• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.1-15
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• 2017

Daecheong Reservoir was made by the construction of a large dam (>15 m in height) on the middle to downstream of the Geum River and the discharge systems have the watergate-spillway (WS), a hydropower penstock (HPP), and two intake towers. The purpose of this study was to investigate the limnological anomalies of turbid water reduction, green algae phenomenon, and oligotrophic state in the lower part of reservoir dam site, and compared with hydro-meteorological factors. Field surveys were conducted in two stations of near dam and the outlet of HPP with one week intervals from January to December 2000. Rainfall was closely related to the fluctuations of inflow, outflow and water level. The rainfall pattern was depended on the storm of monsoon and typhoon, and the increase of discharge and turbidity responded more strongly to the intensity than the frequency. Water temperature and DO fluctuations within the reservoir water layer were influenced by meteorological and hydrological events, and these were mainly caused by water level fluctuation based on temperature stratification, density current and discharge types. The discharges of WS and HPP induced to the flow of water bodies and the outflows of turbid water and nutrients such as nitrogen and phosphorus, respectively. Especially, when hypoxic or low-oxygen condition was present in the bottom water, the discharge through HPP has contributed significantly to the outflow of phosphorus released from the sediment into the downstream of dam. In addition, HPP effluent which be continuously operated throughout the year, was the main factor that could change to a low trophic level in the downreservoir (lacustrine zone). And water-bloom (green-tide) occurring in the lower part of reservoir was the result that the water body of upreservoir being transported and diffused toward the downreseroir, when discharging through the WS. Finally, the hydropower effluent was included the importance and dynamics that could have a temporal and spatial impacts on the physical, chemical and biological factors of the reservoir ecosystem.

• Particle and aerosol research
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• v.13 no.3
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• pp.127-132
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• 2017

In this paper, the effect of the irradiation of the median-frequency of ultrasonic wave on the aqueous solution have been investigated. In addition, the decomposition ability of radical species was observed using phytoncide oil of 0.1 wt %. By observing the degree of decomposition while maintaining magnetic stirring, the unirradiated aqueous solution maintained turbid condition and the particle size of the oil was the same as the initial size. On the other hand, the irradiated aqueous solution presented that the transparency degree became good after 3 days and became to the same as the original purified water after one week. The particle size of the after 3 days was about 0.1 to $0.5{\mu}m$. From these results it could be demonstrated that when a medium frequency (about 400 kHz) is applied to the aqueous solution, decomposition ability of radical species are formed and the medium frequency irradiation system can be possible to purify the turbid aqueous solution.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.4 s.31
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• pp.75-81
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• 2004

Because geological types and land cover conditions of Imha basin have a very weak characteristics to soil erosion, most soil particles (low into river and bring about high density turbidity in Imha reservoir when it rains a lot. This study used GIS-based RUSLE model and analyzed soil erosion to make basic data for the countermeasures of turbidity reduction in Imha reservoir. Total soil erosion amounts was evaluated as 5,782,829 ton/yr using rainfall data(2003) and especially Dongbu-basin was extracted as most source area or soil erosion among Imha sub-basin. Also it was evaluated that soil erosion amount by RUSLE model was suitable by applying turbidity survey data.

• Korean Journal of Materials Research
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• v.28 no.12
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• pp.685-690
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• 2018

In this study, a multifunctional ophthalmic lens material with an electromagnetic shielding effect, high oxygen permeability, and high water content is tested, and its applicability is evaluated. Metal oxide nanoparticles are applied to the ophthalmic lens material for vision correction to shield harmful electromagnetic waves; the pyridine group is used to improve the antibacterial effect; and silicone substituted with urethane and acrylate is employed to increase the oxygen permeability and water content. In addition, multifunctional tinted ophthalmic lens materials are studied using lens materials with an excellent antibacterial effect (2,6-difluoropyridine, 2-fluoro-4-pyridinecarboxylic acid) and functional (UV protection, high wettability) lens materials (2,4-dihydroxy benzophenone, 2-hydroxy-4-(methacryloyloxy)benzophenone). To solve problems such as air bubbles generated during the polymerization process for the manufacturing and turbidity of the lens surface, polymerization conditions in which the defect rate is minimized are determined. The results show that the polymerization temperature and time are most appropriate when they are $110^{\circ}C$ and 40 minutes, respectively. The optimum injection amount of the polymerization solution is 350 ms. The turbid phenomenon that appears in lens processing is improved by 10 to 95 % according to the test time and conditions.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.359-366
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• 2007

