Received: 23 May 2017; Accepted: 13 July 2017; Published: 24 July 2017

Abstract: Changes in the water level of , the largest inland lake in China, directly affect the ecological security of Qinghai province and even the northwest of China. This study aimed to investigate the lake level and identify causes of changes in the lake level of Qinghai Lake. The results showed that the lake level was 3196.55 m in 1959 and gradually declined to 3192.86 m in 2004, with an average decreasing rate of 8.2 cm·year−1 over 45 years. However, the lake level increased continuously by 1.04 m from 2005 to 2010. During the period 1961–2010, the annual average temperature showed an increasing trend in the Qinghai Lake basin, at a rate of 0.32 ◦C/decade, and the annual precipitation showed obvious fluctuations with an average precipitation of 381.70 mm/year. Annual evaporation showed a decreasing trend (−30.80 mm/decade). The change in lake level was positively correlated to precipitation, surface runoff water and groundwater inflow into the lake and negatively correlated to evaporation from the lake surface. The total water consumption by human activities merely accounted for a very small part of precipitation, surface runoff inflow and groundwater inflow (1.97%) and of lake evaporation (1.87%) in Qinghai Lake basin. The annual water consumption of artificial afforestation and grass plantation accounting for 5.07% of total precipitation, surface runoff inflow and groundwater inflow and 5.43% of the lake evaporation. Therefore, the water level depended more on climatic factors than on anthropogenic factors.

Keywords: lake level; climatic factors; human activities; Qinghai Lake; Tibetan Plateau

1. Introduction The Tibetan Plateau, also known as the Qinghai-Tibetan Plateau, is the highest plateau in the world, with an average altitude of over 4000 m [1–3]; the permafrost over the Tibetan Plateau comprises approximately 70% of all of the permafrost regions in China [4]. The harsh natural conditions (low temperature and hypoxia) have won this area the reputation as the third pole of the world [5–7]. Qinghai Lake, the largest lake in China, is a special ecological function area in the northeastern Tibetan Plateau. Without Qinghai Lake, the sand in Tsaidam would devour most of China and the whole of northern China would become a desert [8]. Therefore, Qinghai Lake is important for sustaining the ecological safety of the northeastern Tibetan Plateau [9], because it is not only a natural barrier to prevent the spread of the desertification of the west to the east, but also as it has a significant influence on the climate in the Basin [10]. Thus, the ecological status of Qinghai Lake basin is extremely momentous. Changes in the water level of Qinghai Lake directly affect the ecological system

Water 2017, 9, 552; doi:10.3390/w9070552 www.mdpi.com/journal/water Water 2017, 9, 552 2 of 13 of Qinghai province and even the northwest region [11], as well as the security of water resources in the Yellow River [12] and, in turn, the daily lives of people in the region. A considerable amount of research has focused on the influence of climate change on lakes elsewhere in China [13–16] and abroad [17–19]. Some of these studies have focused on climatic factors [20–22], while others were concerned with human activities [23]. Climatic factors such as precipitation, evaporation, and temperature variation would affect changes in the lake water level and its hydrological processes. Lee [4] has used re-tracked Enivsat radar altimeter measurements to generate water level change time series for Qinghai Lake and Lake Ngoring, in the northeastern Qinghai–Tibetan Plateau, and examined their relationships to precipitation and temperature changes. Additionally, human activities such as agriculture, dam construction, reservoir operation etc., may have an impact on changes in the water level. Hu [24] has concluded that climate change was the main reason for the changes, while human activities have had little influence on Qinghai Lake. Although there have been a number of studies on Qinghai Lake, the effect of artificial forestation and grass planting on the water level of Qinghai Lake has not been considered in those previous studies. The water level has severely declined from 1959 to 2004 and has recovered from 2005 to 2010, which has stimulated more interest in studying the hydrological conditions of the lake [25]. The recent rise of the water level in Qinghai Lake is undoubtedly good news for stakeholders in Qinghai Province, China. However, until now, the reasons for lake level changes in Qinghai Lake have not been fully understood; therefore, it is urgent to achieve a full understanding of variations in the lake level, linked with climatic factors and anthropogenic activities. Specifically, the objectives of this study were (1) to reveal the variation in the lake level of Qinghai Lake during the period 1959–2010; (2) to investigate the variation in the climate, human activities, artificial afforestation and grass plantation during the period 1961–2010; and (3) to analyze the cause of the increased lake level in recent years. Additionally, the results can provide a reference for the control structure for the water of Qinghai Lake.

2. Materials and Methods

2.1. Study Area Qinghai Lake is the largest closed-basin lake in China with no surface water outflow. It is located between 36◦150–38◦200 N and 97◦500–101◦200 E in the lowest valley in the northeastern Qinghai-Tibetan Plateau. The water surface area of Qinghai Lake is approximately 4317.69 km2, with a length (west to east) of 104 km and a width (north to south) of 62 km. The lake water is saline and alkaline, with a pH value of 9.23, a relative density of 1.01 and a salinity of 14.13 g/L, respectively. The area of Qinghai Lake basin is 29,661 km2, of which the mountain area accounts for 68.6%, while the rest is comprised of valley and plain areas. The topography of the basin decreases from the northwest to the southeast (Figure1). The basin is an inter-montane basin surrounded by Datong Mountain, Riyue Mountain, Qinghai South Mountain and Amuniniku Mountain. The Qinghai Lake basin has been of interest because it is one of the most sensitive regions to global climate changes; it is influenced by the East Asian monsoon, the Indian monsoon, northwest aridity and Tibetan Plateau coldness. Therefore, the climate of the region is characterised as having a dry cold, low rainfall, high wind and strong solar radiation. Simultaneously, the broad water body of Qinghai Lake adjusts the local climate, resulting in a typical semi-arid and cold plateau-climate. In general, the temperature declines from southeast to northwest in the basin; the average annual temperature is between −1.1 ◦C and 4.0 ◦C, with an extreme maximum temperature ranging from 24.4 ◦C to 33.7 ◦C and an extreme minimum temperature of between −26.9 ◦C and −35.8 ◦C. Precipitation is the main source of rivers, lakes and the groundwater of the Qinghai Lake basin. The average annual precipitation is between 300 mm and 450 mm, while evaporation is relatively high; the average annual evaporation is about 930 mm [26]. Water 2017, 9, 552 3 of 13 Water 2017, 9, 552 3 of 13

