集水區水質受到集水區內土地變遷影響，過去研究已確定兩者的定性關係，然而量化關係的討論則相對缺乏。本研究以翡翠水庫集水區監測資料，利用皮爾森相關分析，分別探討河川流量、集水區土地變遷對承受水體水質影響。結果顯示土地利用對水質的影響主要於懸浮固體物、總磷與氨氮，對生化需氧量、溶氧等則影響不顯著。土地利用型態中，市集、農地、草地對營養鹽類與懸浮固體物有正向關係，林地則有負向關係。另外，本研究以各土地面積比例為自變數，建立營養鹽水質之多元迴歸公式，並利用土地利用變遷預測，可推估未來不同土地利用變遷情境下，可能的水質變化。
Land use change in a watershed results in the changing water quality in the receiving waterbody. This causality has been confirmed descriptively but the quantitative relationship was lacked. This study used the observed data in the Feitsui Reservoir watershed to identify the effects of water quality caused by streamflow and land use. Pearson product-moment correlation was used to define the significance and multiple regression analysis was applied to link the relationship. Results show that landuse change affects significantly on suspended solid, total phosphorous, and ammonia-nitrogen, and the less effects on biochemical oxygen demand and dissolved oxygen. Urban land, agricultural land, and grassland have positive significant effects on nutrients and suspended solid, which means tmore urban, agricultural, and grass land in a watershed results in more nutrient and suspend solid concentration in receiving waterbody. On the contrary, forest land has negative effects on these pollutants. A multiple regression formula consisted of several land use was finally built to predict water quality. Combining with land use scenario and the regression equations, the future water quality can be predicted.
