题目 Title

Spatial-temporal evolution of sediment transport in the upper Yangtze River Basin considering the cumulative impacts of mega reservoirs.

期刊 Journal

CATENA (IF= 6.2)

作者 Author

Wang KY; Huang L; He GJ; Fang HW; Chen MH; Wang DC; Wu XH

摘要 Abstract

The intensive construction of large dams in the upper Yangtze River Basin (UYRB) has formed large-scale cascade reservoirs and obviously altered the flow regime and sediment transport of the basin. However, few studies have quantitatively described the cumulative impact of these reservoirs on sediment interception. In this study, a flow and sediment transport model that fully considers the operation processes of 24 mega reservoirs in the UYRB was established, and the spatial and temporal variations in sedimentation from 2011 to 2080 were elucidated, assuming repeated series of daily input flow discharge and sediment concentration during 2011-2020 and monthly water operation levels of 24 reservoirs during 2018-2021 as boundary conditions. The results showed an annual average sedimentation of more than 300 Mt in the UYRB during 2011-2060, which falls to 270 Mt in the period 2061-2080, and more than 80% of the sedimentation occurs in the flood season. Nearly 80% of the total sedimentation during 2010-2080 was observed in the mainstream reservoirs, especially the four mega reservoirs in the lower Jinsha River and the Three Gorges Reservoir (TGR), which accounted for 31.9% and 22.7% of the total sedimentation, respectively. The proportion of sedimentation in mainstream reservoirs will further increase with increasing operation periods. Most reservoirs in the UYRB will not reach sedimentation equilibrium by 2080, except for reservoirs in the Min River Basin. The ratio of siltation capacity to average annual sediment yield determines the percentage of residual siltation capacity of each reservoir. The operation of the cascade reservoirs in 2013-2020 had no more immediate impact on the middle and lower Yangtze River than that in 2003-2012, when the TGR started impoundment. However, the joint operation of these cascade reservoirs has changed the spatial distribution of sedimentation in the UYRB, and will lead to prolonged impacts on downstream channel erosion.

简介 Brief introduction

长江上游水库的大量建设在流域形成了大型的梯级水库群，这显著改变了流域的水沙输移过程，但目前鲜见定量描述大型梯级水库群对泥沙输移累积影响的相关研究。有鉴于此，本研究建立了一个考虑长江上游24座梯级水库运行的一维水沙输移模型，并模拟了流域2011-2080年间的泥沙输移时空变化过程。研究表明：2011-2060年间，长江上游流域年均淤积泥沙超过3亿吨，而这一数值在2060-2080年间下降至2.7亿吨，其中，每年汛期淤积量的占比超过80%；2010-2080年间，近80%的泥沙淤积出现在干流水库中，其中，金沙江下游的四座大型水库与三峡水库的泥沙淤积量分别占总淤积量的31.9%和22.7%；随着水库运行时间的增加，干流水库所占的淤积比例将会进一步增大；除了岷江流域的水库以外，长江上游大多数水库在未来60年不会达到冲淤平衡状态；梯级水库的累积影响明显改变了长江上游泥沙的淤积分布特征，并导致泥沙更容易沉积在水库中，同时会对长江中下游河道的侵蚀产生更长期的影响。

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