The aim of this project was to properly understand the changing trend of water quality in those types of water bodies over the passage of time by monitoring the water quality of rivers, beach, oceans, reservoirs and groundwater in the five counties located in the central part of Taiwan. Water quality was assessed by sixty-nine water-monitoring stations along eighteen rivers and affiliated branches, which monitoring was conducted once every month. The results showed that in central Taiwan, most of monitoring stations (about 98%~100%) were categorized to non(slightly)-polluted level in the Shihu river Basin, besides, the highest ratio of monitoring stations (about 19%~27%) categorized to severely-polluted level was observed in the Beigang River Basins. The river channel in some waterways consisted of loose gravel so rain water runoff led to a higher level of suspended solids in the waters, which examples include the Da-an River, Wu River, Jhuoshuei River, Sin HuWei River and Beigang River basins. The better water quality from the rivers north of the Dajia River Basin (upstream) can be observed, which may resulted from good weather conditions, however, the down stream monitoring showed that accumulation of pollutants was observed, which may resulted from the discharge of industrial effluent and household sewage. The sea water quality monitoring consisted of twenty-three monitoring stations located in Class-A and Class-B marine environments, which monitoring was conducted once every season. There was a significant variation of water quality can be observed in the monitoring stations which placed near terrestrial discharge sources, however, overall water quality was similar to the previous reported results in recent years. The beach water quality consisted of two monitoring stations, which were monitored once per month from June to September. The findings from Qiding beach and West-Ocean Educational Sea World beach were classified, the results showed that not only the water quality was normally excellent but also the highest ratio was classified as “Good” category. The water quality of eight reservoirs was monitored once every season. The results indicated that there was the highest proportion of oligotrophic ratings for the water quality of the Jih-Yueh-Tan Reservoir, on the contrary, there was the highest proportion of eutrophic ratings for that of the Ta-Pu Reservoir. In addition, a significant decrease of the Carlson trophic state index was observed in the Ta-Pu Reservoir; however, a significant increase of that was observed in the Ming-Te Reservoir and Tou-She Reservoir, while the water quality changes of each season at the other reservoirs were within historical norms. The groundwater quality monitoring was conducted through one hundred and twelve wells spread across five counties in past years. For general monitoring items except volatile organic compounds (VOCs), the forty-five monitoring wells among the total ones were conducted once every season, other thirty-six monitoring wells were conducted once every six months, the other thirty-one monitoring wells were conducted once a year, respectively; however, as for VOCs, which was monitored once a year for total one hundred and twelve wells. The results showed that the main findings including ammonia nitrogen, iron, and manganese, exceeding groundwater Class-B monitoring criteria were similar as previous reported results in recent years. Ammonia nitrogen readings from monitoring wells in Changhua County and Yunlin County were higher than that from other regions. Moreover, the groundwater monitoring of VOCs showed that a slight concentration of methyl-tert-butyl ether and chloroform was measured within only two wells, which did not exceed the second category groundwater pollution control standard. Eventually, the water quality of each monitoring wells was evaluated by means of both Stiff diagram (Stiff pattern) and Piper diagram, which exhibited a consistent trend for the changes of each season.

Water Quality Monitoring, Water Quality Standards, Method Detection Limit