Water quality simulation on an artificial estuarine lake Shiwhaho, Korea

The water quality of the recently constructed Shiwhaho, whose original purpose was to reserve freshwater, has deteriorated due to increased incoming waste loadings and the semi-enclosed nature of hydrodynamics. To improve the water quality, sluice gates were operated to allow free exchange of water with the sea. The Shiwhaho, connected to the Yellow Sea through narrow gates, is affected mainly by wind forcing, flushing by gate operation and river flows, which are analyzed using seasonal field observations. As a predicting tool, a three-dimensional finite volume model CE-QUAL-ICM is incorporated into a finite element hydrodynamic model, TIDE3D. In coupling these two different modules, a new error minimization technique is applied by considering conservation of mass. Model tests for 1 year after calibration and validation show that eutrophication and other biological changes reach quasi-steady state after 60 days, thus, it would be necessary to consider moderate ramp up option to remove initial uncertainties. Sediment–water interaction might be neglected in the long-term simulation, since its effect is not a big concern. Simulated results show eutrophic processes in an estuarine lake and suggest some active circulation to improve water quality.