Effects of Store Water Application of the Three-Gorges Reservoir on Yangtze River on Water and Sediment Characteristics in the Dongting Lake

According to the measured water and sediment data,using comparative analysis,the paper analyzed systematically the effects of store water application of the Three-Gorges reservoir on Yangtze river on water and sediment characteristics in the Dongting lake.The results indicated that:(1)The ratios of split-flow and sediment diversion at the three outfalls of Jingjiang river reduced separately from 18.5%,21.4% to 11.7% and 13.6%,which resulted in that the proportions of runoff and sediment discharge via the three outfalls into Dongting lake compared total runoff and total sediment discharge reduced respectively from 41.5%,82.9% to 21.6%,58.5%;(2)Average annual water and sediment volume into the Dongting lake decreased respectively 531×108 m3,4 715×104 t,sediment deposition rate in the lake basin reduced from 70.4% to 39.5% with a decreased range of 30.9%;(3)Average annual water level amplitude in the west,south and east of the Dongting lake decreased respectively 1.23 m,1.45 m and 1.88 m;(4)Sluicing capacity was greater than sediment deposition in the lake basin,deposited sand grain trends to thinning,sediment output ratios in the west and southeast of the Dongting lake present all synchronous increasing trend.The variations of water and sediment characteristics were of great significance towards prolonging the lifetime of the Dongting lake and easing the flood dangers as well as they brought about a series of eco-environment problems in the lake area.