Analysis of the controls on the sedimentation in The Three Gorges Reservoir

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Yi Xiao, Xuhui Fu, Jiang Hu, Sichen Tong

Tuesday 30 june 2015

9:15 - 9:30h at Oceania (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) River morphodynamics

Parallel session: 4B. Sediment - River

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The reservoir sedimentation is not only related to the inlet and outlet flow-sediment discharge conditions,but also the river pattern of the reaches in its backwater area.Based on the long record of annual runoff and suspended sediment load at the control horological stations on the upper Yangtze River and the main tributaries(Minjing River,Jia Lingjiang River) in the past 60 years, this paper applied the Mann-Kendall test and R/S analysis method to detect the temporal-spatial distributions of the variations in annual runoff-sediment transport and their changing trends; combined a developed 2-D numerical model with the field measurements at the typical reach in The Three Gorges Reservoir, the hydrodynamics process is simulated to analyze the relationship between the river pattern and the distribution of the reservoir sedimentation. The results indicated that:(1) annual runoff in Minjiang River would keep a decreasing trend like the change pattern; annual runoff in Jia Lingjiang River changed from decrease to increase in 2009 and would keep its raising pattern; the fluctuation of the annual runoff on the main steam of the upper Yangtze River is small; as the control point of the Three Gorges Reservoir, the change pattern of the Cuntan station is below the critical line, illustrates that the decreasing trends is not obvious, there may be hardly to occur a rapid decrease in the following years;(2)there would be a obvious decreasing trend in the suspend load on the upper Yangtze River except Minjiang River, the reduction of the sediment transport in the Jia Lingjiang River would keep the current level while the Cuntan station would maintain a apparent decline trend;(3)Different river channel pattern may lead to the difference in the hydrodynamics condition, the main sedimentation located at the Meander, broad-valley, and the braided river sections in the TGR, the planform distribution of the deposition would keep the present pattern, and the rate of the sedimentation would slow down subsequently.