SWM : Smart Water Management

Understanding effects of thermal pollution and acidification has long been a concern of aquatic ecologists, but it has been little explored in the stream ecosystems in Korea. This study was conducted to elucidate the effects of thermal wastewater effluent (TWE) and acid rain on water quality and periphytic algae in a small mountain stream, the Buso stream, a tributary located in the Hantan River basin. A total of five study sites were selected in the upstream area including the inflowing point of thermal wastewater effluent (HSW), one upstream site (BSU), and three sites below thermal effluent merged into the stream (1m, 10m and 300m for BSDS1, BSD2, and BSD3, respectively). Field surveys and laboratory analyses were carried out every month from December 2015 to September 2016. Water temperature ranged 1.7~28.8℃ with a mean of 15.0℃ among all sites. Due to the effect of thermal effluent, water temperature at HSW site was sustained at high level during the study period from 17.5℃ (Jan) to 28.8℃ (Sept) with a mean of 24.2±3.7℃, which was significantly higher than other sites. Thermal wastewater effluent also brought in high concentration of nutrients (N, P). The effect of TWE was particularly apparent during dry season and low temperature period (Dec ~ Mar). Temperature effect of TWE did not last toward downstream, while nutrient effect seemed to maintain in longer distance. HSW site was eutrophic throughout the study period with the predominance of filamentous periphytic algae, such as Oscillatoria tenuis and Stigeolonium lubricum, and showed significant difference both in water quality and periphyton species composition(p<0.01). pH ranged 5.1~8.4 with a mean of 6.9 among all sites during the study period. The pH decrease was attributed to seasonal acid rain and snow fall, and their effects was identified by acidophilic diatoms dominated mainly by Eunotia pectinalis and Tabellaria flocculosa during March and August. These findings indicated that water quality and periphyton assemblages in the upstream region of Buso Stream were affected by thermal pollution, eutrophication, and acidification, and their confounding effect was seasonally variable.