石門水庫每年供應台北、桃園、新竹等22個鄉鎮的民生、農業與工業用水約22億立方公尺，而集水區環境變異可能影響之經濟利益、人民健康等範疇相當廣大，因此其上游環境地質影響性不可輕忽。本研究以2003年2月至2008年1月間，石門水庫集水區與蓄水區中17個水質測站資料為主，輔以同時期復興鄉之人文環境變化資料如垃圾量和人口資料，結合集水區自然環境因子如山崩、土地利用與降雨做時空變化之分析，來探討上游自然作用與土地開發等影響。並綜合RPI指數(River Pollution Index)和Carlson指數(Carlson Trophic Index)對水質以生化指標及優養化程度來整體探討集水區上游地質環境之變化與成因，並據此找出集水區可能污染源及造成污染之原因。 分析各項資料發現幾點特別的現象：1.蓄水區與集水區水質易受颱風與豪雨沖刷導致水質惡化。2.硝酸氮在阿姆坪、三民、湳仔溝三個測站之數值異常高於其他測站，並且有地緣關係。3.當地崩塌地多位於主流附近，導致主支流懸浮固體濃度差異極大。4.當地人口呈現負成長，且人口增減似乎受選舉等政治活動影響。5.由以往掩埋法改為焚化法，可能因環保法律條例管制產生大幅度的垃圾減量現象。 Water quality of reservoir seriously affects living environment and economic growth of the water-supplied area. Shihmen Reservoir is the third largest reservoir in Taiwan, its watershed can be contaminated by different ways. In order to understand the water quality and pollution factors of Shihmen Reservoir, water quality data of 17 sites from reservoir and watershed, dated from Feb. 2003 to Jan. 2008, were analyzed to establish River Pollution Index and Carlson Trophic Index. The relationships among parameters of water quality and local cultural environment were then examined. The results of this study indicate that: (1) Typhoon and cloudburst can easily deteriorate the water quality. (2) Amuping, Sanmin, and Nanzaigou site consistently exhibit high contents of nitrate nitrogen. (3) Landslides happened mostly around the main stream area with high contents of suspended solid instead of the smaller scaled branch streams areas Dahan River. (4) A negative growth and effects of political activities on local population can be observed. (5) Waste disposal was changed from open dump to incineration, which reduced the tonnage of waste successfully since 2004.
