The aim of this project was to monitor the water quality of rivers, ocean, reservoirs and groundwater in the six counties located in the central part of Taiwan. The monitoring data obtained in this work could be used to evaluate the current condition and to predict the quality changing trend of the water systems, and to provide information for the Environmental Protection Organization to make the pollution control policy.
A total of 75 water-monitoring stations spread among the 19 rivers of the six counties were established, and the monitoring frequency was set to be once per month. The data obtained this year showed that the water quality of the Si-hu, Da-jia and Da-an River Basins were good among the rivers monitored, with an annual proportion of more than 88.8% to be of no (or slight) pollution. Meanwhile, the Lu-gang and Sin-huwei Rivers as well as the Bei-gang River Basin had a higher percentage, ranging from medium to high levels of pollution, with better water quality in their upper streams, but higher concentrations of ammonia and nitrogen contaminants in lower streams. In August when typhoon Morak hit Taiwan, mountain areas in central Taiwan experienced torrential rains, which had washed away the riverbeds, resulting in a change of water quality to some rivers, such as Wu River Basin, Sin-huwei River and Bei-gang River Basin, with higher concentrations of suspended solids in water, deteriorating their water quality. Because of geological characteristics in the Zhuoshui River Basin, its water quality appeared grey and murky. On the whole, among 50.6% of the 19 rivers surveyed this year were found to be of no (or slight) pollution, and 32.5% fell into the medium pollution level. The result was somewhat better than those of the past two years.
The ocean water quality in the central part of Taiwan was also monitored. According to the data collected, the water quality near the seashores of Hsiang-shan (in Hsin-chu County), Tai-chung Harbor, and Chang-hwa all met the Water Quality Criteria of category B, while that of Yun-lin seashore met the Criteria of category A. The results monitored this year were satisfactory to quality standard for the marine environment quality for categorized sea waters. Water quality this year was generally better than the past years. At most monitoring stations to the south of Taichung Harbor, the content of nutrition salt in the water was found at the lowest level in the second and third seasons. Other monitored results were about the same as those in past years.
For monitoring of water quality on beaches, Tung-hsiao Beach was chosen as a target. The area was monitored eleven times this year and results showed that the water quality of Tung-hsiao Beach was good. It may be rated as superior as a result of preliminary grading. When samples were taken in July and August, due to passing fronts and rainfalls, and the effect of merging of river waters, the result monitored at beaches showed somewhat deteriorated water quality.
The water quality monitoring of the eight reservoirs was conducted once per season. As shown by the results of this year’s monitoring, with comparison made to the water quality standard for Category A land area and ground level water bodies, the results showed that the water quality of Sun-Moon Lake reservoir met the criteria. The other reservoirs were found to have failing pH values, not satisfying Category A water standards for land area and ground level water bodies. Of all reservoirs in central Taiwan, the water quality of the Sun Moon Lake Reservoir was the best, rated as 100% oligotrophe; followed by the Wushe Reservoir having a rating of 75.0% oligotrophe and 25.0% mesotrophe. The water quality of the Ta-pu Reservoir was the worst, rated as 100% eutrophe year round. The water quality of the Li-yu-tan Reservoir and Te-chi Reservoir was rated as oligotrophe to mesotrophe. The water quality of the Yung-ho-shan Reservoir, Ming-ter Reservoir and Tou-ser Reservoir was rated as mesotrophe to eutrophe.
Finally, the monitoring of groundwater was conducted through 93 wells spread across the six counties. The data show that, among the monitoring items, ammonia nitrogen, iron, and manganese were found to be in excess of the Quality Control Criteria, and the same results were also observed in past years. It is worth to noting that ammonia nitrogen in the groundwater in Chang-hwa County and Yun-lin County, which could be attributable to the local geological characteristics, was substantially higher than that in the other counties. From graphical analysis of the monitoring items of groundwater obtained from each well using Stiff-plotting and Piper-plotting, the Stiff-plotting method shows that Ca2 and HCO3-+CO32- have the highest percentage, which is 61.0%, while the Piper-plotting method shows that the Area I has the highest percentage, which is 57.5%. A general trend similar to those in the past three years was observed, indicating that the groundwater quality in the area has no substantial changes.