• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.383-391
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• 2020

In this study, Hunt's analytical solution and Ward & Lough's analytical solution for two-layered leaky aquifer system were used to estimate stream depletions due to shallow and deep groundwater pumping, and their differences were compared. Depending on the combination of the separation distance between the stream and the well, the transmissivity and the storage coefficient of the aquifer, and the leakage coefficient between the upper and lower layers, the stream depletion, which is the amount of stream water reduction compared to the amount of groundwater pumping, for each of 45,000 cases was calculated for both shallow and deep groundwater pumping, and the differences were analyzed quantitatively. When the leakage coefficient was very small, with a value of 10^-61/d, the difference in the average five-year stream depletion due to the pumping of shallow and deep groundwater showed a large deviation of up to 0.9 depending on the given hydraulic characteristics; this value exponentially decreased as the stream depletion factor (SDF) increased. This exponential relationship gradually weakened as the leakage coefficient increased due to interaction effects between layers, resulting in a small difference of up to 0.2 when the leakage coefficient reached 10^-31/d. Under the condition of greater interlayer hydraulic connectivity, there was little influence of the depth of groundwater pumping on the stream water reduction.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.36-39
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• 2002

온양온천 지역 지하수에 대한 수질 조사결과, 심부 피압대수층에서 산출되는 온천수의 수질이 천층의 저온지하수에 강하게 영향을 받고 있음이 확인되었다. 본 연구에서는 이들 두 종류의 물 사이에서 매우 높은 상대적인 농도차이를 보이는 불소이온농도를 이용하여 천층지하수의 영향정도를 정량화할 수 있었다. 이 같은 방법으로 계산된 천층지하수 영향정도는 온천수취수정에 따라 다르게 나타나고 있었으나, 최소 10 %에서 최대 50%에 이르는 것으로 확인되었다. 이와 같은 관찰결과는 오염에 취약하지 않은 것으로 알려진 심부의 피압대수층도 과도한 양수가 이루어지게 되면 오염에 취약한 천층부의 지하수를 다량 심부로 유입시킴으로써, 점차 오염되어질 수 있음을 보여주는 것이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.220-220
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• 2019

천부대수층-심부대수층-하천-양수정 시스템에 대해 개발된 Ward & Lough 해석해와 국내 시험유역을 대상으로 개발된 양수량 대비 하천수 감소량 산정공식 (한강홍수통제소, 2018)을 광주천인근에 실제로 위치한 지하수 관정에 적용하여 지하수 취수로 인해 하천의 수량에 미치는 영향을 분석하였다. 분석 대상관정은 하천에서 약 67 m 떨어진 공업용수 공급을 위한 지하수개발 이용시설로서 착정심도 100 m, 착정구경 150 mm, 취수계획량 $200m^3$/일, 수중펌프 5 Hp 등의 시설제원을 가진다. 해석해 및 경험공식 적용을 위한 기본 입력자료로 투수량계수, 저류계수 등의 수리상수값은 해당 관정의 지하수개발 이용 영향조사서에서 발췌하였고, 측정되지 않은 일부 입력값은 문헌조사를 통해 적절한 값을 가정하여 사용하였다. 하천의 수량에 미치는 지하수 양수 영향을 예측한 결과 지하수 허가기간 5년동안 취수계획량의 약 80 %를 넘는 하천수 감소율이 발생하는 것으로 분석되었다. 연구 대상관정과 같이 하천에 매우 근접한 지역에서 지하수를 이용할 경우 하천수 취수에 준하는 영향을 보일 수 있기 때문에 수자원의 효율적인 이용을 위해서는 하천수와 하천 인근 지하수의 통합적 관리가 필요할 것이다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.280-283
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• 2005

한국원자력연구소 내 심부시추공(YS-01, 500m)에 설치된 다중패커시스템(multi-packer system)을 이용하여 양수(pumping) 시 GL. $-457.5{\sim}-500m$ 구간의 지하수에 대한 중요한 지화학 파라미터인 pH, 산화-환원전위, 용존산소 및 전기전도도 등을 장기간 측정하였다. 이에 따르면 현장측정자료는 시간이 경과함에 따라 변화되며 장시간이 경과된 후에 안정화됨을 보여주고 있다. 특히, 산화-환원전위의 경우는 10일이 경과되었음에도 계속 변화하고 있다. 심부지하수 뿐만 아니라 일반 지하수의 경우에도 이러한 파라미터 측정 시 안정화시간에 대하여 유의하여야 할 것이다.

