台湾屏东县东港溪拦溪堰对其周边地下水水质及水产养殖的影响

The impacts of Tongkong River Weir in Taiwan Pingdong on the groundwater contamination and aquaculture

为了解设于屏东县新园乡界河以东港溪上的拦河堰对当地地下水的影响进行一系列研究。首先对台湾西南沿海的屏东县新园乡1989年10月东港溪拦溪建堰前后地下水水质及等水位线数据进行了分析,同时逐月收集东港溪拦溪堰周边的佳冬乡养殖池所用的井水、池水、浮游生物、日本鳗鲡(Anguilla japonica)及虾等数据,进行分析与比较。此外,用以上2个乡的地下水进行了鳗鲡幼苗水族箱养殖试验,并检验分析试验后的鳗鱼。各项分析结果表明,拦溪堰的兴建使新园乡的地下水水位降低,附近污染河川的水渗入了地下,对养殖生物的健康产生不同程度的影响。因此建议,在旱季应减少对东港溪拦溪堰水的抽取量;台湾西部尤其是新园乡的水产养殖活动应予以减少。

Seawater intrusion problems occur along almost the entire western coast of Taiwan, and often cause ground water contamination and affect the health of cultured organisms. In the coastal town of Hsinyuan, Pingtung County, southwestern Taiwan, these problems progressed much faster. A river weir built to extract subsurface water from the Tongkong River was suspected of causing these problems, so a study evaluated the effect of the weir on groundwater quality. Hsinyuan and the nearby town of Chiatung were used for comparison. Groundwater quality and water table contour line data before and after construction of the weir were analyzed. Samples of well water, pond water, plankton, and cultured fish （Japanese eel Anguilla japonica ） and shrimp from ponds in these five regions were collected and analyzed on a monthly basis. An aquarium test using groundwater from each region to raise Japanese eel fingerlings was also conducted. These results were combined to evaluate the influence of the groundwater quality of each region on the health of cultured fish. The results revealed that construction of the weir lowered the groundwater table, and caused contaminated river water and seawater to intrude into groundwater of the Hsinyuan area, adversely impacting the health of cultured fish. These results suggest that the groundwater drawdown rate of the Tongkong River should be reduced in the dry season. Additionally, aquaculture activities along the western coast must be reduced, especially in the Hsinyuan area. Some other solutions are also proposed. This study further shows that Japanese eel is a reliable environmental biomonitor.