Eutrophication study of twenty reservoirs in Taiwan

Taiwan is an island off the southeastern coast of China with total area of roughly 36,000 km(2). The geographic position of Taiwan is between 21 degre es 45 ' 25 " to 25 degrees 56 ' 31 " north latitude and 119 degrees 18 ' 3 " to 124 degrees 34 ' 30 " east longitude and includes both tropical and su btropical areas. The study was carried out at twenty main reservoirs in Tai wan area from 1994 to 1998. The study revealed that the water quality of mo st reservoirs gradually deteriorated during the study period. Total phospho rus concentrations over 60 mug/L were observed in 12.5% of these reservoirs in 1994, but in 22.2% of these reservoirs in 1998. Total nitrogen concentr ations over 1.0 mg/L were observed in 37.5% of these reservoirs in 1994, bu t in 94.4% of these reservoirs in 1998. Secchi disc transparency below 2 m was observed in 75% of these reservoirs in 1994, but in 83.3% of these rese rvoirs In 1998. Chlorophyll a concentrations over 15 mg/m(3) were observed in 12.5% of these reservoirs in 1994, but in 27.8% of these reservoirs in 1 998. The TN:TP mass ratios (wt/wt) of all the studied reservoirs except Aku ngting Reservoir, Fongshan Reservoir, and Chengching Reservoir are higher t han 16. The study results on nutrient limitation indicated that phosphorus is the primary limiting nutrient in Taiwan reservoirs except Akungting Rese rvoir, Fongshan Reservoir, and Chengching Reservoir.