• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.1 no.1
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• pp.1-8
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• 2005

Aquifer Thermal Energy Storage (ATES) can be a cost-effective and renewable geothermal energy source, depending on site-specific and thermohydraulic conditions. To design an effective ATES system having the effect of groundwater movement, understanding of thermohydraulic processes is necessary. The heat transfer phenomena for an aquifer heat storage are simulated by using FEFLOW with the scenario of heat pump operation with pumping and waste water reinjection in a two layered confined aquifer model. Temperature distribution of the aquifer model is generated, and hydraulic heads and temperature variations are monitored at the both wells during 365 days. The average groundwater velocities are determined with two hydraulic gradient sets according to boundary conditions, and the effect of groundwater flow are shown at the generated thermal distributions of three different depth slices. The generated temperature contour lines at the hydraulic gradient of 0.001 are shaped circular, and the center is moved less than 5 m to the direction of groundwater flow in 365 days simulation period. However at the hydraulic gradient of 0.01, the contour center of the temperature are moved to the end of east boundary at each slice and the largest movement is at bottom slice. By the analysis of thermal interference data between two wells the efficiency of the heat pump system model is validated, and the variation of heads is monitored at injection, pumping and no operation mode.

• Water for future
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• v.27 no.1
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• pp.79-88
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• 1994

This study was conducted to analyse groundwater flow in the Bugok hot spring area using the MODFLOW model which can simulate three dimensional groundwater flow both in confined and unconfined aquifers. Based on this study the following conclusions were obtained: 1) The hydraulic conductivity and the specific storage of the aquifer were 0.0135 m/day and 0.020, respectively, and the model-predicted groundwater elevation agreed well with the observed one. 2) Simulation results showed that the groundwater level declines at the end of the one-year simulation period when the annual recharge rate is small and the annual pumping rate high, which is the worst combination. Except that combination, the groundwater level does not decline at the end of one-year simulation period indication the pumping rates used were allowable. 3) The safe yield depends upon the magnitudes of the recharge and pumping rates. The pumping rate should not produce excess decline of groundwater level around April when the water level is the lowest in a year.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.303-308
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• 2004

It is recently reported that the importance of environmental impact assessment(EIA) about groundwater outflow problems is beingy raised in the case of tunnel excavation during railroad construction. The EIA about groundwater outflow into railroad tunnel is generally performed using the results of numerical analysis embodied through groundwater flow modeling program like MODFLOW. The basic data for this modeling include (1) the geological and hydrogeological investigation data along the planned block of tunnel excavation, (2) total amount of outflowed groundwater during tunnel excavation, and (3) the status of groundwater level fluctuation in the water-supply wells distributed in the planned block of tunnel excavation. In this study, the authors analyzed the cases of the computational modeling about groundwater outflow in three planned blocks of railroad tunnel, and suggest the environmental impact factors and mitigation plan during EIA of tunnel excavation in railroad construction.

• Geotechnical Engineering
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• v.10 no.1
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• pp.47-62
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• 1994

It has been well known that the rainfall-triggered rise of groundwater levels is one of the most important factors resulting the instability of the hillside slopes. Thus, the prediction of porewater pressure is an essential step in the evaluation of landslide hazard. This study involves the development and verification of numerical groundwater flow model for the prediction of groundwater flow fluctuations accounting for both of unsatu나toed flow and saturated flow on steep hillside slopes. The first part of this study is to develop a nomerical groundwater flow model. The numerical technique chosen for this study is the finitro element method in combination with the finite difference method. The finite element method is used to transform the space derivatives and the finite difference method is used to discretize the time domain. The second part of this study is to estimate the unknown model parameters used in the proposed numerical model. There were three parameters to be estimated from input -output record $K_e$, $\psi_e$, b. The Maximum -A-Posteriori(MAP) optimization method is utilized for this purpose, . The developed model is applied to a site in Korea where two debris avalanches of large scale and many landslides of small scale were occurred. The results of example analysis show that the numerical groundwater flow model has a capacity of predicting the fluctuation of groundwater levels due to rainfall reasonably well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.5
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• pp.321-326
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• 2011

