三峡水库运行初期的泥沙淤积特点

Sedimentation characteristics in the Three Gorges Reservoir during the initial operation stage

  • 摘要: 针对三峡蓄水运行后的泥沙淤积问题,基于实测资料,采用输沙率法和断面法分析了三峡水库运行初期的泥沙淤积特点.结果表明:三峡水库2003—2013年泥沙淤积总量为15.31亿t,平均排沙比为24.5%,均较论证阶段降低;库区泥沙淤积主要分布在常年回水区的宽谷和弯道河段,宽谷段全断面发生淤积、弯道断面流速较小一侧淤积、峡谷无累积性淤积;常年库区近坝段泥沙淤积速度逐年减小,而上段泥沙淤积速度则呈增大趋势;淤积物粒径沿程分选不明显,常年回水区淤积物中值粒径多在0.01 mm以下.库区峡谷段深泓线无明显变化、尚未出现泥沙淤积三角洲、库尾泥沙淤积上延和尾水抬高不明显,据此初步推断峡谷河段存在富余挟沙力而成为局部侵蚀基准面,整个库区将无统一平衡比降的趋势.

     

    Abstract: The sedimentation characteristics in the Three Gorges Reservoir (TGR) are studied by analyzing measured sediment load and cross section data. Results indicate that the total deposition amount and effective sediment export ratio from 2003 to 2013 are 1.531 billion tons and 24.5%, respectively, and both are less than those estimated during design. The sediment is primarily deposited in the wide and curved reaches in the permanent backwater region. It distributes evenly over the cross sections in the wide reaches and on the side of the sections with low velocity in the curved reaches. No deposition occurs in gorges. The deposition rates near the dam tend to decrease, while those of the upper reaches are increasing. The longitudinal particle size variation is not obvious, and the median particle diameters of the deposition in the permanent backwater region are mostly less than 0.01 mm. The thalweg of the gorge reaches have no changes, and the deposition delta is not found. The deposition in the backwater zone and the associated increasing of the tail water level are less than previous estimations. These suggest that the gorge reaches play a role of a local erosion base level due to their sufficient sediment carrying capacities, and it is unlikely that a unified equilibrium bed slope will be developed in the TGR.

     

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