• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.251-252
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• 2008

Si-Hwa tidal power station is using difference of the ebb and flow. The active power is dependent on up and down sea water level but if it is drastically changed because of a typhoon or waves the generator terminal voltage and active power is changed that is a chief cause of power station unstability. Therefore this paper arrange a present state of power or frequency fluctuation and generator terminal phase difference in case of occurrence a drastic change of sea water level.

• Journal of Korea Water Resources Association
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• v.48 no.4
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• pp.269-279
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• 2015

Nowadays, the world has suffered by natural disaster of climate change due to global warming. Korea has also faced with similar situation. To prevent these natural disaster, Four Major River Management has conducted. One of conducted content in Four Major River Management is the levee maintenance which classified into fill-up the inland, levee of reinforcement and so on. These maintenances may make the characteristics of groundwater flow change and affect to the levee safety (piping phenomenon). Therefore, analysis on groundwater fluctuation according to level of riverside and inland should be required. This study focus on levee of Hoe stream, which is connected to Nakdong river, and piping safety factor in the levee analyzed by using pore water pressure. Besides, groundwater fluctuation, which is depended on level of riverside and inland, is simulated by using the SEEP/W (2D ground water model). This simulation considered steady flow and unsteady flow. As a result, piping safety factor increased due to rising the inland level. Piping safety factor of riverside was effected by only river water level. Therefore, external levee factor considering inland level raising and suitable control of river water level is need to increase piping safety factor.

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.227-233
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• 2009

Most of hydrological processes of groundwater recharge generally are occupied a rainfall, and recharged an aquifer along infiltrate into subsurface. These processes mainly have an influence by hydrological characteristics and topographic gradient of the aquifer. Development of water resources and its management is not good because of temporal and spatial disproportion in local rainfall. In order to deal with insufficiency of water resources from now on, development of groundwater dam requires a plan of a sustainable of new water resources. These are necessary that investigation of construction area of groundwater dam, effective groundwater development interconnected with surface water and groundwater, and assessment of an application of groundwater dam for utilization of water resources. Tn this study we were derived the input data by geological survey, hydraulic and hydrological analysis around Hoengchun-river, located in Hadong-gun, Gyeongsangnam Province where is a plan area for construction of groundwater dam. Based on input data we were carried out the interconnected analysis of surface water and groundwater using the SWAT-MODFLOW, and predicted groundwater fluctuation of its construction before and after.

• Korean Journal of Ecology and Environment
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• v.50 no.3
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• pp.337-354
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• 2017

Cyanobacteria Aphanizomenon population is widely distributed in the world, and well known as harmful algae by producing toxins and off-flavor materials, thus belonging to one of the taxa that became more interested in the field of limnoecology. In this study, the frequency, intensity, and duration of Aphanizomenon occurrence were increased with the abnormal drawdown of water level in the winter in Boryeong Reservoir, and the spatial and temporal characteristics of them are compared with each other in the perspective of hydrometeorology (1998 to 2017) and limnology (2010 to 2017). In Korea, Aphanizomenon flourished mainly in high temperature, and the appearance in the low temperature was rare in total five times. The harmful cyanobacteria Aphanizomenon was observed in the low temperature (December to February) in Boryeong Reservoir from 2014, and then reached a maximum value of $2,160cells\;mL^{-1}$ in January 2017. In addition, the period exceeding $1,000cells\;mL^{-1}$ at this time was more than 3 months. This was simultaneously associated with abnormal water level fluctuation in the low temperature ($<10^{\circ}C$). The large drawdown of water level in the winter season has the potential to promote or amplify the germination and development of harmful algae. Also, subsequent water quality and ecological impacts(e.g., algal toxins and off-flavor substances) need to be considered carefully.

• Journal of Korea Water Resources Association
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• v.45 no.5
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• pp.465-472
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• 2012

Recently, as the development of water front and natural type river is gradually increasing, it is mostly the case in that the flow analysis is implemented by only the flood level of the starting point without the tidal effect when the flood water level of the starting point is highly estimated than the high tidal water level in the design of river adjacent to an estuary. This research has analyzed the variation of tidal current for Oncheon river in Busan using Delft-3D program, considering that the tidal effect can cause the change of the flood water level of the starting point although the flood water level is higher than the flood tide level. As a result, considering the tidal effect at downstream boundary condition, water level indicates a periodicity of tide in particular region and the fluctuation range of water level is extended to upstream.

