洪泽湖风生流对风场和水位变化响应特征

Responses of wind-driven circulation to wind field and water level variations in Lake Hongze

深入认识大型湖泊在不同风速、风向和水位下三维风生流结构特征对于湖泊污染控制、生态恢复及资源的开发利用具有重要意义.本文在构建笛卡尔坐标系下洪泽湖三维水动力模型的基础上,利用2次全湖30个点位流场监测数据验证了模型精度.基于1975-2020年长系列风场观测数据,确定了洪泽湖典型风速风向.在此基础上,模拟了16种不同风向,13种不同风速和20种不同水位工况条件下洪泽湖三维风生流结构.结果表明:水动力模型可以较好地刻画洪泽湖三维湖流变化特征.洪泽湖风生流结构随风向变化呈现出较大空间差异.风生流流速随着风速的升高呈加速上升趋势,其中表层水体流速上升幅度远高于其他水层.在2.4 m/s东风驱动下,溧河洼、成子湖和南部湖区垂向平均流速随着水位上升呈先升高后降低的趋势,3个湖区分别在12.7、12.4和12.2 m水位下流速达到最大值.

An improved understanding of the three-dimensional structure of wind-driven currents under different wind speed,wind direction and water levels is highly valuable for lake pollution control,ecosystem restoration as well as resources utilization.In this study,a three-dimensional hydrodynamic model was setup and validated using observed current profiler data for Lake Hongze.Typical features of wind speed and wind direction were determined using 46-yr wind observational data.The spatial structure of lake current was simulated under 16 wind directions,13 wind speeds and 20 water levels.Results suggest that the hydrodynamic model generally captured the dynamics of three-dimensional current structure in Lake Hongze.Wind-driven currents exhibit considerable difference with the switch of wind direction.Current velocity increases rapidly with the raising of wind speed,and the surface layer is much more pronounced than other four vertical layers.The vertical-averaged current velocity in the lake basins of Lihewa,Chengzihu and Southern Basin exhibit a unimodal pattern with the raises of water level,with velocities peak at water levels of 12.7 m,12.4 m and 12.2 m for the three basins,respectively.