• Journal of the Korean Geographical Society
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• v.41 no.6 s.117
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• pp.670-681
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• 2006

The purpose of this study is to clarify the behavior of subsurface water flow during rainfall on the hillslope in the Dongguneung experimental basin. As a result of the study, the following conclusions were obtained. Under the total rainfall of 20mm, there were no groundwater level changes. However, it was found that total rainfall amount and rainfall intensity were important factors to change groundwater level in hilly slope. Also the rainfall duration and preexisted rainfall amount were important factors to change it on the head hollow. To analyze the modification of 'U-shaped Gol' landform, the pattern of return flow and through flow have to check during storm events. The microgeomorphic change of head hollow is based on the pattern of subsurface water flow.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.406-411
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• 2014

Serious problems in reclaimed land agriculture are high soil salinity and poor vertical drainage, so desalinization in these soils is very difficult. Also, although desalinization is accomplished in reclaimed top soils, before long, soils are resalinized according to capillary rise of salts from the subsurface soils. To resolve these problems, multi-layered soil columns with subsurface layer of macroporous medium utilizing coal bottom ash (CBA) were constructed and the effects of blocked resalinization of these soils were investigated. In this experiment soil samples were collected from Munpo series (coarse-loamy, nonacid, mixed, mesic, typic Fluvaquents). The soil texture was silt loam and the EC was $33.9dS\;m^{-1}$. As for groundwater seawater was used and groundwater level of 1 cm from the bottom was maintained. The overall rate of capillary rise was $2.38cm\;hr^{-1}$ in soil 60 cm column, $0.25cm\;hr^{-1}$ in topsoil (30 cm) + CBA (5 cm) + subsurface soil (10 cm) column and $0.08cm\;hr^{-1}$ in topsoil (30 cm) + CBA (10 cm) + subsurface soil (10 cm) column. In multi-layered soil columns with CBA 20, 30 cm layer, wetting front due to capillary rise could not be seen in top soil layer. After 70 days capillary rise experiment water soluble Na+ accumulated in top soil of soil columns with CBA 20, 30 cm was diminished by 92.8, 96.5% respectively in comparison with Na+ accumulated in top soil of soil 60 cm column because CBA layer cut off capillary rise of salts from the subsurface soil. From these results we could conclude that the macroporous layer utilizing CBA placed at subsurface layer cut off capillary rise of solutes from subsurface soil, resulting in lowered level of salinity in top soil and this method can be more effective in newly reclaimed saline soil.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.1
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• pp.67-86
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• 1980

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.6
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• pp.450-458
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• 1991

The thermal structures and their spatio-temporal fluctuations in the upper 200m layer off the southeast coast of Korea are studied using the bimonthly temperature data for 17years(1967-1983) at 37 stations. We analyzed the fluctuations of the temperatures in the surface(0-100m) and in the subsurface(100-200m) layers. The fluctuations of temperatures in the surface water are dominated by the annual variation, whereas the subsurface layer temperatures contain considerable non-seasonal fluctuations. The distributions of water temperature anomalies in the subsurface layer are closely related with those in the surface layer. The predominant periods of temperature fluctuations in the subsurface layer, other than the annual variation, are 14 and 70 months. The period of 14 months coincides with that of the pole tide or Chandler wobble. The cluster analysis shows that our study area can be divided into the cold, the frontal and the warm regions.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.305-312
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• 2017

The most effective way to distinguish subsurface interfaces that produce various geophysical responses is through the integration of multiple geophysical methods, with each method detecting both a complementary and unique set of distinct physical properties relating to the subsurface. In this study, shallow seismic reflection (SSR) and ground penetrating radar (GPR) surveys were conducted at the Cheongju-Gadeok site of the Korea National Groundwater Monitoring Network to map the water table, which was measured at 12 m depth during the geophysical surveys. The water table proved to be a good target reflector in both datasets, as the abrupt transition from the overlying unsaturated weathered rock to the underlying saturated weathered rock yielded large acoustic impedance and dielectric constant contrasts. The two datasets were depth converted and integrated into a single section, with the SSR and GPR surveys conducted to ensure subsurface imaging at approximately the same wavelength. The GPR data provided detailed information on the upper ~15 m of the section, whereas the SSR data imaged structures at depths of 10-45 m. The integrated section thus captured the full depth coverage of the sandy clay, water table, weathered rock, soft rock, and hard rock structures, which correlated well with local drillcore and water table observations. Incorporation of these two geophysical datasets yielded a synthetic section that resembled a simplified aquifer model, with the best-fitting seismic velocity, dielectric constant, and porosity of the saturated weathered layer being $v_{seismic}=1000m/s$, ${\varepsilon}_r=16$, and ${\phi}=0.32$, respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.19 no.3
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• pp.4449-4461
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• 1977

Subsurface Drinage Problems arise from many causes. Flatland tends to be poorly drained, particularly where the subsoil permeability is low. There are many wet areas, however, where there is no evident connection between the area of seepage, or a high water table, and the topography of the site. High water tables may occur where the soil is either slowly or rapidly permeable, where the climate is either humid or arid, and where the land is either sloping or flat. This study is to bring light on subjects relating to increasing yield of crop and possibility of double crops a year in water logging paddy fields. Obtained results are briefly summarized as follows: 1. Effect of crop-yield in the plot A resulted 20.2 percent higher than the ordinary plot with yield of brown rice. 2. Possibility of double-crops a year is investigated. Effect of the barley production of the test plot resulted 168.2 percent higher than the other uplands near test plot with the yield of 1977 production and it is 3.8 percent higher compare with the yearly yields. 3. Decreasing depth of water level was measured 23.9mm per day and 14.3mm per day at the test plot and ordinary plot respectively and the amounts of subsurface drainage measured 30mm to 35mm per day. It is required that the relief well should be controled carefully and adequately. 4. Mean depth of ground water levl was measured 0.4∼0.5m regardless the width of corrugated pipe. It is significantly lowere than the ordinary plot(0.15∼0.20m) 5. The ground temperature of the test plot is higher 1 degree of centigarade or more than the ordinary plot and soil moisture content of the ordinary plot is higher 12.4∼27.8 percent than the plot reversely. There should be a relationship between rising of ground temperature and soil moisture.

