大汶河梯级拦蓄水库富营养化评估
Eutrophication assessment in cascade reservoirs of Dawen River

基于大汶河沿线4个监测点2007—2014年水质资料，分析溶解氧、化学需氧量、氨氮等9项指标的年际变化特征，采用灰色模式识别模型评价大汶河水质状况。通过9个梯级水库2015年丰、平、枯水期水质现场调查，分析氮、磷营养盐时空变化特征，运用加权综合营养状态指数法评价梯级水库营养状态。结果表明：2007—2014年间，受流域内各项减排措施影响，大汶河有机污染得到有效缓解；受拦蓄工程影响，河段内TP明显变优，TN总体变差；灰色综合指数表明，水质状况整体有所好转，且季节波动趋于平稳。因污染程度不同，梯级水库富营养化状态有明显差异，部分库区丰水期和枯水期已分别爆发蓝藻和硅藻水华，不同水期因下泄流量不同等造成流动条件的差异，对库区水质有较大影响，水污染程度、工程拦蓄与运行造成的流动条件差异共同对库区内藻类生长与爆发产生重要影响。
Based on water quality data of 4 stations in the Dawen River from 2007 to 2014, this paper analyzed the inter-annual variability of 9 indicators such as dissolved oxygen, chemical oxygen demand, ammonia nitrogen etc., and evaluated water quality by a Grey Model. By the site investigation of 9 cascade reservoirs during the rich, average and dry period in 2015, the spatiotemporal variation of nitrogen and phosphorus nutrients were analyzed, nutritional level was assessed by TLI.The results show that during the period of 2007 to 2014, the organic pollution have been effectively alleviated by the emission reduction measures in the basin, the concentrations of TP have been meliorated obviously while the concentrations of TN have been aggravated integrally by the construction of cascade reservoirs. The grey comprehensive index shows that the water quality of the Dawen River is improved and the seasonal fluctuations tend to be stable. The state of eutrophication has apparent difference among cascade reservoirs because the contamination vary in degree. Part of the reservoirs have been experienced cyanobacteria and diatom blooms during rainy and dry seasons. The different flow conditions induced by different discharge in corresponding season have great influence on water quality of the reservoirs., the difference of flow condition caused by the water pollution level, damming and impoundment have a significant impact on the growth and bloom of algae in reservoirs.