• The Journal of Engineering Geology
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• v.27 no.3
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• pp.313-322
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• 2017

The purpose of this study is to estimate the surface and subsurface flows through the modelling of the model area and facility agricultural complex, and to calculate the groundwater recharge rate through water budget analysis. From results of surface flow modeling, the surface water is flowed to a depth of about 1 to 5 meters from the upper region (northeast) to the lower region (southeast) of the Miryang River. At the M01 point (upper), the observed surface water flux and the model surface water flux are consistent. At the M02 points (lower), the observed surface water flux and the model surface water flux are a difference of 1%. From results of subsurface flow modeling, the depth of groundwater is similar to elevation in the river and higher to the forest area. Ground water depth considering groundwater pumping is that the model values appears higher than the observed values to be within 1.5 m. From results of surface-subsurface integrated modeling, the groundwater recharge area is estimated about 90% of the model area, and the groundwater recharge rate is estimated $1.92{\times}10^5m^3/day$. From results of annual water budget analysis, the groundwater recharge rate per unit area is estimated to be 503.9 mm/year, and average annual rainfall is estimated at around 39%.

• Journal of Korea Water Resources Association
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• v.33 no.1
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• pp.61-72
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• 2000

The purpose of this study is to improve the method of evaluating groundwater recharge by using grid-based soil moisture routing technique. A model which predicts temporal variation and spatial distribution of soil moisture on a daily time step was developed. The model uses ASCII-formatted map data supported by the irregular gridded map of the GRASS(Geographic Resources Analysis Support System)-GIS and can generate daily and monthly spatial distribution map of surface runoff, soil moisture content, evapotranspiration within the watershed. The model was applied to Ipyunggyo watershed($75.6\;\textrm{km}^2$) located in the upstream of Bocheongchun watershed. Seven maps; DEM(Digital Elevation Mode]), stream, flow path, soil, land use, Thiessen network and free groundwater level, were used for input data. Predicted streamflows resulting from two years (l995, 1996) daily data were compared with the observed values at the watershed outlet. The results of temporal variations and spatial distributions of soil moisture are presented by using GRASS GIS. As a final result, the monthly predicted groundwater recharge was presented.sented.

• Journal of Korea Water Resources Association
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• v.47 no.9
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• pp.743-752
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• 2014

Delay time for groundwater recharge means the travel time from the bottom of soil layer to groundwater through vadose zone after infiltration from rainfall. As it is difficult to measure delay time, we suggested an empirical formula which is derived by using linear regression between altitude and delay time. For the regression analysis, 4 major gauging watersheds were chosen (Hancheon, Kangjeongcheon, Oedocheon, Cheonmicheon) with 18 measured groundwater level stations. To verify this empirical formula, derived equation from linear reservoir theory was applied to compute delay time and to compare estimated amounts of groundwater recharge using both methods. The result showed good agreement. Furthermore, if derived empirical formula would be linked with SWAT model, the spatial time delay effect in the watershed could be reflected properly.

• Journal of Environmental Science International
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• v.28 no.9
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• pp.737-749
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• 2019

In this study, the sensitivity analysis of hydraulic conductivity and separation distance (distance between injection well and pumping well) was analyzed by establishing a conceptual model considering the hydrogeologic characteristics of facility agricultural complex in Korea. In the conceptual model, natural characteristics (topography and geology, precipitation, hydraulic conductivity, etc.) and artificial characteristics (separation distance from injection well to pumping well, injection rate and pumping rate, etc.) is entered, and sensitivity analysis was performed 12 scenarios using a combination of hydraulic conductivity ($10^{-1}cm/sec$, $10^{-2}cm/sec$, $10^{-3}cm/sec$, $10^{-4}cm/sec$) and separation distance (10 m, 50 m, 100 m). Groundwater drawdown at the monitoring well was increased as the hydraulic conductivity decreased and the separation distance increased. From the regression analysis of groundwater drawdown as a hydraulic conductivity at the same separation distance, it was found that the groundwater level fluctuation of artificial recharge aquifer was dominantly influenced by hydraulic conductivity. In the condition that the hydraulic conductivity of artificial recharge aquifer was $10^{-2}cm/sec$ or more, the radius of influence of groundwater level was within 20 m, but In the condition that the hydraulic conductivity is $10^{-3}cm/sec$ or less, it is confirmed that the radius of influence of groundwater increases sharply as the separation distance increases.

