Water age distribution of the Lake Taihu and impact of the Yangtze River to Lake Taihu Water Transfer Project on the water age

Abstract

太湖作为典型的风生流湖泊，风场对水体运输和交换的过程起着重要的作用.基于环境水动力学模型EFDC源程序建立了染色剂模型以及水龄模型，借助水龄研究太湖水体的长期输运过程和更新速率特征，从而为太湖的调水工程管理提供科学依据.本文在研究春、夏、秋、冬季不同风场作用下太湖的水龄季节性分布特征的基础上，结合太湖实测风速、流量数据及“引江济太”工程调水运行的现状，着重分析了望虞河枢纽调水运行以及新沟河工程对太湖水龄分布的影响.数值试验的模拟结果表明：太湖水体交换受季风影响明显，春、夏季的水龄相对较大、水体交换较差；靠近湖流入口处的地方水龄较小，远离入口的地方水龄较大；水流流向与风向一致时水龄减小，水循环加快，反之则减慢.望虞河引水引工程能够减小贡湖及湖心区的水龄，加快贡湖湖区及湖心区的水循环；新沟河工程引水能够减小梅梁湖区的水龄，改善该湖区的水质.引水工程的实施对加快整个太湖的水循环做出重要贡献.;Lake Taihu is a typical wind-driven lake, and wind plays an important role in process of water exchange and concentration transportation. Based on Environmental Fluid Dynamics Model (EFDC), water age model and conservative dye model were set up to study characteristics of seasonal water age distribution and to further reveal the impacts of the Wangyu River Water Transfer Project and the Xingou River to the Lake Taihu Transfer Project on water age distribution on basis of winds, inflow and outflow, operations of existing water transfer projects. It is concluded that by the numerical test results, water exchange of Lake Taihu is mainly influenced by the monsoons. Water age is comparably larger in the spring and summer, which indicates the water exchange rate in the spring and summer is lower than that in the autumn and winter. Water ages near inflow locations are comparably smaller, and the locations far from the inflows are larger. Water age is smaller when the flow direction is the same as wind direction, while the exchange of water is increased at the same time and on the contrary water exchange is reduced. During operation of the Wangyu River Water Transfer Project, the water ages of the Gonghu Bay and Middle Lake Taihu are basically reduced, and water exchange is increased in the areas. During operation of the Xingou River Water Transfer Project, the water ages of the Meiliang Bay are basically reduced, and water quality is improved in the area. The water exchange of Lake Taihu will be significantly improved with continuous or occasional transfer operations.