Two-dimensional Numerical Modeling of Water Quality Variation by Gates Operation in the Seonakdong River

This study has used RMA2 model and RMA4 model, which are depth-averaged two-dimensional flow andwater-quality prediction models, to analyze the variation of the water-quality by the gates operation in theSeonakdong River. Sensitivity analysis is performed to get the Manning coefficient and the coefficient ofeddy viscosity for RMA2 model, and to get the diffusion coefficient for RMA4 model. Since the numericalsimulation using RMA2 and RMA4 models did not consider tributary pollutant load except for that of JomanRiver, it could make a little difference from the natural phenomenon. Nevertheless, the numericalsimulation shows that the discharge of 30m3/s, which is the continuous inflow from the Daedong-gate, canmake it possible to achieve the target water-quality (BOD 4.3mg/L) of Nakbon-N watershed about 10 dayslater if the Daejeo-gate could remain opened in connection with the Noksan-gate operation.