• Journal of the Korean Society of Groundwater Environment
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• v.6 no.3
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• pp.133-139
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• 1999

The geostatistical method Kriging is used to estimate the areal distributions of the depth to the water table and the altitude of the water table measured from the sea level. A northern part of the city of Pohang, Kyeong-Buk, Korea has been chosen and the digital map of the area with 1:5,000 scale from the National Geographic Information System (NGIS) project by National Geographic Institute has bun used to reproduce the ground surface distribution. The water table depth appears to be in the range between 7 m and 9.5 m except a few localities where mountain tops exist and the use of groundwater for agicultural purposes is believed to be heavy. The overall distribution of the water table altitude shows a monotonic gradual decrease from the west to the east (seaward direction from the inland) and to the south with maximum rate approximately at 90 m over 6 km in horizontal distance and indicates that the groundwater is moving several meters per day there.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.165-176
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• 1995

Dongrae is one of the most famous hot spring resort area in the Republic of Korea. The water temperature ranges $50^{\circ}C{\sim}66$. The chemical composition of the thermal water is quite different from normal groundwater. $Na^+$ and $Cl^-$ are the main components, measured more than 75%, $Ca^{+{+}}$ is contained about 22% and the other ions such as $SO_4$ or $HCO_3$ are the minor components. The heat source is uprising along the fracture zone of granite which is indicated as a subsurface high temperature belt. During the research period of 1991~1992, the groundwater table was lowered down to the depth of about 100 m according to continuous increase of daily use of thermal water. The groundwater table was fluctuated with an amplitude of day, weak or seasion. The groundwater table was the lowest at 18:00 h in a day and also lowest at the weekend for the week period. There was a relavent relationship between drawdown and the amount of thermal water use on a long term base. To protect such a rapid drawdown of groundwater table, Dongrae resort area is now asked to take strong municipal control for the daily use of thermal water.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.4
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• pp.82-95
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• 1980

This paper complies the results of the studies so far made on the subsoil improvement of subsurface drainage systems for wet paddy fields (those were located in the Gum-Ho area in Kyung Buk province) which had poor permeability and a high water table. In general, a drainage problem is an excess of water on the ground surface which can effect the productivity and bearing capacity of the soil. With drain pipe systems, (According to their depths and spacing) it may be possible to correct that problem. The experimentation consisted of three test plots, two of which included drain pipe systems with varing depths and width spacing of the pipes. The third plot (C) was an ordinary plot being exempt of a drain pipe system. In detail, the depth of plot A was 80 cm, and the width spacings began at 2. Om and increased by 2. Om up to 10. 0m. The depth of plot B was 60cm and the width spacing was the same as plot A. These tests were performed to research specific details; such as crop yeild, bearing capacity of the soil, the amount of underdrainage, surface cracks, root distribution, the water table level, the consumptive water depth and the soil moisture content. The test period lasted three years, from 1977 thru 1979. The results obtained were as follows: 1. During the test period, the weather conditions for the area tested were in accordance with the annual average for that area. Furthermore the precipitation factor during the spring cultivation season, the intermediate drainage period and the harvest drainage period was of optimum conditions for controling surface cracks, because of less precipitation than evaporation. 2. The difference in the level of the ground water table in plots A and B was hardly noticable, but the difference in the test plots and the ord. plot was greatly noticable. The test plots (A, B) were 30 to 40cm lower than the ordinary plot. On the whole, the ground water table of the ord. plot always stayed at a level of 15-20cm beneath the surface of the soil, the ground water table of the test plot A showed The difference in the depth of the pipe lower than the test plot B, while the test plots showed a remarkable descending effect. 3. The soil temperature in plot A was slightly core than in plot B with a difference of 0. 47$^{\circ}$C, but plot A was 1. 6$^{\circ}$C higher than the ord. plot during the flooding period, but after drainage the temperature difference climed to 2. 0$^{\circ}$C. 4. During the 3rd test year, the values of the cracks were recorded with the values of 59cm in plot A, 42cm in plot B and 15cm in the ordinary plot. Plots A and B had increased 2.5 times the value of the first year while the ordinary plot had remained the same. 5. The root weight of the rice was measured at a value of 77.2 gr. for plot A, 73.5 gr. for plot B and 65.3 gr. for the ord. plot. Therefore, the root growths in plots A and B were much more energetic than in the ord. plot. 6. The consumptive water depth measured during the 3rd year resulted in the values of 26. 0mm per day for plot A, and 24.9 mm per day for plot B, respectively. Therefore, both plot A and plot B maintained the optimum consumptive water depths, but the ordinary plot only obtained the value of 12.3 mm per day, which clearly showed less than the optimum consumptive water depth which is 20 to 30 mm/day. 7. The soil moisture content is in direct relationship to the ground water level. During drainage, test plot A decreased in its ground water level much more rapidly than the other two plots. Therefore, plot A had a much less soil moisture content. But this decreased water level could be directly effected by the weather conditions. 8. The relationship between the bearing capacity and the soil moisture content were directly inversely proportional. It can be assumed that the occurence of soil creaks is limited by the soil moisture content. Therefore, the greater the progress of the surface creaks resulted in a greater bearing capacity. So, tast plot A with a greater amount of surface cracks than the other test plots resulted in a greater bearing capacity. But, the bearing capacity at the harvest season could be effected by the drainage during the intermediate drainage period and by the weather conditions. 9. Comparing the production of the test plots to the ord. plot; there was an increased value of 840kg for plot A, 755kg for plot B and 695kg for the ord. plot in the rough rice. Therefore, plot A had an increase of 20% over the ordinary plot. The possibility of producing double crops was investigated. The effects on barley production in the test plots showed a value of 367kg per 10 acres, which substantiated the possibility of double crops because that value showed an increased value over the average yearly yield for those uplands. 10. So as a result, it can be recommended that by including a drain pipe system with the optimum conditions of an (80cm centimeter) depth and a (l0m) spacing will have a definite positive effect on the over all production capacity and quality of wetpaddy fields.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.299-299
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• 2017

