• The Journal of Engineering Geology
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• v.14 no.2
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• pp.189-197
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• 2004

For a long time, groundwater has been used for a substitution for surface water but recently many problems have risen due to shortage of water resources and decrepitude of waterwells. Pneumatic fracturing technique is likely to be an efficient way to solve the problem of tile wells, in which pressure under the ground is applied to increase the amount of ground water. When applied pressure is given artificially to unstabilize the rock stress or to remove substances between fractures the groundwater can inflow. As the air pressure applied on the base rocks is stronger, permeability is getting higher, thus producing much groundwater than ever before. The result of this study show 15% increase of pumping rate in the P-5 well. After pneumatic fracturing pumping rate changed from 26m3/day to 30m3/day, drawdown rate increase from 51.12m to 56.58m, and specific yield also increased from 0.51m3/day to 0.53m3/day.

• Journal of the Korean Professional Engineers Association
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• v.27 no.6
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• pp.72-84
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• 1994

This is about an environmental study of groundwater interference by hydrodynamic dispersion between the well A and well C in Dongsam-dong, the Yeongdo Island, Pusan, Korea. The groundwater in the study wells come from the fracture zones deeply seated in welded lapilli rhyodacitic tuff of the Late Cretaceous Yucheon Group. The boring depth at the well A is 190 meters, and the optimal pumping rate of the well A is about 100 cubic meters per day therein. The fractured aquifers in impermeable welded tuff show the conjugate fracturing type and are of anisotropic. The aquifers along two fracture zones in the well A are 80 and 100 meters in depth, respectively. It is not suggested that those fractured aquifers are simply connected between the well A and C. The sea level fluctuation by ebb and high tides in a day is not effective to the groundwater table in the well A. The pumping for 15 days at the well A doesn't give rise to any changes of the groundwater levels in the neighbor well C. The radius of influence of the well A is measured as less than 200 meters. The measuring electric conductivity for the test of salt tracer doesn't testify any relationship between the well A and the well C. There is the main difference between the well A and the well C on the basis of the water analysis of those wells. the well A is located in the high content zone of salt much over the standard value for drinking, whereas the other wells B. C. D are in the low content area of salt below the standard value. It is elucidated for the high content zone of salt in Yeongdo around the well A to have been uplifted over 20 meters.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.119-129
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• 2020

Sand dam is a successful water harvesting method in mountainous areas with ephemeral rivers. The success is dependent on several factors including material type, hydrogeology, slope, riverbed thickness, groundwater recharge, and streamflow. In this study, the effect of a sand dam on the groundwater level in the Chuncheon area, South Korea was assessed using the MODFLOW model. Using the model, multiple scenarios were tested to understand the groundwater head before and after the construction of the sand dam. The effect of groundwater abstraction before and after sand dam construction and the sand material type were also assessed. The results show, the groundwater level increases substantially after the application of a sand dam. The comparison of model outputs, simulated groundwater head before and after sand dam application with and without pumping well, shows a clear difference in the head. The material type has also an effect on the groundwater head. As the conductivity of the material increases, the head showed a significant rise.

• 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.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.17-23
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• 2002

Pumping tests were carried out from seven wells in fractured rocks. The time-drawdown data were obtained from pumping wells and corrected for the elapsed time of step drawdown test using Cooper-Jacob's method. A statistical method. the least square of error, was used to yield the coefficient of aquifer losses, the coefficient of well losses, and the power which indicates the severity of the turbulence. The values of the power range from 1.65 to 6.48. The well losses result mainly from turbulent flow caused by radial flow nearby pumping wells. The turbulent flow depends on Reynolds number. Since the hydraulic characteristics of fractured rocks control the fluid velocity, the value of the power is an important factor to understand the aquifer system of fractured rocks.

• Journal of Soil and Groundwater Environment
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• v.9 no.2
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• pp.54-63
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• 2004

