Journal of Geographical Sciences ›› 2017, Vol. 27 ›› Issue (4): 463-480.doi: 10.1007/s11442-017-1387-3

• Research Articles • Previous Articles     Next Articles

Mechanisms of suspended sediment restoration and bed level compensation in downstream reaches of the Three Gorges Projects (TGP)

Wei ZHANG1(), Yunping YANG2,*(), Mingjin ZHANG2, Yitian LI1, Lingling ZHU3, Xingying YOU1,4, Dong WANG5, Junfeng XU2   

  1. 1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
    2. Key Laboratory of Engineering Sediment, Tianjin Research Institute for Water Transport Engineering, Ministry of Transport, Tianjin 300456, China
    3. Bureau of Hydrology, Changjiang Water Resources Commission, Wuhan 430010, China
    4. Hubei Provincial Water Resources and Hydropower Planning Survey and Design Institute, Wuhan 430064, China
    5. Changjiang River Scientific Research Institute, Wuhan 430010, China
  • Received:2016-06-30 Accepted:2016-11-18 Online:2017-04-20 Published:2017-04-20
  • Contact: Yunping YANG E-mail:wzhang97082@whu.edu.cn;yangsan520_521@163.com
  • About author:

    Author: Zhang Wei, specialized in river and coastal dynamics, sediment transport, mathematical modelling of fluvial processes. E-mail: wzhang97082@whu.edu.cn

  • Supported by:
    National Natural Science Foundation of China, No.51479146, No.51579123, No.51509012;Fundamental Research Funds for Central Welfare Research Institutes, No.TKS160103;No.TKS150102;The National Key Research & Development Programs, No.2013BAB12B01;National Key Research Program of China, No.2016YFC0402106

Abstract:

River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects (TGP) has started to become apparent: (1) reduction in flood duration and discharge, and significant reduction in sediment load. Although there was some restoration in downstream sediment load, the total amount did not exceed the pre-impoundment annual average; (2) in 2003-2014, the d > 0.125 mm (coarse sand) load was restored to some degree, and to a maximum at Jianli Station, which was mainly at the pre-impoundment average. After restoration, erosion and deposition characteristics of the sediment was identical to that before impoundment. The degree of restoration during 2008-2014 was less than during 2003-2007; (3) after TGP impoundment, there was some restoration in d < 0.125 mm (fine sand) sediment load, however, it was lower than the pre-impoundment average; (4) due to riverbed compensation, the d > 0.125 mm sediment load recovered to a certain degree after impoundment, however, the total did not exceed 4400×104 t/y. This was mainly limited by flood duration and the average flow rate, and was less affected by upstream main stream, tributaries, or lakes. Restoration of d < 0.125 mm suspended sediment was largely controlled by upstream main stream, tributaries, and lakes, as well as by riverbed compensation. Due to bed armoring, riverbed fine suspended sediment compensation capability was weakened; (5) during 2003-2007 and 2008-2014, Yichang to Zhicheng and upper Jingjiang experienced coarse and fine erosion, lower Jingjiang experienced coarse deposition and fine erosion, Hankou to Datong had coarse deposition and fine erosion, and Chenglingji and Hankou was characterized by coarse deposition and fine sand erosion in 2003-2007, and coarse and fine erosion in 2008-2014. This difference was controlled by flood duration and number at Luoshan Station.

Key words: sediment restoration, riverbed compensation, TGP, middle and lower reaches of the Yangtze River