• Journal of Environmental Science International
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• v.16 no.5
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• pp.571-581
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• 2007

The mechanism of water pollution in Lake Shihwa, one of highly eutrophicated artificial lakes in Korea, has been studied using a numerical 3D physical-biochemical coupled model. In this study, the model was applied to estimate the contribution of land-based pollutant load to water quality of heavily polluted Lake Shihwa. The chemical oxygen demand(COD) was adopted as an index of the lake water quality, and the spatial distribution of an average COD concentration during the summer from 1999 to 2000 was simulated by the model. The simulated COD showed a good agreement with the observed data. According to reproducibility of COD, the high-est levels between 8 and 9 mg/L were shown at the inner site of the lake with inflow of many rivers and ditches, while the lowest was found to be about 5 mg/L at the southwestern site near to dike gate. In the pre-diction of water quality of Lake Shihwa, COD showed still higher levels than 3 mg/L in case of reduction of 95% for land-based pollutant load. This suggests that the curtailment of land-based pollutant load is not only sufficient but the improvement of sediment quality or the increase of seawater exchange should be considered together to improve a water quality in Lake Shihwa.

• Journal of Environmental Impact Assessment
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• v.18 no.6
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• pp.331-346
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• 2009

The serious problem facing two-dimensional finite element hydraulic model is the treatment of wet and dry areas. This situation is encountered in most practical river and coastal engineering problems, such as flood propagation, dam break analysis and so on. Especially, dry areas result in mathematical complications and require special treatment. The objective of this study is to investigate the wet and dry parameters that have direct relevance to model performance in situations where inundation of initially dry areas occurs. Several numerical simulations were carried out, which examined the performance of the marsh porosity method of RMA-2 model to investigate for application of parameters. Experimental channel with partly dry side slopes, straight channel with irregular geometry and Han river were performed for tests. As a result of this study, effectively applied marsh porosity method provide a reliable results for flow distribution of wet and dry area, it could be further developed to basis for extending to water quality and sediment transport analysis.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.233-238
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• 2003

Due to the impermeability of outer wall facilities such as Breakwaters which dissipates the wave energy and keeps harbor tranquility, the enclosed area of harbor becomes partially blocked and the water exchange can be reduced. Recent trends of port development protect water quality and emphasize Water-Front, so the method which enhances the circulation of harbor waters and the dilution of the water pollutants are studied. The best improvement of water quality is a remove of pollutant source on land, but an enclosed port must be enhanced the tidal exchange. For this end, the best improvement may be made a drain-route on the existing outer wall facilities. In this study, the numerical computations were carried out to predict the circulation of harbor waters and the tidal exchange through the drain-rout in the polluted harbor(Samchonpo-guhang) located at the east coast of South Sea. Computational models adopting FDM(Finite Difference Method) were used here and were already verified from the previous studies und ocean survey. As a result of this study, circulation and the tidal exchange at the harbor before and after introduction of drain-route were assessed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6447-6454
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• 2013

Seawater intake systems have significant problems due to seawater pollution, suspended solids, unstable intake and maintenance etc. An underground type seawater intake system was newly developed to overcome the existing weaknesses and was facilitated in Gyukpo port. In this study, to check the performance of the new system, the samples for water quality and the 3-D numerical modeling test were conducted. The five times test included the COD, total nitrogen, total phosphorus, pH, and suspended solid for the intake system. The analyses show that the COD, total nitrogen, total phosphorus, PH showedminor changes before and after. On the other hand, the change in suspended solids was significant and water was purified below 5 mg/l, first level fisheries water, after. The numerical model adopted the RNG $k-{\epsilon}$ algorithm and the CFX model based on the finite volume method. The porosity algorithm was used to reproduce filtered-sand, outer diameter, and thickness. The numerical results showed that the double pipe is advantageous in that it provides a uniform pressure between the inner and outer pipe for the flow to be stable. In addition, the use of multiple intake pipes did not interfere with the discharge reduction of 0.98 at the both intake pipes compared with the central intake pipe.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.3
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• pp.831-840
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• 2016

Hydrodynamic condition can be used to predict particle movement within water column and the results used to optimize environmental conditions for effective site selection, setting of environmental quality standard, waste dispersion, and pathogen transfer. To predict the extent of movement of particle from land, 3D hydrodynamic model that includes particle tracking module was applied to Geoje Bay and to calibrate particle tracking model, floating buoy measurement is operated. The model results show that short time is required for particles released into system from river to be transported to the shellfish farming area. It takes about 2 days for the particles to shellfish farming area under mean flow condition. It meant Geoje Bay, especially shellfish farming area is vulnerable to anthropogenic waste from river.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.105-111
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• 2008

To improve the stability of levee structure, it is required to use good quality fill materials, intensive management, appropriate hydraulic structure and construction of cut-off wall. In particular, the most important factor of levee construction technology is to use bed sediment for its safety. In this study, seepage model test and numerical analysis were performed based on a standard section of levee recommended in the river design standard of korea (2005). The results of test and analysis show that most of the bed soil is a sand (SP in USCS), which does not satisfy the permeability criteria for levee materials ($< k=10^{-3}cm/sec$), thus for the safety of levee it is required to adopt a stabilizing method such as good quality soil mixing, water content control.