Figure 1. Location of the Qinghai Lake Basin.Basin.

Qinghai Lake receives discharges from more than 40 rivers, of which 16 tributaries tributaries have a catchment area greater than 300 km2..TheThe major major rivers rivers are are the the Buha Buha River, River, Shaliu Shaliu River, River, Haergai Haergai River, River, Ganzi River,River, DaotangDaotang River River and and Heima Heima River River (Table (Table1). Four1). Four of those of those rivers rivers contribute contribute 77.1% 77.1% of the of total the runofftotal runoff intothe into lake. the lake. The riversThe rivers are distributed are distributed asymmetrically, asymmetrically, with with large large rivers rivers in the in northwest the northwest and smalland small rivers rivers in the in southeast. the southeast. The majorThe m waterajor water sources sources of the of rivers the rivers are mainly are mainly precipitation precipitation and snow and melt.snow Themelt. modern The modern glacier glacier are distributed are distributed at the source at the ofsource the Buha of the River, Buha covering River, covering an area of an 13.9 area km of2 and13.9 akm reserve2 and a of reserve 5.9 × 10 of8 5.9m3 ,× respectively. 108 m3, respectively. The huge The glacier huge provides glacier provides melt water melt of water0.1 × 10of 80.1m 3× per108 yearm3 per on year average. on average.

Table 1.1. Characteristics of flowflow into Qinghai LakeLake fromfrom itsits mainmain rivers.rivers.

Catchment Length of Mean Annual Percentage of Total River Name Catchment Length of Mean Annual Percentage of Total River Name Area (km2) River (km) Discharge (108 m3) Runoffs into the Lake Area (km2) River (km) Discharge (108 m3) Runoffs into the Lake Buha R. 14,337 286 7.83 46.9% BuhaShaliu R. R. 14,3371442 105.8 286 2.51 7.8315.0% 46.9% ShaliuHaergai R. R. 1 1442425 109.5 105.8 2.42 2.5114.5% 15.0% Haergai R. 1425 109.5 2.42 14.5% Heima R. 107 17.2 0.11 0.7% Heima R. 107 17.2 0.11 0.7% Total of the Total of the above17,311 518.5 518.5 12.87 12.8777.1% 77.1% Jiermengabove R. 1092 112 Ungauged - GanziJiermeng R. R. 1092 369 112 47.4Ungauged Ungauged - - DaotangGanzi R. R. 369 743 47.4 60Ungauged Ungauged - - Daotang R. 743 60 Ungauged -

Groundwater in the Qinghai Lake basin mainly comes from precipitation and surface runoff. Groundwater in the Qinghai Lake basin mainly comes from precipitation and surface runoff. Because of previous tectonic actions and long-term physical and chemical weathering, the rocks in Because of previous tectonic actions and long-term physical and chemical weathering, the rocks in the Qinghai Lake basin are relatively developed and easily accept the infiltration and recharge of the Qinghai Lake basin are relatively developed and easily accept the infiltration and recharge of precipitation. In the permafrost zone above 3800 m, there is generally a freezing layer of water precipitation. In the permafrost zone above 3800 m, there is generally a freezing layer of water underground. Due to the cold climate, abundant precipitation and surface freezing in winter, underground. Due to the cold climate, abundant precipitation and surface freezing in winter, groundwater recharge is greatly reduced. When the temperature rises in summer, the upper layer of groundwater recharge is greatly reduced. When the temperature rises in summer, the upper layer of the frozen layer becomes ablated by 1–3 m and groundwater recharge is greatly increased. the frozen layer becomes ablated by 1–3 m and groundwater recharge is greatly increased. The main choice for artificial grass in the area has been cold and drought-resistant, salt-tolerant The main choice for artificial grass in the area has been cold and drought-resistant, salt-tolerant plants such as Caragana jubata (Pall.) Poir., Artemisia desertorum Spreng., Leymus secalinus (Georgi) plants such as Caragana jubata (Pall.) Poir., Artemisia desertorum Spreng., Leymus secalinus (Georgi) Tzvel., Achnatherum sibiricum (Linn.) Keng, and Stipa glareosa P. Smirn. Artificial afforestation has

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Tzvel., Achnatherum sibiricum (Linn.) Keng, and Stipa glareosa P. Smirn. Artificial afforestation has been dominated by shrubs such as Hippophae rhamnoides Linn., Potentilla fruticosa Linn., and Potentilla glabra.

2.2. Data Preparation and Analysis Precipitation, temperature and evaporation data from 1959 to 2010 were obtained from the national meteorological stations in Qinghai Lake basin (Table2). The average annual precipitation levels of the Gangcha, Haiyan and Gonghe meteorological stations were 381.7, 385.1, and 319.5 mm, respectively. The level of precipitation decreased from the northern mountainous area to the south. Precipitation over the lake was calculated from precipitation data in the Gangcha, Haiyan and Gonghe meteorological stations surrounding Qinghai Lake.

