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<p>How the strong segmentation of cascade reservoir dams and the spatiotemporal changes of sediment retention volume affect the river morphology adjustment in the reservoir area is a scientific issue worthy of exploration. This study aims to reveal the adjustment mechanism of the thalweg longitudinal profile of cascade reservoirs. This study focuses on the Xiangjiaba and Xiluodu reservoirs located in the lower reaches of the Jinsha River. Utilizing multi-period observational data of thalweg elevation in reservoir reaches both before and after dam construction, the research employs statistical, geomorphological, and sedimentological methodologies to analyze variation characteristics in the measured curves, trend curves, and theoretical fitting curves of the thalweg longitudinal profile. The investigation ultimately reveals two distinct adjustment patterns in the longitudinal profiles of these cascade reservoirs: the concave curve type and the convex curve type. The former is characterized by weak riverbed scouring and silting changed to rapid aggradation in the upstream section of the reservoir area after dam closure, then changed to slow aggradation in the whole reservoir area, which is the common feature of reservoirs that were built earlier and are relatively located in the downstream (such as the Xiangjiaba Reservoir). The latter is characterized by a straight line or concave curve type with weak riverbed scouring and silting before the dam closure changed to a convex curve type with strong siltation after dam closure, which is the characteristic of reservoirs that were built later and are relatively located in the upstream (such as the Xiluodu Reservoir). The adjustment of the cascade reservoir longitudinal profile is controlled by the spatiotemporal changes of the sediment deposition volume and sedimentation rate in the reservoir area, and the alternating changes of the hydrodynamic gradient and regulation mode affect the spatial heterogeneity of the sedimentation rate. The research results are helpful for understanding the adjustment mechanism of the cascade reservoir longitudinal profile in similar areas and have a guiding role in predicting the adjustment trend of the cascade reservoir longitudinal profile without observation data.</p>

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Adjustment of thalweg longitudinal profiles in response to sediment silting in cascade reservoirs: A case study of the lower Jinsha River

  • 期刊论文

  • 发表日期：

    2025年7月15日

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  • Suiji Wang

摘要

How the strong segmentation of cascade reservoir dams and the spatiotemporal changes of sediment retention volume affect the river morphology adjustment in the reservoir area is a scientific issue worthy of exploration. This study aims to reveal the adjustment mechanism of the thalweg longitudinal profile of cascade reservoirs. This study focuses on the Xiangjiaba and Xiluodu reservoirs located in the lower reaches of the Jinsha River. Utilizing multi-period observational data of thalweg elevation in reservoir reaches both before and after dam construction, the research employs statistical, geomorphological, and sedimentological methodologies to analyze variation characteristics in the measured curves, trend curves, and theoretical fitting curves of the thalweg longitudinal profile. The investigation ultimately reveals two distinct adjustment patterns in the longitudinal profiles of these cascade reservoirs: the concave curve type and the convex curve type. The former is characterized by weak riverbed scouring and silting changed to rapid aggradation in the upstream section of the reservoir area after dam closure, then changed to slow aggradation in the whole reservoir area, which is the common feature of reservoirs that were built earlier and are relatively located in the downstream (such as the Xiangjiaba Reservoir). The latter is characterized by a straight line or concave curve type with weak riverbed scouring and silting before the dam closure changed to a convex curve type with strong siltation after dam closure, which is the characteristic of reservoirs that were built later and are relatively located in the upstream (such as the Xiluodu Reservoir). The adjustment of the cascade reservoir longitudinal profile is controlled by the spatiotemporal changes of the sediment deposition volume and sedimentation rate in the reservoir area, and the alternating changes of the hydrodynamic gradient and regulation mode affect the spatial heterogeneity of the sedimentation rate. The research results are helpful for understanding the adjustment mechanism of the cascade reservoir longitudinal profile in similar areas and have a guiding role in predicting the adjustment trend of the cascade reservoir longitudinal profile without observation data.