• Fisheries and Aquatic Sciences
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• v.7 no.4
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• pp.204-214
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• 2004

The effect of wind. stresses on the flow and water quality has been examined, particularly focused on the environment of oyster farms in Gamak Bay, by a two dimensional numerical model. In autumn (wind: $45.0^{\circ}$, 4.3 m/s), the overall flow turned out to be stronger than any other seasons and in addition, a pair of anticlockwise and clockwise vortices has been created at the northwest of the bay. Consequently, the wind in autumn seemed efficient not only for growing oyster but also for reducing the water pollution as the flow becomes much more active. In summer an anoxic condition appeared around the northwest of the bay where the flow is stagnant. According to a field survey, the majority of oyster farms tended to be densely distributed around the areas where DO concentration is high. Furthermore, oyster farms with a high production (over 1,300 kg per hanging string of 100 m) were distributed along with approximately 4 of Ch-a concentration. This suggests that oyster production is closely related to the concentration of DO or Ch-a.

• Journal of Environmental Science International
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• v.26 no.2
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• pp.211-220
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• 2017

For areas with the diverse contamination sources, the change of 4-nitrophenol contamination and impact of potential contamination sources have been evaluated using monitoring data and a numerical model (HydroGeoSphere). The model considered several parameters including land cover, precipitation, and flow rate. And, the model has been performed to investigate the effect of decay rate of 4-nitrophenol. The results of the simulations showed that the influence on 4-nitrophenol in downstream was mainly greater than that in upstream, and the tributaries did not significantly affect the mainstream because of their low flow rates. In addition, the effect of contamination sources was simulated for each section, then the measured data were higher than the corresponding simulated data in most sections of the Geumho river. In particular, the impact of the potential contamination sources in the upstream area was much higher than that in the other area, thus more monitoring data for the upstream area is required.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.353-357
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• 2015

A new method is proposed for water resources using aquifers in coastal areas. These aquifers are generally filled with saline water due to seawater intrusion and consequently being left unutilized. Surface water can be injected into these aquifers and recovered for water quality enhancement and stored water. Injection and pumping wells are used. For this technique to be successful protection of pumping well from seawater intrusion is an essential issue. Salt water pumping can be used to prevent saline water upconing. Numerical analysis demonstrated that a properly designed and executed salt water pumping well can protect a freshwater pumping well from salt water intrusion.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.279-293
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• 1995

The most obvious and easily recognizable sources of potential water pollution are point sources such as domestic and industrial wastes. But recently, the potential effects of nonpoint sources on water quality have been increased apparently. In order to evaluate the characteristics and the effects of nonpoint sources on water quality, this study was performed in Suyeong Bay from May, 1992 to July, 1992. The depth-averaged 2-dimensional numerical model, which consists of the hydrodynamic model and the diffusion model was applied to simulate the water quality in Suyeong Bay. When flowrate was $65.736m^3/s,$ the concentration of pollutants (COD, TSS and VSS) at Oncheon stream (Sebeong bridge) during second flush were very high as much as 121.4mg/l of COD, 1148.0mg/l of TSS and 262.0mg/1 of VSS. When flowrate was 4.686m^3/s, the concentration of pollutants $(TIN,\;NH_4\;^+-\;N,\;NO_2\;^--N\;and\;PO_4\;^{3-}-P)$ during the first flush were very high as much as 20.306mg/1 of TIN, 14.154mg/1 of $NH_4\;^+-N$, 9.571mg/l of $NO_2\;^--N$ and l.785mg/l of $PO_2\;^{3-}-P$ As results of the hydrodynamic model simulation, the computed maximum velocity of tidal currents in Suyeong Bay was 0.3m/s and their direction was clockwise flow for ebb tide and counter clockwise flow for Hood tide. Four different methods were applied for the diffusion simulation in Suyeong Bay. There were the effects for the water quality due to point loads, annual nonpoint loads and nonpoint loads during the wet weather and the investigation period, respectively. The efforts of annual nonpoint loads and nonpoint loads during the wet weather seem to be slightly deteriorated in comparison with the effects of point loads. However, the bay was significantly polluted by the nonpoint loads during the investigation period. In this case, COD and SS concentrations ranged 2.0-30.0mg/l, 7.0- 200.0mg/l in ebb tide, respectively. From these results, it can be emphasized that the large amount of pollutants caused by nonpoint sources during the wet weather were discharged into the bay, and affected significantly to both the water quality and the marine ecosystem. Therefore, it is necessary to consider the loadings of nonpoint pollutants to plan wastewater treatment plant.