The aim of this project was to monitor the water quality of rivers, oceans, reservoirs and groundwater in the five 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 to provide information for the Environmental Protection Organization to devise a pollution control policy.
A total of 73 water-monitoring stations spread among the 19 rivers was established, and the water quality monitoring result was set to be once per month. The data obtained for this year showed that the water quality of the Si-hu, Da-an and Dajia River Basins had improved, with this year’s proportion of more than 90.9% having no (or slight) pollution. Meanwhile, the Lu-gang, Sin-huwei and Bei-gang River Basins had a higher percentage, ranging from medium to high levels of pollution. As for the rivers in the central regions, the up-stream water quality was generally superior, while the down-stream ammonia and nitrogen concentrations were higher. From June to October this year, higher rainfall had accumulated in the central region of Taiwan, where riverbeds were washed away, resulting in slightly higher concentrations of suspended solids in some rivers, such as the Wu River Basin, Jhuoshuei River Basin, Sin-huwei River Basin and Bei-gang River Basin, deteriorating their water quality. Because of geological characteristics in the Zhuoshui River Basin, water quality was grey and murky on regular days. On the whole, 49.3% of the 19 rivers surveyed this year were found to have no (or slight) pollution and 32.0% were found to have medium pollution levels. The water quality this year slightly deteriorated.
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 (Hsinchu County), Taichung Harbor and Chang-hwa Coastal area was rated as 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. During the second season of monitoring, abundant plankton growth was found, and Chlorophyll A values detected by some monitoring stations was the highest when compared to the past years. Water quality in the second and third seasons was better than that in the first and fourth seasons. On the whole, the trend of water quality was similar to past years.
Water quality of Chi-ting and Tung-hsiao Beach was monitored. The area was monitored nine times this year and results showed that the water quality of Chi-ting and Tung-hsiao Beach was better than past years. The ratios of those rated superior are 100% and 89% respectively. The water quality of beaches may be affected by rainfall and merging river flows, resulting in changes to their water quality.
The water quality of eight reservoirs was monitored once each season. The results show that the water quality of the Sun-Moon Lake Reservoir was the best among all dams monitored, which meets the water quality criteria of Class-A. In terms of the water quality of reservoirs in central Taiwan, the water quality of the Sun Moon Lake Reservoir, Te-Chi Reservoir and Wushe was rated higher at oligotrophe to mesotrophe all year round (75%-25%); followed by the Tou-She Reservoir having a rating of oligotrophe to mesotrophe (25%-75%). The water quality of Yong-he-shan Reservoir was rated at mesotrophe (100%) this year; the Ming-te Reservoir and Li-yu-tan Reservoir were rated at mesotrophe to eutrophe (75%-25%), while the Ta-pu Reservoir had the worst water quality rated at eutrophe (100%).
The monitoring of underground water quality was conducted through 97 wells spread across five 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. Of the volatile organic compounds in the underground water, only the trichloroethylene in one monitored well exceeded the Underground Water Class B Contaminant Control Standards. On the whole, only the measured ammonia nitrogen values in wells in Changhua County and Yunlin County were 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 59.1% for Ca2+ and HCO3- , while the Piper-plotting method showed that Area I had the highest percentage, which was 51.1%. The trend was found to be consistent with the results of analysis conducted in the past years.