• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.119-120
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• 2004

Urban groundwater has a unique hydrologic system because of the complex surface and subsurface infrastructures such as deep foundation of many high buildings, subway systems, and sewers and public water supply systems. It generally has been considered that increased surface impermeability reduces the amount of groundwater recharge. On the other hand, leaks from sewers and public water supply systems may generate the large amounts of recharges. All of these urban facilities also may change the groundwater quality by the recharge of a myriad of contaminants. This study was performed to determine the factors controlling the recharge of deep groundwater in an urban area, based on the hydrogeochemical characteristics. The term ‘contamination’ in this study means any kind of inflow of shallow groundwater regardless of clean or contaminated. For this study, urban groundwater samples were collected from a total of 310 preexisting wells with the depth over 100 m. Random sampling method was used to select the wells for this study. Major cations together with Si, Al, Fe, Pb, Hg and Mn were analyzed by ICP-AES, and Cl, N $O_3$, N $H_4$, F, Br, S $O_4$and P $O_4$ were analyzed by IC. There are two groups of groundwater, based on hydrochemical characteristics. The first group is distributed broadly from Ca-HC $O_3$ type to Ca-C1+N $O_3$ type; the other group is the Na+K-HC $O_3$ type. The latter group is considered to represent the baseline quality of deep groundwater in the study area. Using the major ions data for the Na+K-HC $O_3$ type water, we evaluated the extent of groundwater contamination, assuming that if subtract the baseline composition from acquired data for a specific water, the remaining concentrations may indicate the degree of contamination. The remainder of each solute for each sample was simply averaged. The results showed that both Ca and HC $O_3$ represent the typical solutes which are quite enriched in urban groundwater. In particular, the P$CO_2$ values calculated using PHREEQC (version 2.8) showed a correlation with the concentrations of maior inorganic components (Na, Mg, Ca, N $O_3$, S $O_4$, etc.). The p$CO_2$ values for the first group waters widely ranged between about 10$^{-3.0}$ atm to 10$^{-1.0}$ atm and differed from those of the background water samples belonging to the Na+K-HC $O_3$ type (<10$^{-3.5}$ atm). Considering that the p$CO_2$ of soil water (near 10$^{-1.5}$ atm), this indicates that inflow of shallow water is very significant in deep groundwaters in the study area. Furthermore, the P$CO_2$ values can be used as an effective parameter to estimate the relative recharge of shallow water and thus the contamination susceptibility. The results of our present study suggest that down to considerable depth, urban groundwater in crystalline aquifer may be considerably affected by the recharge of shallow water (and pollutants) from an adjacent area. We also suggest that for such evaluation, careful examination of systematically collected hydrochemical data is requisite as an effective tool, in addition to hydrologic and hydrogeologic interpretation.ion.ion.

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.45-55
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• 2011

We examined the interactions between surface and groundwater through (1) flowmeter logging, (2) measurements of seasonal and vertical changes in temperature within a well, and (3) geochemical analyses of water samples from nine groundwater-monitoring wells. At two wells adjacent to a stream, subsurface water was found to flow from the stream to a surrounding alluvial fan, and the seasonal change in groundwater temperature is similar to those of surface water and air. Geochemical analyses at two wells indicated hydro-geochemical features affected by streamwater inflow, showing seasonal variations. Accordingly, these two wells are located in an area with active interaction between surface water and groundwater. The Thermochron I-button used in the present study is useful for this type of study of groundwater?surface water interaction because of its low cost and small size.

• Journal of Soil and Groundwater Environment
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• v.8 no.1
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• pp.57-67
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• 2003

Nitrate contamination by human activities is a serious problem to water-supply in agricultural area. Shallow groundwater is the main source of water-supply, but it is very sensitive to contamination. Study area for nitrate contamination is a region of Iljuk, Kyunggi where is an agricultural area having many livestock facilities in various scales. As a result, the points having availability of incoming of external contaminant are 77%, and the ones over the Drinking Water Limit (DWL) are 32～42%. For a nitrogen isotope analysis, all the points having availability of incoming of external contaminant have $\delta$$^{15}$ N-NO$_3$ values over 5$\textperthousand$, and the points of 59% are strongly affected by nitrogen originated from animal wastes. The major source of nitrate in this area is intensive livestock facilities. Even though a livestock facility had enclosed, it affects groundwater quality for a long time. The chemical property of contaminant source is various according to animal species in surface water, but not in groundwater since some solutes are removed by reactions during an inflow to subsurface.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.103-109
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• 2020

