• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.233-240
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• 2004

Most of hydrological analyses in the field of water resources are launched by gathering and analyzing rainfall data. Several methods have been developed to estimate areal rainfall from point rainfall data and to fill missing or ungaged data. Thiessen and Reciprocal Distance Squared(RDS) methods whose parameters are only dependent on inter-station distance are classical work in hydrology, but these techniques do not provide a continuous representation of the hydrologic process involved. In this study, kriging technique was applied to rainfall analysis in Nakdong river basin in order to complement the defects of these classical methods and to reflect spatial characteristics of regional rainfall. After spatial correlation and semi-variogram analyses were performed to perceive regional rainfall property, kriging analysis was performed to interpolate rainfall data for each grid Thus, these procedures were enable to estimate average rainfall of subbasins. In addition, poor region of rainfall observation was analyzed by spatial interpolation error for each grid and mean error for each subbasin.

• Journal of Environmental Science International
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• v.26 no.10
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• pp.1135-1146
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• 2017

At riverbank filtration sites, groundwater levels of alluvial aquifers near rivers are sensitive to variation in river discharge and pumping quantities. In this study, the groundwater level fluctuation, pumping quantity, and streamflow rate at the site of a riverbank filtration plant, which produces drinking water, in the lower Nakdong River basin, South Korea were interrelated. The relationship between drawdown ratio and river discharge was very strong with a correlation coefficient of 0.96, showing a greater drawdown ratio in the wet season than in the dry season. Autocorrelation and cross-correlation were carried out to characterize groundwater level fluctuation. Autoregressive model analysis of groundwater water level fluctuation led to efficient estimation and prediction of pumping for riverbank filtration in relation to river discharge rates, using simple inputs of river discharge and pumping data, without the need for numerical models that require data regarding several aquifer properties and hydrologic parameters.

• Korean Journal of Environment and Ecology
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• v.22 no.6
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• pp.625-631
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• 2008

We used the visitation aspect of dabbling ducks(Anas spp.) to investigate the estuarine ecosystem of Nakdong River and to compare the data collected during two periods: trom May, 1989 to April 1993 and from May, 2002 to April 2006. Over for the 8 years of field surveys, 356,110 individuals from 11 species of dabbling ducks(Anas spp.) were observed in the Nakdong estuary. In the early 1990s, the average number of species gradually increased from October through November, whereas the highest numbers of species were recorded in October during the second survey period. The average number of individuals recorded during the second period was 2-3 times higher than that observed in the 1990s. Statistical analysis using a t-test indicated that the number of individuals showed significant difference at 5% level between November and February in both the early 1990s and the mid-2000s. During the winter, dabbling ducks select both estuarine wetlands as resting sites and rice paddy as feeding sites. More wintering migrants including ducks would visit to Nakdong river if we provide with enough rice paddy near the estuary. The farmland around Nakdong estuary is used by dabbling ducks as a habitat, we hope it must be conserved thoroughly. CRP(crop reserve program), implemented by the local government of Kangseo-gu, Busan City is effective in conserving rice paddy; therefore, the CRP program need to be continuously applied in the Nakdong river basin.

• Journal of Korea Water Resources Association
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• v.55 no.5
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• pp.383-392
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• 2022

The restoration of the Nakdong River estuary is one of the most important projects of the Ministry of Environment, Republic of Korea. A real-scale experiment of gate operation was executed from 2019 to 2020, and a pilot operation was performed in 2021. The gate of Nakdong River Estuary Barrier (NEB) is supposed to be continuously opened based on the experiment results. Many critical decisions should be made immediately during the experiment based on the real-time measured data and numerical analysis considering the seawater inflows. The decision-making sequence was made systematically with the accurate estimation of seawater inflow. The estimation of seawater inflow is the main research objective and the equations of seawater inflow were developed, reflecting the structural characteristics of NEB. The inflow equations were developed in two forms, overflow and underflow. ADCP (Acoustic Doppler Current Profiler) was used to measure seawater inflow, check the accuracy of the developed equations, and derive the flow coefficient. The comparison error of the developed equations was about 3% compared to the measured data.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.272-281
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• 1995

The residual Polychlorinated biphenyls(PCBs) in the sediment of the Kumho River basin were measured because the Nakdong River was considered to be affected by the environmental quality of Kumho River. PCBs in the sediment were chlorinated and converted into Decachlorinated biphenyl(DCB) which showed the single peak in the GC-ECD chromatogram. The detectable concentrations of PCBs was 0.5ng/g in the sediment. PCBs in the 21 sediment samples was of Kumho River located at 7.5km from conjunction of Nakdong River were not detected from 100 samples. 49% of samples was showed lower than 50ng/g, and 9% did more than 400ng/g. The mean of PCBs concentrations was 131ng/g. The means of COD and organic carbon were 14.5mg/g and 3.41%, respectively. The relationship between PCBs were concentration and the distance from conjunction with Nakdong River was not significant. The concentration of PCBs were varied with the depth of the sediment down to the 250cm depth. The concentrations of PCBs in the depth 0-20cm and 50-90cm were higher than the mean concentration of PCBs. Along the cross of the stream, the concentrations of PCBs were 142ng/g at the center and 126 and 131ng/g at the river sides.