Recently, ground source heat pump (GSHP) systems have been introduced in many modem buildings which use the annually stable characteristic of underground temperature as one of the renewable energy uses. However, all of GSHP systems cannot achieve high level of energy efficiency and energy-saving, because their performance significantly depends on thermal properties of soil, the condition of groundwater, building loads, etc. In this research, the effect of thermal properties of soil on the performance of GSHP systems has been estimated by a numerical simulation which is coupled with ground heat and water transfer model, ground heat exchanger model and surface heat balance model. The thermal conductivity of soil, the type of soil and the velocity of groundwater flow were used as the calculation parameter in the simulation. A numerical model with a ground heat exchanger was used in the calculation and, their effect on the system performance was estimated through the sensitivity analysis with the developed simulation tool. In the result of simulation, it founds that the faster groundwater flow and the higher heat conductivity the ground has, the more heat exchange rate the system in the site can achieve.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1494-1501
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• 2008

Recently, the demand of water resources is constantly increasing due to the substantial increase of population, economy, and living standard. However, it is expected that the water resources should undergo serious problems of poor quality of water as well as shortage of water supply in the near future. Additionally, thoughtless groundwater development have caused to dry river and stream. In this study, the effectiveness of dry stream protection plan is evaluated by using 3-D groundwater flow modeling for the study area which is located in Namyangju of Kyoungi Province. Aquifer tests are performed to obtain the input data of the model. To analyze causes of dry stream using modeling results that water balance is analyzed for situations of before and after closing the wells.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.517-526
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• 2018

As groundwater recharge shows the heterogeneity in space and time due to land use and soil types, estimating daily recharge by integrated hydrologic analysis is needed. In this work, the SWAT-MODFLOW model was applied to compute daily based groundwater recharge in Jangseong region. The accuracy of the model was evaluated by comparing the observed and calculated values of the unsteady groundwater flow levels after calibrating the observed and calculated flow rates of the stream for a hydrological analysis. The estimated hydrologic components showed a strong correlation with each other and significant spatial variations regarding the groundwater recharge rate in accordance with the heterogeneous watershed characteristics such as subbasin slope, land use, and soil type. Overall, it was concluded that the coupled hydrologic models were capable of simulating the spatial variation with respect to the hydrologic component process in surface water and groundwater. The average recharge rate was estimated at approximately 20.8%.

• The Journal of Engineering Geology
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• v.29 no.2
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• pp.113-122
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• 2019

In this study, the flow analysis to evaluate the extent of groundwater decline and the effect of the small valleys caused by the decrease of groundwater level in the construction of road tunnel, and the pollutant movement analysis to evaluate pollution of nearby water source by pollutant discharge during tunnel construction, respectively. The decrease of the groundwater during the 30 month tunnel excavation period was maximum 27 m and it was found to be the largest within 50 m from the tunnel center. The flow of groundwater is shown in the form of flowing into the tunnels and the effects of groundwater level decline were observed up to a tunnel radius of 200 m. As a result of the numerical modeling of the contaminant transport to examine the influence of the polluted water discharge from the tunnel, the range of the turbid water generated at the end of the tunnel is up to 120 m and it is estimated that the risk of contamination of the small river is not large.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1259-1267
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• 2015

In Korea, rural groundwater development faces new challenge, which have not been experienced so far. The problem is a groundwater depletion by the water curtain cultivation (WCC) during winter season. This study investigates the groundwater depletion using three-dimensional finite difference groundwater flow program, MODFLOW to verify the water budget of the shallow aquifer of Cheongweon area. Interdisciplinary research, which has become a worldwide trend, has been adopted in studying groundwater modeling in field scale. In particular, the method of groundwater recharge estimation adopted precise modeling techniques, SWAT to groundwater flow modeling. Based on qualified field data, the model calibrated and validated its reliability. The objective of this study is to simulate various stream-aquifer interactions according to groundwater pumping with artificial boundaries, such as weirs and drainage system. We also analyzed a seasonal variation of cumulative water budget of the site to quantify the groundwater depletion and recovery in the pumping field.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.32-35
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• 2002

In order to characterize the migration of DNAPL in rock fractures, the dynamic macromodified invasion percolation (DMMIP) model, that is able to reflect the viscous force of groundwater in a fracture network, is suggested. DMMIP simulations are verified against the laboratory expenments, which shows a good qualitative and quantitative agreement.