洪水事件对碧流河水库水质影响

受全球气候变化的影响,暴雨洪水事件发生频率呈增加趋势,水库作为流域内重要的控制性水利工程,洪水过程中水质安全面临严重威胁。以碧流河水库为例,对建库以来7场典型洪水前后水质状况进行分析,结果表明,洪水过程能够减弱碧流河水库水体的热分层结构,影响溶解氧垂向分布;洪水过程影响较大的水质指标为六价铬、大肠菌群、高锰酸盐指数、氨氮和总磷,洪水过后上升趋势较为明显;空间上来说,洪水对入库口断面的影响大于对坝前断面的影响,碧流河水库地形特征能够减弱洪水异重流对坝前水质的影响;评价结果显示洪水过后碧流河水库水质变差,但整体上能够满足地表水环境质量标准中水源地要求;洪水期间入库污染物主要来自流域非点源污染。分析认为,通过源头治理、入库口拦截、合理调度等措施可以减轻洪水事件对水库水质的影响。

Impact of flood events on water quality of the Biliuhe reservoir

The frequency of ex tr eme floo ds is increasing due to t he impact of g lo bal climate chang e. Reser voirs, as an important water co nser vancy project , suffer ed fr om serious w ater qualit y problems during flo od ev ents in the river basin. This study too k the Biliuhe r eser vo ir as an example and analysed the water quality data befo re and after seven flo od events since the dam w as co nstr ucted. T he r esults show ed that floo ds could w eaken the thermal str atification o f the Biliuhe reser voir and influence the vert ical distribution of disso lv ed ox yg en. Flood ev ents had gr eat impacts o n water quality v ariables of hex avalent chrom ium, coli2 fo rm bacteria, permang anate index , ammonia and t otal phospho rus, w hich had incr eased aft er the floo d event. In terms of spatial distribut ions, the concentr ation of po llutants at the entr ance section of t he r eser vo ir w as gr eater than the fr ont of the dam. T he topog raphic characteristics o f the Biliuhe r eser voir could w eaken the impact of floo d density flow o n the w ater quality in fro nt of the dam. T he assessment results indicated that the w ater qualit y gr ade of the r eser voir become w orse after the flood, but it meet the env iro nmental quality standards for surface water. The po llutants ent ering the reserv oir during f loo ds mainly come fr om the no n2point so ur ce pollution in the Biliuhe r eser vo ir basin. The countermeasur es such as contro lling non2point so ur ce po llutants, intercept ion at the entr ance o f the reservo ir, reasonable r egulation during flo ods pro cess could alleviate the im pact of floo d e2 v ents on the wat er quality o f the Biliuhe r eservo ir.