三峡工程运用后长江松滋口分流变化特征与发展趋势研究
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长江科学院

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Study on the Variation Characteristics and Development Trends of Flow Diversion at Songzikou on the Yangtze River After the Operation of the Three Gorges Project
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Key Laboratory of river and lake management and flood control in the middle and lower reaches of the Yangtze River of MWR,Yangtze River Scientific Research Institute

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    摘要:

    松滋河是荆江分流入洞庭湖的主要通道之一,其分流变化对江湖防洪、水资源利用及水环境生态具有重要影响。基于实测资料分析与物理模型试验,研究了三峡工程运行后长江干流与松滋口河段水沙演变及河床冲刷对分流的影响关系。结果表明:与1990-2002年相比,2003-2022年期间枝城站年均输沙量减少约90.6%,松滋口分沙量亦同步减少约87.1%;2003-2022年期间枝城至杨家脑河段平滩河槽冲刷2.39亿m3,平均冲深2.3m,河床显著粗化,而松滋口门段平滩河槽冲刷4325万m3,平均冲深3.0m,近期与干流卵石夹沙河床形成冲刷速率差异;根据物理模型结果预测,未来在次饱和水流长期作用下引起长江干流杨家脑以下沙质河床持续下切,导致杨家脑水位出现不同程度下降,致使分流减少,其中枝城站7000m3/s流量下2035年、2050年水位分别下降1.58m和2.57m,相应松滋口分流量减少8.3%、16.7%;但口门内外河床不对等冲刷,口门段沙质冲刷速率更高,使过水断面扩大,至2035年末,即使考虑杨家脑水位下降的影响,松滋口分流仍呈不同程度增大,其中枯水期枝城站7000m3/s流量下分流反增20.8%,杨家脑水位下降与口门内外不对等冲刷的贡献率分别为-33%和133%;随着流量增大,二者对分流变化的影响贡献率数值均显著增大,但抵消后对分流量变幅的影响不大,相关影响或主要集中于中枯水期。河床组成分异通过调控冲刷进程维持了松滋口分流稳定,枯水期分流增加有利于洞庭湖水资源调配,但会一定程度降低干流水位并影响中枯水期航道畅通。

    Abstract:

    The Songzi River is one of the primary channels through which the Jingjiang River diverts water into Dongting Lake, and changes in its water diversion have significant implications for flood control in the river-lake system, water resource utilization, and water environmental ecology. Based on analysis of measured data and physical model experiments, this study investigates the relationships among water-sediment evolution, riverbed scouring, and diversion changes in the Yangtze main channel and Songzi Mouth reach following the operation of the Three Gorges Project.The results show that compared with the period from 1990 to 2002, the annual average sediment transport at Zhicheng Station decreased by approximately 90.6% during 2003–2022, with a synchronous reduction of about 87.1% in sediment diversion at Songzi Mouth. From 2003 to 2022, the bankfull channel between Zhicheng and Yangjiaonao experienced a total scouring volume of 239 million m3, with an average scouring depth of 2.3 m, leading to significant riverbed coarsening. In contrast, the bankfull channel at the Songzi Mouth reach was scoured by 43.25 million m3, with an average scouring depth of 3.0 m, forming a differential scouring rate compared to the pebble-sand mixed bed in the main channel.Physical model predictions indicate that long-term action of subsaturated flow will cause continuous downcutting of the sandy riverbed downstream of Yangjiaonao in the Yangtze main channel, leading to progressive declines in water levels at Yangjiaonao and corresponding reductions in diversion at Songzi Mouth. For a discharge of 7000 m3/s at Zhicheng Station, water levels at Yangjiaonao are projected to decrease by 1.58 m and 2.57 m in 2035 and 2050, respectively, resulting in diversion reductions of 8.3% and 16.7%. However, asymmetric scouring between the inner and outer parts of the mouth (with higher scouring rates in the sandy mouth reach, expanding the cross-sectional flow area) leads to increased diversion at Songzi Mouth by the end of 2035, even considering the water level decline at Yangjiaonao. During low-flow periods (with a discharge of 7000 m3/s at Zhicheng Station), diversion actually increases by 20.8%, with contribution rates of -33% from the Yangjiaonao water level drop and 133% from asymmetric mouth scouring. As the discharge increases, the absolute values of both contribution rates rise significantly, but their combined effect results in minimal net change in diversion volume, suggesting that these influences are primarily concentrated during medium- to low-flow periods.The differential riverbed composition regulates the scouring process and maintains stable diversion at Songzi Mouth. Increased low-flow diversion is beneficial for water resource allocation in Dongting Lake, but it may moderately lower main channel water levels and affect navigation during medium- to low-flow periods.

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  • 收稿日期:2025-02-21
  • 最后修改日期:2025-04-29
  • 录用日期:2025-04-29
  • 在线发布日期: 2025-07-22
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