Acta Geographica Sinica ›› 2016, Vol. 71 ›› Issue (7): 1241-1254.doi: 10.11821/dlxb201607012

• Geomorphology • Previous Articles     Next Articles

Suspended sediment recovery and bedsand compensation mechanism affected by the Three Gorges Project

Yunping YANG1(), Mingjin ZHANG1, Yitian LI2, Wei ZHANG2, Xingying YOU2,3, Lingling ZHU4, Dong WANG5   

  1. 1. Key Laboratory of Engineering Sediment, Tianjin Research Institute for Water Transport Engineering, Ministry of Transport, Tianjin 300456, China
    2. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
    3. Hubei Provincial Water Resources and Hydropower Planning Survey and Design Institute, Wuhan 430064, China
    4. Bureau of Hydrology, Changjiang Water Resources Commission, Wuhan 430010, China
    5. Changjiang River Scientific Research Institute, Wuhan 430010, China
  • Received:2015-11-20 Revised:2016-03-15 Online:2016-07-25 Published:2016-07-25
  • Supported by:
    National Natural Science Foundation of China, No.51579123, No.51479146, No.51509012;The National Key Research & Development Programs, No.2013BAB12B01;Research on Key Techniques of Channel Regulation in The Sand-Gravel Reach (Yichang to Changmenxi) Downstream The Three Gorges-Gezhouba Projects, No.TKS05115018

Abstract:

Construction of basin reservoir projects can change the water and sediment transport processes in the lower reaches. The effects of the Three Gorges Project (TGP) on water and sediment transport in lower reaches are emerging. Specifically: (1) The duration and volume of floods in the lower reaches of TGP declined sharply. The sediment value was of such a low concentration that the water was nearly clear. The suspended sediment discharge gradually recovered downwards but its total amount still could not outcompete the annual average of that before the impoundment of TGP. (2) The sediment with d > 0.125 mm recovered to some extent in 2003-2014 (more in 2003-2007 than in 2008-2014) and basically recovered to the average value before the impoundment at the Jianli Station. After recovery, its transport trend in the lower reaches was in line with that before the impoundment. (3) After the impoundment, sediment with d < 0.125 mm recovered to some extent but its total amount was still less than the average of before the impoundment. (4) The recovery of sediment with d > 0.125 mm was mainly from river-bed erosion but with an amount not exceeding 44 million t/y which was primarily limited by duration and average flow of floods and secondarily by the upper mainstream, tributaries between river sections and the sub-sink effects of lakes. Recovery of the suspended sediment with d < 0.125 mm was controlled by the upper mainstream, tributaries between river sections, the sub-sinks of lakes and river-bed compensation. The suspended sediment compensation from river-bed decreased due to the coarsening of bedsands. (4) In 2003-2007 and 2008-2014, both coarse and fine sands were eroded in the Yichang-Zhicheng section in the upper Jingjiang River while coarse sands deposited and fine sands eroded in the lower Jingjiang River. In the Hankou-Datong section, coarse sands deposited and fine sands eroded. From 2003 to 2007, coarse sands deposited while fine sands eroded in the Chenglingji-Hankou section. In 2008-2014, both coarse and fine sands eroded in the Chenglingji-Hankou section. The differences were caused by the duration and volume of the floods in the Luoshan Station.

Key words: sediment recovery, bedsand compensation, Three Gorges Reservoir, middle and lower reaches of the Yangtze River