Water Level Fluctuation And Its Response To Climate In The West Of The Tibetan Plateau

Lake as a regional water body summary,its area,water level and volume changes are a comprehensive reflection of the basin climate change.Lakes as a key node of the ecosystem have an important impact on the ecological environment.The Tibetan Plateau lakes are extremely sensitive to climate change,which is an important carriers to reveal climate change and regional response.Based on the data of remote sensing images and radar altimetry data,through the study of the typical closed lake in the western Tibetan Plateau,the time series of lake area and water level fluctuation in the study area during 2003-2009 were analyzed,and the relative water quantity changes series of lakes were established.Based on the meteorological station data and satellite precipitation data in the basin,the main influencing factors of the lake change were analyzed,and the response of the closed lake change to the climate was discussed,so as to provide reference for global change.The main results are as follows:During the period from 2003 to 2009,the water level of Ngangla Ring Tso and Rinchen Shubtso was the turning point in early 2006,showing a tendency to decrease first and then increase,and the rate of increase was higher than the rate of decline.During the year,the annual water level of lake in October or November reached the highest value in the year,February or March for the lowest value in the year.From 2003 to 2005,the water level of Ngangla Ring Tso was increased by 0.65m,with an average of 0.22m/a.The water level in 2006-2009 increased by 1.14m,with an average of 0.38m/a.From 2003 to 2005,the water level of Rinchen Shubtso decreased by 0.23m,with an average of 0.08m/a.And the water level in 2006?2009 increased by 0.78m,with an average of 0.26m/a.The area of lakes in 2005 or 2006 as the turning point,also showed the first shrinkage and then growth trend,the overall trend of decline for the shrinking.From 2003-2009,the rate of change of area of Ngangla Ring Tso is 19.5%and the minimum value is 495.23m2.And the change rate of the area of Rinchen Shubtso is 1.01%and the minimum is 186.07 m2.The area time series had small peak in winter and spring,and the autumn was large peak.From the spatial changes,the obvious changes in the area of the lake are mainly distributed in the eastern,southwest,west and Renqing clams in the southwest regionThe overall change trend of the relative water quantity is consistent with the area and water level,and then decrease and then increase.From 2003 to 2009,the average value of the cumulative change of the relative amount of water in Ngangla Ring Tso is-2.05×107m3,and the average value of the relative water change is-0.40×106m3.And the average change.And the average value of the cumulative change of the relative water quantity in Rinchen Shubtso is-0.94×107m3,and the average value of the relative water change is-0.03×106m3.During the year,the avenrage value of the cumulative change of the relative water quantity in Ngangla Ring Tso in summer and winter months was-3.27×107m3 and-2.63×107m3,repectively,and the average value of relative water quantity was0.15×106m3 and 0.003×106m3.And the average value of the cumulative change of the relative water quantity in Rinchen Shubtso in summer and winter months was 0.70×107m3 and-1.32×107m3,repectively,and the average value of relative water quantity was-0.04×106m3 and-0.10×106m3.The difference in the variation of lake water is mainly due to the change of water quantity in summer and winter months.Climate change is the driving factor of dynamic change of lakes,and Ngangla Ring Tso and Rinchen Shubtso are very sensitive to climate fluctuation.Precipitation,temperature,ground temperature,evaporation and other parameters are closely related to lake area and water level changes.In the case of Ngangla Ring Tso,the change of long-term precipitation directly leads to the change of surface runoff and lake precipitation,which is the main factor of the lake changesand the change of relative humidity and evaporation is the secondary factor.In the case of Rinchen Shubtso,changes in ground temperature and evaporation led to changes in the amount of glacier and permafrost in the basin,which is the main factor of the lake changes,and the change of temperature and precipitation is the secondary factor.Under similar climatic conditions,the lake has a significant differences in the response of climate change.The basin area of Ngangla Ring Tso is large,the supply coefficient is large,the spatial distribution of precipitation is inconsistent,and the coefficient of variation is large.Due to the distribution of glaciers,the runoff,and precipitation,the water level of Ngangla Ring Tso changes drastically.Basin area of Rinchen Shubtso is small,the supply coefficient is small,the variation coefficient of precipitation is small,the lake water quantity is stable,the lake change is relatively small.