基于2010 年汛期与非汛期太湖流域西部宜溧河及西苕溪22 个断面水样实测分析数据，选取高锰酸盐指数(COD_Mn)、总磷(TP)、总氮(TN)、氨氮(NH₃-N)为主要研究指标，利用单因子评价法和综合评价法对两条典型河流汛期与非汛期水质状况及差异，以及两者间不同时期及沿程水质变化进行了对比分析，并从社会经济、自然地理等角度探讨了其产生的原因。结果表明：宜溧河流域平均水体污染程度总体高于西苕溪流域，污染程度更差。宜溧河非汛期各断面的COD_Mn、TN、NH₃-N 及TP含量均明显高于汛期的含量，水质状况更为恶劣，而西苕溪汛期的平均水质状况基本劣于非汛期。受流域内城镇空间布局以及工业污染企业的空间分布等因素的影响，河道水体水质状况的空间差异性比较显著。宜溧河段入湖河流水质污染主要来源于点源，汛期下游受到一定程度的非点源污染。西苕溪水质污染主要来源于面源污染，汛期污染物主要是由降雨径流带入河中，下游受到一定程度的点源排放影响。

Principal pollutants in the waters were compared between Yili River and Xitiaoxi River located in the west and southwest of Taihu basin, based on field observations at various sampling sites in July and November in 2010. Several factors which might induce the pollutants in these inflows were also analyzed related with the socio-economic, geographical and other aspects in the Taihu basin. Several indicators were selected in this study, including chemical oxygen demand (COD_Mn), total phosphorus (TP), total nitrogen (TN) and ammonia-N (NH₃-N). Field observations were carried out at 22 river sections and all selected indicators were monitored. Results show that COD_Mn, TN, NH₃-N and TP of Yili River in non flood season were significantly higher than that in flood season. Water quality of Xitiaoxi River in flood period was worse than that in non flood season. Water quality of Yili River is worse than that of Xitiaoxi River. Because of the spatial distribution of urban areas, population, industrial pollution and other business factors, the spatial variation of water quality of both rivers is very obvious. Yili River is mainly polluted by point source pollution. While the downstream of the river is also affected by non-point source pollution in the flood period. Water pollution of Xitiaoxi River mainly comes from non-point source pollution, which is caused by rainfall and runoff carrying most of the pollutants into Xitiaoxi River in flood season.The pollution of the downstream of Xitiaoxi River is also affected by emissions from point sources.