Saltwater intrusions occur widely in tidal river channels, significantly changing the vertical distribution of mainstream velocity and density (salinity). They are vital to the hydrodynamic conditions of lateral withdrawal. In this study, a 3-D numerical model was constructed and validated through experimental tests, and the hydrodynamic characteristics of lateral withdrawal under saltwater intrusion were investigated. Additionally, the vertical distribution effects of mainstream velocity, withdrawal velocity, and density stratification were analyzed. Under non-uniform mainstream velocity conditions, with larger surface velocity than bottom velocity, the division width of the upper layer is smaller, while the local secondary circulation is stronger than that of the lower layer. Secondary circulation is top-shaped and weakens as the withdrawal velocity increases. When salinity stratification exists, the division width of the lower layer decreases, and the secondary circulation is stronger than that of the upper layer; meanwhile, the vertical water exchange increases. The influence of mainstream velocity is greater than that of salinity stratification. Under these two factors, the sediment entering the intake increases, and submerged vane, sill, and weir measures should be adopted. This research represents an advance in lateral withdrawal hydrodynamic research and provides support for engineering design in estuarine areas.

咸水入侵在潮汐河道中广泛发生，大大改变了主流流速和密度（盐度）的垂直分布。它们对于侧向抽水的水力条件至关重要。在这项研究中，建立了一个3-D数值模型并通过实验测试进行了验证，并且研究了盐水入侵下侧向抽水的水动力特性。另外，分析了主流速度，抽出速度和密度分层的垂直分布效应。在非均匀主流速度条件下，表面速度大于底部速度的情况下，上层的分割宽度较小，而局部二次循环则比下层的循环强度大。二次循环是顶部形的，并且随着排出速度的增加而减弱。存在盐分分层时，下层的分割宽度减小，二次循环强于上层。同时，垂直水交换增加。主流速度的影响大于盐度分层的影响。在这两个因素的作用下，进入进水口的沉积物增加，应采取淹没叶片，门槛和堰的措施。这项研究代表了侧向抽水流体动力学研究的一项进步，并为河口地区的工程设计提供了支持。垂直水交换增加。主流速度的影响大于盐度分层的影响。在这两个因素的作用下，进入进水口的沉积物增加，应采取淹没叶片，门槛和堰的措施。这项研究代表了侧向抽水流体动力学研究的一项进步，并为河口地区的工程设计提供了支持。垂直水交换增加。主流速度的影响大于盐度分层的影响。在这两个因素的作用下，进入进水口的沉积物增加，应采取淹没叶片，门槛和堰的措施。这项研究代表了侧向抽水流体动力学研究的一项进步，并为河口地区的工程设计提供了支持。