基于MIKE21的西安昆明池(试验段)换水能力特征研究

Research on characteristics of water change capability of Kunming Lake(test section)in Xi’an based on the MIKE 21 Model

以西安昆明池(试验段)为研究对象,基于MIKE21建立二维水动力-染色剂耦合模型,对昆明池(试验段)的换水能力进行了定量的研究分析。结果表明:受人工岛及湖岸地形影响,昆明池(试验段)流场多形成大小不一的环流,湖区流速在0.004~0.09 m/s之间,且较大流速多出现在人工岛及湖岸附近;换水周期沿水体主流方向大致呈阶梯递增趋势,其中西部湖区换水周期普遍大于东部湖区;整个湖区换水能力快慢并存,约10%的水域换水周期不超过10 d,40%的水域换水周期不超过17 d,70%的水域换水周期不超过34 d,不足10%的水域换水周期在35 d以上;提高西部湖区水体的换水能力,避免其出现水质恶化问题,是保障整个昆明池(试验段)水环境系统健康可持续运行的关键所在。

Taking Kunming Lake(test section)in Xi’an as the research object,a two-dimensional hydrodynamic-staining agent coupling model was established based on MIKE21 to quantitatively analyze the water exchange capacity.The results showed that the flow field of Kunming Lake(test section)often forms circulations of different sizes due to the influence of artificial islands and lakeshore topography.The flow rate of the lake area is usually between 0.004 m/s and 0.09 m/s,and the relative larger flow rates often occur near the artificial islands and lakeshores.The hydraulic retention time is roughly stepping up along the main direction of the water flow,and the lake is divided into four different areas.The hydraulic retention time in the western lake area is generally longer than that in the eastern lake area,and the water exchange capacity of the whole lake area coexists,the hydraulic retention time of about 10%of the area does not exceed 10 days,40%of the area does not exceed 17 days,70%of the area does not exceed 34 days,and less than 10%of the area is longer than 35 days.Improving the water exchange capacity of the western lake area to avoid water quality deterioration is the key to ensuring the healthy and sustainable operation of the water environment system of Kunming Lake(test section).