114 / 2025-05-23 09:11:44

Scouring characterization of riverbed in the near-dam river channel under cascade reservoirs

Cascade reservoirs; Xiangjiaba reservoir; Near-dam river channel; Riverbed scouring

The changes of sediment scouring and siltation in the downstream of cascade reservoirs have a significant impact on bank slope stability and navigation. Since 2012, Xiangjiaba, Xiluodu, Wudongde and Baihetan power stations had successively stored water and operated to intercept the sediment of Jinsha River layer and layer. A large amount of sediment was deposited in the cascade reserviors and scoured to the river channel below Xiangjiaba reservoir. Based on the observation data since the preparation of the Xiangjiaba Reservoir project, this paper studied the scouring pattern of the river channel below Xiangjiaba Reservoir on the lower Jinsha River. The results showed that the riverbed downstream of Xiangjiaba was generally scoured, and a total of 25.88 million m³ of sediment was flushed from 2008 to 2024 in the section below Xiangjiaba to Yibin River (29.8 km long), but the scouring intensity was weakened significantly. The thalweg of the river section from Xiangjiaba to the Yibin main stream is jagged, and from 2008 to 2024, the thalweg of this section shows a gradual downcutting trend, with the maximum decrease value of 8m (24.1 km from the dam). Localized scouring of important water-related works did not exceed the expected extent. The rivered at the downstream of the Xiangjiaba dam was obviously coarsened after reservoir impoundment. The thalweg high convex section of the downstream of the dam had not decreased significantly, and the cumulative decline of the low water level at 2000 m³/s was about 0.49 m (from 2012 to 2024).