Sedimentation characteristics in the Three Gorges Reservoir during the initial operation stage

The sedimentation characteristics in the Three Gorges Reservoir (TGR) are studied by analyzing measured sediment load and cross section data. Results indicate that the total deposition amount and effective sediment export ratio from 2003 to 2013 are 1.531 billion tons and 24.5％, respectively, and both are less than those estimated during design. The sediment is primarily deposited in the wide and curved reaches in the permanent backwater region. It distributes evenly over the cross sections in the wide reaches and on the side of the sections with low velocity in the curved reaches. No deposition occurs in gorges. The deposition rates near the dam tend to decrease, while those of the upper reaches are increasing. The longitudinal particle size variation is not obvious, and the median particle diameters of the deposition in the permanent backwater region are mostly less than 0.01 mm. The thalweg of the gorge reaches have no changes, and the deposition delta is not found. The deposition in the backwater zone and the associated increasing of the tail water level are less than previous estimations. These suggest that the gorge reaches play a role of a local erosion base level due to their sufficient sediment carrying capacities, and it is unlikely that a unified equilibrium bed slope will be developed in the TGR.