选取国内外常用的水动力学模型(EFDC)和典型的浅水湖泊(太湖),采用拉丁超立方取样(LHS),研究湖泊水动力模块中常用的5个重要参数(风拖曳系数、床面粗糙高度、涡粘性系数、紊流扩散系数以及风遮挡系数)对湖体水位和流速的影响。结果表明:针对大型浅水湖泊,湖泊岸线形状和湖底地形、湖泊周围地形、湖泊水面风场对模拟结果产生决定性影响。尤其是在湖湾区和周边地形比较复杂的地区,风场参数对水动力模拟结果不确定性的贡献率最大。在垂向上,表层流速受到参数不确定性的影响最大,底层次之,中层最小。床面粗糙高度对水动力模拟结果不确定性贡献率较风场参数要小,水体涡粘滞系数和扩散系数影响则更小。故在选择大型浅水湖泊水动力模型参数时,要充分考虑湖泊岸线和周围地形,着重率定风场参数以及床面粗糙高度。
This study conducts parametric uncertainty and sensitivity analysis of large shallow lake hydrodynamic models.The Environmental Fluid Dynamics Code(EFDC) model is applied to simulate the flow velocity and water level in Lake Taihu that is characterized by its shallowness and large surface area.The Latin hypercube sampling(LHS) method is used to sample values for five uncertain parameters in the EFDC model,which including the wind drag coefficient,the roughness height,the eddy viscosity coefficient,the turbulent diffusion coefficient,and the wind shelter.The results show that uncertainties of simulated hydrodynamics process exist due to the contributions of model parameter uncertainties.The extents and ranges of uncertainties in large lake hydrodynamic models(e.g.,EFDC) are highly associated with the spatiotemporal distribution of winds,shorelines,lake's bottom topography,and geography around the lake.Among those parameters,the wind drag coefficient and the wind shelter play the most important role in the spatial distribution of modeled velocity and water level,especially in those semi-closure bays and the lake regions with complex topography in the lake.Vertically,the velocity in the surface layer is also largely influenced by the two wind parameters,followed by the velocity of bottom layer,and the middle velocity has a minimal impact.The roughness height also makes a contribution to the uncertainty of simulated hydrological process.However,the uncertainties of viscosity coefficient and turbulent diffusion coefficient have no clear effect on model simulations.Therefore,the wind drag coefficient,the wind shelter,and the roughness height should be paid much attention when calibrating a hydrodynamic model of larg shallow lakes.Additionally,LHS is a cost-effective sampling method to reduce the number of parameters needs to be calibrated and to improve the accuracy of numerical simulations.