• Journal of Korean Society on Water Environment
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• v.30 no.1
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• pp.44-59
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• 2014

Despite the implementation of TMDL, the water quality in lower watershed of Nam river dam has worsened continuously since 2005. Multifarious pollution sources such as cities and industrial districts are scattered around it. Nam river downstream bed slope is very gentle towards the downstream water flow of slows it down even more, depending on the water quality deterioration is accelerated eutrophication occurs. In this study, the mainstream in lower watershed of Nam river dam region to target aquatic organic matter by phytoplankton growth contribution was evaluated by statistical analysis. and statistical evaluation of water quality and the accuracy of forecasting, model calibration and verification procedures by completing QUALKO2 it's eutrophic phenomena that occur frequently in the dam outflow through scenarios predict an increase in water quality management plans to present the best should.

• Journal of Korea Water Resources Association
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• v.47 no.11
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• pp.1017-1026
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• 2014

To investigate the effect of upstream dam operation and river water use on the downstream flows, SWAT-K watershed model was applied to the Paldang Dam watershed of the Han River basin. Analysis results from 2001 to 2009 showed that outflows from the multi-purpose dams such as the Soyanggang Dam and Chungju Dam much have a strong influence on the downstream flows during both the low- and high-flow seasons. This resulted an increase of low-flow at the Paldang Dam, the end of Pukhangang, and the Yangpyeong stage station by $100.57m^3/s$, $33.01m^3/s$, and $49.66m^3/s$, respectively. Whereas, the impact of river water use was hardly found in the Pukhangang, and also was not significant in the (Nam)hangang. Therefore, the effect of small dam such as the Hoengseong Dam or river water use would be able be excluded for long-term runoff analysis. But, in the case of the areas with a large amount of water use, a sufficient information such water-intake and water movement also must be taken into account like this study.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.9-19
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• 2016

The objective of this study was to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for runoff estimation in the Nam river dam watershed. Input data for the SWAT model were established using spatial data (land use, soil, digital elevation map) and weather data. The SWAT model was calibrated and validated using observed runoff data from 2003 to 2014 for three stations (Sancheong, Shinan, Changchon) within the study watershed. The $R^2$ (Determination Coefficient), RMSE (Root Mean Square Error), NSE (Nash-Sutcliffe efficiency coefficient), and RMAE (Relative Mean Absolute Error) were used to evaluate the model performance. Parameters for runoff calibration were selected based on user's manual and references and trial and error method was applied for parameter calibration. Calibration results showed that annual mean runoff were within ${\pm}5%$ error compared to observed. $R^2$ were ranged 0.64 ~ 0.75, RMSE were 2.51 ~ 4.97 mm/day, NSE were 0.48 ~ 0.65, and RMAE were 0.34 ~ 0.63 mm/day for daily runoff, respectively. The runoff comparison for three stations showed that annual runoff was higher in Changchon especially summer and winter seasons. The flow exceedance graph showed that Sancheong and Shinan stations were similar while Changchon was higher in entire fraction.

• Water for future
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• v.28 no.1
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• pp.91-106
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• 1995

An investigation into the rainfall variability in time and space in the Nam River dam basin of Korea was made with use of the coefficient of variation and the correlation coefficient. The Nam River dam basin is a small mountainous watershed where the wind direction and orography are the dominant influences on the pattern and distribution of rainfall. It was found that the characteristics of rainfall distribution vary with elevation, position, wind direction. And in the three directions considered, it was found that there is the related formulation dependent on the distance between two stations. The resultrs of this study on the temporal and spatial characteristics of rainfall can be used in the design of raingauge networks, hydrological forecasting, and so on in the Nam River dam basin.

• Economic and Environmental Geology
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• v.44 no.6
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• pp.525-532
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• 2011

In this study, the usefulness of underground dam as a means for the sustainable development of groundwater, and its performance in the management of groundwater resources were analyzed. The fully integrated SWAT-MODFLOW was applied to the Ssangcheon watershed in Korea to evaluate the effectiveness of groundwater dam construction. After construction, the groundwater level raised in the upstream area of groundwater dam while lowered in the downstream area. Also, it is shown that the exchange rate of river-aquifer interactions increased in the upper area of the dam. Since the storage capacity of the aquifer largely increased in the upper area of the dam, the exploitable groundwater could be greatly increased as much. This study demonstrated that a groundwater dam was a very useful measure to increase the available storativity of groundwater aquifers. It also represented that the combined analysis using SWAT-MODFLOW was helpful for the design and opeation of groundwater dam in the Ssangcheon watershed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.407-415
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• 2018

This study analyzed the role of dams for the flood control by the observed and simulated hourly flood discharge data. The study area was the Nakdong river basin with Andong and Imha dams. For the analysis 31 flood events from 1997 to 2010 were selected. In the analysis of the flood reduction rate (FRR) of dam itself, the FRR was not decreased with higher size of floods which is not as we expected. In order to see the trend of flood reduction rate depending on the flood size, flood discharge volume presents it better than peak flood discharge. In the comparison of the flood reduction effects of the two dams, Andong dam has 7% larger flood reduction influence at the Sungju gauging station (SGS) located farthest from the selected watershed. Comparing the ratio of the watershed area based on the covered size of the SGS, the FRR of dam is smaller than the area rate. The impact of FRR of dam showed that the FRR fell below 10% when reaching the size of watershed area corresponding to 8.5 times of the size of watershed area of the dam which is larger than Namhan river basin (7 times).