Due to the climate changes in Korea, the numbers of both torrential rain events and drought periods have increased in frequency. Water management practice against water shortage and flooding is one of the key interesting for field crop cultivation, and groundwater often serves as an important and safe source of water to crops. Therefore, the objective of this study is to evaluate the effect of groundwater table levels on soil water content and soybean development under two different textured soils. The experiment was conducted using lysimeter located in Miryang, Korea. Two types of soils (sandy-loam and silty-loam) were used with three groundwater table levels (0.2, 0.4, 0.6m). Mean soil water content during the soybean growth period was significantly influenced by groundwater table levels. With the continuous groundwater level at 0.2m from the soil surface, soil water content was not statistically changed between vegetative and reproductive stage, but the 0.4 and 0.6m groundwater table level was significantly decreased. Lower chlorophyll content in soybean leaves was found in shallow water table treatment in earlier part of the growing season, but the chlorophyll contents were non-significant among water table treatments. Groundwater table level treatments were significantly influenced on plant available nitrogen content in surface soil. The highest N contents were observed in 0.6m groundwater table level. It is probably due to the nitrogen loss by denitrification as the result of high soil water content. The length and dry weight of primary root was influenced by groundwater level and thus the highest length and dry weight of root were observed in 0.6m water table level. This result showed that soybean root growth did not extend below the groundwater level and increased with the depth of groundwater table level. The results of this study show that the management of groundwater level can influence on soil characteristics, especially on soil water content, and it is an important practice of to reduce yield loss caused by the water stress during the crop growing season.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.1
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• pp.2895-2903
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• 1973

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.2
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• pp.195-202
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• 1995

This experiment was performed to characterize the optimum water table level for the growth and yield of barley(var. Olbori) and wheat(var, Grumil), Olbori and Grumil were grown in the 550 liter plastic pot filled with silt loam or sandy loam, During the whole growth period, the water table adjusted to be 20, 30, 40, 50, and 70cm, Higher water table was resulted in the decrease in plant height and top dry weight, but in the increase of the ratio of top to root dry weight, especially in barley, This suggested that high water table level affected more the growth of top than that of root, The number and area of green leaves were decreased as the water table was higher than 30 to 40cm at the late growth period(May 18, 1993), The largest number and area of green leaves were shown at 50cm of water table in sandy loam and at 70cm in silt loam, As the water table was high, the leaf chlorophyll content was low, And barley was affected more significantly than wheat by soil texture, The photosynthetic activity was decreased remarkably at 20cm water table, Heading period was 2 to 3 and 4 days earlier at the 20cm water table of sandy loam in barley and wheat, respectively, However this earlier heading was not shown in silt loam, Grain filling was accelerated 5 to 7 days earlier in barley and 10 days in wheat grown at 20cm water table, The highest yield was present at 50 and 70cm water table, The yield was decreased remarkably at 20cm water table, resulting that yield reduction ratio of barley was 71.1% and 72, 2%, and that of wheat was 41.0% and 60, 0% in sandy loam and silt loam, respectively, High water table decreased the number of spike per unit area, but increased the seed weight per spike in barley, However, High water table reduced the seed weight per spike in wheat. There was significant correlation between yield and leaf chlorophyll content in wheat and barley, Yield was correlated significantly with green leaf area in barley, and with top dry weight, ratio of top to root dry weight chlorophyll content and photosynthetic activity in wheat. The optimum water table was 50 to 70cm in wheat and barley, They grew fairly well at 30cm water table of sandy loam, and at 40cm of silt loam.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.509-516
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• 2002

