• Geophysics and Geophysical Exploration
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• v.9 no.3
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• pp.225-230
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• 2006

Fluid replacement and conductivity logging have been applied to three boreholes in coastal aquifer in order to identify permeable fractures and to estimate the origin of saline groundwater. Fluid replacement technique measures and monitors the change of borehole fluid conductivity with depth under ambient or pumping condition after replacing the original borehole fluid with different one (by pumping out original one and injecting simultaneously new one at the hole bottom). After the replacement of borehole fluid, the change of fluid conductivity can be the direct indicator of the intake flow of formation water through aquifer such as permeable fractures or porous formations. The conductivity profiles measured with times therefore indicate the locations of permeable zone or fractures within the open hole or the fully slotted casing hole. As a result of fluid conductivity logging for three boreholes at coastal area in Yeonggwang, Jeonam Province, it is interpreted that the seawater intrusion in this area is not by remnant saline groundwater after land reclamation but mainly by intrusion of saline water through fractured rock. This approach might be useful for assessing the characteristics of seawater intrusion, the design of optimal pumping, the mitigation of seawater intrusion using freshwater injection, and estimating the hydraulic characteristics in coastal aquifer.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.505-513
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• 2016

The qualitative distribution of a fractured aquifer was characterized by electrical resistivity surveying as a part of basic groundwater investigation in Jangseong. The results were then used to choose sites for observation wells. The locations and distributions of permeable discontinuities were studied by analyses of temperature logs, a borehole image-processing system (BIPS), and hydraulic pressure testing using a double packer. The pressure test showed that the size of the discontinuities correlated with the Lugeon value and the results of the temperature log. The results show that temperature measurement is an effective method to identify permeable discontinuities, with the temperature difference correlating with the size of the aperture of the discontinuity.

• Journal of Soil and Groundwater Environment
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• v.18 no.6
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• pp.48-55
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• 2013

This study aimed at characterizing unsaturated zone at the source zone area contaminated by DNAPL and investigating feasibility of soil vapor extraction (SVE). Five boreholes with three multi-level screens at the depth of 3.0~4.5 m, 5.5~7.0 m, and 8.0~12.0 m were installed at the source zone. Pneumatic tests were performed to determine the permeability of porous medium. Permeability was estimated to be 81.6 to 203.7 darcy, depending on the applied solutions, which was contradicted by grain size analysis of cored soil samples leading to 3.51 darcy. This is due to air flow through gravel pack during the early stage of pneumatic test. Pressure-drawdown curve in the late stage also well showed the leaky aquifer type, indicating air leakage to the ground. Air flow tests were also carried out to investigate air flow connectivity between multi-level wells, indicating that the horizontal air flow was well developed between the lower screens of the wells, not between the upper and middle screens due to the leakage to the surface. For the SVE test, there was no noticeable variation in TCE vapor concentration between three different test runs: 1. 8 hours daily for 5 days, 2. 24 hours together with air blowing at another well (BH1), 3. five consecutive days. Even for five-day consecutive test, total amount of removed TCE was estimated only to be as low as 46.5 g.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.11-21
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• 2013

In-situ test to find the change of $Fe^{2+}$ and $Mn^{2+}$ concentrations and ion contents in groundwater was conducted during two pumping tests at the riverbank filtration site, where is the riverine area of the Nakdong River in Changnyeong-Gun. Groundwater was sampled at one pumping well and 10 monitoring wells during a 5 steps drawdown pumping test with the rates from $500m^3/day$ to $900m^3/day$ and a constant pumping test with $800m^3/day$. The change in ion concentration of groundwater was more remarkable during a step drawdown pumping test than a constant pumping test. Especially, the decrease in $Fe^{2+}$ and $Mn^{2+}$ concentrations was distinct in a step drawdown pumping test and it happens predominantly along the direction that the radius of pumping influence was small due to a good aquifer connectivity to a pumping position. The precipitation and the oxidation of iron and manganese were caused by an air inflow and a disturbance in groundwater flow due to an abrupt change in pumping rate. The pumping rate and spatial distribution of an aquifer around a pumping well need to be considered as an important factor for the development of in-situ iron and manganese treatment technology.

