Study on development and improvement of simulation model for environmental prospect of lake water system

建立了两种浅水湖泊水流运动数值模型。这两个模型都是基于有限元法的二维非恒定流模拟模型，但一个是水平的，另一个是垂直的，前者可以模拟水平方向的水流运动，如果流速在垂直方向上均匀分布，则可以用于污染物的流入、流出、扩散和稀释分析。该模型被用于分析在霞浦湖和在lnbanuma湖的流态。结果发现，风的影响是主要的霞浦湖，和抽水操作是非常有效的在lnbanuma湖。原计划中的三维模型尚未完成，但通过提高数值稳定性，已接近最后阶段，后者可计算垂直水流运动，适用于追踪微囊藻等漂浮物。利用该模型研究了稀释水在港口排放时对漂浮物的影响。另一方面，对某坝库长期浑水问题进行了野外试验和垂向一维模型试验研究。实地研究的目的是收集大洪水前后的水文和水质数据。利用这些数据研究了浑水的形成过程。通过一维模型的研究，验证了幕墙和旁通道对防止水库入水与浑水混合的有效性，从而使水库水环境问题的模拟模型基本完善，但仍需进一步完善，以取得更好的前景。

Two kinds of numerical models were developed for analyzing flow movement in a shallow lake. They are both two dimensional unsteady flow simulation models based on the finite element method, but one is horizontal and the other is vertical.The former model can simulate horizontal water movement and can be used for the analyzes of pollutants' inflow, outflow, diffusion and dilution, if velocities are vertically equally distributed. This model was used for analyzing flow patterns in the Kasumigaura lake and in the lnbanuma lake. It was found that wind effects were primary in the Kasumigaura lake, and pumping operations were strongly effective in the lnbanuma lake. Three dimensional model, which was in the original plan, is not completed, although now approaching final stages through improving its numerical stability.The later model can calculate vertical water movement and is suitable for tracing floating materials, such as microcystis. This model was used to investigate bahaviors of floating materials when dilution water was released in a harbor. Released water may be hot or cold.On the other hand, the long-term muddy water problem in a dam reservoir was studied at field, and in vertical one dimensional simulation model as well. The field study was aimed at gathering hydrological and water-quality data before and after large flood. These data were used to investigate muddy water generating process. One dimensional model was used for examining the effectiveness of curtain wall and bypass channel, which might be used to prohibit inflow water from being mixed with muddy water in a reservoir.Through the above studies, simulation models for solving water envitonmental problems are nearly completed but should be improved to gain a better prospect.