Table 2. National meteorological stations in the Qinghai Lake basin.

Initial Altitude Automatic Automatic Station Establishment Working Latitude Longitude of Station Station Station Name Time of Station Time (m) Model Manufacturer Gangcha 1957/7/1 1957/7/1 37◦19050” 100◦08016” 3301.5 Milos500 VAISALA Haiyan 1955/1/1 1976/1/1 36◦54020” 100◦59022” 3010.0 CAWS600 Huayun Gonghe 1953/1/1 1966/11/1 36◦16027” 100◦37006” 2835.0 Milos500 VAISALA

Water level records and runoff data during the period 1959–2010 originated in hydrological stations in the lake (Table3). The runoff in ungauged catchments was estimated based on the runoff in gauged catchments with the same underlying surface. The total runoff into the lake was then calculated as the sum of the runoff in gauged catchments and the estimated runoff for the runoff in ungauged catchments. The formula of the runoff in ungauged catchments could be written as follows:

Rungauged = S × Rgauged (1)

S = Sungauged/Sgauged (2) where Rungauged was the daily runoff in ungauged catchments, Rgauged was the daily runoff in gauged catchments, S was the area correction coefficient, Sungauged was the area of the ungauged catchments, and Sgauged was the area of the gauged catchments.

Table 3. Hydrological stations in Qinghai Lake basin.

Station Catchment River Latitude Longitude Measured Years Name Area (km2) Buha R. Buha estuary 37◦02000” 99◦44000” 14337 1957.05–Now Jiermeng R. Jiermeng 37◦10000” 99◦29000” 926 1958.05–1960.12 Shaliu R. Gangcha (2) 37◦19000” 100◦08000” 1442 1958.04–Now Haergai R. Haergai (2) 37◦14000” 100◦30000” 1425 1958.05–1963.12 1958.11–1961.12 Heima R. Heima R. 36◦43000” 99◦47000” 107 1964.8–1994.12

Evaporation from the lake was estimated by the following formula:

E = E20 × K1 (3) where E was the evaporation from the lake, E20 was the evaporation rate measured by a 20 cm pan in the Gangcha meteorological station, and K1 was 0.614, the conversion coefficient between E20 and E [27]. The transpiration water consumption of the artificial vegetation, which reduced the runoff into the Qinghai Lake from afforestation and grass, could be calculated by the water consumption quota Water 2017, 9, 552 5 of 13 Water 2017, 9, 552 5 of 13 1 WA= q  (4) of the afforestation vegetation and the corresponding1000 vegetation area. The formula could be written as follows: where W was the total transpiration water consumption1 of the artificial vegetation, q was the water W = q × A (4) consumption quota of the afforestation vegetation1000 (mm), and A was the corresponding vegetation wherearea (mW2).was the total transpiration water consumption of the artificial vegetation, q was the water consumptionAs Qinghai quota Lake of the is a afforestation closed inland vegetation lake, its (mm),water andbalanceA was equation the corresponding could be written vegetation in the areafollowing (m2). form: As Qinghai Lake is a closed inlandh  lake, P  Rsits water E  Rbalanceg   equation could be written in the(5) following form: where  h was the yearly change in ∆theh = lakeP + levelRs − (mm),E + R Pg was± ε the annual precipitation over the lake(5) (mm), Rs was the yearly surface runoff water inflow into the lake (mm), E was the annual evaporation where ∆h was the yearly change in the lake level (mm), P was the annual precipitation over the lake from the lake surface (mm), and Rg ±  was the annual groundwater inflow into the lake and error (mm), Rs was the yearly surface runoff water inflow into the lake (mm), E was the annual evaporation (mm). It was noted that Rg ±  is calculated by the lake water balance model. from the lake surface (mm), and Rg ± ε was the annual groundwater inflow into the lake and error In this study, the Mann–Kendall trend test was used to investigate the trends of the climate (mm). It was noted that Rg ± ε is calculated by the lake water balance model. factors (temperature, precipitation, evaporation) in Qinghai Lake. All the trends were investigated In this study, the Mann–Kendall trend test was used to investigate the trends of the climate factors with MATLAB R2014a software. Pearson correlation coefficients were calculated by SPSS Statistic (temperature, precipitation, evaporation) in Qinghai Lake. All the trends were investigated with 22.0. MATLAB R2014a software. Pearson correlation coefficients were calculated by SPSS Statistic 22.0. 3. Results 3. Results

