1984~2019年南四湖水域变化特征及原因分析

Analysis of Variation Characteristics and Reasons of Water Area of Nansi Lake from 1984 to 2019

湿地水域面积是湿地健康的重要指标,关系到湿地演替和生态功能的有效发挥。基于2019年Landsat 8 OLI数据,选择归一化水体指数(NDWI)、改进的归一化水体指数(MNDWI)、水体指数2015(WI2015)及自动水体提取指数(AWEI)4个水体指数提取南四湖水域面积,对比Sentinel-2A数据面向对象分类后的参考图层,得出区域水体最优水体指数为WI2015。进而利用WI2015提取1984~2019年间的16个特征年份的南四湖枯水期水域面积,分析近35年来南四湖水域面积的时空变化特征及原因。结果表明,1984~2019年间,南四湖水域面积总体呈现较大波动,2011年后,特别是2013年后水域面积趋于平稳,且大于多年均值。年际间水域变化的频繁区域主要集中于南阳湖、昭阳湖西部及微山湖西部和北部。降水在年际尺度上控制着南四湖水域面积的变化趋势,水域面积与其前一年的年降水量显著正相关(R=0.64,P<0.01)。同时,南水北调东线工程调水减小了年际水域面积变化的幅度,是近年来维持南四湖水域稳定的一个重要原因。

Wetland water area is an important indicator of wetland health,which is related to the effective play of wetland succession and ecological function.Based on the Landsat 8 OLI data in 2019,four water body indexes(NDWI,MNDWI,WI2015 and AWEI)were selected to extract the water area of Nansi Lake.Compared with the reference layer after the object-oriented classification of Sentinel-2 Adata,the optimal water body index was WI2015.Then,the water area of Nansi Lake from 1984 to 2019 was extracted by WI2015,and the temporal and spatial characteristics and reasons of the water area of Nansi Lake in recent 35 years were analyzed.The results show that from 1984 to 2019,the water area of Nansihu Lake showed a large fluctuation.After 2011,especially after 2013,the water area tended to be stable and larger than the multi-year average.The sensitive areas of interannual water changes are mainly concentrated in the majority of Nanyang Lake,the west of ZhaoyangLake,and the Wwest and north of Weishan Lake.The precipitation in the previous year controls the change trend of the water area of Nansi Lake,and the water area has a significant positive correlation with the annual precipitation of the previous year(R=0.64,P<0.01).The East Route Project of the South-to-North Water Transfer,reduces the change range of the water area,which is an important reason for maintaining the stability of the water area of Nansi Lake in recent years.