三峡蓄水初期水库近坝区水环境特性分析

Water environmental properties at the near dam region of the Three Gorges Reservoir in the initial impoundment period

通过现场观测和数值模拟的方法,对三峡水库近坝区在蓄水初期的水流和水环境特性进行了分析。对蓄水初期的溶解氧、BOD、COD和NH3-N、Cu等水质参数进行了观测,将蓄水初期水质资料与蓄水之前的结果进行了对比,分析了近坝区水环境变化趋势。采用大涡模拟紊流模型,考虑水体表面的热交换,对三峡近坝区的流动和水温分布特性进行了模拟。研究结果表明,三峡水库蓄水初期近坝区水流特性明显改变,主要表现为水深增加、流速变缓,部分地段有回流区出现。水质指标变化不明显,坝前断面溶解氧浓度、悬浮物浓度有所降低,和悬浮物密切相关的污染物总磷、重金属也随之降低;蓄水初期139m水位时坝前水域尚没有出现温度分层现象。

The hydrodynamic and environmental properties are investigated at near dam region in the water impoundment period of Three Gorges Reservoir based on site observation and numerical model. The water quality parameters, such as DO, BOD, COD, NH3-N, Cu, are observed during the impoundment period. The resuhs are compared with that before impoundment. By using the large eddy simulation model and considering the heat transfer on the free surface, the velocity field and temperature distribution at near dam region are simulated. The results show that the hydro-dynamic behavior has remarkably changed, i. e.water depth is increased, flow velocity is cereased and the recirculation region may be formed. The water quality has little changes, the concentrations of the dissolved oxygen and the suspended materials are decreased, the concentrations of TP and heavy metal substances are decreased consequently. The thermo stratification has not appeared when the water level reached 139m.