• Journal of Soil and Groundwater Environment
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• v.11 no.2
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• pp.45-55
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• 2006

A 2-D unconfined flow model is developed to analyze annual variations of groundwater level and bank filtration rate (BFR) for an experimental riverbank filtration site in Koryeong, Korea. Two types of boundary conditions are examined for the river boundary in the conceptual model: the static head condition that uses the average water level of the river and the dynamic cyclic condition that incorporates annual fluctuation of water level. Simulations show that the estimated BFR ranges $74.3{\sim}87.0%$ annually with the mean of 82.4% for the static head boundary condition and $52.7{\sim}98.1%$ with the mean of 78.5% for the dynamic cyclic condition. The results illustrate that the dynamic cyclic condition should be used for accurate evaluation of BFR. Simulations also show that increase of the distance between the river and the pumping wells slightly decreases BFR up to 4%, and thereby indicate that it is not a critical factor to be accounted for in designing BFR of the bank filtration system. A sensitivity analysis is performed to examine the effects of model parameters such as hydraulic conductivity and specific yield of the aquifer, recharge rate, and pumping rate. The results demonstrate that the average groundwater level and BFR are most sensitive to both the pumping rate and the recharge rate, while the water level of the pumping wells is sensitive to the hydraulic conductivity and the pumping rate.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.61-70
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• 2010

In case of groundwater recharge estimation using water table fluctuation method, specific yield affects the accuracy and confidence level of recharge rate. Nevertheless, there have been few studies on the method for the accurate estimation of specific yield in Korea. Specific yield estimated from the relationship between rainfall and groundwater levels is reasonable compared to the other methods. However, lots of factors such as artificial pumping, evapotranspiration by the plants, and a sudden increase in water levels by a heavy rainfall can affect the pattern of groundwater levels' fluctuation and make an over-estimated or under-estimated specific yield. This study obtained a reasonable specific yield by using a daily or 12 hourly average of rainfall and groundwater levels measured in a dry season.

• Journal of Korea Water Resources Association
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• v.37 no.6
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• pp.499-507
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• 2004

In this study, the fully coupled SWAT-MODFLOW model is developed by using the type of embedment MODFLOW in SWAT. Since SWAT model has semi distributed features, its groundwater component can't consider distributed parameters such as hydraulic conductivity, storage coefficient and spatially variable natures such as distribution of groundwater heads and pumping rate and so forth. The main purpose of this study is to overcome these limitations. This linkage is completed considering the interaction between stream network and aquifer to reflect boundary flow. To correspond HRU in SWAT to grid in MODFLOW, HRU-GRID conversion tool using DEM is newly suggested. As groundwater recharge of MODFLOW can be estimated accurately by SWAT model, the reliability of groundwater discharge and total runoff of watershed could be greatly enhanced.

• Journal of Environmental Science International
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• v.24 no.12
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• pp.1691-1703
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• 2015

When constructing tunnels, it is important to understand structural, geological and hydrogeological conditions. Geumgeong tunnel that has been constructed in Mt. Geumjeong for the Gyeongbu express railway induced rapid drawdown of groundwater in the tunnel construction area and surroundings. This study aimed to analyze groundwater flow system and baseflow using long-term monitoring and groundwater flow modeling around Geumgeong tunnel. Field hydraulic tests were carried out in order to estimate hydraulic conductivity, transmissivity, and storativity in the study area. Following the formula of Turc and groundwater flow modeling, the annual evapotranspiration and recharge rate including baseflow were estimated as 48% and 23% compared to annual precipitation, respectively. According to the transient modeling for 12 years after tunnel excavation, baseflow was estimated as $9,796-9,402m^3/day$ with a decreasing tendency.

• Journal of Soil and Groundwater Environment
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• v.16 no.5
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• pp.53-66
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• 2011

Groundwater which infiltrated in recharge areas discharges in the forms of evapotranspiration, baseflow to streams, groundwater abstraction and eventually flows into the sea. This study characterized radon-222 concentration and electrical conductivity (EC) in coastal groundwater discharge, well groundwater, Ilkwang Stream water, and seawater in the coastal area of Busan Metropolitan City and subsequently estimated groundwater discharge rate to the sea. The median value of Rn-222 concentration is highest in well groundwater (18.36 Bq/L), and then decreases in the order of coastal groundwater discharge (15.92 Bq/L), Ilkwang Stream water (1.408 Bq/L), and seawater (0.030 Bq/L). The relationship between Rn-222 concentration and EC values is relatively strong in well groundwater and then in seawater. However, the relationship is not visible between coastal groundwater discharge and Ilkwang Stream water. The groundwater discharge rate to the sea is estimated as $3,130m^3$/day by using radon mass budget model and $16,788m^3$/day by using Darcy's law.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.2
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• pp.101-106
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• 1999

