• Journal of Korean Society of Environmental Engineers
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• v.36 no.12
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• pp.821-827
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• 2014

The 4major river project has caused changes in flow and water quality patterns in major rivers in Korea including the Nakdong River where several toxicant release accidents have had occurred. Three dimensional hydrodynamic model, the Environmental Fluid Dynamics Code (EFDC), was applied to evaluate the effect of geomorphological change of the river on the advection and dispersion patterns of a conservative toxic pollutant. A hypothetical scenario was developed using historical data by assuming a toxic release from an upstream location. If there is a toxic release at the Gumi Industrial Complex, the toxic material would be detected after 2.22 and 9.83 days at Chilgok and Gangjung weir, respectively, in the new river system. It was estimated that they took at least 12 times longer than those with the river conditions before the project. Effect of relocation of intake towers for Daegu Metro City to upstream of Gumi City was also evaluated using the developed modeling system. It was observed that hydraulic residence time would be increased due to decreased flow rate and thus due to lowered water level. However, peak concentration differences were found to be about 2% lower in both places due to increased dispersion effect after the relocation.