In South Korea, various discussions are continuing over the algae problem caused by the dam, which was established during the four-river restoration project in 2012.Japan, on the other hand, has long established a dam, but no problems like Korea have emerged.In order to examine these differences, we conducted research on the dam around the Nakdong River and the Tama River and the Onga River, the rivers of Korea.In the upstream of each weir, water temperature and pH were observed higher than in the downstream, and the concentration of nitrogen decreased in the upstream of the weir.
