Monitoring Waters And Glacier Changes For Sarez Lake In Central Asia By Using Remote Sensing Technology

Sarez Lake,located in the inaccessible Pamirs,is known as the largest plateau dammed lake.Lake level in Sarez Lake rised in volatility for many years.The collapse of the dam will make the lake flow out and bring about a disaster to the people in Central Asia.There is a lack of specific research on the characteristics and driving factors of volume change in Sarez Lake.Combined with Landsat imagery,ICEsat and Cryosat-2 altimetry data,and DEM data,this article monitored the water resources change in Sarez Lake and the change in the elevation and volume change of glaciers in this basin.Moreover,combined with meteorological data,multi-factor correlation analysis was conducted to explore the driving factors of water resources changes in the Sarez Lake.The main research contents and innovative results are as follows:(1)The research extracted the time series of the area and volume change from1972 to 2019.It employed Landsat and ASTER GDEM data,using an adaptive water extraction algorithm by combining global-local threshold segmentation technology and normalized water index to make sure the accuracy of the shoreline of Sarez Lake during 1972-2019.Then combined with the in-situ water level time series,the volume change of Sarez Lake was monitored.The results show that the volume change rised at a mean rate of 0.012 km~3/yr from 1972 to 2018.(2)Considering on the high-altitude mountain ice caps and glaciers characterized by complex terrain,this research established a technique for monitoring the elevation change of high-altitude mountain ice caps and glaciers by proposing a method of altimeter waveform optimization classification to select the effective observations,and combinding the modified pseudo-repeat track method.Based on the ICESAT and Cryosat-2 altimeter data,the glacier elevation change in the Sarez Lake Basin from2003 to 2019 was monitored.(3)The surface area,surface elevation and volume change of glaciers in the Basin of Sarez Lake was estimated.The results show that the volume of glaciers in the basin increased at a mean rate of 0.193 km~3/yr from 2003 to 2009,and decreased at a mean rate of 0.312 km~3/yr from 2010 to 2019.(4)The driving factors for the changes in the water resources of Sarez Lake was analyzed by using meteorological data such as temperature,precipitation and potential evapotranspiration,as well as the inflow of Sarez Lake and the glacier changes in this basin.The results show that the precipitation and evapotranspiration in Sarez Lake remain relatively stable,and there is no significant correlation with the changes of the water resources of Sarez Lake.There is a significant positive correlation between the discharge of the Morghab River and the volume change of Sarez Lake.Combined with the analysis of glacier changes in the Sarez Lake Basin,it is found that more than15.4%of the average annual glacier melt contributes to the runoff of the Morghab River,which affects the water quantity change of the Sarez Lake.