• Water for future
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• v.19 no.3
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• pp.267-276
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• 1986

This study aims at the development of flood runoff model by comparing and analyzing nonlinear models with linear models in rier basins. The models which are used at the analysis are Nash model and Runoff function method as linear models, and Tank model and Storage function method as nonlinear models. The results, which are obtained from the analysis of these models by using hydrologic data of a representative basin in Nakdong river, Wi-chun basin, show that the peak time, peak flow and flood hydrogrphs by nonlinear models are better than those by linear models in comparison with observed ones, and that nonlinear models are suittable as flood runoff model.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.67-79
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• 2010

Korea water resources corporation (K-Water) has developed the real-time water resources management system for the Nakdong and the Geum River basin to efficiently operate multi-purpose dams in the basins. This study has extended to the Han River basin for providing an effective ending target storage of a month to the real-time water resources management system using Sampling Stochastic Dynamic Programming (SSDP), consequently increasing the efficiency of the reservoir system. The optimization model were developed for three reservoirs, named Soyang, Chungju, and Hwacheon, with high priority in terms of the amounts of effective capacity and water supply for the basin. The number of storage state variable for each dam to set an optimization problem has been assigned from the results of sensitivity analysis. Compared with the K-water operating policy with the target water supply elevations, the optimization model suggested in this study showed that the shortfalls are decreased by 37.22 MCM/year for the required water demands in the basin, even increasing 171 GWh in hydro electronic power generation. In addition, the result of a reservoir operating system during the drawdown period applied to real situation demonstrates that additional releases for water quality or hydro electronic power generation would be possible during the drawdown period between 2007 and 2008. On the basis of these simulation results, the applicability of the SSDP model and the reservoir operating system is proved. Therefore, the more efficient reservoir operation can be achieved if the reservoir operating system is extended further to other Korean basins.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.59-64
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• 2012

The correlation between hydrologic performance design parameters of small hydro power(SHP) sites and rainfall condition have been analyzed for major river systems. The model, which can predict flow duration characteristic of stream, was developed to estimate the inflow caused from rainfall. And another model to predict hydrologic performance for SHP plants is established. Based on the models developed in this study, the hydrologic performance characteristics for SHP sites have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems. It was found that the hydrologic performance design parameters such as specific design flowrate and specific output were affected by rainfall condition in basin area of SHP sites.

• Korean Journal of Environmental Biology
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• v.29 no.3
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• pp.180-194
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• 2011

In this study, We were investigated the interrelationships between epilithic diatom communities and physico-chemical factors at Banbyeon stream, Gilan stream and Nakdong river in the Lake Imha basin from September 2008 to June 2009. Epilithic diatom communities were identified a total 120 taxa which were composed to 2 Orders, 3 Suborders, 7 Families, 22 Genera, 108 species and 12 varieties. The dominant species were 4 taxa, which were Achnanthes alteragracillima, A. convergens, A. minutissima and Fragilaria construens var. venter during the investigation periods at 8 sites. Correlation coefficients between epilithic diatom communities and physicochemical factors were from -0.94 to 0.97. Correlation coefficients (r) between turbidity, QHEI and density, species number and indices of diatom communities were from -0.18 to 0.42 which was showed lower values than the values of chemical factors. Correlation coefficients (r) between QHEI and Epilithic diatom communities were showed the low values. Correlation coefficients (r) between TP and diatom indices (DAIpo, TDI) were 0.79 and 0.78, respectively. Therefore, epilithic diatom communities were greatly influenced by TP.

• Journal of Korea Water Resources Association
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• v.44 no.5
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• pp.339-350
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• 2011

This study developed a climate informed Bayesian nonstationary frequency model which allows us to forecast seasonal summer rainfall at Nakdong River. We constructed a 37-year summer rainfall data set from 10 weather stations within Nakdong river basin, and two climate indices from sea surface temperature (SST) and outgoing longwave radiation (OLR) were derived through correlation analysis. The selected SST and OLR have been widely acknowledged as a climate driver for summer rainfall. The developed model was applied first to the 2010-year summer rainfall (888.1 mm) in order to assure ourself. We demonstrated model performance by comparing posterior distributions. It was confirmed that the proposed model is able to produce a reasonable forecast. The forecasted value is about 858.2 mm, and the difference between forecast and observation is about 30 mm. As the second case study, 2011-year summer rainfall forecast was made using an observed winter SSTs and an assumed 50% value of OLRs. The forecasted value is 967.7 mm and associated exceedance probability over average summer rainfall 680 mm is 92.9%. In addition, 50-year return period for summer rainfall was projected through the nonstationary frequency model. An exceedance probability over 1,400 mm corresponding to the 50-year return level is about 73.7%.