金沙江下游白鹤滩水库运行初期泥沙淤积特征OA

The Baihetan Hydropower Station,as the second cascade in the lower reaches of the Jinsha River,is situated in a reser-voir area prone to frequent landslides and debris flows,resulting in substantial sediment yield.Following reservoir impoundment,significant sedimentation is expected to accumulate within the reservoir,potentially compromising its storage capacity and impairing the comprehensive benefits of the hydropower project.Based on measured cross-sectional data from Baihetan Reservoir,this study analyzes the spatiotemporal evolution of sedimentation before and after impoundment.The results indicate that:prior to impound-ment(2013-2021),the main river channel exhibited a sedimentation pattern characterized by"initial deposition followed by ero-sion",while four major tributaries largely maintained a balance between sedimentation and erosion,with the exception of Heishui River,which experienced cumulative deposition.After impoundment(2021-2023),a total of 82.796 million m3 of sediment was deposited in the reservoir.The mainstem and tributaries accounted for 75.4％and 24.6％of the total deposition,respectively,with the most pronounced sedimentation occurring in Heishui River and Xiaojiang River.Inter-annually,influenced by the high-dam effect on sediment density and deposition,sedimentation in the mainstem and tributaries was predominantly concentrated in the first year after impoundment,contributing 71.8％of the total deposition.Sedimentation decreased annually thereafter,with a"pseudo-erosion"phenomenon observed in 2023.Intra-annually,both the main river and tributaries experienced deposition during flood seasons and erosion during non-flood seasons.Longitudinally,the backwater area continued to undergo slight erosion,while major deposition occurred between the confluences of Xiaojiang River and Yili River.A significant fining trend in sediment particle size was observed along the flow path,with median grain size decreasing progressively closer to the dam.In terms of reservoir ca-pacity distribution,sedimentation occurred primarily below the dead water level,resulting in a 1.14％reduction in dead storage.In contrast,the zone between dead water level and normal storage level experienced net erosion,leading to a 0.14％increase in regulating storage.From a longitudinal profile perspective,influenced by upstream sediment sources,the perennial backwater area below the Pudu River confluence exhibited relatively uniform uplift,with average bed elevation increases ranging from 1.8 m to 2.3 m across different river segments.Regarding tributary sedimentation patterns:Pudu River displayed banded deposition;the estuaries of Yili River,Xiaojiang River,and Daqiao River exhibited delta-type sedimentation;while Heishui River,significantly affected by backwater sedimentation from the mainstem,faces a potential risk of sediment bar formation.