• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.141-154
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• 2020

The accidents of toxic chemical spill into rivers are increasing in recent years due to expansion of heavy industries in Korea. In order to respond to the chemical spills, accident response systems have been established for both main rivers and tributary rivers. However, since these accident response system adopted the water quality models imported from the foreign countries, it is difficult to acquire the model parameters and to calibrate and validate the water quality models. Therefore, this study developed a depth-averaged two-dimensional river water quality model to analyze the behavior of hazardous chemicals in rivers and proposed an efficient simulation execution framework by identifying the significant reaction mechanisms considering the characteristics of the toxic chemicals. The depth-averaged two-dimensional river water quality model CTM-2D was upgraded by adding reaction terms representing mechanisms of the adsorption, desorption, and volatilization of toxic chemicals. In order to verify the model, the analytical solution was compared with the numerical solution, and results showed that the error was less than 0.1%. In addition, the model was applied to a virtual scenario which is a water pollution accident at the confluence of the Nakdong River - Kumho River, and model results showed that an efficient simulation could be carried out by activating only significant reactions which were assessed by the sensitivity analysis.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.3
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• pp.211-216
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• 2007

The quality of tap water on the whole water-supply system, from a large filtration plant to a private faucet, has to be guaranteed the standards of drinking water. At this point in time, however, the supply process of the tap water has not been monitored and managed scientifically. The piped water, especially the most small-scale reservoirs(underground or overhead type) are always exposed to various contaminations and impurities. Recently monitoring systems of water-quality were spread on some large filtration plants or distributing reservoirs. In particular, the water quality monitoring method using the internet is adopted into some local government whose inhabitants can check up the water quality anytime and anywhere. The construction of this system that has to apply a large scale needs, and has a limitation on the small water-supply system, such as apartments, public facilities and small-scale underground or overhead reservoirs. In this work, we suggest the integration system of individual water-quality sensor modules that have a low price. By using the developed integration system and monitoring program operated on the internet, the system managers of reservoirs can monitor and manage water-quality characteristic values of drinking water in online. Since the proposed system was modularized, the system can be applied easily into various reservoirs with a low cost and regardless of its scale, small or large.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.6
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• pp.1-12
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• 2018

The objectives of this study were to develop a system linking hydrologic and water quality models considering the mechanisms of agricultural reservoir and paddy cultivation and to evaluate whether the developed system simulates hydrologic and water quality processes better than a hydrologic model that do not consider the mechanisms. The system consisted of Hydrological Simulation Program-Fortran (HSPF) as a watershed model, Module-based hydrologic Analysis System for Agricultural watersheds (MASA) as reservoir water balance model, and Chemical, Runoff and Erosion from Agricultural Management System-Paddy (CREAMS-PADDY) as a hydrologic and water quality model for paddy fields. This study carried out on the Seolseong-Cheon watershed in Icheon, and the water level and water quality had been monitored for two years at the outlet of the watershed. According to the results of this study, the performance of the simulation using HSPF-MASA-CREAMS-PADDY system was better than others, but they did not show a statistically significant difference. This seemed to be due to the uncertainty of the farming data and the water quality data of the reservoir. Therefore, if accurate input data for the system is obtained, HSPF-MASA-CREAMS-PADDY system could be used to model an agricultural watershed to obtain more realistic results. The results of this study could be utilized to the modeling of agricultural watersheds in Korea where paddy rice cultivation is dominant.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.1
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• pp.33-39
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• 2018

As the retrieval accuracy of PWV estimates from GPS measurements is proportional to the accuracy of water vapor WMT, the WMT model is a significant formulation in the conversion of PWV from the GPS ZWD. The purpose of this study is to develop a MWMT model for the retrieval of highly accurate GPS PWV using the radiosonde measurements from six upper-air observing stations in the region of Korea. The values of 1-hr PWV estimated at four GPS stations during one year are used to evaluate the validity of the MWMT model. It is compared to the PWV obtained from radiosonde data that are located in the vicinity of GPS stations. Intercomparison of radiosonde PWVs and GPS PWVs derived using different WMT models is performed to assess the quality of our MWMT model for Korea. The result in this study indicates that the MWMT model is an effective model to retrieve the enhanced accurate GPS PWV, compared to other GPS PWV derived by Korean annual or global WMT models.

• Water Engineering Research
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• v.1 no.3
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• pp.199-208
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• 2000

The relationship between areal total phosphorus(TP) and areal hydraulic loading was identified and used as defining the trophic state of the reservoir. And three simple, conceptual TP models were tested against the measured in-reservoir TP concentration. The analyses were based on water quality data measured in the Ki Heung reservoir for two years. The results showed that Ki Heung reservoir has undergone eutrophic state, and Dillon's and Vollenweider's TP models were in close agreement with the measured annual mean TP concentration. However, the OECD's model understimated the measured annual mean TP concentration in the Ki Heung reservor. A discussion is given for the hypothetical application of TP loading plot which might be useful for establishing the TP control program in the resavoirs/lakes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1395-1408
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• 2014