• Journal of Soil and Groundwater Environment
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• v.10 no.5
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• pp.70-76
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• 2005

It is expected that use of groundwater wells for contaminated groundwater remediation, artificial groundwater recharge and geothermal heat pump systems is increasing in the future in Korea. Some practical confusions may be produced due to lack of regulations related to permits and registrations of these types of wells. This short note is intended to draw attention of relevant professionals by shortly introducing some relevant code of state regulations in Missouri, USA.

• Economic and Environmental Geology
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• v.47 no.6
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• pp.635-643
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• 2014

Sustaiable development yield of groundwater in Korea has been determined according to 10 year drought frequency of groundwater recharge in the standard mid-sized watershed or relatively large area of district. Therefore, the evaluation of groundwater impact in a small watershed is hard to apply. Fot this purpose, a novel approach to estimate cell based sustainable development yield of groundwater (SDYG) is suggested and applied to Gyeongju region. Cell based groundwater recharge is computed using hydrological component analysis using the SWAT-MODFLOW which is an integrated surface water-groundwater model. To estimate the potential amount of groundwater development, the existing method which uses 10 year drought frequency rainfall multiplied by recharge coefficient is adopted. Cell based SDYGs are computed and summed for 143 sub-watersheds and administrative districts. When these SDYGs are combined with groundwater usage data, the groundwater usage rate (total usage / SDYG) shows wide local variations (7.1~108.8%) which are unseen when average rate (24%) is only evaluated. Also, it is expected that additional SDYGs in any small district could be estimated.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.66-81
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• 2014

A Fortran program was developed to determine the optimal locations of an artificial recharge well. Three objective functions were considered: (1) maximizing the recovery rates, (2) maximizing the injection rates, and (3) minimizing the coefficient of variation of the increased pumping rates. We also suggested a new aggregate objective function which combined the first and the third objective functions. The model results showed that locating the injection well inside the cluster of pumping wells was desirable if either the recovery or the injection rate was taken into account. However, the injection well located outside the cluster evenly increased the pumping rates in existing pumping wells. Therefore, for clustered pumping wells, installing an injection well at the center or the upstream of the pumping wells seems beneficial. For linear arrangement of pumping wells parallel to the constant head boundary, locating the injection well in the upstream was recommended. On the contrary, in case of the linear arrangement perpendicular to the constant head boundary, the injection well installed on both sides of the central part of the pumping wells was preferable.

• Journal of Soil and Groundwater Environment
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• v.23 no.6
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• pp.37-45
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• 2018

The source of Chusan Spring water in the Ulleungdo is the precipitation in the Nari caldera basin, which permeates in the Trachitic pumice and tuff area and moves downward, outflowing at the lithologic boundary between the trachyte and Nari tuff. It is known that the discharge rate of the Chusan Spring is large enough to be used for the small hydroelectric power generation, but the exact discharge rate and hydrogeologic characteristics have not been known. The discharge rates of the Spring were measured 11 times, which ranged from $15,220m^3/d$ to $36,278m^3/d$. The discharge rates, measured by the automatic level recorder, for two-year period, were $20,000{\sim}38,000m^3/d$. The variation of discharge rates did not coincide with rainfall event, but showed daily increases of $3,000{\sim}5,000m^3/d$. The annual discharge rate excluding the evapotranspiration and the surrounding stream discharge corresponded to 70.6% of the annual precipitation of the recharge area. Therefore, meteorological observations at the Nari basin, rather than the Ulleung-do meteorological station, are more appropriate to properly interpret the discharge characteristics of the Chusam Spring and the recharge rate of the basin.

• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.54-59
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• 2007

In this study, a semi-analytical model to address groundwater level fluctuations in response to precipitations and its infiltration is developed through mathematical modeling based on water balance equation. The developed model is applied to a prediction of groundwater level fluctuations in Hongcheon area. The developed model is calibrated through a nonlinear parameter estimator by using daily precipitation rates and groundwater fluctuations data of a same year 2003. The calibrated input parameters are directly applied to the prediction of groundwater fluctuations of year 2004 and the simulated curve successfully mimics the observed. The developed model is also applied to practical problems such as a prediction of a effect of reduced recharge due to surface coverage change and a induced water level reduction. Through this study, we found that recharge to precipitation ratio is not a constant and may be a function of a precipitation pattern.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.22-27
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• 1998

A grid-based soil moisture routing model(GRISMORM) was developed to assess the information of groundwater recharge using spatial data such as Landsat TM and digital elevation model etc.. The model predicts the hydrologic components, that is, surface runoff, subsurface runoff, baseflow and evapotranspiration at each grid elements by grid-based water balance computation.