Impacts of Three Gorges Reservoir´s water storage on flow-sediment characteristics of Dongting Lake

Based on the field surveyed data of flow-sediment, the subject of Three Gorges Reservoir´s water storage operation influence on flow-sediment characteristics of Dongting Lake is systematically studied by the comparison method. The results are represented as follow: Firstly, flow and sediment diversion ratios of Three Outlets of Jinjiang River respectively decrease from 18.5 % and 21.4% to 11.7% and 13.6%, which causes the ratios of Three Outlets occupying the total inflow quantity in runoff volume and sediment discharge respectively decline from 41.5% and 82.9% to 21.6% and 58.5%. Secondly, average inflow flow-sediment discharge in several years respectively reduces 531×10⁸m³ and 4715×10⁴t. Silting rate of the lake basin decreases from 70.4% to 39.2%, and the degression scope is 31.2% Thirdly, average change rates of water level in west, south and east Dongting lake in several years respectively decrease 1.23m, 1.45m and 1.88m. Lastly, the erosion of lake basin is more than the silting and the diameter of silty sediment particles tends thinner. And sediment discharge ratios of west and northeast Dongting Lake both synchronously rise.