The inflow rate is of interest in the design of underground structures such as tunnels and buried pipes below the groundwater table. Soil permeability governing the inflow rate significantly affects the hydro-geological behavior of soils but is difficult to estimate due to its wide range of distribution, nonlinearity and anisotropy. Volume changes induced by stress can cause nonlinear stress-strain behavior, resulting in corresponding permeability changes. In this paper, the nonlinearity and anisotropy of permeability are investigated by conducting Rowe cell tests, and a nonlinear permeability model considering anisotropy was proposed. Model modification and parameter evaluation for field application were also addressed. Significance of nonlinear permeability was illustrated by carrying out numerical analysis of a tunnel. It is highlighted that the effect of nonlinear permeability is significant in soils of which volume change is considerable, and particularly appears in the short-term flow behavior.

• Journal of Soil and Groundwater Environment
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• v.28 no.2
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• pp.1-11
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• 2023

Groundwater-surface water interaction was evaluated using water quality parameters (temperature and electrical conductivity), distributions of stable water isotopes (δ²H and δ ¹⁸O), and Rn-222 in lagoon water, groundwater, and seawater at three coastal lagoons (Songji (SJ), Youngrang (YR), and Sunpo (SP) Lagoon) in South Korea. From the results of composition and distributions of δ²H and δ¹⁸O, it was found that groundwater fraction of lagoon water in YR Lagoon (76%) was slightly higher than those of SJ (42%), and SP (63%) Lagoon. Based on Rn-222 mass balance model, groundwater discharge into SJ Lagoon in summer 2020 was estimated to be (3.2±1.1)×10³ m³ day^-1, which showed a similar or an order of magnitude higher than the results of previous studies conducted in coastal lagoons. This study can provide advanced techniques to evaluate groundwater-surface water interaction in coastal lagoons, wetlands, and lakes, and help to determine the effects of groundwater on coastal ecosystems.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.125-148
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• 1993

Groundwater flow in fractured rock masses is controlled by combined effects of fracture networks, state of geostafic stresses and crossflow between fractures and rock matrix. Furthermore the scaie dependent, anisotropic properties of hydraulic parameters results mainly from irregular paftems of fracture system, which can not be evaluated properly with the methods available at present. The basic assumpfion of discrete fracture network model is that groundwater flows only along discrete fractures and the flow paths in rock mass are determined by geometric paftems of interconnected fractures. The characteristics of fracture distribution in space and fracture hydraulic parameters are represented as the probability density functions by stochastic simulation. The discrete fracture network modelling was aftempted to characterize the groundwater flow in the vicinity of existing large cavems located in Wonjeong-ri, Poseung-myon, Pyeungtaek-kun. The fracture data of $1\textrm{km}^2$ area were analysed. The result indicates that the fracture sets evaluated from an equal area projection can be grouped into 6 sets and the fracture sizes are distributed in longnormal. The conductive fracture density of set 1 shows the highest density of 0.37. The groundwater inflow into a carvem was calculated as 29ton/day with the fracture transmissivity of $10^{-8}\textrm{m}^2/s$. When the fracture transmissivity increases in an order, the inflow amount estimated increases dramatically as much as fold, i.e 651 ton/day. One of the great advantages of this model is a forward modelling which can provide a thinking tool for site characterization and allow to handle the quantitative data as well as qualitative data.

• Economic and Environmental Geology
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• v.49 no.5
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• pp.361-370
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• 2016

It is well known that the inflow of rainwater and the infiltration of groundwater to sewerage (I/I) increase the sewage and burden sewage treatment plants and lower their treatment efficiency. Therefore, it is important to estimate the amount of I/I. In this study, well groundwaters, public water supplies (PWSs), and sewage and rainwater channels were investigated to check whether oxygen and deuterium isotopes could be used as a tool for I/I estimation. This study shows that the isotopic composition of PWS in Jeonju area is very consistent over time and distinctly lighter than the circulating local rainwater (CLR) because it is supplied from Yongdam Dam, which is located about 40 km inland to the east in the mountainous area. Considering the fact that sewage mostly originates from the PWS, we could calculate the amounts of CLR in the sewerage from a monitoring station using unaffected rainwater and tap water as mixing end members. The calculation revealed that the CLR fraction ranged from 50% to 90% depending on observation time. This is well supported by the dilute natures of the sewages at the station. The fraction of PWS in investigated well waters were about 46%, indicating that leaking of PWS is very serious and is an important groundwater source in the study area. Since the infiltration of such groundwater may not alter the isotopic composition of sewage significantly, the actual I/I would be much greater than the calculated ones.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.91-99
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• 2011