3.1.3.1. VariationVariation ininthe theLake LakeWater WaterLevel Level TheThe variation variation in in the the lake lake level level during during the the period period from from 1959 1959 to 2010 to 2010 is shown is shown in Figure in Fig2.ureThere 2. There was awas significantly a significantly decreasing decreasing trend trend in the in the lake lake level level during during the the period period 1959–2004. 1959–2004. Generally, Generally, the the lake lake levellevel waswas 3196.553196.55 m in 1959 1959 and and gradually gradually fell fell to to 3192.86 3192.86 m min in2004, 2004, resulting resulting in a in total a total decline decline of 3.69 of 3.69m, with m, with an average an average decreasing decreasing rate rate of 8.2 of 8.2cm· cmyear·year−1 over−1 over 45 years. 45 years. However, However, there there appeared appeared to be to a besignificant a significant increasing increasing trend trend during during the period the period of 2005 of– 2005–2010;2010; the lake the level lake had level risen had by risen 1.04 by m, 1.04 which m, whichgreatly greatly stimulated stimulated recent recent interest interest in studies in studies of the oflake. the lake. FigureFigure3 3shows shows annual annual water water level level changes changes in in Qinghai Qinghai Lake Lake over over 52 52 years, years, of of which which lake lake level level declineddeclined forfor 31 31 years, years, with with an an average average decreasing decreasing rate rate of of 16.9 16.9 cm cm··yearyear−−1,1, andand increasedincreased oror flattedflatted forfor 2020 yearsyears with with an an average average increasing increasing rate rate of of 12.5 12.5 cm cm··yearyear−−11.. Correspondingly, thethe lakelake areaarea decreaseddecreased fromfrom 4548.30 4548.30 km km22 inin 19591959 toto 4255.424255.42 kmkm22 inin 20002000 andand thenthen increasedincreased toto 4288.774288.77 kmkm22 inin 2010.2010. DuringDuring thethe period 1959 1959–2010,–2010, there there were were five five change change-points,-points, namely namely 1966, 1966, 1968, 1968, 1988, 1988, 1990, 1990, and and2004, 2004, respectively respectively (Figure (Figure 2). Considering2). Considering the real the realfluctuant fluctuant situation situation of Qinghai of Qinghai Lake, Lake, the time the timeseries series(1959 (1959–2010)–2010) could could be divided be divided into intotwo twodistinguishable distinguishable periods, periods, namely namely 1959 1959–2004–2004 and and 2005 2005–2010.–2010.

FigureFigure 2.2. VariationVariation ofof thethe waterwater level level in in Qinghai Qinghai Lake Lake from from 1959 1959 to to 2010. 2010.

Water 2017, 9, 552 6 of 13 Water 2017, 9, 552 6 of 13

Water 2017, 9, 552 6 of 13

FigureFigure 3. Annual3. Annual water water level level changeschanges in in Qinghai Qinghai La Lakeke over over 52 52years years..

3.2. Variation of Climate Factors 3.2. Variation of Climate Factors The linear regressionFigure 3. exhibits Annual wateran annual level changes average in Qinghai temperature Lake over with 52 anyears upward. trend in the TheQinghai linear Lake regression basin during exhibits the period an annual 1961– average2010 (Figure temperature 4), at a rate with of 0.32 an upward °C/decade. trend In particular in the Qinghai, 3.2. Variation of Climate Factors ◦ Lakethe basin annual during average the period temperature 1961–2010 increase (Figure was4 ),greater at a rate from of 0.321991 toC/decade. 2010, reaching In particular, 0.41 °C/decade. the annual ◦ averageMeanwhile, temperatureThe linear the annualregression increase average exhibits was temperature greater an annual from during average 1991 the to period 2010,temperature reachingof 2005 with–2010 0.41 an was upwardC/decade. 1.1 °C trendhigher Meanwhile, in than the the annualthatQinghai during average Lake 1961 basin temperature–2004. during The seasonalthe duringperiod warming 1961 the– period2010 of the(Figure of Qinghai 2005–2010 4), at Lake a rate wasbasin of 0.32 1.1 was ◦°CC al/decade. higherso obvious, thanIn particular with that the during, 1961–2004.warmingthe annual The trend seasonalaverage of 0.22 temperature warming °C/decade, of increase the0.19Qinghai °C/decade, was greater Lake 0.33 basin °Cfrom/decade, was 1991 also toand 2010, obvious, 0.45 reaching°C/decade, with 0.41 the respectively, warming°C/decade. trend of 0.22fromMeanwhile,◦C/decade, spring tothe winter. 