翡翠水庫不同土地利用集水區營養輸入輸出之研究

Water and nutrient cycling of upstream watersheds has major impact on the quality and quantity of water in the downstream reservoir. Feitsui Reservoir supplies water for the use of several millions of people in Taipei so that the quality and quantity of water in the reservoir is critical for water use in Taipei. A team of researchers has been working on biogeochemical cycle in the Feitsui Reservoir but not the upstream watersheds. Rainwater and streamwater chemistry are examined in this study on upstream watersheds covered by natural forests and watersheds with tea plantation on the upstream of the reservoir. Rainwater was monitored on one watershed of natural forest and one with tea plantation and streamwater was monitored on two watersheds each of the two types of watersheds. Concentration of N and S in rainwater was higher for the tea plantation watershed than the natural forest watershed suggesting that the development of tea plantation affects the composition of atmospheric deposition in the area. Concentration of most ions in streamwater differed significantly between the two watersheds of each watershed type possibly due to the differences in geology and geomorphology between the watersheds. Concentration of most ions in streawater was significantly higher in the tea plantation watersheds than the natural forest watersheds. Thus, more ions was output from the watershed to the reservoir with the possibility of accelerating eutrophication of the reservoir. Concentration of most ions was negatively correlated with water quantity likely as a result of dilution. More significant differences were found in the tea plantation watersheds than the natural forest watersheds probably because of the higher concentrations of ions in the former than the latter. Starting from the second year, the effect of typhoon disturbance on nutrient input-output and the input-output of dissolved carbon will be included in order to link the effects of landuse changes to carbon cycle and global climate change.