Open dump of refuse causes groundwater and soil contamination by leachate and air pollution by LFG(Landfill Gas). In this paper, in order to perform a study about reduction of high leachate and LFG collection & control, using a 3-D, 2-phase, transient FDM model, the analysis of simultaneous flow of leachate and LFG has been carried out. In present numerical analysis it is assumed that 58 percents of LFG will evaporate to the ambient air and the recharge rate of a landfill be 12 percent of the average precipitation per year. All other data were excerpted at the point of 1995 when three refuse layers had been buried. From numerical analysis we concluded that maximum head value is approximately 26 mH2O<-에이치투오 (2.52 atm) in the center of the system and that installing venting trench plays an important role in landfill stabilization. Evan with the assumption of three layers constructed and low recharge rate applied, it is found that cumulative leachate and LFG productions will be 15.1 million 세제곱미터, 5.58 billion 세제곱미터, respectively after 40 years.

• Journal of Environmental Science International
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• v.24 no.4
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• pp.505-514
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• 2015

The grid-based water balance of watershed scale was assessed in the mountainous area of Pyosun catchment in Jeju Island after analyzing precipitation, evapotranspiration, and runoff from January 2008 to December 2013. The existing results of direct runoff, evapotranspirtion, and groundwater recharge comparing to precipitation were presented 22.0%, 25.6%, and 52.4%, respectively, in Pyosun catchment. However, this study indicated each component shows 14.5%, 24.2%, and 61.0%, respectively, in the mountainous area of Pyosun catchment. Therefore, groundwater recharge rate in the mountainous area appears higher than 10% comparing to the overall catchment. It would be analyzed that the amount of direct runoff is relatively small. Moreover, this difference could be generated because of the spatial discontinuities in the process of estimating the total amount of precipitation in the mountainous area. Therefore, the grid-based spatial analysis to maximize the spatial continuity would be useful for providing a more reasonable result when the total amount of water resources are evaluated in mountainous areas in the future.

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.20-29
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• 2012

The green house on the waterfront is air-conditioned by a water-source heat pump system with riverbank filtration water. In order to supply riverbank filtration water in alluvium aquifer, the riverbank filtration facility for water intake and recharge, two pumping wells and one recharge well, has been constructed. The research site in Jinju, Korea was chosen as a good site for riverbank filtration water supply by the surface geological survey, electrical resistivity soundings, and borehole surveys. In the results of two boreholes drilling at the site, it was revealed that the groundwater table is about 3 m under the ground, and that the sandy gravel aquifer layer in the thickness of 6.5 m and 3.5 m occurs at 5 m and 7 m in depth below the ground level respectively. To prevent the recharge water from affecting the pumped water which might be used as heat source or sink, the distance between pumping and recharge wells is designed at least 70 m with a quarter of recharged flow rate. It is predicted that the transfer term, the recharge water affects the pumping well, is over 6 months of heating season. Hydrogeological simulation and underground water temperature measurement have been carried out for the pumping and recharge well positions in order to confirm the capability of sustainable green house heating and cooling.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.995-1005
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• 2005

The study with laboratory sandbox model has been carried out to address potential use of reclaimed water, as a countermeasure artificially recharging the coastal aquifer, to effectively prevent from seawater intrusion due to overexploitation. It also investigated plausibility for either preserving or recovering the freshwater interface facing with seawater intrusion. To do this, we assessed hydraulic properties in artificial aquifer seawater/freshwater interface) depending upon the variation of extraction, storage and injection of reclaimed water. The variation of interface between freshwater and seawater were visualized by Surfer 8(Golden Software, USA) according to given experimental conditions. The interface between seawater and freshwater has been sensitively influenced by the change of extraction rate, where seawater zone migrated much faster into freshwater zone even though extraction rate became decreased. However, decreasing recharge rate could slow down moving of saline water zone toward freshwater zone. When the recharge was solely introduced into the sand box model, saline water intrusion was retarded than those of recharge and extraction working together. And also, the level of salinity of saline water was diluted by artificial recharge. It finally revealed that the artificial recharge would hydraulically avoid seawater intrusion while the freshwater sources could be conservatively utilized.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.17-20
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• 2002

The environmental tracers of $^3$H and NO$_3$ were investigated in terms of vertical connections between basaltic aquifers and underlying sedimentary formations of Seoguipo formation that is not found in eastern coastal area and U formation. In western coastal area, $^3$H shows values less than 0.5TU In the wells completed in Seoguipo formation whereas it is greater than 2TU in other area. For the wells in western area, NO$_3$ concentrations are below background level though the nearby land uses are mainly agricultural. The groundwater heads are much lower in eastern coastal area than western area in spite that recharge rate of eastern area is 1.7 times higher than that of western area. The basaltic aquifer is thicker by 70m in eastern coastal area than in western coastal area, which is insufficient to explain much lower groundwater heads in eastern area. These hydrogeological characteristics suggest that for the basaltic aquifers, the Seoguipo formation acts as a lower boundary which could limit downward groundwater flow in basaltic aquifers whereas the U formation is unlikely.