Shrinking of Dongting Lake and its weakening connection with the Yangtze River: Analysis of the impact on flooding

In this article, the shrinking of Dongting Lake and its progressively weakening connection with the Yangtze River and their impact on flooding before and after the implementation of the Three Gorges Project are analyzed. In recent decades, human activity combined with natural processes has altered the flow of the middle reach channel of the Yangtze River and interfered with its connection with Dongting Lake. This has resulted in progressively more frequent flooding in the area. This study uses hydrological data to analyze the annual maximum discharge and annual maximum stage development of the middle reach of the Yangtze River and Dongting Lake. In recent decades before the Three Gorges Project became operational in 2003, the annual maximum discharge and the maximum stage recorded in the middle reach of the river downstream of Dongting Lake had increased, a result of the weakening of the flood regulation function of Dongting Lake; the annual maximum stage at Luoshan station (downstream, close to the confluence of the Yangtze River and Dongting Lake) had risen by about 2.0 m during 1955–2005, (1.5 m attributed to annual maximum discharge and 0.5 m to river channel deposition). Observational data recorded after the Three Gorges Project was put into operation in 2003, it can be seen that deposition in the Dongting Lake has nearly ceased and the lake׳s connection with the Yangtze River is stable. It is evident that the flood regulation function of Dongting Lake will continue, and that during the lifetime of the Three Gorges Project, the flood situation in the middle reach of the Yangtze River and Dongting Lake will remain stable.