基于EFDC模型的洱海水温模拟

洱海是处于富营养化初期的高原中深水湖泊,夏秋季节没有明显的温跃层,具有独特的水温垂向分布特点。为掌握洱海水位、水温等要素的变化规律,分析其可能造成的影响,采用环境流体动力学(EFDC) 模型建立了洱海三维水动力模型,并用拉丁超立方采样(LHS)和标准秩回归(SRR)方法对影响水温的重要参数进行了敏感性分析。结果表明:湖体水温对太阳短波辐射中的快速波占比(FSWRATF)和快速衰减系数(SWRATNF)2个参数的变化较为敏感,而对太阳短波辐射慢速衰减系数(SWRATNS)的敏感性较弱;洱海水温的空间分布主要呈南北方向变化,且随季节变化明显,春夏季水温自北向南递减,秋冬季水温南北低、中间高,这可能与洱海湖盆地形及出入流河口位置有关。洱海水温模拟结果较好地拟合了水温的弱分层现象,对解释洱海营养盐的垂向分布特征、藻华发生条件等具有重要意义。

Water temperature simulation of Lake Erhai based on EFDC model

Lake Erhai, which is in the early stage of eutrophication, is a deep plateau lake. There is no obvious thermocline in summer and autumn with unique vertical distribution of water temperature. To learn the changing rules of the hydrodynamic elements such as water level, water temperature and to analyze the effects possibly caused by them, the three-dimensional hydrodynamic model of Lake Erhai was established based on Environmental Fluid Dynamics Code (EFDC). The Latin Hypercube Sampling (LHS) and Standard Rank Regression (SRR) methods were employed to perform the water temperature parameters sensitivity analysis. It was found that the water temperature of the lake was sensitive to the change of the two parameters, including the proportion of fast wave in shortwave radiation (FSWRATF) and the coefficient of shortwave radiation rapidly attenuated in water (SWRATNF), while the effect of the coefficient of shortware radiation slowly attenuated in water (SWRATNS) was not significant. The water temperature spatial distribution mainly changed in the north-south direction, and obviously changed with seasons. Water temperature in Lake Erhai featured in decreasing from the north to the south in spring and summer, and north-south low, intermediate high in autumn and winter, which might be correlated with Lake Erhai Basin’s terrain and the location of the estuaries. The simulation results perfectly fit the weak str.pngication of water temperature in Lake Erhai, which was of great significance for explaining the vertical distribution of nutrient and algal bloom occurrence conditions there.