Non-equilibrium sediment transport in the Three Gorges Reservoir

Based on field data analysis and mathematical model simulation, the non-equilibrium sediment transport law in the Three Gorges Reservoir under large water depth was studied. It is revealed that, after the reservoir was put into operation, the flood propagates in the form of gravity wave, and the suspended sediment transported from the Cuntan to Huanglingmiao is lagged behind the flood for a long time. By considering the unsteady flood process, the calculated sediment deposited in the reservoir is more than that predicted in the past. Most fine sediment particles are deposited in the reservoir and the different percentage of particles in size does not obviously make the calculation result. This phenomenon can not be explained by non-equilibrium sediment transport theory if the flocculatiou is not considered. When flocculation of fine sediment is taken into account, the simulated reservoir outlet concentration is in good agreement with observation data. It implies that the flocculation may exist in the reservoir and further study on this phenomenon is needed.