钱塘江河口一维盐度动床预报模型及应用

钱塘江河口为强涌潮、高含沙量、河床冲淤剧烈的河口,其盐度输移时空变化受河床冲淤的反馈影响十分显著。建立了考虑河床冲淤变化的一维盐度动床数学模型,耦合求解水沙运动、河床冲淤及盐度输移过程,数值计算方法采用守恒性较好的有限体积法。验证结果表明:河床冲淤对氯度的影响非常显著,动床模型的结果与实测基本吻合,在长历时盐度预报中采用动床模型是必要的。应用该模型分析了钱塘江河口咸水入侵对上游建库、治江缩窄工程等人类活动的响应,探讨了杭州城市供水水源保证率。结果表明,新安江水库、河口治理缩窄工程对改善河口淡水资源利用、保障杭州市供水安全显著;供水保证率要达95%以上,需采取上游水库泄水调度和新建备用水库等措施。

1-D movable bed numerical forecast model of salinity of the Qiantang River estuarine reach and its application

The Qiantang River estuary is an alluvial estuary with strong tidal bore, high sediment concentration and easy changeable riverbed. The interaction between tide and fluvial feedback has great effects on saltwater intrusion. In this paper, a 1-D numerical forecast model of salinity has been developed in the light of riverbed deformation, and the process of water flow, sediment transport, river bed deformation and salinity are fully coupled solved. The governing equations of the model are solved by an explicit finite-volume method with good conservation performance. The verification results show that the riverbed deformation has great influence on chlorine, and the chlorine computed by the movable-bed numerical model agrees well with the measured. Therefore, it is necessary to adopt the movable-bed numerical model in long-duration salinity forecast. Finally, the model is used to investigate the response pattern of saltwater intrusion in the Qiantang River estuary to human activities, such as construction of Xin'anjiang-reservoir and the Qiantang River estuary narrowing regulation. And the problem of the water supply guarantee rate of Hangzhou city is also discussed. The results show that Xin'anjiang-reservoir and the Qiantang River estuary regulation engineering have a significant effect on improving the estuarine freshwater resources and ensuring the safety of water supply of Hangzhou city. In order to raise the water supply guarantee rate to 95%, the measures of scheduling release water discharge from the upstream reservoir and building a new backup reservoir should be taken.