The turbidity in several wells of Samdong-myeon, Ulsan, exceeded potable groundwater standard (1 NTU). Mineralogical analysis showed that the fine suspended particles are ferrihydrite spheres with a size of less than $0.5\;{\mu}m$ and helical iron-oxidizing bacterial filaments, and their aggregates. Ferrihydrite was almost amorphous only showing two electron diffraction rings, and contained Si and P. Helical bacterial filaments were almost replaced by ferrihydrite. The helical bacteria have played an important role in the ferrihydrite formation by becoming the loci for ferrihydrite precipitation as well as oxidizing ferrous iron. The physicochemical conditions of low pH, low redox potential, high Ca concentration, and high alkalinity are consistent with the hydrogeochemical characteristics of carbonate groundwater, implicating that the inflow of deep ferriferous carbonate groundwater and its oxidation have caused the ferrihydrite turbidity in several wells of the study area.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.21-35
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• 2016

This study is to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for multi-purpose dams and multi-function weirs operation in Namhan river basin ($12,577km^2$) of South Korea. The SWAT was calibrated (2005 ~ 2009) and validated (2010 ~ 2014) considering of 4 multi-purpose dams and 3 multi-function weirs using daily observed dam inflow and storage, evapotranspiration, soil moisture, and groundwater level data. Firstly, the dam inflow was calibrated by the five steps; (step 1) the physical rate between total runoff and evapotranspiration was controlled by ESCO, (step 2) the peak runoff was calibrated by CN, OV_N, and CH_N, (step 3) the baseflow was calibrated by GW_DELAY, (step 4) the recession curve of baseflow was calibrated by ALPHA_BF, (step 5) the flux between lateral flow and return flow was controlled by SOL_AWC and SOL_K, and (step 6) the flux between reevaporation and return flow was controlled by REVAPMN and GW_REVAP. Secondly, for the storage water level calibration, the SWAT emergency and principle spillway were applied for water level from design flood level to restricted water level for dam and from maximum to management water level for weir respectively. Finally, the parameters for evapotranspiration (ESCO), soil water (SOL_AWC) and groundwater level fluctuation (GWQMN, ALPHA_BF) were repeatedly adjusted by trial error method. For the dam inflow, the determination coefficient $R^2$ was above 0.80. The average Nash-Sutcliffe efficiency (NSE) was from 0.59 to 0.88 and the RMSE was from 3.3 mm/day to 8.6 mm/day respectively. For the water balance performance, the PBIAS was between 9.4 and 21.4 %. For the dam storage volume, the $R^2$ was above 0.63 and the PBIAS was between 6.3 and 13.5 % respectively. The average $R^2$ for evapotranspiration and soil moisture at CM (Cheongmicheon) site was 0.72 and 0.78, and the average $R^2$ for groundwater level was 0.59 and 0.60 at 2 YP (Yangpyeong) sites.

• Journal of Environmental Science International
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• v.27 no.8
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• pp.651-663
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• 2018

The hydrochemistry of groundwater from 47 wells in the Chungwon area, Korea was analyzed to examine the occurrence of natural radionuclides like uranium and radon. The range of Electrical Conductivity (EC) value in the study area was $67{\sim}1,404{\mu}S/cm$. In addition to the high EC value, the content of cations and anions also tends to increase. Uranium concentrations ranged from $ND{\sim}178{\mu}g/L$ (median value, $0.8{\mu}g/L$) and radon concentrations ranged from 80~12,900 pCi/L (median value, 1,250 pCi/L). Uranium concentrations in one well, that is 2.8% of the samples, exceeded $30{\mu}g/L$, which is the Maximum Contaminant Level (MCL) proposed by the US Environmental Protection Agency (EPA), based on the chemical toxicity of uranium. Radon concentrations in three wells, that is 6% of the samples, and one well, that is 2.8% of the samples, exceeded 4,000 pCi/L (AMCL of the US EPA) and 8,100 pCi/L (Finland's guideline level), respectively. Concentrations of uranium and radon related to geology of the study area show the highest values in the groundwater of the granite area. The uranium and radon contents in the groundwater were found to be low compared to those of other countries with similar geological settings. It is likely that the measured value was lower than the actual content due to the inflow of shallow groundwater by the lack of casing and grouting.