青藏高原西北部河流提取及季节变化差异分析

River Extraction and Analysis of Seasonal Variation Difference on the Northwestern of Tibetan Plateau

河流是地球水循环的一个重要环节,准确获取山区河流信息对于区域内的水资源评价和生态修复方面都有重要作用。基于2019~2021年Sentinel-2影像,利用多光谱指数法自动区分河流、湖泊及冰川,结合随机森林方法,并以MERIT DEM为地形条件,自动提取青藏高原西北部多时态、高分辨率的河网,结合第二次冰川编目划分了不同补给类型的集水区,进一步计算了河流面积和宽度的季节变化。结果表明,在这3 a内丰水期和枯水期的河流平均面积分别达到了7161.64±22.73 km2和4066.02±35.19 km2,Kappa系数和总体精度均达到了0.8以上,冰川补给类型和非冰川补给类型的河流平均面积季节变化率分别为0.34和0.23,冰川补给类型平均宽度季节变化大部分比非冰川补给类型变化大。冰川补给类型的河流宽度和面积变化比非冰川补给类型的河流变化整体更加明显,该研究表明冰川融水对河流径流的变化有重要的影响。

Rivers play an important part of the earth's water cycle,and it is significant to extract mountain river information accurately for water resource evaluation and ecological restoration.According to Sentinel-2 images from 2019 to 2021,and the multi-spectral index method was used to distinguish rivers,lakes and glaciers auto⁃matically by combining with the Random Forest(RF),and MERIT DEM was used as the terrain condition to extract the multi-temporal and high-resolution river automatically.Combined with the second glacier inventory dataset of China,the catchment of different recharge types were divided,the percentage change in river area and width was further calculated to describe the seasonal changing rate.The results showed that the average ar⁃ea of the river in the wet season and the dry season has reached 7161.64±22.73 km2 and 4066.02±35.19 km2 during 2019~2021,respectively,and both the Kappa coefficient and the overall accuracy are larger than 0.8.The average seasonal changing rates of river areas of glacier-fed types and non-glacier-fed were 0.34 and 0.23,respectively.The seasonal variation of the average width of glacial-fed rivers was mostly larger than that of non-glacial-fed rivers.The results showed that the changes in width and area of glacier-fed rivers are much larger than that of non-glacier-fed rivers,suggested that glacial meltwater has an important impact on the changes of river runoff.