1973—2017年西藏盐湖湖面动态变迁及对气候波动的响应

Dynamic Changes of Saline Lakes in Xizang and Its Response to Climate Fluctuations from 1973 to 2017

西藏是我国主要盐湖成盐区之一,蕴藏着丰富的矿产资源。应用遥感和地理信息系统技术,从5个时间段的Landsat遥感影像中提取了西藏面积大于20 km^(2)的93个盐湖(不包括干盐湖),影像成像时间分别为1973—1977年、1990年前后、2000年前后、2010年前后和2017年,建立了西藏盐湖空间数据库,并分析了其1973—2017年的变化趋势。结论为:(1)总体上盐湖总面积呈增加趋势,且2000年之后,盐湖扩张趋势加剧,至2017年,被研究盐湖总面积已增至1990年前后的1.68倍。(2)从20世纪70年代至90年代,西藏中北部盐湖呈萎缩趋势,其余地区扩张。(3)盐湖湖面变迁与气候波动密切相关,1971—1990年气温和降雨量波动不大,引起西藏中北部盐湖萎缩的主要原因为冰川和冰雪融水补给的减少;1991—2017年气温升高降雨量增加、蒸发量减少,导致西藏盐湖呈现全面扩张的趋势。(4)扎布耶盐湖湖面动态变迁遥感解译结果与扎布耶长期观测站水位观测数据基本一致。1973—2009年其水位整体上呈波动式上升的趋势,而从2009年开始有所下降。landsat8从2013年开始免费提供多时相的遥感影像,可做西藏盐湖动态变迁的持续观测。盐湖水深和成分应作为以后重点解决的问题。

Xizang is one of the main saline lake distribution areas in China.The surface extents of 93 saline lakes,with the area larger than 20 km^(2),in the study area were delineated from Landsat images obtained in 1970’s,1990’s,around 2000,around 2010,and 2017 based on RS and GIS.The dynamic changes of these lake surface areas from 1970’s to 2017 were analyzed.The results were as followed:(1)The total surface areas of these saline lakes increased by 68%during 1990’s to 2017;(2)during 1970’s to 1990,saline lakes with area decreasing mainly distributed in the northern and middle parts of Xizang.Since 2000,most lakes have expanded;(3)Dynamic changes of saline lake areas are closely related to climate fluctuations.From 1971 to 1990,there were few temperature and rainfall fluctuations,and the decrease of glacier and snowmelt water supply caused the shrinkage of saline lakes in the northern and middle parts of Xizang.From 1991 to 2017,the temperature and rainfall increased while the evaporation decreased,leading to the overall expansion of saline lakes in Xizang.(4)The remote sensing interpretation of Zabuye Salt Lake areas are basically in agreement with the long-term data on water level from the monitoring station.From 1973 to 2009,the water levels of Zabuye Salt Lake showed an overall upward trend,and then,declined.Landsat 8 provides free multi-temporal remote sensing images from 2013,which can be used for continuous observation of the saline lake dynamic changes in Xizang.The change of areas and chemical compositions of saline lakes should be highlighted in the future research.