清末以来洞庭湖区通江湖泊的时空演变

本文利用清光绪22年以来17个时段的多种历史地图和航天航空遥感数据,采用遥感解译、数据统计分析与历史对比方法,分析清末以来洞庭湖区通江湖泊面积的时序变化,探究空间演变特征。结合水利部门发布的典型年份监测数据,检验了遥感获取的湖泊面积精度,误差仅为0.62%。结果显示：洞庭湖通江湖泊面积从1896年的5216.37 km²减少到2019年的2702.74 km²,萎缩率为48.19%。1949年前的53年为明显萎缩期,年均萎缩15.66 km²;20世纪50年代为陡崖式萎缩期,年均萎缩139.05 km²;20世纪60—70年代为快速萎缩期,年均萎缩21.66 km²;1980年以来为基本稳定期,年均萎缩0.13 km²,面积仅减少了5.10 km²。就具体湖泊而言,东洞庭湖是各通江湖泊中面积萎缩最大的湖泊,减幅为922.60 km²;其次是目平湖,减幅为588.05 km²;再次是南洞庭湖,减幅为448.37 km²;七里湖的面积变化很小,但经历了先扩张后萎缩的过程。1998—2002年实施“退田还湖”工程,洞庭湖面积增加了10.50 km²。总体而言,清末以来洞庭湖区通江湖泊的演变主要表现为大通湖的封闭析出、整修南洞庭湖的湖垸置换与南迁、围垦西洞庭湖的局部残存、东洞庭湖的三面合围以及1998年特大洪灾后有限的“退田还湖”。本文为长江流域生态修复和环境保护战略提供了客观资料和技术支撑。

Spatio-temporal evolution of riparian lakes in Dongting Lake area since the late Qing Dynasty

In order to analyze the spatio-temporal evolutions of Dongting Lake in modern times, this paper investigated the temporal changes of the riparian lake areas in Dongting Lake area since the late Qing Dynasty using various historical maps and remote sensing data since 1896 AD (the 22nd year during the Emperor Guangxu's reign in the Qing Dynasty). The remote sensing data interpretation, statistical analysis and historical comparison methods were used to test the accuracy of the remote sensing based lake areas with the observation data from the Ministry of Water Resources of China. The results showed that the overall error rate was only 0.62%, and after 1896, the riparian lake areas in Dongting Lake decreased from 5126.37 km² to 2702.74 km², with an annual atrophy rate of 48.19%. The 53 years before the founding of the People's Republic of China was a period of obvious lake shrinkage, with an annual average decrease of 15.66 km². The 1950s was a period of rapid atrophy (134.33 km² per year), and the 1960-1970s was a period of rapid shrinkage, with an annual rate of 21.66 km². The riparian lake areas in Dongting Lake only reduced by 5.10 km² since the 1980s. In terms of the areas for each lake, the East Dongting Lake was the lake with the largest shrinkage (922.60 km²) since 1935, followed by the Muping Lake (a decrease of 588.05 km²), and the South Dongting Lake (decrease of 448.37 km²). The change in areas of Qili Lake was relatively small in recent decades. The areas of Dongting Lake increased by 10.50 km² during 1998-2002 due to the implementation of returning farmland to lake. In general, the evolution of riparian lakes in Dongting Lake area since the late Qing Dynasty was characterized by the closure and separation of Datong Lake, the replacement of the embankments for the South Dongting Lake, the local remains of the West Dongting Lake, the three-sided enclosure of East Dongting Lake and the limited operation of returning farmland to lake after the catastrophic flood in 1998. This study may provide data and technical support for the ecological restoration and environmental protection strategy of the Yangtze River Basin.