藏东南易贡湖历史水面形态重构及演化过程分析

Analysis of Historical Water Surface Reconstruction and Evolution Process of Yigong Lake in Southeast Tibet

近年来青藏高原湖泊呈持续扩张趋势,泥石流、冰湖溃决等自然灾害发生频率与强度不断增加,给该地区及下游区域的水资源管理、水灾害防治和可持续发展带来一系列重大挑战。对此,建立藏东南易贡湖高原水体指数模型(TNDWI),收集整理1101景遥感影像,重构易贡湖1986~2020年35年水面形态,并分析湖泊历史水面形态演化过程。结果表明,TNDWI对高原水体分类的用户精度均高于96.70%,总体精度均超过98.75%,Kappa系数介于0.972~0.992,分类精度与一致性优于传统水体指数法;2000年堰塞湖溃决对易贡湖水面形态的演化过程影响显著,溃决后水面面积由14.44±2.70 km^(2)显著萎缩至10.99±1.94 km^(2)(P<0.001);Mann-Kendall突变检验表明,水面形态演化过程的突变节点发生在2000年(枯水期除外);Morlet小波周期分析结果表明,水面面积的周期性振荡规律在2000年以后呈衰弱趋势。研究结果克服了高海拔堰塞湖监测资料缺失问题,为易贡湖生态修复与综合治理提供了数据基础,为该类型区域的生态环境状况定量研究提供了新思路。

The lakes on Tibetan Plateau are expanding continuously,and the frequency and intensity of natural disasters(debris flow,glacial lake outburst)are increasing,which brings a series of challenges to water resources management,water disaster prevention and sustainable development in Tibetan Plateau and its downstream areas.Taking Yigong Lake as the research object,this paper establishes Tableland NDWI(TNDWI)based on 1101 remote sensing images.Then the water surface morphology of Yigong Lake from 1986 to 2020 is reconstructed to analyze evalution process of historical water surface morphology in lake.The results show that the user accuracy of the TNDWI for the classification of plateau water bodies is higher than 96.70%,the overall accuracy is higher than 98.75%,and the Kappa coefficient is between 0.972 and 0.992,and the classification accuracy and consistency are better than the tranditional NDWI;The 2000 Yigong landslide has a significant impact on the evolution process of water surface morphology of Yigong Lake;Water surface area after dam-break reduces from 14.44±2.70 km^(2) to 10.99±1.94 km^(2)(P0.001).Mann-Kendall mutation test results show that the change trend of water surface morphology has a mutation in 2000(except in dry season);Morlet wavelet periodic analysis results show that the periodic oscillation law of lake area has gradually weakened since 2000.This study overcomes the lack of monitoring data of high altitude barrier lake,providing data basis for the ecological restoration and comprehensive treatment project of Yigong Lake as well as new idea for the quantitative study of the ecological environment in the region.