Ji-Sung Lim, Jae-Ho Lee, Young-Woo Kim, Sang-Hoon Lee, Hyang-Gi Kim, Tae-Joo Park and Im-Gyu Byun
Institute for Environmental Technology and Industry, Pusan National University, 63beon-gil, Geumjeong-gu, Busan, Republic of Korea
Mulgeum intake station located in downstream the Nakdong River supplies raw drinking water of Busan metropolitan city in South Korea. As eight weirs were constructed by ‘Four Major River Restoration Project’ in Nakdong River during 2009~2012, water environment of Nakdong River had changed significantly. Therefore, the changes of algae occurrence and water qualities were monitored and analyzed to evaluate the effects of weir construction on water environment using the each three years’ data before and after of weir construction. As a result, water qualities in downstream the Nakdong River were improved after weir construction. Chl-a, BOD, T-P and PO4-P concentration were significantly decreased after weir construction. Especially the average Chl-a concentration was decreased from 119 mg/m3 to 47 mg/m3 in winter. This phenomenon of Chl-a decrease is well corresponded with the decline of T-P and PO4-P. And it is considered that the improvement of water qualities in downstream Nakdong River is affected with the cut off effect of nutrients by the weirs in midstream and upstream. So algae occurrence in upstream and midstream the Nakdong River should be studied later.
Keywords: Algae, Nakdong River, Water quality, Weir, chl-a.