| 英文摘要 |
The aim of this project was to monitor the water quality of rivers, oceans, reservoirs and groundwater in the six counties located in the central part of Taiwan, to properly understand the changing trend of water quality in those types of water bodies over the passage of time, and evaluate and analyze the pollution to all water bodies that was conducted 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 Si-hu , Da-an, and Dajia River Basins was good, with an annual proportion of more than 80.2% to be of no (or slight) pollution. Meanwhile, Lu-gang, Sin-huwei and Bei-gang River Basins had a higher percentage, ranging from medium to high levels of pollution, with better water quality in their upper streams of the rivers in the central region, but higher concentrations of ammonia and nitrogen contaminants in lower streams. From April to September this year, higher rainfall had accumulated in the central region of Taiwan, where riverbeds were washed away, resulting in slightly high concentrations of suspended solids in some rivers, such as Wu River Basin, Sin-huwei River Basin and Bei-gang River Basin, deteriorating their water quality. Because of geological characteristics in the Zhuoshui River Basin, its water quality was grey and murky on regular days. On the whole, 47.4% of the 19 rivers surveyed this year were found to be of no (or slight) pollution, and 34.3% were found to be of medium pollution level. There was not much difference of water quality between that period and the past two years.
The monitored result of water quality in oceans was compared with the standard of environmental quality of seas and oceans. The water quality of offshore Hsiang-shan (of Hsinchu County), Taichung Harbor and Chang-hwa Coastal area was rated Class-B ocean environment water body, and offshore Yun-lin was rated Class-A ocean environment water body. The results monitored this year were satisfactory to quality standard for the marine environment quality for categorized sea waters. On the whole, water quality in the second and third seasons was better than that in the first and fourth seasons, and the trend of water quality was similar to the past years.
Water quality of Tung-hsiao Bathing Beach was monitored. The area was monitored ten times this year and results showed that the water quality of Tung-hsiao Bathing Beach was good. It may be rated as superior as a result of preliminary grading. Water quality of beaches may be affected by rainfall and merging river flows, resulting in changes to their water quality.
Water quality of eight reservoirs was monitored once each season. At certain survey points of all reservoirs, water quality was found unsatisfactory to the standards for Class-A land surface water body. Among reservoirs in central Taiwan, the water quality of Sun Moon Lake Reservoir was the best, rated at 100% oligotrophe all year round; followed by Te-Chi Reservoir and Li-Yu-Tan Reservoir having a rating of 50.0% oligotrophe and 50.0% mesotrophe. The water quality of Ta-pu Reservoir and Ming-de Reservoir was the worst, rated at 100% eutrophe all year round. Others, such as Wu-she Reservoir was rated in a range from oligotrophe to mesotrophe. Yong-he-shan Reservoir and Toushe Reservoir were rated at mesotrophe.
The monitoring of underground water quality was conducted through 95 wells spreading across six counties. The data obtained this year showed that, items exceeding underground water Class-B monitoring criteria were about the same as results found in previous years, mainly ammonia nitrogen, iron, and manganese. It is worth noting that ammonia nitrogen in wells in Chang-hwa County and Yun-lin County was higher than in other counties, which may be due to local geological characteristics. According to the assessment of water quality of all monitored wells, using Stiff-plotting analysis, the highest percentage was 65.0% for Ca2+ and HCO3-+CO32- , while the Piper-plotting method showed that Area I has the highest percentage, which was 58.9%. The trend was found to be consistent with the results of analysis conducted in the past years.
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