Slow sand filtrations have been widely used for water treatment in small communities, however their capacity is often limited by high turbidity in the raw water. For this reason, several pre-treatment facilities were required for a slow sand filter. Turbidity removal from the highly turbid raw water was investigated in roughing filters as a pre-treatment process. The roughing filters followed by rapid mixing tank were operated in the form of a contact filtration. In several jar tests, the predetermined optimum aluminium sulfate (alum) doses for turbid water of 30 and 120NTU were 30 and 50mg/L, respectively. At the optimum alum dose, physically optimum parameters including G value of $220sec^{-1}$ and rapid mixing time of 3 minutes were applied to the contact filtration system. Without addition of alum, the filtrate turbidity from the roughing filters, packed respectively with different media such as sand, porous diatomite ball and gravel, was in the range of 5~30NTU at filtration velocities of 30 and 50m/day. However, the application of a contact filtration to roughing filters showed stably lower filtrate turbidity below 1.0NTU at filtration velocity of 30 m/day. Although the filtration velocity increased to 50m/day, filtrate turbidity was still below 1.0NTU in both single and double layer roughing filters. At influent turbidity of 120NTU, the filtrate turbidity was over 5 NTU in the triple layer roughing filter, which shortened the filter run time. The flocs larger than $10{\mu}m$, formed in the rapid mixing tank, were almost captured through the roughing filter bed, while the almost flocs smaller than $10{\mu}m$ remained in filtrate.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.247-263
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• 2008

A two-dimensional (2D) reservoir hydrodynamics and water quality model, CE-QUAL-W2, is employed to simulate the hydrothermal behavior and density current regime in Andong Reservoir. Observed data used for model forcing and calibration includes: surface water level, water temperature, dissolved oxygen and suspended solids concentration. The model was calibrated to the year of 2003 and verified with continuous run from 2000 till 2004. Without major adjustments, the model accurately simulated surface water levels including the events of large storm. Deep-water reservoirs, like Andong Reservoir, located in the Asian Monsoon region begin to stratify in summer and overturn in fall. This mixing pattern as well as the descending thermocline, onset and duration of stratification and timing of turnover phenomenon were well reproduced by the Andong Model. The temperature field and distinct thermocline are simulated to within $2^{\circ}C$ of observed data. The model performed well in simulating not only the dissolved oxygen profiles but also the metalimnetic dissolved minima phenomenon, a common1y occurring phenomenon in deep reservoirs of temperate regions. The Root Mean Square Error (RMSE) values of model calibration for surface water elevation, temperature and dissolved oxygen were 0.0095 m, $1.82^{\circ}C$, and $1.13\;mg\;L^{-1}$, respectively. The turbid storm runoff, during the summer monsoon, formed an intermediate layer of about 15 m thickness, moved along the metalimnion until being finally discharged from the dam. This mode of transport of density current, a common characteristic of various other large reservoirs in the Asian summer monsoon region, was well tracked by the model.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.43-50
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• 2020

The Doam Lake watershed is one of the non-point source management areas announced by the Ministry of Environment, and is a constant problem for the stream ecosystem dut to Storm water. In this study, a total of 48(rainfall) and 47(non-rainfall) sites were investigated for the entire watershed (Samyangcheon, Chahangcheon, Hoenggyecheon, Yongpyeongcheon, Songcheon, Lake Doam) on August 15, 2019 and on October 18, 2019 to estimate the source of turbid water in the Doam Lake watershed. Subsequently, water quality analysis was performed on Suspended Soild (SS), Turbidity, Total Phosphorus (TP), Total Nitrogen (TN), and Biochemical Oxygen Demands (BOD) and correlation among water quality parameters was analyzed based on the analyzed samples. As a result, most of the turbid water generated during rainfall was in highland fields. During rainfall, Hoengyecheon had the highest average SS concentration among all streams, and during non-rainfall, the average SS concentration was highest in Yongpyeongcheon, so the two stream were selected as vulnerable areas. However, since Yongpyeongcheon may be a temporary phenomenon due to river construction, additional continuous monitoring is required. Therefore, in the Doam Lake watershed, intensive management is required for vulnerable areas.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1187-1198
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• 2008

