• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.36-43
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• 2007

In the case of single well pumping tests the storativities are generally overestimated. To compensate these errors, the effective wellbore radius should be introduced as a distance to an imaginary observation well in the time-drawdown analysis. Effective wellbore radius can be calculated through step drawdown tests or using skin factor equation. But both are of trial-and-error methods guessing real storativity values and, therefor, are difficult to apply to the field conditions. An equation was developed to estimate effective wellbore radius from storativity values obtained from pumping well data. For this study, a total of 136 time-drawdown data set were used to derive the equation. The effective wellbore radius were estimated first by changing them till the storativity values obtained from the pumping-well data match the ones based on the observation-well data. Then the equation was regressed from the relation between effective wellbore radius and the storativity values obtained from the pumping-well data. It is believed that the equation would be useful in estimating effective wellbore radius from the single well tests.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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• pp.81-84
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• 2000

Two-layer aquifer system with fractional flow dimension is composed of contiguous two layers: Layer 1 (lower layer) and Layer 2 (upper layer) with different permeability and specific storage each other. For this aquifer system, we assume that groundwater flow originates only from Layer 1 on the pumping well. The aquifer system considers wellbore storage and skin effects on the pumping well. Dimensionless drawdown curves for different flow dimensions are analyzed for different lambda (λ, crossflow coefficient) values, kappa ($textsc{k}$, permeability ratio between Layer 1 and Layer 2) values and omega ($\omega$, storativity ratio between Layer 1 and Layer 2) values. The curves for Layer 1 and Layer 2 show characteristic trend each other.

• Journal of Soil and Groundwater Environment
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• v.13 no.3
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• pp.15-20
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• 2008

The investigation on the previous paper(Jn. of KoSSGE vol.12, no.3), which proposed three empirical equations for the different aquifers was carried out. To draw out a single equation from the three different equations the mean value of the involution factors was adopted allowing different proportional coefficients for the different aquifers. On the other hand it was found that the square root value of storativity ratio, ${\sqrt{{S_p}/{S_o}}}$ in each well is almost equal to its wellbore radius ratio, ${r_e}/{r_w}$. From this fact, the proportional coefficients can be substituted with assumed aquifer storativity and a generalized empirical equation for the effective wellbore radius has been derived.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.61-64
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• 2005

The calculated characteristics of groundwater within the Youngsan river basin are : casing depth-17.1m, well depth-74.8m, natural water-2.6m, pumping water-43.9m, yields-391$m^3/D$, transmissivity-16.3$m^3/D/m$, storativity-0.068. As far as hydrogeological units are concerned, in casing depth, weathered granites are deepest followed by gneiss, volcanics, and sediments. In major aquifer development areas, sediments are deepest followed by volcanics, granites and gneiss in more shallow areas, Altogether, the major aquifar development depth of the Youngsan river basin is within the $35{\sim}60m$ range.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.592-596
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• 2003

연구지역에서 설치된 6개의 관정을 대상으로 양수시험을 실시하였다. Neuman method를 이용하여 연구지역의 투수량계수(transmisivity)와 저유계수(storativity) 및 비산출율(specific yield)을 구한결과 투수량계수는 1$\times$$10^{-6}$~9.135$\times$$10^{-6}$ $m^2$/s 이며, 저유계수는 0.0002~0.0085, 비산출율은 0.3~0.4의 값을 보인다. 계산된 투수량 계수를 이용하여 수리전도도(hydraulic conductivity)를 구하였다. 양수정의 심도보다. 깊은 관정에서 계산된 수리상수 값은 큰 값을, 얕은 관정에서는 작은 값을 보여 양수시험시 양수정과 관측정의 깊이에 대해 고려가 필요하다.

• Economic and Environmental Geology
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• v.44 no.3
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• pp.239-246
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• 2011

Groundwater in small islands is used as main water resource but the overuse of groundwater may cause seawater intrusion and temperature decrease in geothermal wells. This study aimed to characterize the hydrogeology of Maeum-ri area in Seokmo Island of Ganghwagun using long-term monitoring at groundwater wells and geothermal wells. In the monitoring period seasonal water level change, consistent drop or increase of water levels are not detected. The groundwater temperature about 10m below ground surface shows year cycle variation having two to five months difference with ambient temperature cycle. The storativity was calculated by tidal method. The storativity estimated by adapting tidal efficiency factor showed some larger values than that by using tidal time lag. The result suggested that the tidal method assuming several assumptions on aquifer condition may produce broad ranges but the calculated ranges at this application are reasonable. The similar shape of groundwater level change and tidal effects was observed at several wells clustered east-south-east direction which may implicate the distribution of vertical fracture system strongly related with groundwater flow channels. The applied methodology and study results will bc valuable to evaluate optimal pumping rate for the preservation of groundwater resources, and to manage geothermal development.

• 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.

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.27-38
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• 2000

We hydrogeologically studied a mountainous area and its vulnerability to groundwater contamination. Groundwater flow and recharge occur mainly through a network of fractures in this areaTransmissivity and storativity obtained from slug, slug interference, and pumping tests range from 3.2$\times$10$^{-3}$ to 2.0$\times$10$^{-2}$$m^2$/min and 1.3$\times$10$^{-7}$ to 9.15$\times$10$^{-4}$, respectively. The groundwater was contaminated bylivestock activities in the upgradient. The groundwater in the downgradient residential area wasthreatened by the upgradient livestock activities.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.85-89
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• 2005

Lineament maps are the important tools that may reveal points of groundwater recharge, flow and development. In particular, groundwater flows and yields in mountainous area, composed of crystalline rocks with many fractures, are governed mainly by the lineaments corresponding to fractures, joints and faults. Lineaments may give important information on the best distribution of wells and their management. For two districts; Pohang and Cheonan, the relationship between lineament and groundwater factors was analyzed. To compare groundwater productivity, storativity, and transmissivity of a well site along the distance to lineament, the distances to lineament was regrouped into five groups with an equal range, 100m, for the Pohang district and they are also divided into five groups with an equal range, 150m, for the Cheonan district. From the results of the Spearman Rank Correlation Analysis and Kendall Analysis for each group, the means of SPC and T of wells which are located near lineaments generally have large values. The means of SPC and T show a reverse linear relationship with a lineament distance, but the means of S shows a disperse distribution and no distinct linear relation. Result of the linear regression model between SPC and lineament length density shows that it will be effective to use the lineament length density map when finding the optimal well site on a regional scale.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.111-120
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• 1999

Leachate flow behavior due to intermediate cover soil of low hydraulic conductivity and the applicability of pumping method for reducing the leachate level in the landfill are analyzed with the numerical flow model, MODFLOW. Using the hydraulic conductivity and storativity data obtained from the field pumping and slug tests(Jang and Cho, 1999), the hydraulic condition within the landfill is validated. The optimum rate of pumping, the radius of influence, and the efficiency of horizontal drain are analyzed for reducing the leachate level in the landfill. From the results of the analyses, the barrier effect that the buried cover soil of low hydraulic conductivity prevents the vertical movement of leachate flow through the cover soil, which is found from the in-situ geotechnical studies(Jang and Cho, 1999), is identified again. Also, the installation of horizontal drains to the pumping well can increase the pumping rate from 120 ton/day per a well to 300 ton/day. The length of horizontal drain did not influence significantly on the drawdown-time curve of leachate in the landfill.