The influence of dam construction on water quality in the lower Geum River, Korea

Abstract

AbstractThe Geum River has been faced with extreme environmental change due to the construction of three dams in midstream since 2012 (Four Major River Restoration Project). We hypothesized that suspended solids (SS) and total particulate phosphorus (TPP) decreased after the dam construction. To test our hypothesis, we investigated the influence of the dam construction on water quality by measuring possible impacts of decreasing SS, total phosphorus (TP), and TPP on the ecosystem in the lower Geum River and the Geum River estuary. For this study, we chose one site to compare the monthly water quality data pre‐construction (2008) and post‐construction (2015). Dissolved oxygen and pH were not significantly different between pre‐ and post‐construction, while electric conductivity (EC) increased. The increase in the EC may be related to a decrease in river discharge (RD) after the dam construction. As we expected, TP and TPP decreased post‐construction, but SS did not show significant differences between pre‐ and post‐construction. This suggests that the decline of TPP concentrations post‐construction were not related to SS levels. The explosive algal bloom and sedimentation of the algae may be an important factor in explaining the decrease in TP and TPP. The decline of SS, TP, and TPP flux to the lower Geum River was observed. This could be a potential reason for the erosion of the mud flat of the Geum River estuary in the future. Therefore, to determine the long‐term effects of the SS and the phosphorus fluxes to the lower Geum River, these factors should be monitored periodically over longer periods of time than this study.