Many reservoirs in Korea and their downstream environments are under increased pressure for water utilization and ecosystem management from longer discharge of turbid flood runoff compared to a natural river system. Turbidity($C_T$) is an indirect measurement of water 'cloudiness' and has been widely used as an important indicator of water quality and environmental "health". However, $C_T$ modeling studies have been rare due to lack of experimental data that are necessary for model validation. The objective of this study is to validate a coupled three-dimensional(3D) hydrodynamic and particle dynamics model (ELCOM-CAEDYM) for the simulation of turbid density flows in stratified Daecheong Reservoir using extensive field data. Three different groups of suspended solids (SS) classified by the particle size were used as model state variables, and their site-specific SS-$C_T$ relationships were used for the conversion between field measurements ($C_T$) and state variables (SS). The simulation results were validated by comparing vertical profiles of temperature and turbidity measured at monitoring stations of Haenam(R3) and Dam(R4) in 2004. The model showed good performance in reproducing the reservoir thermal structure and propagation of stream density flow, and the magnitude and distribution of turbidity in the reservoir were consistent with the field data. The 3D model and turbidity modeling framework suggested in this study can be used as a supportive tool for the best management of turbidity flow in other reservoirs that have similar turbidity problems.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.671-674
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• 2005

Atmospheric correction over the ocean part is more important than that over the land because the signal from the ocean is very small about one tenth of that reflected from land. In this study, the Spectral Shape Matching Method (SSMM) developed by Ahn and Shanmugam (2004) is evaluated using Landsat imagery acquired over the highly turbid Saemangeum Coastal Area. The result of SSMM is compared with COST model developed by Chavez (1991 and 1997). In principle, SSMM is simple and easy to implement on any satellite imagery, relying on both field and image properties. To assess the potential use of these methods, several field campaigns were conducted in the Saemangeum coastal area corresponding with Landsat-7 satellite's overpass on 29 May 2005. In-situ data collected from the coastal waters of Saemangeum using optical instruments (ASD field spectroradiometer) consists of ChI, Ap, SS, aooM, F(d). In order to perform SSMM, we use the in-situ water-leaving radiance spectra from clear oceanic waters to estimate the the path radiance from total signal recorded at the top of the atmosphere (TOA), due to the reason that the shape of clear water-leaving radiance spectra is nearly stable than turbid water-leaving radiance spectra. The retrieved water-leaving radiance after subtraction of path signal from TOA signal in this way is compared with that estimated by COST model. The result shows that SSMM enabled retrieval of water-leaving radiance spectra that are consistent with in-situ data obtained from Saemangeum coastal waters. The COST model yielded significantly high errors in these areas.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.18-18
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• 2012

In Japan, about 67% of the land is covered by forests and about 41% of them consist of plantations. About 35% of the plantations consist of old-aged plantations of older than 50 yearsand the percentage is projected to 67% in ten years' time. Although the trees of these plantations are supposed to be cut for timber production, most of them remain unmanaged and thus overcrowded mainly due to declining domestic forest industry. Since the forests are mostly located in headwater watershed, there are growing concerns about the degradation of water resources by these unmanaged plantations. To understand the ecohydrological processes in these plantations and examine the effect of intensive 50-60 % thinning to increase infiltration rate and reduce overland flow and soil erosion by recovering understory vegetation, the JST-CREST project "Development of Innovative Technologies for Increasing in Watershed Runoff and Improving River Environment by the Management Practice of Devastated Forest Plantation (Representative: Yuichi Onda)" has been launched since 2009. The ultimate objective of this project is to provide potential scenario to enhance low flow discharge in drought period and reduce turbid material in high flow period. We have been conductingintensive field observation campaign in five research sites across Japan. In Fukuoka site, integrated ecohydrological observations have been conductedin two contrastive watersheds since 2010. Intensive 50% thinning was conducted from January to April 2012 and comparative studies of ecohydrological processes before and after thinning have been started. The interim results from all the sites of this project will be presented in the 3rd International Congress for Forest and Water in a Changing Environment held in Fukuoka during 18-20 September, 2012 (http://www.forest.kyushu-u.ac.jp/~ecohydrol/3ForestWater/index.html).