长江口规划工程影响下的咸潮入侵数值模拟

3D Numerical Simulation of the Impacts of Planned Estuarine Projects on Saltwater Intrusion in the Yangtze Estuary

基于无结构网格数值模型FVCOM建立了长江口三维盐水输运模型,模型经充分验证后能够合理刻画长江口水动力和盐度输运过程,并成功对2010—2014年多次咸潮倒灌过程进行后报模拟,计算结果与实测吻合较好。以2014-01—02咸潮入侵事件为背景模拟三峡运行后河口规划工程对长江口咸潮入侵和倒灌的影响。结果表明河口规划工程整体上减弱南支咸潮入侵和倒灌,但使口门地区盐度增大,北支下段咸潮上溯稍有增强。规划工程减弱青草沙水库和陈行水库受咸潮入侵的影响,但使东风西沙水库取水口盐度增大,尤其在南支规划工程的作用下盐度最大值和平均值均有所增大,这主要是受扁担沙护滩潜堤的阻流作用影响而使入侵和倒灌的盐水团落潮不畅形成滞留。未来十年随着长江口规划工程的推进、上游水沙条件变异及其引起的地形冲淤变化,需进一步开展系统的咸潮入侵演变和影响研究。

Based on the unstructured numerical model FVCOM,a 3D saltwater transport model for the Yangtze Estuary is established.The model is validated on flow and salinity processes,and the comparison with observations suggest that the model is able to reproduce the saltwater intrusion events in 2010-2014.The impacts of planned estuarine projects on the saltwater intrusion in the Yangtze Estuary from January to February 2014 is investigated with numerical simulations,and the results show that the planned estuarine projects reduce the saltwater intrusion and spilling over,while the salinity in the mouth area is increased and the upstream saltwater intrusion of lower North Branch is slightly enhanced.Planned projects reduce the impacts of saltwater intrusion on the Qingcaosha and Chenhang Reservoirs,but increase the salinity at the intake of the Dongfengxisha Reservoir,particularly under the influence of the projects within the South Branch which increases both the maximum and mean salinity.This is primarily attributed to the submerged dikes along the Biandan Shoal,which hinder the ebb flow and thus cause retention of intruded saltwater near the reservoir.With the construction of the planned projects in the Yangtze Estuary and the variation of river input as well as its resulted bathymetry change in the next decade,further systematic studies on variation of saltwater intrusion and its impacts are needed.