• 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.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.249-260
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• 2005

Dynamics of phytoplankton community were monthly examined at two sites in Lake Juam from January to December 2003. One site is located near the Dam, an intake tower, where obtain a drinking water resource, the other site is located in the shallow region, Mundeok-bridge, the upstream or effluent part of lake. During the study, there made little the differences in physicochemical factors between two sites, but numbers of species and standing crops of phytoplankton differ remarkably. Totally, 41% of green algae and 35.8% of diatoms were comprised of total phytoplankton species, while 46.3% of dinoflagellates and 27.6% of cyanobacteria contributed in total standing crops of Phytoplankton community. Cyanobacterium Microcystis aeruginora and diatom Fragilaria crotonensis dominated the Dam site during a warm season, while dinoflagellates Peridinium bipes and Asterionella formosa were at the shallow region during a cold season, respectively. According to the CCA analysis, dissolved oxygen, chemical oxygen demand and total phosphate strongly affected the growth of P. bipes with low water temperature. In addition, the increment of total nitrogen and water temperature affected biomass of a cyanobacterium M. aeruginosa. Collectively, it may suggest that the majority of annual primary production of Lake Juam is covered by two dominant species Peridinium bipes in cold season and Microcystis aeruginosa in warm season.