0.19 annual◦C/decade, Analyzing average temperature 0.33further◦C/decade,, in duringvirtue andofthe the period 0.45 Mann◦C/decade, of–Kendall 2005–2010 test, respectively, was the 1.1 Z °Cstatistic higher from of springthan the to winter.temperaturethat Analyzing during 1961was further, –4.692004. (|Z| The in virtue> seasonal 1.96), ofwhich thewarming Mann–Kendallshowed of the that Qinghai the test,annual Lake the average basin Z statistic was temperature also of theobvious, temperature showed with notthe was onlywarming an upward trend oftrend, 0.22 but°C/decade, also that 0.19 the °Ctrend/decade, is signi 0.33ficant °C/decade, at a 95% and confidence 0.45 °C /decade,level. respectively, 4.69 (|Z| > 1.96), which showed that the annual average temperature showed not only an upward fromFigure spring 5 toshow winter.s the Analyzingvariation in further annual, inprecipitation virtue of the in QinghaiMann–Kendall Lake during test, the the Z period statistic studied of the. trend, but also that the trend is significant at a 95% confidence level. Thetemperature MK test wasshow 4.69ed that(|Z| the> 1.96), Z statistic which ofshowed the annual that the precipitation annual average was 1.49temperature (|Z| < 1.96), showed which not Figureshowedonly an5 thatupwardshows the downward thetrend, variation but also trend inth atof annual the trendannual precipitation is precipitation significant in at Qinghai was a 95% not confidence significant Lake during level. at a the95% period confidence studied. The MKlevel. testFigure It showedwas 5shown show thats that the the variationthe Z statisticannual in precipitationannual of the annualprecipitation showed precipitation ina fluctuantQinghai was Lake tre 1.49nd during (|Z|during the < the 1.96), period period which studied 1961 showed–. that the2010The downward , MKwith test an averageshow trended precipitationthat of thethe annualZ statistic of 381.70 precipitation of mm·the annualyear− was1. Inprecipitation general, not significant it declined was 1.49 at from a(|Z| 95% the < confidence 1.96),1960s whichto the level. It was1970s,showed shown followed that that the the bydownward annual an increase precipitationtrend towards of the annual the showed 1980s, precipitation asa fluctuant well aswas a trendnot slight significant duringdecrease at the within a 95% period confidence the 1961–2010, 1990s, with anincreasinglevel. average It was again precipitationshown from that the the 1990s of annual 381.70 to the precipitation mm 2000s.·year The−1 annual.showed In general, average a fluctuant it declinedprecipitation trend fromduring was the the377.1 1960s period mm· to year1961 the− 1970s,1– followedand2010 415.6, by with an mm· an increase averageyear−1 during towards precipitation the theperiod 1980s,of s381.70 1961 as– mm·2004 wellyear and as− a12005. slightIn general,–2010, decrease respectively. it declined within from the the 1990s, 1960s increasingto the again1970s, fromAs followed theshown 1990s in by Fig toanure the increase 6, 2000s.annual towards evaporation The annualthe 1980s, from average aas 20 well cm precipitation evaporationas a slight decrease pan was obviously 377.1 within mm fluctuated the·year 1990s,−1, and decreasincreasinging duringagain from the period the 1990s of 1961 to the–2010, 2000s. with The a generalannual averagedecreasing precipitation trend (−30.80 was mm/decade). 377.1 mm·year The−1 415.6 mm·year−1 during the periods 1961–2004 and 2005–2010, respectively. annualand 415.6 evaporation mm·year− 1showed during thea significant periods 1961 decreasing–2004 and trend 2005 based–2010, onrespectively. the MK test ; the Z statistic of As shown in Figure6, annual evaporation from a 20 cm evaporation pan obviously fluctuated, annualAs evaporation shown in Fig wasure − 6,2.31 annual (|Z| evaporation> 1.96). The frommaximum a 20 cm evaporation evaporation was pan 1743.5 obviously mm in fluctuated 1979 and, decreasingthedecreas minimum duringing during evaporation the the period period was of of 1961–2010, 1961 1136.9–2010, mm with with in 1989. a ageneral general Meanwhile decreasing decreasing, annu trendal trendaverage (−30.80 (− mm/decade). evaporation30.80 mm/decade). wasThe The annualaboutannual 202.9 evaporationevaporation mm during showed showed the period a asignificant significant 2005–2010 decreasing decreasing, lower than trend trendthat based during based on 1961 the on – theMK2004. MKtest ;test; the Z the statistic Z statistic of of annualannual evaporation evaporation was was−2.31 −2.31 (|Z| (|Z| > >1.96). 1.96). The maximum evaporation evaporation was was 1743.5 1743.5 mm mm in 1979 in 1979 and and the minimumthe minimum evaporation evaporation was was 1136.9 1136.9 mm mm in 1989. in 1989. Meanwhile, Meanwhile annual, annual average average evaporation evaporation was was about 202.9about mm during 202.9 mm the d perioduring the 2005–2010, period 2005 lower–2010, than lower that than during that during 1961–2004. 1961–2004.

