洪水事件对碧流河水库水质影响

Impact of flood events on water quality of the Biliuhe reservoir

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。

The frequency of extreme floods is increasing due to the impact of global climate change.Reservoirs,as an important water conservancy project,suffered from serious water quality problems during flood events in the river basin.This study took the Biliuhe reservoir as an example and analysed the water quality data before and after seven flood events since the dam was constructed.The results showed that floods could weaken the thermal stratification of the Biliuhe reservoir and influence the vertical distribution of dissolved oxygen.Flood events had great impacts on water quality variables of hexavalent chromium,coliform bacteria,permanganate index,ammonia and total phosphorus,which had increased after the flood event.In terms of spatial distributions,the concentration of pollutants at the entrance section of the reservoir was greater than the front of the dam.The topographic characteristics of the Biliuhe reservoir could weaken the impact of flood density flow on the water quality in front of the dam.The assessment results indicated that the water quality grade of the reservoir become worse after the flood,but it meet the environmental quality standards for surface water.The pollutants entering the reservoir during floods mainly come from the non-point source pollution in the Biliuhe reservoir basin.The countermeasures such as controlling non-point source pollutants,interception at the entrance of the reservoir,reasonable regulation during floods process could alleviate the impact of flood events on the water quality of the Biliuhe reservoir.