喜马拉雅山北坡冰碛湖库容计算及变化——以龙巴萨巴湖为例

Reservoir Capacity Calculation and Variation of Moraine-dammed Lakes in the North Himalayas:A Case Study of Longbasaba Lake

喜马拉雅地区冰湖溃决洪水灾害日益受到人们重视。作为估算冰湖溃决洪峰流量和模拟洪水演进的必要参数之一,冰湖库容量准确计算十分重要。2009年9月对西藏定结县龙巴萨巴湖科考时,应用HydroboxTM高分辨率回声测深仪对该湖进行了测深试验,共采集6916个离散数据点,测得冰湖最深处为101.94m,平均水深47.50m。结合同一时段Landsat TM遥感影像解译结果,通过构建不规则三角网模拟龙巴萨巴湖湖盆形态,并计算出该湖2009年库容量为0.64×108m3。利用GIS技术对1977-2008年不同年份的LandsatMSS、地形图、LandsatTM和ASTER遥感影像进行数字化,结果表明近30年来龙巴萨巴湖长度和面积均呈增加趋势,且自2000年以来更为显著。利用不同时期龙巴萨巴湖面积和计算的库容量,得到冰碛湖库容—面积计算公式,可为喜马拉雅地区其他冰碛湖库容量估算提供理论参考。龙巴萨巴湖的扩张方向与其母冰川后退方向保持一致。通过对龙巴萨巴湖所在区域中国境内5个气象站点气温、降水数据的年代际变化分析,表明冰湖规模扩大是气候变暖和冰川退缩的产物。

Glacial Lake Outburst Flood（GLOF） hazards have been paid more attention in Himalayan region.The accurate calculation of reservoir capacity of glacial lake is very important for estimating outburst flood peak discharge and simulating flood evolution.The Longbasaba Lake,located in Dingjie County of Tibet,is a potential dangerous moraine-dammed lake.Its depth was measured by Hydrobox TM high resolution echo sounder and 6916 samples were collected in field investigation held in September 2009.The maximum depth and average depth of Longbasaba Lake were found to be up to 101.94 m and 47.50 m,respectively.Based on the same time Landsat Thematic Mapper（TM） image interpretation,lake basin shape was simulated by constructing Triangulated Irregular Network（TIN） and the reservoir capacity was 0.64 × 10 8 m 3.Furthermore,multi-source remote sensing images from 1977 to 2008,such as Landsat MSS,topographic map,Landsat TM and ASTER,were interpreted and digitalized by a GIS software.The result showed that the length and area of Longbasaba Lake were increasing in the last 32 years and the tendency was more significant since 2000.The empirical formula of volume-area of moraine-dammed lake was built by analyzing the volume and area in different periods,which could be used to calculate the reservoir capacity of other moraine-dammed lakes in the Himalayan region.Finally,based on the analysis of the interdecadal variations in temperature and precipitation from five weather stations in this region,and the same direction of lake expansion with the glacier recession,it could be demonstrated that the area increase of Longbasaba Lake was due to climate warming,glacier ablation and retreat.