中文摘要：

基于太湖流域典型丘陵水源地平桥河流域12个采样点的水质监测数据,综合运用聚类分析和主成分分析法对平桥河流域水质时空变化及影响因素进行分析。聚类分析显示,按照水质相似性将平桥河流域水质分为枯水期、平水期、丰水期3个季节时段和中上游丘陵河谷区、下游紧邻平桥镇的平原区、下游暗沟出口区3个典型空间区域。主成分分析显示：（1）枯水期水质以氮污染为主导因素,磷和有机污染次之,受流量减小、流速缓慢导致的营养盐富集的影响加大;平水期水质以氮污染为主导因素,磷污染次之,受茶园等大量施肥导致的农业面源污染的影响;丰水期水质以氮和磷污染为主导因素,受到水稻种植等农业活动和大量降雨径流的影响。（2）中上游丘陵河谷区水质以氮和磷污染为主导因素,有机污染次之,受到茶园种植等农业活动导致的面源污染的影响;下游紧邻平桥镇的平原区水质以氮和磷的污染为主导因素,有机污染次之,受到居民生活污水和农业生产的影响;下游暗沟出口区水质以氮污染为主导因素,有机污染和磷污染次之,受到生活污水、农业生产和畜禽养殖的影响。研究结果可为太湖流域丘陵区水源地保护和管理提供参考。

英文摘要：

Multivariate statistical methods such as cluster analysis （CA） and principle component analysis （PCA） were used to analyze the spatial and temporal variations and influencing factors of the water quality in a typical hilly water source of the Taihu Lake basin： Pingqiao River watershed. The water samples were collected first at 12 sampling sites along the Pingqiao River. Then the hierarchical CA grouped 12 months into three seasons （dry season, normal season and wet season） and classified the 12 sampling sites into three groups （hierarchical hills valley region, the town of downstream adjacent to Pingqiao plains and the downstream drainage outlet region） based on different seasons and levels of pollution. PCA results showed that： （1） In the dry season, the water quality was mainly determined by levels of nitrogen, phosphorus and organic matter levers, and it was affected by substantial reduce in runoff and the enrichment of nutrients; In the normal season, water quality was mainly determined by the levels of nitrogen and phosphorus, and it was influenced by non-point source pollution from agricultural activities such as plantation; While in the wet season, water quality was mainly determined by the nitrogen and phosphorus, and it was affected by agricultural activity （mainly crop plantation rice） and a substantial storm discharge with high of nutrients. （2） In the hierarchical hills valley region, water quality was mainly determined by nitrogen, phosphorus and organic matter, and it was affected by non-point source pollution （tea plantation）; In the town of downstream adjacent to Pingqiao plains, water quality was mainly determined by nitrogen, phosphorus and organic matter, and it was affected by domestic sewage and agricultural production; While in the downstream drainage outlet region, the water quality was mainly determined in order of nitrogen, organic matter and phosphorus, and it was effected by Sewage from agricultural production and livestock breeding. Our research coul