• Korean Journal of Ecology and Environment
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• v.35 no.1 s.97
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• pp.36-44
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• 2002

The spatial and temporal trends of water qualities in Lake Soyang was statistically analyzed in this study. The water qualities include nutrients, ionic contents and chlorophyll-a (Chl-a) measured during 1993${\sim}$2000. The rainfall intensity and runoff from the catchment appeared to play an important role in water quality trends in the lake. According to seasonal Mann-Kendall test, conductivity, TP, and Ctl-a did not show any trends of increase or decrease over the 8 year period, while TN declined slightly. It was found that the variation of TP was a function of interannual inflow and rainfall. In the analyses of spatial trend, conductivity, based on the mean by site, showed a downlake decline over the eight year period. Minimum conductivity was found in the headwaters during summer monsoon of July to August and near the dam during October. This result indicates a time-lag phenomenon that the headwater is diluted by rainwater immediately after summer monsoon rain and then the lake water near the dam is completely diluted in October. During summer period, TP and TN had an inverse relation with conductivity values. Concentrations of TP peaked during July to September in the headwaters and during September in the downlake. Also, TN increase during the summer and was more than 1.5 mg/L regardless of season and location, indicating a consistent eutrophic state. Values of Chl-a varied depending on location and season, but peaked in the midlake rather than in the headwaters during the monsoon. Regression analyses of log-transformed seasonal Chl-a against TP showed that value of $R^2$ was below 0.003 in the premonsoon and monsoon seasons but was 0.82 during the postmonsoon, indicating a greater algal response to the phosphorus during the postmonsoon. In contrast, TN had no any relations with Chl-a during all seasons.

• Journal of Korean Society on Water Environment
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• v.27 no.2
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• pp.200-209
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• 2011

The purpose of the study is to optimally manage sewage treatment plant with analysis of phosphorus contribution and improvement of water quality contributing rate in the effect of inflowing point of effluent and Pal-Dang lake after reducing T-P discharge from large scale public sewage treatment plant at upstream of Pal-Dang lake. Also, this study, for enforcement of T-P in effluent, plans optimal management of effluent T-P through examining propriety of environmental, technological, and economical aspect such as water quality standard of domestic and foreign T-P and related policy. In regarding optimal management of T-P discharged from public sewage treatment plant located in upstream of Pal-Dang lake, the study drew following conclusions. With the optimal management of public sewage treatment plant, it showed that a pollution level became higher in the order of Sumgang E in South-Han river, C in Dalcheon, B1 B2, A in North-Han river, and J in Kyungancheon, and it is required reduction of T-P first. The highest value in analysis of benefit-costs from sewage treatment plant in the selected research area was Kyungan B, and the others are with the order of Jojong A, Bokha A, Kyungan A, and Yanghwa A. With result of this study, all 14 areas are required more enforced phosphorus treatment. The study resulted that the most top priority areas were Hangang F, Sumgang B, and Gyungan A, top priority areas were Bokha A, Dalcheon B, and Cheongmi A, priority areas were Hangang E, Heukcheon A, Gyungan B, and Jojong A, and potential areas were Sumgang A, Yanghwa A, Dalcheon A, and Hangang D. It seems to be appropriate to apply 0.2 mg/L of T-P treatment for water supply source reservation, 0.5 mg/L for the other areas by locally, and 0.2~0.5 mg/L for biological nitrogen phosphorus treatment method and 0.5~1 mg/L for Conventional Activated Sludge by technologically. Also, it may be appropriate to apply 0.2 mg/L for the most top priority area(I), 0.3 mg/L for the top priority area(II), 0.4 mg/L for priority area(III), and 0.5 mg/L for potential area(IV) by the separation of priority area.

• Journal of Environmental Impact Assessment
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• v.18 no.6
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• pp.401-409
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• 2009

Multivariate statistical approaches to classify sampling sites with measuring their similarity by water quality data and understand the characteristics of classified clusters have been discussed for the optimal water quality monitering network. For empirical study, data of two years (2005, 2006) at the 9 sampling sites with the combination of 2 depth levels and 7 important variables related to water quality is collected in Yongdam reservoir. The similarity among sampling sites is measured with Euclidean distances of water quality related variables and they are classified by hierarchical clustering method. The clustered sites are discussed with principal component variables in the view of the geographical characteristics of them and reducing the number of measuring sites. Nine sampling sites are clustered as follows; One cluster of 5, 6, and 7 sampling sites shows the characteristic of low water depth and main stream of water. The sites of 2 and 4 are clustered into the same group by characteristics of hydraulics which come from that of main stream. But their changing pattern of water quality looks like different since the site of 2 is near to dam. The sampling sites of 3, 8, and 9 are individually positioned due to the different tributary.

