• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.17-28
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• 2010

As a preliminary survey to improve efficiency of well-based permeable reactive barrier system for groundwater remediation, this site-scale study was carried to identify the flowpaths and controlling factors of plume at a remediation site in Suwon City, Korea. A total of 22 monitoring wells were installed as a grid system in the $4m{\times}4m$ square area by 1-m interval. For the groundwater characterization, various tests were performed including water-level monitoring, water sampling & analysis, pumping and slug tests, and tracer tests. The aquifer appeared to be unconfined with hydraulic conductivities (K) ranging from $2.6{\times}10^{-4}cm/s$ to $9.5{\times}10^{-3}cm/s$. The average linear velocity of groundwater was estimated to be $2.94{\times}10^{-6}m/s$, and the longitudinal dispersivity of a conservative tracer to be $5.94{\times}10^{-7}m^2/s$. Groundwater plume moves preferentially through the high-K zones, and the relatively high ion concentrations along the low-K zones implying deterred groundwater flow. Consequently, the spatial variation of hydraulic conductivity caused by aquifer heterogeneity and anisotropy appears to be the most important factor to maximize the effect of plume treatment system for application of in-situ groundwater remediation techniques.

• Journal of Korea Water Resources Association
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• v.50 no.11
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• pp.795-802
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• 2017

This study shows the assessment methodology for the water resources of subsurface dams. The study area is SSangcheon subsurface dam. It is at the estuary of SSangcheon watershed forming the unconfined alluvial aquifer. there are several candidate area which are geologically similar to it at East coast. The groundwater level was computed by a 2-D FDM model, where the watershed discharge is the input as the infiltration term. The baseflow computed as the mean value of 3 watershed dischrge model is $0.5m^3/sec$. And considering the inflow near the baseflow as the dry season inflow, The groundwater level according to the change of inflow and pumping rate was computed. Specifically, Using the real pumping rate $28000m^3/day$ which is equal to the supply amount of drinking water to Sokcho city, The inflow which induce the descended groundwater level to the bottom of aquifer or the ascended groundwater level that cause the surface flow was eatimated. The simulation for increased pumping rate and additional well construction to increase the water resources, was executed. And at the extreme dry season, available pumping rate was estimated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.4
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• pp.243-248
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• 1993

In this research, unsteady groundwater flow in unconfined and homogeneous three layer aquifers is studied theoretically and experimentally. Numerical solutions are obtained by Runge Kutta and Runge Kutta Gill method after transforming the governing nonlinear partial differential equations to nonlinear ordinary differential equations. Experimental apparatus includes a test section filled with fine, medium and coarse sands. Experimental results are compared with the numerical solutions and both experimental and numerical results correspond well with each other. This numerical approach may be also applied to the cases which have more aquifers.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.509-529
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• 2019

This study performs to evaluate the role of filter material at alluvial well for intake of riverbank filtration and the applicability and improvement effect of dual filter well. To achieve this objective, dual filter intake well and single filter intake well were installed with different filter conditions at riverbank free surface aquifer in soil layer then we evaluated filter material condition, permeability, optimum yield and well efficiency according to yield in drawdown test. As a results, we assumed forming dual filter layer minimizes sudden speed changes at boundary between aquifer and filter layer by cushioning of groundwater flow. This suppresses warm current then intake groundwater efficiently, therefore it seems decreasing peripheral groundwater level changes in spite of higher intake water amount than single filter intake well. Furthermore, we confirmed by test, installing dual filter improves permeability, optimum yield and well efficiency. The result will be used by combining with former study to set up standard of design/construction of dual filter intake well at alluvial aquifer layer. Furthermore, we expect this result will be used to prove application effect of dual filter intake well compared to single filter one and radial collector well which are mainly applied on riverbank filtration.

• The Journal of Engineering Geology
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• v.27 no.4
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• pp.405-416
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• 2017

This study evaluated a model unconfined aquifer comprising a sand or gravel layer, a filter layer, a pumping well, and an observation well. The model was employed in step drawdown tests and then used to assess the permeability of each test tank. The optimal yield and well efficiency were then calculated. Evaluation of yield by step in sand layer filters of equal thickness gave optimized watering rates of 22.03 L/min in the double filter and 19.71 L/min in the single filter. The double filter's yield was 115.0% that of the single filter. A comparison of double and single filters, each 10 cm thick, showed the double filter to have a maximum yield of 182.7%. Yields for the gravel layer were 73.56 L/min for a double filter and 65.47 L/min for a single filter of the same thickness; the former value is 112.3% of that of the latter. Comparison of double and single filters with 10-cm-thick gravel layers revealed that the double filter had a maximum yield of 160.9%. Results for sand wells showed the double filter to have a maximum efficiency of 70.4% and the single filter to have a minimum efficiency of 37.1%. Gravel-layer well efficiencies were >66.5% for both double and single filters (each 30 cm thick), but only 22.5% for a 10-cm-thick single filter. This study confirms that permeability improved as the filter material became thicker; it also shows that a double filter has a higher yield and well efficiency than a single filter. These results can be applied to the practical design of wells.