Figure 4. Annual average temperature change in Qinghai Lake basin from 1961 to 2010.

Figure 4. Annual average temperature change in Qinghai Lake basin from 1961 to 2010. Figure 4. Annual average temperature change in Qinghai Lake basin from 1961 to 2010.

WaterWater2017 2017,,9 9,, 552 552 77 ofof 1313 Water 2017, 9, 552 7 of 13

FigureFigure 5.5. AnnualAnnual precipitationprecipitation changechange inin QinghaiQinghai LakeLake basinbasin fromfrom 19611961 toto 2010.2010. Figure 5. Annual precipitation change in Qinghai Lake basin from 1961 to 2010.

FigureFigure 6.6. AnnualAnnual evaporationevaporation changechange fromfrom aa 2020 cmcm evaporationevaporation panpan inin QinghaiQinghai LakeLake basinbasin fromfrom 19611961 Figure 6. Annual evaporation change from a 20 cm evaporation pan in Qinghai Lake basin from 1961 toto 2010.2010. to 2010.

3.3.3.3. VariationVariation inin HumanHuman ActivitiesActivities 3.3. Variation in Human Activities GenerallyGenerally speaking,speaking, waterwater consumptionconsumption byby humanhuman activitiesactivities mainlymainly includedincluded humanhuman andand Generally speaking, water consumption by human activities mainly included human and livestock,livestock, agriculturalagricultural irrigationirrigation andand industrialindustrial waterwater use.use. livestock, agricultural irrigation and industrial water use. TheThe populationpopulation numbernumber inin thethe studystudy areaarea experiencedexperienced aa rapidrapid increaseincrease inin thethe 1980s,1980s, waswas basically The population number in the study area experienced a rapid increase in the 1980s, was basically stablestable duringduring the the 1990s 1990s and and slightly slightly increased increased in thein the 2000s, 2000s while, while the the number number of livestock of livestock showed showed two stable during the 1990s and slightly increased in the 2000s, while the number of livestock showed opposingtwo opposi variationng variation trends, trends, a rapid a growthrapid growth before thebefore 1970s the and 1970s a slow and growtha slow afterwards.growth afterwards. Human two opposing variation trends, a rapid growth before the 1970s and a slow growth afterwards. andHuman livestock and livestock water consumption water consumption in the Qinghai in the Qinghai Lake basin Lake was basin a net was consumption, a net consumption, with a with water a Human and livestock water consumption in the Qinghai Lake basin was a net consumption, with a consumptionwater consumption quota ofquota 40 L/day of 40 perL/day human per human and 15 and L/day 15 L/ perday livestock. per livestock. Human Human and livestock and livestock water water consumption quota of 40 L/day per human and 15 L/day per livestock. Human and livestock consumptionwater consumption is shown is in shown Figure7 .in The Fig averageure 7. annualThe average human andannual livestock human water and consumption livestock water was water consumption is shown in Figure 7. The average annual human and livestock water approximatelyconsumption was 0.15 approximately× 108 m3 from 0.15 1961 × to10 2010.8 m3 from 1961 to 2010. consumption was approximately 0.15 × 108 m3 from 1961 to 2010. TheThe areaarea ofof agriculturalagricultural irrigationirrigation grewgrew rapidlyrapidly inin thethe 1960s;1960s; however,however, itit greatlygreatly decreaseddecreased inin The area of agricultural irrigation grew rapidly in the 1960s; however, it greatly decreased in recentrecent years,years, duedue toto environmentalenvironmental protectionprotection (Figure(Figure8 ).8). According According to to the the comprehensive comprehensive plan plan of of recent years, due to environmental protection (Figure 8). According to the comprehensive plan of nationalnational waterwater resources,resources, thethe waterwater consumptionconsumption quotaquota forfor agriculturalagricultural irrigationirrigation inin thethe QinghaiQinghai LakeLake national water resources, the water consumption quota for agricultural irrigation in the Qinghai Lake areaarea waswas aboutabout 4852.624852.62 mm33/(hectare/(hectare··year).year). On On the the basis of the irrigation areaarea and the irrigationirrigation waterwater area was about 4852.62 m3/(hectare·year). On the basis of the irrigation area and the irrigation water consumptionconsumption quota,quota, thethe averageaverage annual annual agricultural agricultural irrigation irrigation water water consumption consumption was was 0.59 0.59× ×10 1088m m33 consumption quota, the average annual agricultural irrigation water consumption was 0.59 × 108 m3 inin thethe studystudy areaarea fromfrom 19611961 toto 2010.2010. in the study area from 1961 to 2010. Industry in the Qinghai Lake area started later and the handicraft industrial system gradually Industry in the Qinghai Lake area startedstarted later andand thethe handicrafthandicraft industrialindustrial systemsystem gradually came into being in the early 1960s. Then, industrial water use started to develop from 1973 (Figure came into into being being in in the the early early 1960s. 1960s. Then Then,, industrial industrial water water use started use started to develop to develop from 1973 from (Fig 1973ure (Figure9). According9). According to the regional to the indus regionaltrial industrial water consumption water consumption quota (145 quotam3/10,000 (145 yuan) m 3/10,000 and the yuan)water 9). According to the regional industrial water consumption quota (145 m3/10,000 yuan) and the water andconsumption the water rate consumption (about 40%), rate the (about average 40%), annual the average industrial annual water industrial consumption water was consumption about 4.76 × was 104 consumption rate (about 40%), the average annual industrial water consumption was about 4.76 × 104 aboutm3 in the 4.76 whole× 104 periodm3 in the of study whole. period of study. m3 in the whole period of study.

Water 2017, 9, 552 8 of 13 WaterWater 2017 2017, 9,, 95,52 552 8 of8 of 13 13

Figure 7. Total surface runoff and human and livestock water consumption in the Qinghai Lake FigFigureFigureure 7. 7.7. Total TotalTotal surface surface surface runoff runoff runoff and and and human human human and and and livestock livestock livestock water water water consumption consumption consumption in in the the in Qinghai Qinghai the Qinghai Lake Lake catchment. catchmentLakecatchment catchment.. .

FigFigureFigureure 8.8. 8. TotalTotal Total surface surface surface runoff runoff runoff and and and agricultural agricultural agricultural irr irrigation irrigationigation in in in the the the Qinghai Qinghai Qinghai Lake Lake Lake catchment catchment. catchment. .

Figure 9. Total surface runoff and industrial water consumption in the Qinghai Lake catchment. FigFigureure 9. 9. Total Total surface surface runoff runoff and and industrial industrial water water consumption consumption in in the the Qinghai Qinghai Lake Lake catchment catchment. . 3.4. Variation of Artificial Afforestation and Grass Plantation 3.43.4. Variation. Variation of of Artificial Artificial Afforestation Afforestation and and Grass Grass Plantation Plantation In order to prevent and control soil erosion, restore the natural vegetation and reduce the area InIn order order to to prevent prevent and and control control soil soil erosion, erosion, restore restore th the enatural natural vegetation vegetation and and reduce reduce the the area area of vegetation degeneration, large-scale artificial afforestation and grass plantation has taken place in ofof vegetation vegetation degeneration, degeneration, large large-scale-scale artificial artificial afforestation afforestation and and grass grass plantation plantation has has taken taken place place in in Qinghai Lake basin in recent years. However, artificial vegetation mainly took up water to maintain its QinghaiQinghai Lake Lake basin basin in in recent recent years. years. However, However, artificial artificial vegetation vegetation mainly mainly took took up up water water to to maintain maintain normal growth, which in turn reduced the surface runoff into the lake. itsits normal normal growth, growth, which which in in turn turn reduced reduced the the surface surface runoff runoff into into the the lake. lake. Artificial vegetation transpiration was another essential water consumption, which could be ArtificialArtificial vegetation vegetation transpiration transpiration was was another another essential essential water water consumption, consumption, which which could could be be calculated by the water consumption quota of the afforestation vegetation and the corresponding calculatedcalculated by by the the water water consumption consumption quota quota of of the the afforestation afforestation vegetation vegetation and and the the corresponding corresponding artificial afforestation and grass plantation area (Formula (4)). Because of the lack of measured artartificialificial afforestation afforestation and and grass grass plantation plantation area area (Formula (Formula 4). 4). Because Because of of the the lack lack of of measured measured data data data about vegetation transpiration in this area, the vegetation transpiration quota was determined aboutabout vegetation vegetation transpiration transpiration in in this this area, area, the the vegetation vegetation transpiration transpiration quota quota was was determined determined according to the relevant articles with a similar area or the same vegetation [28]. The water consumption accordingaccording to to the the relevant relevant articles articles with with a asimilar similar area area or or the the s amesame vegetation vegetation [28] [28]. .The The w waterater quota of artificial vegetation in Qinghai Lake area is shown in Table4. consumptionconsumption quota quota of of artificial artificial vegetation vegetation in in Qinghai Qinghai Lake Lake area area is is shown shown in in Table Table 4. 4.

