摘要
The historical water quality data (1991 -2006) of Yuqiao Reservoir,which is the major source of drinking water for the city of Tianjin,were analyzed and assessed.The monitoring data,including temperature,pH,DO,CODMn,NH3 - N,NO2 - - N,NO3 - - N,TN,TP,Chl - a and transparency,were obtained at three sampling sites ( Sanchakou,Kuzhongxin,Baxia) that located in Yuqiao Reservoir.The results showed that Yuqiao Reservoir was not contaminated seriously and the water quality was acceptable.However,the concentrations of TN were usually higher than the Class Ⅲ of the national compulsory standard for water bodies intended for the abstraction of drinking (GB3838 -2002).Moreover,the contents of Chl - a were significantly higher than the standard in some sampling campaigns.Thus,the eutrophication problem in Yuqiao Reservoir should bepaid more attentions.The principal components analysis of the monitoring site mentioned above suggested that the factor contribution rate of eutrophication kept getting lower along the flow,as a result of which the water quality in outlet area was better than that of inlet.The concentration of TP should play an important role in eutrophication outbreak.The risk of eutrophication would rise comparatively higher in the season both of summer and autumn for the increased TP and Chl - a loads coming from the high temperature and heavy precipitation.The changes of annual mean concentration of TN and TP presented an undulatory property,while TN had shown an increased trend to entire reservoir since 2003,as well as TP except Baxia monitoring site.The simulation by using water quality model Bathtub combined with watershed loading model GWLF indicated that livestock breeding and agricultural planting were the two leading contributions of non - point pollution sources around the reservoir to the risk of eutrophication rising.