• Journal of the Korean Association of Geographic Information Studies
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• v.2 no.2
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• pp.45-58
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• 1999

Digital map is utilized for an effective display of the distributions of the hydrogeological variables such as water table height(hydraulic head) and log-transmissivity(lnT) in north Pohang, KyungBug. Specifically the geostatistical method kriging is used to construct the distributions in an unconfined aquifer from a finite set of measured data. The experimental variograms for both the head and lnT suggest spherical models with nugget of 0 and range of 6km. The kriged results by using these variograms show that the head decreases primarily from the west to the east with a large peak in the north-western part and lnT is at the maximum level in the central part with outwardly decreasing trend. The constructed delineation is also used to calculate the flow field in the region. Finite differences with second order consistency are used to calculate the fluxes in the east(x) and north(y) across a vertical cross-section of unit width and height equal to the thickness of the wet zone in the aquifer. It is demonstrated that the flow is dominantly in the east with diverging trend on the eastern hillside of the water table peak. A few convergent spots also appear.

• Journal of Soil and Groundwater Environment
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• v.10 no.6
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• pp.32-44
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• 2005

314 pumping test data of the National Groundwater Monitoring Wells (NGMWs) are analyzed to present statistical properties of fractured-rock and alluvial aquifers of Korea such as distribution of hydraulic conductivity, empirical relations between transmissivity and specific capacity, and time-drawdown patterns of pumping and recovery test. The mean hydraulic conductivity of alluvial aquifers (1.26 m/day) is 17 times greater than that of fractured-rock aquifers (0.076 m/day). Hydraulic conductivity of fracture-rock aquifers ranges in value over 4 orders of magnitude which coincide with representative values of fractured crystalline rocks and shows distinctive differences among rock types with the lowest values for metamorphic rocks and the highest values for sedimentary rocks. In consideration of the estimated transmissivity with some simplifying assumptions, it Is likely that $32\%$ of groundwater flow for NGMWs would occur through fractured-rock aquifers and $68\%$ through alluvial aquifers. Based on 314 pairs of data, empirical relations between transmissivity and specific capacity are presented for both fractured-rock and alluvial aquifers. Depending on time-drawdown patterns during pumping and recovery test, NGMWs are classified into $4\~5$ types. Most of NCMWs $(83.7\%)$ exhibit the recharge boundary type, which call be attributed to sources of water supply such as streams adjacent to the pumping well, the vertical groundwater flux between fractured-rock and the alluvial aquifers, and the delayed yield associated with gravity drainage occurring in unconfined aquifers.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.333-335
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• 2003

Deep Ocean Water is formed within restricted area including polar sea (high latitude) by cooling of surface seawater and globally circulated in the state of insolation with surface seawater. Although not as obvious as estuaries mixing, Brine groundwater is mixture of recirculated seawater and groundwater. Seawater having high osmotic pressure infiltrate into unconfined aquifer where is connected to the sea. The ions dissolved in seawater are present in constant proportions to each other and to the total salt content of seawater. However deviation in ion proportions have been observed in some brine groundwater. Some causes of these exception to the Rule of constant proportions are due to many chemical reactions between periphery soil and groundwater. While Deep Ocean Water (DOW) have a large quantity of functional trace metals and biological affinity relative to brine groundwater, DOW have relatively small amount of harmful bacteria and artificial pollutants.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.711-716
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• 2010

This study selected the promising area of submarine groundwater discharge(SGD) that flows into the sea following unconfined physical aquifer through the electrical resistivity survey of the land and sea. The submarine groundwater discharge(SGD) mostly flows into the sea following fracture zones, and the detection of the fault zone becomes the important guideline of groundwater discharge. Electrical sounding of the land assessed the groundwater flow and integration possibility according to the location of a fault that is a water path between underground reservoir and surface water as well as a rock fracture. In addition, the study conducted sea electrical resistivity to expand the area with high potential and selected the expected water potential groundwater area. The areas of the study were Busan and coastal areas, and for the terrain analysis, the candidates of the ground exploration were selected after analyzing lineaments that is expanded to coast direction.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1173-1177
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• 2004

현재 다양한 분야에서 널리 사용되고 있는 지하투과레이더(Ground Penetrating Radar, GPR)를 이용하여 지하수면 및 함수량을 추정하였다. 비피압대수층 내에서의 얕은 포화대(saturated zone) 깊이을 산정하는 연구(livari and Doolittle, 1994, van Overmeeren, 1994)와 포화대 상부 습윤대(wetting fronts)의 거동를 조사한 연구(Vellidis et al, 1990) 등에 활용된 바 있는 GPR 기숙을 바탕으로 비피압대수층의 통기대와 포화대 내의 함수량 및 지하수면 추정을 위한 기초 실험을 수행하였다. 지하수면 및 함수량의 현장 적용성을 검증하기 위해서는 시간과 경제적인 면에서 비효율적인 점을 고려하여 사질토로 구성된 실험용 토조를 제작하여 건조시 획득된 GPR 자료, 지하수면의 변화에 따른 GPR 이미지를 비교하여 그 적용성을 검토하고 시${\cdot}$공간적 지하수면의 정확한 추정을 위해서 삼차원으로 비교${\cdot}$검토할 수 있도록 하였으며, GPR 자료의 정확성을 검증하기 위해서 토조 하부에 액주계(piezometer)를 설치하였다. 본 연구에서 적용된 GPR 실험은 획득된 이미지의 해석에 다소 어려움이 있지만 토양을 교란시키지 않고 비교적 간편하게 함수랑 및 지하수면의 위치를 파악하는데 매우 효과적이며, 추가적으로 GPR을 이용한 다양한 실험이 수행된다면 GPR 기술은 향후 기존 방법에서 쉽게 판단하기 어려운 시${\cdot}$공간적인 함수량 및 지하수의 분포 특성을 효율적으로 파악하는데 매우 큰 도움을 줄 수 있을 것이다.