Author(s): Guo; X. H. ; Yao; S. M. ; Guo; C.
Linked Author(s): C SURESH RAM, Luiz G Martins da Silva
Keywords: Three Gorges Project; Songzi Outlet; Diversion of water and sediment; Fixed-bed; Physical model
Abstract: The Songzi River is one of the main channels for diverting the river flow in the Jingjiang River section and is also the top of the “Three Outlets in the South of Jingzhou”. The changes in its diversion have a significant impact on flood control, water resource utilization, shipping, and the water environment ecology of the Songzi River system. In this paper, the characteristics of water and sediment and riverbed scouring changes in the studied river section are analyzed using prototype observation data. The influence of scouring and incision of the downstream sandy riverbed on the diversion of the Songzi River outlet is studied using a fixed-bed physical model test. The following understandings are obtained: During the period from 1955 to 2022, there was no obvious change trend in the annual runoff at the Zhicheng Station. After 2003, the annual sediment discharge at this station decreased significantly. During the period from 2013 to 2022, the average annual sediment discharge at this station decreased further significantly, basically approaching “clear water”. During the period from 2003 to 2022, the scouring volume in the Yichang-Yangjianao River section was 405.02 million m3, with an average scouring depth of approximately 2.13m, and the riverbed composition gradually evolved into a pebble-sand mixed riverbed. Studying the influence of the decrease in tailgate water level under different flow rates on the diversion of the Songzi River outlet, when the flow rate was below 30,000 m3/s, the water level at the tailgate of the model, Yangjianao, decreased significantly. However, due to the influence of nodes and channel regulation structures, the decrease in the water level at the outlet of the Songzi River was not significant, and the reduction in the diversion of the Songzi River was limited. When the flow rate was 7,000 m3/s, the tailgate decreased by 1.58 and 2.57 m respectively, and the corresponding diversion flow of the Songzi River decreased by 10 and 20 m3/s respectively. When the flow rate was 40,000 m3/s, due to the small decrease in the water level at Yangjianao, the corresponding reduction in the diversion flow of the Songzi River was small.
Year: 2024