鄱阳湖水利枢纽工程对水质环境影响研究

鄱阳湖水利枢纽工程的建设,将改变湖内水动力特性,进而影响鄱阳湖的水环境质量。采用水深平均的二维水动力-水质模型对鄱阳湖现状水动力和水质进行模拟验证,水陆边界模拟采用动边界技术,摸拟"高水湖相,低水河相"的湖泊水域变化特征,水质特性为枯水期水质较差,丰水期水质较好,靠近入湖河口的湖区劣于湖心水质,北部出湖水质较好的现状。模型模拟预测在现状外部入流边界和现状污染负荷条件下,3种不同运行方式下,鄱阳湖湖流的时空形态相应发生的变化和相应水质变化。计算结果表明,枯水期大部分区域的水质浓度下降,但尾闾等部分区域有所升高,开闸泄水期前后,水质较现状水质下降,敞泄期的大部分时间,较现状水质基本相似,蓄水期水质变化不大。水动力特性综合水质浓度的改变,增加了局部水体的富营养化风险。研究结果可为枢纽的建设提供科学依据。

Modeling the impacts of Poyang Lake Water Control Projection hydrodynamics and water quality

Poyang Lake Water Control Project planned on the flow channel that connects the lake to the Yangzi River will alter the hydrodynamics and consequently change the water quality. A 2D depth-averaged numerical model with wet and dry front treatment has been applied to improve the understanding of water environment of the Poyang Lake and investigate the effects of the hydraulic construction. The model results were validated against several series of measurements with satisfactory agreements on both hydrodynamics and water quality. According to the computational results, three different operation schemes of the water control project have significant impacts on hydrodynamics in the Poyang Lake especially in low flow peri- od, as a result of the slow lake flow instead of rapid river stream in low flow season. Further analysis of the effects on water quality was carried out. Currently, water quality of the Poyang Lake in low flow sea- son is worse than that in high flow season under present pollution loads. After the water control project is constructed, water quality in most part of the lake is improved in low flow season, while at the inlets of main inflow rivers it becomes worse. When the water control gate is entirely open annually in spring, the water quality get worse than that at present. In the rest time of a year there is no obvious difference among those cases. The results indicate that the risk of lake eutrophication increases at certain place in the Poyang Lake due to the water control project building.