Discussion on the evolutionary trend of Lake Dongting

Abstract

evolution of Lake is determined by three main factors, which are tectonic subsidence, siltation and human impacts. The and basin of Lake Dongting are two different spatial concepts. The basin of Lake Dongting is only one of the components of basin of Lake Dongting, the levees and the farmlands synchronously keep subsiding and relatively actionless due to the tectonic subsidence of the whole Basin. At present, the mean sedimentation rate of Lake East Dongting,Lake South and Lake Muping is 9.43, 19.11, 12.46mm/a, respectively. rate of tectonic subsidence of the lake is low (3～10mm/a), but the capacity of tectonic subsidence still counteract a certain capacity of siltation, which restrains the shrinkage of Lake Dongting. sedimentation rate is bigger than the rate of tectonic subsidence in Lake Dongting. Sandbars will continue to grow and expand, and Lake will still keep the trend of siltation and shrinkage. At present, the whole Basin is subsiding and expanding due to tectonic subsidence, which has no influence on the change of the capacity of storing flood of Lake Dongting, and siltation is playing a main role. capacity of storing flood of Lake will continue to decrease as siltation goes on. During the 80 years after the Three Gorge Dam is completed with the completion of 4350 Project, the sedimentation rate of Lake will reduce to 1.79 mm/a. Then, the trend of siltation of Lake will be restrained.