Water 2017, 9, 552 9 of 13

Table 4. Water consumption quota of artificial vegetation in Qinghai Lake basin (mm).

Vegetation Types and Zoning Annual Water Consumption Quota Haiyan County 282.9 Artificial afforestation Gangcha County 274.0 Gonghe County 277.9 Artificial grass plantation 231.7

The transpiration of newly-planted artificial afforestation and grass plantation in 2001–2005 and 2006–2010 is shown in Table5. The annual average water consumption of artificial afforestation and grass plantation was 1.81 × 108 m3.

Table 5. Artificial afforestation and grass plantation water consumption in Qinghai Lake catchment from 2001 to 2010.

2001–2005 2006–2010 County Vegetation Types Water Consumption (108 m3) Water Consumption (108 m3) Total in Gangcha 0.19 0.17 Gangcha Artificial afforestation 0.13 0.12 Grass plantation 0.06 0.05 Total in Haiyan 0.42 0.39 Haiyan Artificial afforestation 0.39 0.36 Grass plantation 0.03 0.03 Total in Gonghe 0.33 0.31 Gonghe Artificial afforestation 0.20 0.18 Grass plantation 0.14 0.13 Total of the 3 counties 0.94 0.87 Sum Artificial afforestation 0.71 0.66 Grass plantation 0.23 0.21

3.5. Lake Water Balance The lake water balance was calculated based on measured data over a long period. Although errors might exist, the data were close to the actual situation. Thus, groundwater inflow into the lake and the possible error could be calculated according to the water balance equation. The mean annual groundwater inflow was 145.1 mm (Table6). Over the last 50 years, the average annual precipitation over the lake was 389.4 mm, surface runoff inflow into the lake was 300 mm, evaporation from the lake surface was 918.7 mm and the change of lake level was −50 mm (Table6). Overall, the water balance of Qinghai Lake is negative, as indicated by the water level drop-line; 50 mm below the initial lake level between 1961 and 2010.

Table 6. Characteristic of the factors of the water balance of Qinghai Lake from 1961 to 2010.

Descriptive Statistics ∆h (mm) P (mm) Rs (mm) E (mm) Rg + ε (mm) Maximum 342 535.7 673 1068.9 276.1 Minimum −352 268.3 115 796.6 7.4 Mean ± Std. deviation −50 ± 176 389.4 ± 62.7 300 ± 124 918.7 ± 71.2 145.1 ± 67.7

4. Discussion Water level and its variation play important roles in lake ecosystems [29]. As the largest inland lake in China, the variation in the water level of Qinghai Lake has attracted a great deal of attention [30,31]. In our study, the lake water level was shown to have declined from 1959 to 2000, which was consistent Water 2017, 9, 552 10 of 13 with Li [32], who came to the same conclusion that the lake water level had tended to decrease in the years from 1959 to 2000. In addition, we found that there appeared to be a significantly increasing trend during the period 2005–2010. The mean annual water level of Qinghai Lake declined to its lowest level in 2004. Afterwards, the lake level has increased year by year since 2005 and, so far, it has recovered to its level in the 1980s. The rise of the lake level was an important sign for the improvement of the plateau ecological environment in Qinghai Lake. However, the rise of the lake level also resulted in land submergence around Qinghai Lake, especially for the bird island located on the western shore of the Qinghai Lake, which led to continuous limits on bird-breeding. Therefore, effective measures (such as, among others, the construction of an artificial island) should be taken to alleviate the contradiction between the reduction of the breeding ground for birds and the rising water levels in Qinghai Lake. Climate factors such as precipitation, runoff inflow into the lake, evaporation from the lake, atmosphere and lake water temperature might result in the variation in the lake level [33]. In recent years, scientists have studied the sediment geochemistry linked to the hydroclimate variability of Qinghai Lake more and focused less, to some extent, on the effects of climatic factors on lake level variation [34]. As Qinghai Lake was a closed basin with no surface water outflow, the climate factors that had an effect on lake level variation mainly included precipitation over the lake, surface runoff, groundwater inflow into the lake, evaporation from the lake and temperature. Table7 showed the Pearson correlation between the changes in the lake level and the climatic factors. Changes in the lake level (∆h) were significantly and positively correlated to precipitation (P), surface runoff water inflow into the lake (Rs) and groundwater inflow into the lake (Rg) and negatively correlated to evaporation from the lake surface (E), with a correlation coefficient of 0.454, 0.559, 0.302 and −0.394, respectively, and all were significant at a level of less than 0.01 (Table7). We drew the conclusion that increasing precipitation and surface runoff or decreasing evaporation had a significant effect on the increase of the water level, which mainly occurred from 2005 to 2010. The results were highly consistent with the results of previous studies [33,34].

Table 7. Pearson correlation coefficients between ∆h, P, E, Rs and Rg.