• Tunnel and Underground Space
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• v.34 no.4
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• pp.312-329
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• 2024

In various underground research projects such as energy storage and development and radioactive waste disposal targeting deep underground, the characteristics of permeable rock fractures that serve as major pathway of groundwater flow in deep rock aquifer are considered as an important evaluation factor in the design, construction, and operation of research facilities. In Korea, there is little research and database on the location and hydraulic characteristics of permeable rock fractures and the pattern of groundwater flow patterns that may occur between fractures in deep rock boreholes. In this paper, the hydraulic characteristics of permeable rock fractures in deep rock aquifer were evaluated through the analysis of geothermal gradient and pumping test data. First, the deep geothermal distribution was identified through temperature logging, and the geothermal gradient was obtained through linear regression analysis using temperature data by depth. In addition, the hydraulic characteristics of the fractured rock were analyzed using outflow temperature obtained from pumping tests. Ultimately, the potential location and hydraulic characteristics of permeable rock fractures, as well as groundwater flow within the boreholes, were evaluated by integrating and analyzing the geophysical logging and hydraulic testing data. The process and results of the evaluation of deep permeable rock fractures proposed in this study are expected to serve as foundational data for the successful implementation of underground research projects targeting deep rock aquifers.

• Journal of Soil and Groundwater Environment
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• v.11 no.3
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• pp.20-30
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• 2006

Hydrogeochemistry of deep geothermal water (temperature: $42.2-47.9^{\circ}C$) at Heunghae, Pohang was evaluated using core logging, temperature and electrical conductivity (EC) logging before and after pumping tests, chemical analysis of geothermal water with depth, and observation of water quality variations during pumping tests. The geology of the area is composed of highly fractured marine sedimentary rocks. The hydrogeochemistry of geothermal water varies with drilling depth, distance from the coast, and pumping duration. According to the temperature and EC variations during 4 times of pumping tests, main aquifer of the area is considered as the fractured zones (540 to 900 m) developed in rhyolitic rocks. The high content of Na and $HCO_3$ in geothermal water can be explained by the inflow of deep groundwater from inland regulated by dissolution of silicates and carbonates. High TDS, Na and Cl concentrations indicate that the geothermal water was also strongly affected by seawater. The molar ratios of Na:Cl ($0.88{\sim}2.14$) and Br:Cl ($21.0{\sim}24.9{\times}10^{-4}$) deviate from those of seawater (0.84 and $34.7{\times}10^{-4}$, respectively), suggesting that water-rock interaction also plays an important role in the formation of water quality.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.769-777
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• 2016

The objective of this study was to evaluate the stream depletion from groundwater pumping in deep aquifer using the Ward and Lough's analytical solution (2011) which considers a two-layer leaky aquifer system. The calculated results for each pumping from the 110 wells beside streams showed a wide range of non-dimensional stream depletion, that is the streamflow depletion rate divided by the groundwater pumping rate, from lower than 0.1 to more than 0.9 on average for 5 years depending on the specific properties of well location. From the comparison with Hunt's solution (1999) of a single layer aquifer, the Ward and Lough's solution showed about 50% lower than the Hunt's solution due to the difference of hydraulic properties between the first and second layers as well as the lagged effect of vertical leakance. It was also found that the groundwater pumping has a minor effect on the stream depletion if the stream depletion factor (SDF) of the 1st layer is higher than about 1,000 or the SDF of the 2nd layer is higher than about 100, or the vertical leakance is smaller than $10^{-5}s^{-1}$. Furthermore, in the present study, the variations of the stream depletion were assessed according to the magnitude of unmeasured hydraulic properties such as transmissivity and storage coefficient of the 1st layer, vertical hydraulic conductivity of the 2nd layer, the streambed hydraulic conductance.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.415-419
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• 2005