• Water for future
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• v.18 no.1
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• pp.85-94
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• 1985

A method is developed for the separation of the major base flow in a river hydrograph combining the numerical techniques and the empirical methods. The linearized Boussinesq equation and the storage function are used to obtain the base flow recession. The shape of base flow curve made by the recharge of the groundwater table aquifer resulting from rainfall in determined by the Singh and Stall's graphical method, and the continuous from for the curve is approximated by the multiple and polynomial regression. this procedure was successfully tested for the separation of base flow and the establishment of hydrograph in a natural watershed. It was found that the direct numerical method applied to the homogeneous linear second order ordinary differential equation system is not suited to obtain the recession curve, and the case that the loss is generated in the partially penetrating stream can not be solved by the method of this study.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.189-200
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• 1991

The purpose of this study is to examine the cut-off effect in aquifer by chemical grouting. Moreover, injection tests using specially prepared injection equipment of 1.5 shot system which hydrauric condition can be controlled are attempted to investigate the cut-off effect by confirming the gelling condition of samples according to the variation of flow velosity. And the permeability is measured according to changing of time by falling head test in order to consider the durability of grouts. Therefore to increase the cut-off effect in groundwater flow, shortening the gel-time according to the increasement of flow velocity, increasing the concentration and quantity of grouts(grouting ratio) according to the increasement of that, and as another direct method, contracting the distance between grouting holes or enlarging the grouting line should be done. These coefficients should be designed by data based on injection test in laboratory and field.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.375-380
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• 2013

The concept of safe yield places an emphasis on balancing groundwater withdrawal with groundwater recharge but ignores naturally occurring groundwater discharge. Because streams and their alluvial aquifers are closely linked in terms of water supply and water quality, to be properly understood and managed they must be considered together. Therefore, some districts in Kansas have reevaluated their safe-yield policies to account for natural groundwater discharge and stream-aquifer interactions by amending their safe-yield regulations to include a portion of baseflow as the minimum desirable streamflow (MDS). This study proposes a modified safe-yield policy in which the drought flow is chosen as the MDS. Baseflow separation was conducted from streamflow hydrograph and the results are presented as a flow-duration curve. The exploitable groundwater can be determined by subtracting MDS from the cumulative baseflow. This method was tested in the Musimcheon watershed, which was validated for streamflow using the SWAT-K model. The annually averaged exploitable groundwater in the whole watershed was estimated to be 86 mm. The exploitable groundwater amounts were also estimated for each subwatershed in the Musimcheon watershed.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.657-672
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• 2008

The purposes of this study are to investigate the hydrogeochemical characteristics of groundwaters around Keumsan municipal landfill, and to evaluate the contaminant dispersion from the landfill and its environmental impact. To achieve these goals, groundwater quality logging, hydrochemical analysis, multivariate statistical analysis, and contaminant transport modeling were performed. The water quality logging indicated a leaking from the landfill at the depth of 4-12m around a leachate sump. Electrical conductivity data indicated that groundwaters within 70-100m from landfill were affected by the landfill leakage. Principal components 1 and 2 obtained from principal components analysis (PCA) reflect the influence of leachate and the characteristics of aquifer media, respectively. The results of principal component analysis also indicated the natural attenuation processes such as cation exchange, sorption, and microbial biodegradation. The modeling results showed that groundwater flow westward along a valley from the landfill and contaminants transport accordingly.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.23-34
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• 1997

The Nanji-Do ladnfill is an ill-conditioned reclaimed land without pollution intercepting facilities, and has high ground water table and deep stratum. The purpose of this study is to analyze the solute transport in steady-state groundwater flow and to predict the solute dispersion in Nanji-Do landfill using HST-3D model. As results, the groundwater flows radially outward from the center of No. 1 and No. 2 landfills, and large amount of runoff is moved into Han River. The predicted relative concentration of total dissolved solute(TDS) at two years later was 0.25 in the weathering zone, 0.26 in the lower alluvium, and 0.28 in the upper alluvium. Thus, the further pollution to bottom rock and Han River was predicted by comparing the corresponding present values of 0.29, 0.32 and 0.35.