浅水湖泊群连通与调水的二维水动力-水质藕合模型研究

将湖泊群连通并进行引清调水的水环境污染治理模式在浅水湖泊分布比较集中的地区逐渐受到人们的关注.为了探究独立湖泊群相互连通引水后各湖区的水动力水质变化情况,以武汉大东湖生态水网工程的建设为背景,建立了湖泊群二维水动力-水质耦合模型.采用适合复杂边界的非结构化网格,考虑湖底地形和气候条件,考虑污染物的输入、迁移和转化,以及蓝藻等浮游生物的生长条件,分别利用东湖2006年6月和2007年6月的野外数据对所建模型进行参数的率定和校核,并利用2012年6月实测数据对3种引水方案与3种连通模式组合情况下湖泊群的BOD5,TP,TN以及Chl-a等生化指标的变化情况进行模拟,对稳定运行30 d后的模拟结果进行比较分析.结果表明:引水工程中,对于水域面积较大的湖泊,风力作用依旧是影响流场的主要因素;同样的引水流量下,不同的调水方案对水质改善结果有较大差别;湖泊群中隔堤的存在会给湖泊污染治理带来困难,而在湖泊群中适当区域设置生态小岛对水质变化过程影响微弱.

A 2-D Model Coupling Hydrodynamics and Water Quality for the Water Connection and Diversion of Shallow Lake Group

The method of treating water pollution by reestablishing hydraulic connection between lakes and diverting water from a nearby river to the lake group which is seriously polluted is getting wider attention in shallow lake areas. To investigate the variation of hydrodynamics and water quality after lake connection and diversion, we built a 2-D model coupling hydrodynamics and water quality. The Project of East Lake Network in Wuhan was taken as research background. In this model, unstructured grid was adopted to fit the complex boundary, and lake topography and climate conditions were adequately reflected. In addition, the input, transport and transformation of nutrients and pollutants as well as the growing conditions of some algae such as cyanobacteria were taken into account. Moreover, field measurement data in June 2006 and June 2007 were used for the calibration and validation of the model parameters. Then the variation of indexes including BOD₅, TP, TN and Chl-a in three diversion conditions and three connection conditions after 30 days of stable operation were simulated based on the measured data in June 2012.Results suggest that wind force is still the major factor which induces the change of lake flow field for larger lakes in a water diversion project; in the presence of the same diversion flow, different diversion conditions has different effects on the water quality improvement. Dividing dikes in shallow lake group bring difficulties to the control of lake pollution, whereas setting up artificial island at suitable position of the shallow lake has no great impact on the water quality variation.