基隆河流域位在都市化程度相當高的大臺北地區，本研究探討基隆河水質變化之時空關係，水質資料是以環保署在基隆河流域13個河川水質監測站資料為主，分析每個測站自設站以來至2008年12月止的相關水質變化趨勢。基隆河主要污染來源為家庭用水，因此以人口密度做為都市化指標，分析自1981至2008年間13個測站集水區人口密度變化，在上游的3個測站集水區人口密度皆少於每平方公里200人，且在過去近30年間人口密度沒有顯著變化；中游的4個測站集水區人口密度介於每平方公里350到1,200人，在過去近30年間人口密度也沒有明顯變化；下游6個測站集水區人口密度則介於每平方公里1,400到2,900人，且在過去近30年間人口密度有上升的情形。除上游兩個測站外，其他測站溶氧及氨氮濃度都沒有明顯變化的趨勢。中游4個站皆有大腸桿菌與總磷濃度增加的趨勢。下游6個測站皆有生化需氧量降低的趨勢，值得注意的是總磷濃度在13個測站中有9站都有增加的趨勢。溶氧在基隆河中下游統計上沒有明顯變化趨勢，雖然整體上溶氧數值有增加的情形，但是下游4個測站其溶氧仍低於5 mg/L，不利水生生物生存，仍待改善。人口密度不論對魚類或水棲昆蟲群落都呈現顯著負相關，另外在中游介於人口密度在每平方公里500至1,000人地區，水棲昆蟲生物多樣性指數即已出現有較低的情形，顯示水棲昆蟲生物多樣性比魚類生物多樣性對都市化河川更敏感。

Keelung river basin is located at a highly urbanized Taipei metropolitan region. In this study, spatial and temporal changes of water quality of Keelung river was examined. Monthly water quality data of 13 monitoring sites in Keelung river were retrieved online from the environmental water quality information on Taiwan Environmental Protection Administration web site. For each water quality monitoring station, trends of different water quality parameters were analyzed up to the end of 2008. The municipal sanitary wastewater is the major pollution source of Keelung river; therefore, population density was used as an urbanization index for each sub-watershed of these water quality monitoring stations. Annual population densities of 13 sub-watersheds were calculated for the Keelung River water quality monitoring sites from 1981 to 2008. Population densities of 3 monitoring stations at the upstream Keelung river are below 200 persons per km2. There were no significant changes in population densities for these 3 sub-watersheds during past 3 decades. Population densities of 4 monitoring stations at the middle stream of Keelung river are between 350 to 1,200 persons per km2. There were also no significant changes in population densities for these 4 sub-watersheds during past 3 decades. Population densities of 6 monitoring stations at the downstream Keelung river are between 1,400 to 2,900 persons per km2. There were obvious increases in population densities for these 6 sub-watersheds during past 3 decades. Except for two stations at the upstream Keelung river, dissolved oxygen and ammonia concentration were no significant changes. There are increased trends on Escherichia coli and total phosphorus concentrations for 4 monitoring stations at the middle stream of Keelung river. There is a decreased trend on biological oxygen demand for 6 monitoring stations at the downstream Keelung river. In addition, 9 of 13 monitoring stations are with a increased trend of total phosphorus concentrations. Dissolved oxygen of the middle stream and downstream of Keelung river are no significant changes at monitoring stations; however, dissolved oxygen concentrations at 4 monitoring stations from downstream Keelung river were still below 5 mg/L and could be harmful for aquatic organisms. Dissolved oxygen levels still need to improve at the downstream of Keelung river. Population density negatively correlated with both fish and macroinvertebrate assemblages. Biodiversity of macroinvertebrate assemblages began to decrease at sampling locations with population density between 500 to 1,000 persons per km2. Macroinvertebrates seem more sensitive to the effects of urbanization relative to fishes.