대수층 저장 및 회수(ASR)기술의 현장 적용성을 평가하기 위하여 경상북도 울릉군 울릉읍 저동천 상류부근에서 양수시험 및 주입시험을 실시하였다. 양수시험결과 투수계수는 $48.7m^2/day$ 이고, 저류계수는 0.009이며, 비양수량은 $158.2m^2/day$로 계산되었다. 또한 시험정과 관측정은 거의 위상차 없이 같은 수위강하 경향을 보여주며 취수정은 관측정보다 평균적으로 10cm 정도 더 높은 수위강하 폭을 보여주는 것으로 미루어 볼 때 시험정과 관측정의 두 지점은 서로 수리지질학적으로 긴밀히 연결되어 있는 하나의 시스템임을 강하게 시사한다. 이외에도 주입시험 결과 암반구간 대수층은 낮은 투수계수를 가질 뿐만 아니라 낮은 저류계수를 가지기 때문에 ASR에 불리한 조건을 가짐을 알 수 있다. 그러나 상부 충적층 구간에서 실시한 주입시험 결과, 두 지점은 긴밀히 연결된 하나의 시스템으로 두 지점의 심부 암반층과의 연결성은 없고, 대신 상부의 높은 투수계수를 가지는 충적층 구간이 두 지점사이에 서로 긴밀히 연결되어 있는 것으로 파악된다. 또한 잔류 수위가 0으로 떨어지는 것으로 볼 때 주입된 주입수는 저장되지 않고 인근의 저동천으로 빠져나가는 것으로 사료된다. 이상의 사실로 볼 때 본 연구지역은 ASR에 불리한 조건을 가지는 지역으로 최종적으로 판단된다.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.103-115
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• 2000

The formation of brown-colored precipitates is one of the serious problems frequently encountered in the development and supply of groundwater in Korea, because by it the water exceeds the drinking water standard in terms of color. taste. turbidity and dissolved iron concentration and of often results in scaling problem within the water supplying system. In groundwaters from the Pajoo area, brown precipitates are typically formed in a few hours after pumping-out. In this paper we examine the process of the brown precipitates' formation using the equilibrium thermodynamic and kinetic approaches, in order to understand the origin and geochemical pathway of the generation of turbidity in groundwater. The results of this study are used to suggest not only the proper pumping technique to minimize the formation of precipitates but also the optimal design of water treatment methods to improve the water quality. The bed-rock groundwater in the Pajoo area belongs to the Ca-$HCO_3$type that was evolved through water/rock (gneiss) interaction. Based on SEM-EDS and XRD analyses, the precipitates are identified as an amorphous, Fe-bearing oxides or hydroxides. By the use of multi-step filtration with pore sizes of 6, 4, 1, 0.45 and 0.2 $\mu\textrm{m}$, the precipitates mostly fall in the colloidal size (1 to 0.45 $\mu\textrm{m}$) but are concentrated (about 81%) in the range of 1 to 6 $\mu\textrm{m}$in teams of mass (weight) distribution. Large amounts of dissolved iron were possibly originated from dissolution of clinochlore in cataclasite which contains high amounts of Fe (up to 3 wt.%). The calculation of saturation index (using a computer code PHREEQC), as well as the examination of pH-Eh stability relations, also indicate that the final precipitates are Fe-oxy-hydroxide that is formed by the change of water chemistry (mainly, oxidation) due to the exposure to oxygen during the pumping-out of Fe(II)-bearing, reduced groundwater. After pumping-out, the groundwater shows the progressive decreases of pH, DO and alkalinity with elapsed time. However, turbidity increases and then decreases with time. The decrease of dissolved Fe concentration as a function of elapsed time after pumping-out is expressed as a regression equation Fe(II)=10.l exp(-0.0009t). The oxidation reaction due to the influx of free oxygen during the pumping and storage of groundwater results in the formation of brown precipitates, which is dependent on time, $Po_2$and pH. In order to obtain drinkable water quality, therefore, the precipitates should be removed by filtering after the stepwise storage and aeration in tanks with sufficient volume for sufficient time. Particle size distribution data also suggest that step-wise filtration would be cost-effective. To minimize the scaling within wells, the continued (if possible) pumping within the optimum pumping rate is recommended because this technique will be most effective for minimizing the mixing between deep Fe(II)-rich water and shallow $O_2$-rich water. The simultaneous pumping of shallow $O_2$-rich water in different wells is also recommended.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.2
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• pp.159-166
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• 2010

The block-scale groundwater flow system at Olkiluoto site in Finland was simulated. The heterogeneous and anisotropic hydraulic conductivity field for the domain was constructed from the discrete fracture network, which considered only the fractured zones identified in the deep boreholes installed in the study site. The groundwater flow model was calibrated by adjusting the recharge rate and the transmissivities of the fractured zones to fit the calculated hydraulic heads and into- and out-flow rates in the observation intervals of the boreholes with the observed ones. In the calibrated model, the calculated flow rates at some intervals were not in accordance with the observed ones although the calculated hydraulic heads fit well with the observed ones, which revealed that the number of the conduits for groundwater flow is insufficient in the conceptual model for groundwater flow modeling. Therefore, it was recommended that the potential local conduits such as background fractures should be added to the present conceptual model.