In this research, a River Recreation Index Model (RRIM) was developed to provide sufficient information on the water quality of rivers to the public in order to secure safety of publics. River Recreation Index (RRI) is an integrated water quality information for recreation activities in rivers and expressed as the point from 0 to 100. The proposed RRIM consisted of two sub models: Fecal Coliform Model (FCM) and Water Quality Index Model (WQIM). FCM predicted Fecal Coliform Grade (FCG) using a logistic regression and WQIM synthesized water quality parameters of, DO, pH, turbidity and chlorophyll a into Water Quality Index (WQI). FCG and WQI were integrated into RRI by the integrating algorithm. The proposed model was applied to upstream of Gangjeong Weir in Nakdong River, and compared with Real Time Water Quality Index (RTWQI) which is the existing water quality information system for recreation use. The results show that calculated RRI reflected change of integrated water quality parameters well. Especially chlorophyll a showed Pearson correlation coefficient -0.85 with RRI. Also, RRIM produced more conservative index than RTWQI because RRI was calculated considering uncertainty of water quality criteria. Further, RRI showed especially low values when fecal coliform was predicted as low grade.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.825-837
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• 2011

Seonakdong river consists of stagnant sections whose flowrate is controlled by the Daejeo and Noksan gates. As a result, there is not a minimum flow during normal times. The Daejeo and Noksan gates are located at the upstream head and the downstream end of Seonakdong river, respectively. Seonakdong river is an estuarine tributary of Nakdong river, which is a reservoir-like river used for agricultural irrigation, with the gate at the estuary of the river to prevent the intrusion of saline. Since the construction of the water gates, the water quality of the river has become degraded. This could also be due to the internal loading of pollutants, especially nutrients, from the sediments of the river because of the elongated detention time by the water gates. This study was thus conducted for the purpose of evaluating the current hydrologic-cycle system and providing measures for the rehabilitation of the hydrologic cycle. In this research, the daily outflow in Seonakdong River was simulated using the SWAT and SWMM models, and the water quality concentration including BOD, SS, TN, and TP were analyzed. The possibility of the application of SWAT-SWMM hybrid simulation was determined through the verification of both models. The error analysis shows that the results of both SWAT and SWAT-SWMM simulations make good agreements with those of field observations. For the single simulation results of SWAT, $R^{2}$ and NSE are 0.758, 0.511, respectively. For the hybrid simulation results of SWAT-SWMM, those are 0.880, 0.452, which means that the hybrid simulation can give more accurate results for the watershed where both the agricultural and urban areas exist.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.159-171
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• 1990

The purpose of this study was development and application of a multiple box model for long term prediction and control of water quality in estuary reservoir. The model was composed of one main model and two sub models for hydrology and water quality. Water quality constituents for modeling were temperature, chlorophyll-a, BOD, DO, N, and P. The model had been applied to Asan reservoir, and the reservoir had been devided into three boxes-two boxes for a upper layer and one box for a lower layer-to represent stratification. The model appeared satisfactory in representing long term trend of water quality variations by comparing measured and simulated results. According to the application of the model to study alternatives for water quality improvement to deal with increase in future pollution load, use of non-phosphorous detergent for chlorophyll-a, advanced sewage treatment for BOD and T-N, reduction of livestock waste for T-P were evaluated as more effective ones than any others, respectively.

• Journal of Environmental Impact Assessment
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• v.15 no.2
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• pp.121-127
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• 2006

The conventional water quality measurements by point sampling provide only site specific temporal water quality information but not the synoptic geographic coverage of water quality distribution. To circumvent these limitations in temporal and spatial measurements, the use of remote sensing is increasingly involved in the water quality monitoring research. In other to assess a trophic state of Yongdam reservoir using satellite imagery data, I obtained Landsat ETM data and water quality data on 16th September and 18th October 2001. The approach involved acquisition of water quality samples from boats at 33 sites on 16th September and 30 sites on 18th October 2001, simultaneous with Landsat-7 satellite overpass. The correlation coefficients between the DN values of the imagery and the concentrations of chlorophyll-a were analyzed. The visible bands(band 1,2,3) and near infrared band(band 4) data of September image showed the correlation coefficient values higher than 0.9. The October image showed the correlation coefficient values about 0.7 due to the atmospheric effect and low variation of chlorophyll-a concentration. Regression models between the chrophyll-a concentration and DN values of the Landsat imagery data have been developed for each image. The regression model was determined based on the spectral characteristics of chlorophyll, so the green band(band 2) and near infrared band(band 4) were selected to generate a trophic state map. The coefficient of determination(R2) of the regression model for 16th September was 0.95 and that of the regression model for 18th October was 0.55. According to the trophic state map made based on Aizaki's TSI and chlorophyll-a concentration, the trophic state of Yongdam reservoir was mostly eutrophic state during this study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.79-93
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• 2008

Water quality simulations on the Saemangeum inner reservoir have been carried out using EFDC model to understand water quality variations caused by abrupt physical changes due to closing of tidal barrier. According to hydrodynamic simulation, model reproduces not only outer regional dynamics but also inner superelevation very well. Calibration and verification of water quality models accomplished using observed data taken before closing. Also sensitivity tests regarding riverine discharges and tidal flats were done. Due to enlarging of always wet zone caused by super elevation on inner tidal flats, predicted DO decreases at that region as a result of SOD. Moreover shrink of mixing zone after closing of dike causes deteriorating of water quality showing DO as 2 mg/L during summer at Mangyeong and Dongjin estuaries, however it does not spread to middle part of the reservoir. Vertical stratification occurs after closing and shows vertical differences in DO concentration at least 6 mg/L to 7 mg/L in summer season. Most part of the reservoir is getting stratified and it leads to an oxigen deficit zone near bottom.