| 英文摘要 |
The aim of this project was to monitor the water quality of rivers, ocean, reservoir dams and groundwater in six counties located in central Taiwan. The monitoring data obtained in this work can be used to assess the current condition, to predict the changing trend of the water system quality and to provide information for the environmental protection research to develop pollution control policies.
A total of 75 water-monitoring stations were established, spreading along 19 rivers in these six counties, and the monitoring frequency was set as once per month. From the data obtained, the result shows that the water quality of the Si-hu River was the best among the rivers monitored, while the Lu-gang and Bei-gang Rivers were found to contain a relatively high degree of pollution. As to the suspension solids concerned, the density measured from July to September in the Sin Huwei, Bei-gang, Da-jia and Wu Rivers was remarkably higher than that in other months. This is possibly due to a large quantity of rainfall in the mountain areas of these six counties and the landfall of several typhoons during summer season. In summary, 47.3% of the 19 rivers surveyed this year found no pollution, and the rest of other 35.3%, contained medium levels of pollution. The result was slightly better than those during the past two years.
The ocean water quality in 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 met the Water Quality Criteria of Category B, while that of Yun-lin met the Criteria of Category A, and the result shows that the water quality all met the criteria this year (2008). Due to increased rainfall brought by the landfall of a typhoon in August of the third quarter this year, a certain degree of difference was monitored in terms of water temperature, salinity and some heavy metals; however, the monitored water quality value of the fourth quarter returned to the historical monitoring scope.
In this task, three ocean water monitoring stations were established. The water quality of Tung-hsiao Beach Resort was found superior than others based on the results from 7 rounds of sample taking. However, the data obtained in June and July was obviously worse than others, and this fact could be attributed to heavy rainfall and the conflux of rivers.
The water quality monitoring of the said 8 reservoir dams was conducted once per quarter. The results show that the water quality of the Sun-Moon Lake Reservoir Dam, which met the Water Quality Criteria of Category A, was the best among all reservoirs monitored. It belonged to oligotrophe, taking about 42.9% of the year. In addition, the water quality of Ta-pu reservoir, which was the worst among all reservoirs monitored, belonged to eutrophe, taking about 85.7% of the year. In this respect, the Li-Yu-Tan Dam and Der-Ji Dam showed bigger fluctuation of water quality, which ranged from oligotrophe to eutrophe levels. As for other reservoir dams, the Minder Reservoir Dam and Tousher Reservoir Dam belong to mesotrophe to eutrophe levels; whereas, Yunghoshan Reservoir Dam and Wusher Reservoir Dam belong to oligotrophe to mesotrophe levels.
Finally, groundwater monitoring was conducted for 93 wells spread throughout these six counties. The data shows that, among the monitoring items, ammonia nitrogen, iron, and manganese were found to be off from the Quality Control Criteria of Category B, and the same results were also observed during these past years. It is worthy to note that the ammonia nitrogen content of the groundwater in Chang-hwa County and Yun-lin County, which could be attributable to local geological characteristics, was substantially higher than that in other counties. From graphical analysis result of the groundwater monitoring items obtained from each well using Stiff-plotting and Piper-plotting method, the Stiff-plotting method shows that Ca2＋and HCO3－+CO32－ have the highest percentage, which is 62.0%, while the Piper-plotting method shows that the Area I has the highest percentage, which is 53.6%. A general trend similar to those during the past three years was observed, indicating that the groundwater quality in the area has seen no substantial changes.
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