Acta Geographica Sinica ›› 2019, Vol. 74 ›› Issue (1): 131-145.doi: 10.11821/dlxb201901010

• Climate Change and Surface Processes • Previous Articles     Next Articles

Sediment deposition of Modao Creek and Xiangxi River mouth section since the impoundment of the Three Gorges Reservoir

ZHU Lingling1(),XU Quanxi1,YAN Lili2   

  1. 1. Bureau of Hydrology, Changjiang Water Resources Commission, Wuhan 430010, China
    2. Yangtze River Management Office of Zhenjiang City, Zhenjiang 202003, China
  • Received:2018-04-25 Online:2019-01-18 Published:2019-01-18
  • Supported by:
    National Key R&D Program of China, No.2016YFC0402301;Research on the Major Sediment Problems of the Three Gorges Project, No.ZZ2018013001F


There are 66 tributaries in the Three Gorges Reservoir (TGR) area, where most of them witnessed pronounced deposition in mouth reach since the impoundment of the TGR. The lasting sedimentation may lead to the formation of outlet bar at mouth section, which generated adverse effects on storage capacity of the TGR and navigation of tributaries. This paper, taking the Modao Creek and Xiangxi River as examples, examines the characteristics and causes of sediment deposition in their mouth sections based on detailed observation data such as flow, sediment, cross section and channel topography. The results show that: (i) after the impoundment of the TGR, a large amount of deposition occurred in its tributary mouth. The maximum deposition thickness of Modao Creek and Xiangxi River mouth sections exceeded 10 m from 2004 to 2017. Deposition was basically within the range of 15 km of the mouth section, and the strong depositing zone was focused in the reach of about 5 km away from the river mouth. The sediment deposition in the river mouth mainly occurred in the initial operation period of the TGR, and slowed down particularly since 2010 when the cascade hydropower stations in the middle and lower Jinsha River began to operate; (ii) the weakened hydrodynamic condition in dry season at the tributaries mouth, and the significantly reduced sediment-carrying capacity, are the fundamental causes in responsibility to the intense deposition. Sediment deposited at Modao Creek and Xiangxi River mouth sections mainly came from the mainstream in the form of inverted flow, and partially came from their own basin. The deposition range of sediment and its influence on channel morphology were related to local river regime; (iii) Optimized operation of the TGR since 2010 has not affected the sediment deposition in the tributaries mouth. Decreased sediment concentration in mainstream and tributaries and the maintenance the low water level in flood season do not support the formation of outlet bar of tributaries in the TGR.

Key words: Three Gorges Reservoir, Modao Creek, Xiangxi River, backwater effect, sedimentation