基于四种水体指数的艾比湖水面提取及时空变化分析

以Landsat5/7/8系列遥感影像为数据源,利用归一化差异水体指数(Normalized difference water index,NDWI)、改进的归一化差异水体指数(Modified normalized difference water index,MNDWI)、自动水体指数(Automated water extraction index,AWEI)、改进的自动水体指数(Modified automated water extraction index,MAWEI )提取艾比湖水体,建立混淆矩阵对4种水体指数提取结果进行对比分析,利用精度最高指数提取艾比湖面积并通过动态度分析湖泊面积变化趋势,同时对艾比湖面积变化的驱动因素进行分析。结果表明:MAWEI指数精度最高,精度达到95%以上,Kappa系数＞0.94。2000—2003年期间,艾比湖面积从768.93 km²增加至982.27 km²,湖泊面积增加27.74％、动态度为9.24％;2003—2014年期间,湖泊面积减至447.08 km²,湖泊面积缩减54.48％、动态度为-4.95％;2014—2018年期间,湖泊面积再次增加至852.77 km²,湖泊面积增加90.74%、动态度为22.68％;2018-2020年湖泊面积减至593.79 km²,湖泊面积缩减30.36％、动态度为-15.18％,总的来说近20 a艾比湖面积变化呈现先扩张再退缩的趋势。湖泊面积变化与年均降水量呈正相关,与蒸发量呈负相关,与博尔塔拉河和精河径流量呈正相关。水资源的减少及其周围人口、灌溉面积及生产值持续增长引起经济社会总用水量的激增,对湖泊面积变化产生一定的影响。研究成果对艾比湖生态环境保护有一定参考意义。

Water Body Extraction of Ebinur Lake Based on Four Water Indexes and Analysis of Spatial-temporal Changes

The water body of Ebinur Lake is extracted by using normalized difference water index (NDWI),modified normalized difference water index (MNDWI),automatic water extraction index (AWEI) and modified automated water extraction index (MAWEI) with Landsat 5/7/8 series remote sensing images as the data source.The extraction results of the four indexes are compared and analyzed by establishing confusion matrix.MAWEI index is proved to be of the highest precision (over 95%) with the Kappa coefficient greater than 0.94.Furthermore,the area of Ebinur Lake is extracted by using the MAWEI index,and the change of lake area is analyzed through the dynamic degree.From 2000 to 2003,the area of Ebinur Lake increased from 768.93 km² to 982.27 km²,up by 27.74%,and the dynamic degree was 9.24%;from 2003 to 2014,the lake area shrank to 447.08 km²,down by 54.48% with the dynamic degree of -4.95%;from 2014 to 2018,the lake expanded again to 852.77 km²,rising by 90.74% with the dynamic degree reaching 22.68%;and from 2018 to 2020,the lake area reduced again to 593.79 km²,falling by 30.36% with the dynamic degree of -15.18%.In the past two decades,the area of Ebinur Lake displayed a trend of expansion first and then retreat in general.The change of lake area is positively correlated with annual precipitation and the runoff of Bortala River and Jinghe River,while negatively with evaporation.The reduction of water resources as well as the surge of socio-economic water use caused by the steady growth of population,irrigation area,and GDP also have impacts on the change of lake area.