• Water Engineering Research
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• v.2 no.1
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• pp.49-61
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• 2001

A grid-based KIneMatic wave soil-water EROsion and deposition Model(KIMEROM) that predicts temporal variation and spatial distribution of sediment transport in a watershed was developed. This model uses ASCII-formatted map data supported from the regular gridded map of GRASS (U.S. Army CERL, 1993)-GIS(Geographic Information Systems), and generates the distributed results by ASCII-formatted map data. For hydrologic process, the kinematic wave equation and Darcy equation were used to simulated surface and subsurface flow, respectively (Kim, 1998; Kim et al., 1998). For soil erosion process, the physically-based soil erosion concept by Rose and Hairsine (1988) was used to simulate soil-water erosion and deposition. The model adopts single overland flowpath algorithm and simulates surface and subsurface water depth, and sediment concentration at each grid element for a given time increment. The model was tested to a 162.3 $\textrm{km}^2$ watershed located in the tideland reclaimed ares of South Korea. After the hydrologic calibration for two storm events in 1999, the results of sediment transport were presented for the same storm events. The results of temporal variation and spatial distribution of overland flow and sediment areas are shown using GRASS.

• Journal of the Korean Institute of Navigation
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• v.21 no.4
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• pp.39-47
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• 1997

We researched the mechanism on th flucturain of Bottom Cold Water in the western channel of Korea Strait, using 13 years(1981~1933) oceanographic data of FRDA. The bottom cold water in the western channel appears more often in summer and fall than in winter and spring, and its year-to-year variation of temperature is very large. Such variation seems to be closely related with the variations of cold waters in the subsurface layer of the southwestern East Sea. According to the longitudinal temperature distribution along the korean southeastern coast, a density difference occurs all the time at the still deepth between the western channel and the southwestern East Sea. Thus, it is inferred that the cold waters would intrude into the western channle form the subsurface layer in the southwestern East Sea as a density-driven current, and it intensity depends upon the density difference.

• Geosciences Journal
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• v.22 no.6
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• pp.891-902
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• 2018

Techniques for more reliable detection of 3D subsurface flow paths are highly important for most water-related geotechnical projects. In this case study, a magnetometric resistivity method with a new approach and state-of-the-art technology ("Willowstick survey") was applied to the testbed dam (YD dam) site, and its applicability was validated by geotechnical investigation techniques including borehole drilling and sampling, Lugeon test, flow direction and velocity test, and seismic tomography. In addition to the magnetometric survey, a 3D electrical resistivity survey was performed independently and the results were compared and discussed. The electrical resistivity survey was effective in detecting groundwater levels, but it was limited in mapping leakage paths. On the other hand, the Willowstick magnetometric survey effectively detected geologic weaknesses (e.g., fault fracture) and potential leakage paths of the dam site foundation rocks. The results of this research are expected to be effective for water infrastructures where leakage is an important issue.

• Korean Journal of Soil Science and Fertilizer
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• v.51 no.2
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• pp.79-89
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• 2018

Subsurface drip irrigation (SDI) system is considered one of the most effective methods for water application. A 2-year field study was conducted to investigate the effect of SDI systems with various dripline spacing (0.7 or 1.4 m) and position (under furrow or ridge) on soybean (Glycine max L.) production at a sandy-loam soil in Miryang, South Korea. For 2016-2017, average grain yield in SDI irrigated plots, $3.16Mg\;ha^{-1}$, was statistically greater than rainfed irrigated plot ($2.63Mg\;ha^{-1}$). Soybean grain yield averaged $3.25Mg\;ha^{-1}$ for the 0.7 m dripline spacing and $3.07Mg\;ha^{-1}$ for the 1.4 m spacing for the two-year period compared to a rainfed irrigated average of $2.63Mg\;ha^{-1}$ for the same period. Soybean treated with SDI system had significantly greater values of normalized difference vegetation index and stomatal conductance, indicating that soybean plants in SDI plots had greater photosynthetic and stomatal activity due to the higher water availability in soil. Irrigation water use efficiency (IWUE) was greatest in the plot of 0.7 m spacing installed under ridge position than any other plot across growing season. Average soil water content in plots with 0.7 m dripline spacing was $0.21m^3\;m^{-3}$ at 5 cm depth layer, which was 45% greater compared to the plots with 1.4 m spacing, even though the gross irrigation amounts were greater in 1.4 m spacing plots. It is concluded that wide dripline spacing (1.4 m) is probably the more economical installation design for SDI system compared to 0.7 m spacing in this study soil because the initial cost for dripline may be reduced with wide spacing design, even though the IWUE is greater in the plot of 0.7 m dripline spacing.