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The density current of water and sediment in the reservoir is a special phenomenon caused by the sediment laden flow in the river channel diving under the clear water, which is of great significance to the sedimentation reduction and sediment removal of the reservoir. In view of the dramatic increase of sediment in Zipingpu Reservoir in recent years and the serious problem of reservoir siltation, this study built a one-dimensional water and sediment mathematical model of Zipingpu Reservoir by coupling the basic hydrodynamic sediment equation with the density current and studied the water and sediment movement process of the reservoir. The results show that the coupled model can predict the outflow discharge, outflow sediment concentration, thalweg and sedimentation distribution in the reservoir area with good accuracy. The model can provide theoretical basis for the simulation and prediction of different water and sediment scenarios of Zipingpu Reservoir in the future, and provide technical support for the study of water and sediment movement process of sediment laden reservoirs in southwest China and sediment discharge regulation. [ABSTRACT FROM AUTHOR]

Reservoir sediment deposition is an important factor that causes the reduction of effective storage capacity, the increase of operation cost and the shortening of reservoir life. Scientific discrimination of reservoir sediment deposition situation and reasonable sediment discharge measures are effective ways to solve reservoir sediment deposition. Since the Wenchuan earthquake, the amount of sediment entering into the Zipingpu Reservoir has been increased, posing a great threat to the safe operation of the reservoir and the safety of downstream water use. The results of the study show that before the Wenchuan earthquake, the runoff in the upper reaches of the Minjiang River is decreased, and after the earthquake, there is a little recovery, but it is still at the level of dry years. After the earthquake, the amount of sediment entering into the reservoir has been increased significantly. The total amount of sedimentation in the reservoir is 195.2 million m³, accounting for 17.55% of the total reservoir capacity. The sediment is generally deposited in the middle of the reservoir area, and the sedimentation in front of the dam is relatively small. In order to deal with the issue of reservoir sedimentation, the prevention and control measures of reservoir sedimentation to reduce sediment from the upstream, sediment discharge by density current, artificial dredging, and the comprehensive sedimentation reduction method of “sediment regulation in the upper reservoir and water regulation in the lower reservoir” combined with engineering measures and non engineering measures are proposed to provide decision-making suggestions for the healthy and long-term operation of Zipingpu Reservoir. [ABSTRACT FROM AUTHOR]

The evolution of alluvial rivers' deep river lines is of great significance to river regimes and river bed landforms. In order to find out the influence of the changing conditions of water and sediment after the completion of Xiaolangdi Reservoir on the evolution of the deep-water line in the lower reaches of the Yellow River, based on the topographical data measured after the flood in Huayuankou, Sunkou and Hongkou sections from 2002 to 2014, the position of the deep-water line in the lower reaches of the Yellow River was compared and analyzed. The changing trend of, and its relationship with the sand-to-sand coefficient. The results show that: from 2002 to 2014, the migration intensity of deep water in Huayuankou section is the largest, followed by Sunkou, and the smallest in Hongkou. The trend of decreasing and then increasing. The turning point occurs when the incoming sediment coefficient is 0.004-0.006. Among the three sections, the migration intensity of Huayuankou Shenhong is the most sensitive to the change of incoming sediment coefficient, and the incoming sediment coefficient in flood season is the most sensitive. The change played a leading role in the change of Shenhong migration intensity. The effect of water storage and sediment retention in Xiaolangdi Reservoir reduces the sediment arrival coefficient in the lower reaches of the Yellow River, which changes the evolution trend of sedimentation and shrinkage in the main channel, and is also conducive to the stability of the mainstream of the river. [ABSTRACT FROM AUTHOR]