Abstract: The variation of flow and sediment diversion at the three outlets along Jingjiang river and the change of water-sediment transport at the outlet of Dongting Lake are studied on the basis of field data before and after the impoundment of Three Gorges Reservoir. The above changes influence the flood control, navigation and water resources utilization of Dongting Lake, and affect the relationship between the Yangtze River and the Dongting Lake as well. Results indicate that ratios of split-flow and sediment diversion at the three outlets saw no obvious change since the impoundment of the reservoir; whereas the amount of sediment diversion reduced by a large margin. The days of zero-flow at five stations barely changed, with the critical flow in mainstream Yangtze River reduced slightly during zero-flow days at Mituosi station and Kangjiagang station, and changed little at the other three stations. The average annual sediment load had no big decrease at Qilishan station, while the sediment delivery ratio of Dongting Lake increased remarkably, larger than 100% in some specific years.

Key words: Three Gorges Reservoir , three outlets along Jingjiang River , split flow and sediment diversion , Dongting Lake, sediment delivery ratio