• Journal of Korea Water Resources Association
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• v.57 no.2
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• pp.99-110
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• 2024

Paldang Reservoir serves as a crucial water source for the metropolitan area, and national efforts are focused on water quality management. The region near Paldang Dam, where the water intake facility with the greatest depth is located, experiences vertical stratification during the summer. It has been challenging to definitively classify whether this stratification is caused by density currents or summer temperatures. This study aimed to differentiate and analyze stratification due to density currents and temperature variations at key locations in the Paldang Reservoir through vertical water quality measurements. The results allowed us to distinguish between density current and temperature-induced stratification. We found that density currents are primarily caused by temperature differences among inflowing rivers, with flow velocity significantly influencing their persistence. Additionally, based on a combination of monsoon and non-monsoon season characteristics, we classified Paldang Reservoir into regions with distinct river and lake traits.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.205-212
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• 2004

Phosphorus cycle was studied in a deep stratified reservoir in summer monsoon area (Lake Soyang, Korea) by surveying phosphorus input from the watershed and the movement of phosphorus within the reservoir. And the spatial and temporal distribution of phosphorus was modeled with a 2-dimensional water quality model (CE-QUAL-W2), Phosphorus loading was calculated by measuring TP in the main inflowing river (the Soyang River) accounting for 90% of watershed discharge. TP of the Soyang River showed a large daily variation with the flow rate. High phosphorus loading occurred during a few episodic storm runoff laden with suspended sediments and phosphorus. Because storm runoff water on rainy days have lower temperature, it plunges into a depth of same temperature (usually below 20m depth), forming an intermediate turbidity layer with a thickness of 20 ${\sim}$ 30 m. Because of stable thermal stratification in summer the intermediate layer water of high phosphorus content was discharged from the dam through a mid-depth outlet without diffusing into epilimnion. The movement of runoff water within the reservoir, and the subsequent distribution of phosphorus were well simulated by the water quality model showing a good accuracy. The major parameter for the calibration of phosphorus cycle was a settling velocity of detritus, which was calibrated to be 0.75 m ${\cdot}$ $day^{-1}$. It is concluded that the model can be a good simulator of limnological phenomena in reservoirs of summer monsoon area.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.743-754
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• 2000

Model parameters of the WASP5 applied to Saemanguem lake were estimated. The methodology is based on grouping water quality constituents and relevant parameters and successively estimating each group of parameters by a trial-and-error procedure. Chlorophyll-a, nitrogen cycles, phosphorus cycles, BOD and DO were simulated at the complexity level 4. The Saemangeum basin divided into a number of unit sub-watershed. And a water budget model analysis with 22 years from 1975 to 1996 year was examined. In this paper, input data at upstream boundaries of model was made to determine seasonally-averaged flow rate through water budget analysis. Calibration and verification of the model were used seasonal average of water quality measurements in 1997 and 1998 years. Grouping water quality constituents and associated parameters proved to be efficient in estimating a number of model parameters. From the results of model calibration and verification, it was found that quantitative evaluations of nonpoint source for organic matters are essential.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.56-62
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• 2015

The potential impact of water temperature on sea level and air temperature rise in response to recent global warming has been noticed. To predict the effect of temperature change on river water quality and aquatic environment, it is necessary to understand and predict the change of water temperature. Air-water temperature relationship was analyzed using air temperature data at Buan and water temperature data of Shinsi, Garyeok, Mangyeong and Dongjin. Maximum and minimum water temperature was predicted by neural network and the results show a very high correlation between measured and predicted water temperature.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.667-669
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• 2003

A bio-optical model was developed specific for turbid and shallow waters. Special studies were carried out to estimate absorption and scattering properties as well as backscattering probability of suspended matter. The inversion of bio-optical model allows for direct retrieval of turbidity and chlorophyll- a from the visible-near infrared (VNIR) range sensor. Time-series satellite imagery from ASTER AM-1 sensor, were used to monitor the Laguna de Bay water quality condition. Spatial distribution of temperature for the lake was extracted from the thermal infrared (TIR) sensor. Corresponding field surveys were conducted to parameterize the bio -optical model. In-situ measurements include suspended particle and chlorophyll-a concentrations profiles from nephelometric devices and processing of water samples. Hyperspectral measurements were used to validate results of the bio -optical model and satellite- based estimation. This study provides a theoretical basis and a practical illustration of applying space- based measurements on an operational basis.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.479-483
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• 1998

Many computer models have been used for estimating the water quality and evaluating countermeasures. The models such as QUAL2E, STREAM, WASP, CE-QUAL have been applied in the waters so far. Some modeller assumed either that the flow of the waters is steady or that the storage change of the waters is negligible. And someone excluded hydraulic part from the quality simulation. It may cause inaccurate estimations of water flow and quality, particularly when the waters have seawards boundary and more inflow than outflow, etc. In order to show the velocity vector for water quality simulation of Paldang lake in dynamic condition, RMA-2 was performed with the water quantity data in 1997.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.403-407
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• 2001

For the water quality management of stream and lake, it is important to estimate and control nonpoint source loading to meet the water quality standard. So, integrated watershed management is required. BASINS is a multipurpose environmental analysis system for use by regional, state, and local agencies in performing watershed and water quality based studies. BASINS was developed by the USEPA to facilitate examination of environmental information, to support analysis of environmental systems and to provide a framework for examining management alternatives. BASINS contains HSPF which is one of the watershed runoff model. By using HSPF, nonpoint source loading from upper stream watershed was estimated. As a result, the simulated runoff was in a good agreement with the observed data and indicated reasonable applicability for whole watershed.