Correlations ∆h P E Rs Rg Pearson Correlation 1 - - - - ∆h Sig. (2-tailed) - - - - - Pearson Correlation 0.454 ** 1 - - - P Sig. (2-tailed) 0.001 - - - - Pearson Correlation −0.394 ** −0.480 ** 1 - - E Sig. (2-tailed) 0.005 0.000 - - Pearson Correlation 0.559 ** 0.492 ** −0.618 ** 1 - Rs Sig. (2-tailed) 0.000 0.000 0.000 - - Pearson Correlation 0.302 * −0.467 ** 0.394 ** −0.453 ** 1 Rg Sig. (2-tailed) 0.033 0.001 0.005 0.001 - ** Correlation is significant at the 0.01 level (2-tailed). * Correlation is significant at the 0.05 level (2-tailed). ∆h was the change in the lake level (mm), P was precipitation over the lake (mm), E was evaporation from the lake surface (mm), Rs was surface runoff water inflow into the lake (mm), and Rg was groundwater inflow into the lake (mm).

The temperature increase in the basin resulted in an intensified glacier retreat, increased melt water and rising lake level. The reasons for the change in the lake level were roughly similar to the other lakes in the Qinghai-Tibetan Plateau [35,36]. Human activities such as human and livestock water use, agricultural irrigation water consumption, and industrial water consumption, may affect the variation in the lake level. The effect of human activities on lake level variation could be reflected by the effect of lake evaporation and precipitation, surface runoff inflow and groundwater inflow. Water 2017, 9, 552 11 of 13

The average annual water input and lake evaporation were 37.64 × 108 m3, 39.69 × 108 m3 from 1961 to 2010 in the lake, respectively. Meanwhile, the average annual consumption of human activities was 0.74 × 108 m3 from 1961 to 2010. In conclusion, the total water consumption by human activities only accounted for a very small part of the precipitation, surface runoff inflow and groundwater inflow (1.97%) and of the lake evaporation (1.87%) in Qinghai Lake basin. The results revealed that water consumption by human activities had little effect on the water level in Qinghai Lake. Liu et al. (2009) also reported that water consumption by human activities was not the primary cause of the water level in Qinghai Lake. The average annual water input and lake evaporation were 35.76 × 108 m3 and 33.40 × 108 m3 from 2000 to 2010 in the lake, respectively. The average annual water consumption of artificial afforestation and grass plantation was 1.81 × 108 m3, accounting for 5.07% of the total precipitation, surface runoff inflow and groundwater inflow and 5.43% of the lake evaporation. The proportion was so small that it could be considered negligible. Thus, it was implied that water consumption by artificial afforestation and grass plantation also had little effect on the water level in Qinghai Lake. In order to prevent and control soil erosion, restore the natural vegetation and mitigate vegetation degeneration, an artificial afforestation and grass plantation campaign has been conducted in Qinghai Lake basin in recent years. In previous studies, some researchers had maintained the position that the implementation of artificial afforestation in the Qinghai Lake basin might reduce the inflow runoff into Qinghai Lake and bring in a sustained decline of the lake water level, due to its high water consumption, canopy interception as well as its reduced soil moisture infiltration. However, in recent years, the rising water level in Qinghai Lake has attracted public attention, and the concerns that artificial afforestation could lead to the decline of the water level might have been eliminated to some extent. On the contrary, to our knowledge, the result showed that artificial afforestation might be conducive to the rising water level of Qinghai Lake.

5. Conclusions In this study, the variation in the water level in Qinghai Lake, which has a great ecological importance, over a 52-year period from 1959 to 2010 and the variation in climate and anthropogenic factors over a 50-year period from 1961 to 2010 were investigated to evaluate the impacts of anthropogenic and climatic factors. The results showed that lake level was 3196.55 m in 1959, and fell to 3192.86 m in 2004, with an average decreasing rate of 8.2 cm·year−1 over 45 years. However, the lake level increased by 1.04 m from 2005 to 2010. During the period 1961–2010, the annual average temperature showed an increasing trend in the Qinghai Lake basin, at a rate of 0.32 ◦C/decade. The annual precipitation showed obvious fluctuations, with an average precipitation of 381.70 mm·year−1, while annual evaporation experienced a decreasing trend (−30.80 mm/decade). The change in lake level was positively correlated to precipitation, surface runoff water and groundwater inflow into the lake, and negatively correlated to evaporation from the lake surface. The results revealed that water consumption by human activities had little effect on the water level in Qinghai Lake. It was implied that water consumption by artificial afforestation and grass plantation also had little effect on the water level in Qinghai Lake. In conclusion, the water level depended more on climatic factors than on anthropogenic factors, because water consumption by human activities and artificial afforestation and grass plantation accounted for a very small proportion of the average annual precipitation, surface runoff inflow and groundwater inflow and lake evaporation of Qinghai Lake.

Acknowledgments: This study was financially co-supported by the Science and technology project of Qinghai Province (2015-ZJ-902), the National Science-technology Support Plan Projects (2015BAD07B030302) and the Qinghai province science and technology plan program (2014-NK-A4-4). Thanks for providing hydrological data to the Institute of Water Resources and Hydropower of Qinghai Province and for providing meteorological data to the Institute of Meteorological Sciences of Qinghai Province. Water 2017, 9, 552 12 of 13

Author Contributions: Bo Chang and Kang-Ning He conceived and designed the experiments; Run-Jie Li performed the experiments; Zhu-Ping Sheng and Hui Wang analyzed the data; Bo Chang wrote the paper. Conflicts of Interest: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

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