• Journal of Korea Water Resources Association
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• v.46 no.8
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• pp.873-884
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• 2013

In Korea, the rainfall is concentrated in summer under the influence of monsoon climate. Thus, even a small climate change can be significant problems in water resources. As a result, a lot of attention has been focused on climate changes and a number of researches have been conducted in a manner commensurate with the attention to the climate change. This study is intended to forecast the changes in the flow and water quality of the Nam river resulting from the future climate changes in the Nam river basin using a watershed and water quality model. An SWAT model, as a watershed hydrologic model, was established after estimating a climate scenario using an artificial neural network method, and the established model was verified and adjusted using date from the Ministry of Environment to evaluate the applicability of the model. As a consequence, $R^2$ showed more than 0.7 in the simulation test, which satisfies the minimum required level. Results from the SWAT model and the future Namgang dam discharge calculated by HEC-ResSIM is used as input date for QUALKO. The results showed a huge variation in BOD depending on the annual flow of the river, which recorded a maximum difference of 2 mg/L between a rainy season and a dry season. It can be deduced that because rainfall and the runoff of a basin significantly account for the water quality of a river, higher water concentrations are recorded in a dry season in which the flow is not as much as that in a rainy season. It also can be said that water should be reserved in advance to secure water in the Nam river downstream for a dry season and be controlled in an effective and efficient manner to provide better water quality.

• Journal of Wetlands Research
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• v.18 no.3
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• pp.301-312
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• 2016

This study has performed comparative analysis on characteristics of contaminated 35 tributaries on seasonal variation/point discharge load/pollutant distribution of water quality factors(8) in order to understand the effect of the watershed in Nakdong River Basin. As a results, the water quality of $BOD_5$(Biochemical Oxygen Demand), Chl-a(Chlorophyll a) and Fecal E. Coli shows II grade at tributaries of more than 50% without COD(Chemical Oxygen Demand), TP(Total Phosphate), TOC(Total Oxygen Carbon) and TN(Total Nitrogen) factors. The specific discharge(Q) were occupied about 54.4% (19 sites) as $0.05m^3/sec/km^2$ value. Among these results, the contaminant level of Dalseocheon, Hyeonjicheon, Seokkyocheon 1, Uriyeongcheon and Dasancheon was also high, which has to consider a discharged pollutant load(kg/day). The 35 major tributaries of Nakdong River were included in 7 mid-watershed, such as Nakdong Waegwan, Geumho River, Nakdong Goryung, Nakdong Changnyung, Nam River, Nakdong Milyang, Nakdong River Hagueon. Especially, the discharged pollutant load of Nam River and Geumho River also was high according to the amount of discharge such as Kachang dam, Gongsan dam and Nam river dam. Seasonal difference of the water quality factors such as $BOD_5$, TN, SS and Q was observed largely, on the other hand the TP and Chl-a was not. This is guessed due to the precipitation effect of site, biological and physicochemical degradation properties of pollutant and etc. The co-relationship between the seasonal difference and water quality factors was observed using a Pearson correlation coefficients. Besides, the Multiple Regression analysis using a Stepwise Regression method was conducted to understand the effect between seasonal difference and water quality factors/regression equations. As a result, the Multiple Regression analysis was adapted in the spring, summer and autumn without the winter, which was observed high at spring, summer and autumn in the order COD/TP, Chl-a/TOC, TOC/COD/$BOD_5$ water quality factors, respectively.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.413-424
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• 2013

The TMDL, the watershed-oriented water quality management policy, was introduced to inhibit the total amount of pollutant loading generation, and to develop the region environmentally friendly. However, despite the implementation of TMDL, the water quality of Nam river downstream has worsened continuously since 2005. Diverse pollution sources such as cities and industrial zone are scattered around the Nam river. Eutrophication are caused due to deterioration of water quality by low velocity. BOD concentrations in the eutrophic waters affected by the incoming BOD and the autochthonous BOD by the production of phytoplankton. In this study, the quantitative relation of incoming BOD and autochthonous BOD was analyzed for water quality management. The influence of autochthonous BOD was analyzed using QUALKO2 and QUAL2E. Considering the effects of Chl.a, BOD concentration from QUALKO2 model simulations is higher than BOD concentration from QUAL2E model. The results of QUALKO2 showed higher correlation with the measured data. Autochthonous BOD needs to be managed to solve the water pollution problem of Nam river downstream, which is looking for ways to reduce Chl.a by using the increase of the dam outflow and the improvement of the water quality from WWTP.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.221-231
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• 2015

This is a continuous study on the dam effects for the spatial extension of flood data. In this study, flood reduction rates of dams and their influences on downstream using the spatially extended flood data were implemented. Nam-Han River was selected for measuring the impacts of ChoongJu and HoangSung dams. In the evaluations of flood reduction rate at dams, the larger flood events have the lower flood reduction rates for both dams. At the YeoJoo water level station, the analyses of the relations between flood reduction rates and the sizes of watersheds dams located were performed. the sizes of watersheds having a functional dam have highly influenced on the reduction rates of flood. The average of flood reduction rates was smaller than the area rate. For instances, area rates of HoangSung (0.02) and ChoongJu dams (0.6) are larger than the average flood reduction rates for HoangSung (0.01) and ChoongJu dams (0.51), respectively. However, the water level station follows the dam flood reduction characteristics of dams themselves. The spatial effects of dam flood reductions are analyzed based on the three water level stations (GangChun, YeoJoo, YangPyung). The distance of flood reduction rates lower than 0.1 as average flood reduction rate was the area 7 times of watershed having a dam with 0.02 as a minimum reduction rate.