For the purpose of finding out the distributions of groundwater uses, the effect of facilities on the parameter and the correlations among measurements, various statistical analysis were carried out with the data of groundwater quality measurements from January to December in 2002. (1) The rates of groundwater for drinking water were 10.5% in Yungcheon-Gu, 10.2% in Kangdong-Gu, and 9.9% in Eunpyung-Gu. The rates of other uses of groundwater were shown to be 58.1 %(786 wells) for civil defense emergency, 22.1% (299 wells) for contamination-concerning, 9.8%(133 wells) for water quality monitoring, consisting of 90% of all groundwater. (2) The 52.6% of groundwater for drinking were demonstrated to be appropriate while 91.9% for other uses-domestic, industrial, agricultural uses- were shown to be proper. (3) For drinking water, the maximum values of colar, turbidity, NH3-N, F, and Fe were 766.9 degree, 69.16NTU, 860.0 mg/l, 5.6 mg/l and 49.87 mg/l respectively. (4) Comparision of skewness and kurtosis for Seoul groundwater, pH was found to be 0.022 and -0.524, but the T.colony, color, turbidity, NH$_3$-N, NO$_3$-N, Fe and Mn respectively fumed out to be 11.641 and 174.324, 8.501 and 80.260, 5.675 and 32.821, 19.507 and 380.994, 3.323 and 17.436, 10.544 and 134.093 and 5.979 and 39.124. (5) In cases of drinking water wells for emergency, the results of statistical analysis showed that building year of the wells, depth and pumping rate didn't affect on whether it was proper for that use or not. It were shown that there were linear correlations between depth and NO3-N(-0.171) and F(0.332) while the correlation coefficients were 0.381 and -0.169 between the building year of well and depth and pumping rate respectively.

• Journal of the Korean Society of Groundwater Environment
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• v.3 no.1
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• pp.1-8
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• 1996

Coastal waste dump in Pohang is composed of slags and sludge of POSCO. Hydraulic parameters in the coastal waste dump are very different from those in municipal landfills and general unconsolidated or fractured aquifers. In the waste dump pumping or slug tests are not adequate for the estimation of hydraulic parameters. Time-lag and amplitude of the tidal fluctuation of groundwater table are used to determine the hydraulic parameters. Groundwater table at the groundwater observation wells is about 40 cm higher than the sea level. The contributing factors of the groundwater-rise are estimated. Vertical profile of some chemical constituents in groundwater indicates the gradual transition of the fresh groundwater at the uppermost position to the sea water at the bottom.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.529-540
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• 2018

Sand dam is a flow barrier commonly built on small or medium size sandy rivers to accumulate sand and store excess water for later use or increase the water table. The effectiveness of sand dam in increasing the water table and the amount of extractable groundwater is tested using numerical models. Two models are developed to test the hypothesis. The first model is to simulate the groundwater flow in a pseudo-natural aquifer system with the hydraulically connected river. The second model, a modified version of the first model, is constructed with a sand dam, which raises the riverbed by 2 m. In both models, the effect of groundwater abstraction is tested by varying the pumping rate. As the model results show the groundwater after the construction of the sand dam has increased significantly and the amount of extractable groundwater is also increased by many folds. Most importantly, in the second model, unlike the pseudo-natural aquifer system, the groundwater abstraction does not have a significant effect on the water table.

• Journal of Korea Water Resources Association
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• v.45 no.10
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• pp.1051-1067
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• 2012

Increased use of water curtain facilities to keep green house warm during winter cultivation has been known to cause excessive groundwater ion which might lead to decline of groundwater level, resulting in streamflow depletion. Therefore it is required to quantitatively assess the effects of groundwater ion on the streamflow depletion such as magnitude and extent. The objective of this study is to assess the change of stream-aquifer interaction according to groundwater ion near stream. To this end, a green house cultivation land in Sooha-ri, Sindun-myun, Icheon-si, Gyonggi-do was selected as a field experimental site, and monitoring wells were established near and within stream to observe the water level and temperature changes over a long period of time. From the observed water level and temperature data, it was found that the river reach of interest changed to a losing stream pattern during the winter cultivation season due to groundwater level decline around pumping wells near the stream. The continuous exchange rates between stream and aquifer were estimated by plugging the observed water level data series into the experimental relation between head difference and exchange rate, showing the streamflow depletion by 16% of the groundwater pumping rate in Feb, 2011.

• Journal of Environmental Science International
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• v.25 no.1
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• pp.135-146
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• 2016

This study analyzed fluctuations of ground water level of ground water wells developed in Seongsan watershed of Jeju Island until 2013 using MODFLOW, a numerical analysis model. Ground water level shows greater fluctuations from increase of pump capacity compared to the number of ground water wells. The development of ground water at the top of watershed was found to have direct influence on ground water level. Ground water wells developed until 2013 were used to continue pumping for 50 days, and ground water level of coastal region was reduced below 50% compared to the standard water level. In addition, the range of fluctuation of water level was large in the east coast region, which represents the direction of flow of ground water.