本研究於民國92年1月起至12月，在淡水河主流感潮河段，進行多次高、低平潮水質與懸浮細泥之觀測採樣工作及三次的全潮量測採樣，高、低平潮採樣點由淡水河下游往上游方向分別為：淡海、竹圍、關渡、重陽橋、高速公路橋、台北橋、忠孝橋、中興橋等八個採樣點，對於淡水河感潮河段水質與懸浮細泥之空間分佈狀況有進一步瞭解。另為瞭解水文物理特性於時間之分佈情形，於高、低平潮前後，針對關渡及重陽橋採樣點進行重複之觀測採樣工作；全潮量測採樣位置為關渡與竹圍，主要是探討水質與懸浮細泥隨時間的變化。 經分析結果顯示，淡水河河口水文物理特性主要受潮汐與鹽分入侵的影響，鹽分濃度於高、低平潮呈現不同的分佈情形，並可判斷淡水河為部分混合型河口(Partially mixed estuary)；水溫主要受日照、潮汐及季節性的影響；懸浮顆粒之最大濃度常發生於底層水體，於中興橋附近出現最大混濁度(Turbidity maximum)，概因接近鹽分入侵終點或因上游泥砂注入，在關渡站出現之局部最大混濁度係因為河床較深與環流所致；實驗結果顯示水體中顆粒粒徑分佈不均勻，分析結果水中顆粒中值粒徑大小分佈為20~150μm。淡水河底質除關渡及台北橋為砂粒外，其餘各點均為砂礫粒徑均大於0.2mm。水體中顆粒沉降速度分佈並無一規律性約為0.08~0.2 cm/sec。光衰減係數(Ke)與懸浮顆粒濃度的相關性不佳，但與水中鹽度及沙其盤深度(secchi disk depth)有較佳的關係。 Monthly field surveys of suspend sediment were conducted in the Danshuei River estuary from January to December 2003. They include several high and low slackwater surveys and three intensive surveys. Field data were collected sequentially in the upstream direction at eight sampling stations from the Danshuei river mouth to Chung-Hsin Bridge. To get a glimpse of temporal distribution, additional field data were collected at the Kuan-Du and Chong-Yang Bridge before and after slack tides. The intensive survey station cover the Kuan-Du and Zhu-Wei at downriver of Danshuei River, main to confirm water quality and suspended sediments in time variation. The results reveal that hydrologic and physical characteristics in the Danshuei River estuary are affected by the tide and salt intrusion. The salinity data show different spatial distributions at slack before ebb and slack before flood, and approve to determine the Danshuei River for partially mixed estuary. The water temperatures are mainly influenced by sun, tidal and seasons. High concentration of suspend sediment is located at the bottom layer of the Chung-Hsin Bridge and appear the characteristic of turbidity maximum due to the limit of salt intrusion or sediment coming from upriver portion. The particle size distribution of the water column is about 20~150μm from upstream direction to river mouth. The benthic sedimentation of the Danshuei River is belonged to gravel sand at the Kuan-Du and Taipei Bridge, however the other stations are grit and the grid sizes are greater than 0.2 mm. Settling velocities of the water column are about 0.08~0.2 cm/s. The poor relationship exists between in overall extinction coefficient and suspended sediment concentration, but comparison with salinity and secchi disk depth is found in good relationship.
