西藏喜马拉雅山脉中段冰湖变化与溃决特征分析 ——以桑旺错和什磨错为例

年楚河流域是西藏自治区农业相对发达的地区，流域内冰川发育较好，冰川融水是地表径流重要的组成部分，冰湖溃决洪水灾害也威胁着下游村镇和城市。本文利用遥感技术对流域内桑旺错和什磨错两个冰湖特征进行分析，结合实地野外调查，对冰湖变化和溃决特征展开讨论。结果表明：1987-2018年，桑旺错和什磨错都呈扩张趋势，面积分别增加了0.31 km²（5.56%）和0.954 km²（96.9%），变化率分别为0.054 km²·（10a）^-1和0.311 km²·（10a）^-1。桑旺错和什磨错侧碛垄、终碛垄为松散堆积物，结构松散、稳定性差。桑旺错出水口开阔，出水流畅。什磨错没有出水口，在最内侧终碛垄外有渗流。桑旺错和什磨错后缘冰川冰舌相接，冰舌陡峭，冰舌崩塌可能性较大，同时两湖侧碛垄稳定性较低，也存在崩塌的风险。桑旺错溃决风险较小，什磨错溃决风险较大。

Analysis of change and outburst feature of glacial lake in the middle Himalayas of Tibet: take Sangwang Co and Shimo Co as examples

The Nyang Qu Basin is a relatively developed area of agriculture in the Tibet Autono-Mous Region, and it is also a region with more glaciers. On one hand, the glacial Melt water is an important source for surface runoff, on other hand, the flood disasters caused by the glacial lake outburst threaten the lower reaches of the Nyang Qu. One of the examples is the outburst of the Sangwang Co on July 16, 1954 which caused a great damage and casualties. In this study, based on the images of the Landsat TM/ETM⁺ (1987-2018), the QUICKBRID (2015) and the Gofen-1 satellite (2018) as well as the topographic geological data measured in the field, we analyze the changes and the outburst characteristics of two glacial lakes, Sanwang Co and Shimo Co. The results show:during the period from 1987 to 2018, both Sangwang Co and Shimo Co were expanded, with an increase of 0.31 km²(5.56%) and 0.954 km²(96.9%) respectively. The rate of change is 0.054 km²·(10a)^-1 and 0.311 km²·(10a)^-1. The lateral moraine and terminal moraine of the two Lakes are uncompact sediment with loose structure and poor stability. The outlet of Sangwang Co is wide and the water is flowing smoothly. There is no direct water outflow from Shimo Co, but seepage from the innermost side of terminal moraine. The Sangwang Co and Shimo Co are connected with the ice glaciers of the trailing edge glacier. The ice tongues are steep that may have high possibility of ice collapse. Meanwhile, risks of outburst exist for both lakes due to the poor stability of the lateral moraines. The risk of outburst for Shimo Co is higher than that for Sangwang Co.