• Journal of Wetlands Research
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• v.22 no.3
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• pp.178-186
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• 2020

In this study, the elasticity was calculated and sensitivity analysis was performed using air-water temperature data of the major tributaries of the Nakdong River. We developed a nonparametric elasticity analysis technique capable of estimating the confidence interval for elasticity and verifying the hypothesis, and examined its applicability compared to the existing method using the median value. It is analyzed that the elasticity of winter is low and the elasticity of summer and autumn is high, so that the fluctuation of water temperature and water quality according to the fluctuation of air temperature is large. The spatial elasticity tends to be low in the Geumho River area, which is influenced by artificial factors such as sewage treatment plant effluent, small and medium-sized livestock wastewater, and small-scale factory wastewater. Since the elasticity of major tributaries of the Nakdong River is over weak and is reasonable at a significance level of 5%, it was analyzed that the air-water temperature fluctuation caused by climate changes is large.

• Journal of Environmental Science International
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• v.17 no.2
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• pp.257-267
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• 2008

Groundwater recharge characteristics in a fractured granite area, Mt. Geumjeong, Korea. was interpreted using bedrock groundwater and wet-land water data. Time series analysis using autocorreclation, cross-correlation and spectral density was conducted for characterizing water level variation and recharge rate in low water and high water seasons. Autocorrelation analysis using water levels resulted in short delay time with weak linearity and memory. Cross-correlation function from cross-correlation analysis was lower in the low water season than the high water season for the bedrock groundwater. The result of water level decline analysis identified groundwater recharge rate of about 11% in the study area.

• Spatial Information Research
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• v.7 no.1
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• pp.103-117
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• 1999

During the last several years, the geographic information system(GIS) technology has emerged as a very effective tool for analyzing complicated groundwater system Linking GIS to spatially distributed hydrogeological data and groundwater models offers many advantages in the analysis of urban groundwater system. This paper describes the urban hydrogeological application of GIS in Seoul area. This study constructs an urban hydrogeological database via pre- and post-processing of various types of urban hydrogeological data, such as groundwater-level fluctuation, topogaphic data, water chemistry data, subway pimping station data, tidal effect of the Han River, and hydrogeological parameters. A hydrogeological model has been designed to enable importing data from the database and providing the model output for the repetitive manipulation and display in GIS.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.455-458
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• 2004

This study uses time series analyses to evaluate fluctuation of water levels in a geothermal water well due to pumping, in relation to rainfall at Dongrae hot-spring site on the southeastern coast of tile Korean peninsula. The volume of water pumped from the public study wells ranges from 542 to 993 m$^3$/month, and the minimum water level ranged from 35 to 144.7 m during the measured period. Autocorrelation analysis was conducted for the withdrawal rate at the public wells, water levels and rainfall. The autocorrelation of the withdrawal rate shows distinct periodicity with 3 months of lag time, the autocorrelation of rainfall shows weak linearity and short memory with 1 months of lag time, and the autocorrelation of water levels shows weak linearity and short memory with 2 months of lag time. The cross-correlation between the pumping volume and the minimum water level shows a maximum value 1 at a delayed time of 34 months. The cross-correlation between rainfall and the minimum water level shows a maximum value of 0.39 at a delayed time of 32 months.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.617-634
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• 2020

The purpose of this study is to investigate the relationship of between earthquakes and fluctuation of water level in a groundwater well of the active-fault zone and 124 national groundwater monitoring wells in Gyeongju area. The spatial and temporal relationships between the fluctuation of water level and the earthquake were analyzed by the calculation of earthquake effectiveness (ε) and q-factor which are the function of earthquake magnitude and distance from epicenter. Two earthquake events of E1 (April 22, 2019, M 3.8) and E2 (June 11, 2019, M 2.5) show a close relationship with a post-seismic 83 cm decrease and a pre-seismic 76 cm increase in water level at the active fault zone of Dangu-ri, respectively. The spatial analysis of water level fluctuation data in National Groundwater Monitoring Networks caused by earthquake events shows a more distinct response in deep groundwater around fault zones than other area, and a greater change in deep groundwater than shallow groundwater. It's inferred that the decrease and increase in groundwater level are affected by the expansion of fractures and compression of rock mass due to seismic stress, respectively. The effective ranges of ε-value and q-factor of the monitoring well in Dangu-ri were calculated as 2.70E-10~5.60E-10 and 14.4~18.0, respectively.