Rainfall-induced landslides in a weathered granite soil slope have mostly relative shallow slip surfaces above the groundwater table The pore-water pressure of soil above the groundwater table is usually negative. This negative pore-water pressure(or matric suction) has been found to make a large contribution to the slope stability. Therefore, the variation of in-situ matric suction profiles with time in a soil slope should be understood. In this study, a field measurement program was carried out from June to August, 2001 to monitor in-situ matric suctions and volumetric water contents in a weathered granite soil slope. The influence of climatic conditions on the variation of in-situ matric suctions could be found to decrease rapidly with depth. It could be found that decrement of matric suction induced by precipitation is affected not only by the amount and duration of rainfalls but also by the initial matric suction just prior to rainstorms. The soil-water characteristic from the field monitoring tends toward the wetting path of SWCC obtained from the laboratory test.

• Proceedings of the Korean Society of Crop Science Conference
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• 1997.05a
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• pp.80-81
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• 1997

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.3
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• pp.278-284
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• 1995

This experiment was performed to characterize the optimum water table level for the grain quality, seed germination and diastic power of barley(var. Olbori) and wheat(var. Grumil). Olbori and Grumil grew in the 550 liter plastic pot that filled with silt loam or sandy loam. During the whole growth period, the underground water level adjusted to be 20, 30, 40, 50 and 70cm. Filled grain ratio and specific gravity were not affected by soil texture and water table. Low level of water table caused the increase of 1,000 grain weight in wheat and barley, but soil texture didn't. Crude protein content tended to be high as the water table level was high, especially in wheat. Change in crude protein content was affected by underground water level more than soil texture. And the affection was slightly higher in sandy loam than silt loam, but the difference was small. The higher level of water table led to the lower crude lipid content in barley and wheat grain. Crude lipid content of both wheat and barley grain grown in sandy loam was higher than those grown in silt loam. As the water table level down, the ash content of barley and wheat grain tend to increase, especially in sandy loam. Wheat flour yield was not affected by soil texture. It was about 65% at 20cm of water level and above 67% at 40cm water level. The seed germination of wheat and barley was more than 95% when the seeds were placed at 2$0^{\circ}C$ for three days. Regardless of soil texture, the lowest germination was seen at 20cm of water table level. And the seed germination rate increased as the underground water level became low. Above 89% of barley grains were germinated within 48 hours except 20cm level of water table in sandy loam. Diastic power of germinated barley was the lowest at 20cm of water table level, and it was almost unchanged below 30cm of water table level. And also it was not affected by soil texture.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.167-176
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• 1998

On steep hillslopes, saturation zone formations and subsurface flows were monitored through the observation systems of observation wells, tensiometers and trenches. By the 103 mm rain which had fallen on the hillslope with dry soil moisture, the saturation zone began to be formed at the top of hillslope during the rain and developed to be formed within a few hours after the end of rain on all hillslope. Subsurface water outflowed mainly from the soil profile of 0-40 cm depth, but did not outflow from the one of 40-80 cm depth. This saturation zone seemed to be formed by partially saturation of soil. This resulted for two reasons. Firstly, the saturation zone was formed by a smaller amount of rain than that required. Secondly the soil at a certain depth below the water table was unsaturated. Saturation zones formed by pre-rains responded rapidly to rains and subsurface water outflowed mainly from the soil profile of 40-80 cm depth simultaneously with the rising of the water level. The rates of subsurface discharge from the soil profile of 40-80 cm depth to the precipitation were related to the antecedent precipitation although the maximum water levels of saturation zone formed by four rains were similar.