近30年南四湖湿地水域面积时空变化特征分析

Analysis on spatio-temporal variation characteristics of water area of Nansi Lake wetland in recent 30 years

南四湖湿地是被湿地公约组织收录的重要湿地,及时掌握南四湖湿地水域面积的时空动态特征对湿地保护及湿地修复有重要意义。文章以Landsat陆地系列卫星遥感影像为主要数据源,采用修订后的归一化差异水体指数(MNDWI)配合最大类间方差(Otsu)法提取了南四湖近30年的水域面积,分析了南四湖湿地水域面积的年内和年际变化特征。结果表明:(1)MNDWI配合Otsu法可以较好的提取出南四湖的水域面积。(2)近30年来,南四湖湿地水域面积呈现“W”形的年际变化趋势,水域面积年平均值最大为765.48 km^(2),出现在2006年;最小值为329.83 km^(2),出现在2002年。从年内变化来看,水域面积呈现“V”形的变化规律,其中面积最大值均出现在冬季,最小值出现在夏季。(3)南阳湖、独山湖和昭阳湖三个湖泊面积均呈现较明显的年际和年内变化,而在研究时间段内微山湖的水域面积相对稳定且面积较大。研究为南四湖湿地生态环境保护和生态恢复提供了技术和数据支持。

Nansi Lake wetland is an important wetland included by the wetland convention organization.It is of great significance for wetland protection and restoration to grasp the spatio-temporal dynamic characteristics of the water area of Nansi Lake wetland in time.Based on the Landsat satellite remote sensing images,the paper extracted the water area of Nansi Lake in the past 30 years with the modified normalized difference water index(MNDWI)and the Otsu method,and analyzed the characteristics of intra-annual and inter-annual changes of the water area of Nansi Lake wetland.The results showed that:(1)The water area of Nansi Lake could be better extracted by MNDWI combined with the Otsu’s method.(2)In recent 30 years,the water area of Nansi Lake wetland presented a"W"shape inter-annual variation trend.The maximum annual average water area was 765.48 km^(2),which appeared in 2006;the minimum value was 329.83 km^(2),which appeared in 2002.From the perspective of intra-annual changes,the water area showed a"V"shape change rule,in which the maximum area appeared in winter and the minimum value appeared in summer.(3)The areas of Nanyang Lake,Dushan Lake and Zhaoyang Lake all showed obvious intra-annual and inter-annual changes,while the water area of Weishan Lake was relatively stable and large during the study period.The study provides technical and data support for ecological environment protection and ecological restoration of Nansi Lake wetland.