Study on Siltation Characteristics Analysis in Key Reservoirs of Heavily Silt-Carrying Rivers

Abstract

Most of the rivers have a large amount of mud and sand in China. After the construction of reservoirs, the water flow will slow down. The sediment carried by the upstream water will settle, silt up the storage capacity and shorten the service life of reservoirs. Haibowan Reservoir in the main stream of the Yellow River is selected as the study area. This paper was based on the measured data of 37 underwater topographic sections and the hydrologic stations during the four years. It then systematically analyzed the sediment deposition and spatial distribution characteristics in the reservoir area since the operation of the reservoir by using the sediment transport balance method and the section method. The results show that: the water and sediment conditions of the downstream river changed significantly after the reservoir was put into operation in 2014, and the annual average sediment transport decreased from 109 million tons to 21 million tons. From 2014 to 2020, the accumulative sediment deposition of the reservoir area is 313 million tons, and the average sediment discharge ratio decreased greatly, from 68.97% (before the reservoir construction) to 20.10%. The siltation mainly occurs in the “damsite section” and “midstream” of the perennial backwater area, and it is mainly the horizontal siltation with U-shaped section. Both scour and siltation occur in the upper and lower reaches of the reservoir, and the morphology is basically V-shaped. In general, the longitudinal morphology of silting is zonal silting. The sand siltation at the end of the reservoir and the tailrace elevation are not obvious. Therefore, it is preliminarily inferred that there is excessive sand transport capacity at the end of the reservoir, which becomes the local erosion basis, and the whole reservoir will not have a uniform equilibrium decline trend. It is necessary to identify the siltation volume of the reservoir area and analyze the spatial distribution rules and the main influencing factors, because it lays a foundation for the water and sediment regulation and the manual siltation removal.