• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.390-393
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• 2004

This study was carried out to evaluate the acid producing potential of geological materials such as pit wall, waste rock and stream sediments near the abandoned Imgi mine. The 17 samples used in this study were collected and then treated by static test such as Acid Base Accounting and etc. Samples of pit wall and waste rocks with high S content display a NAGpH values below 4.5 and net acid potential. Therefore some cost effective measures such as capping and groudwater flow barriers, will be required to reduce the impacts of ARD from the waste rock impoundment and the pit wall on near the stream.

• Journal of Korea Water Resources Association
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• v.46 no.11
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• pp.1079-1088
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• 2013

Groundwater pumping from a well has different impacts on streamflow depletion because hydraulic properties of the aquifer and the stream bed differ depending on its location. Therefore, quantitative assessment of streamflow depletion due to each groundwater pumping with different well locations is needed for the effective groundwater development and streamflow management. In this study, a watershed-based surface water and groundwater integrated model, SWAT-MODFLOW was used to assess the streamflow depletion near stream reach due to groundwater pumping from a well located within the Sinduncheon watershed. The arbitrary 50 wells among the currently used groundwater pumping wells were selected within the study area and the streamflow responses to each groundwater pumping were simulated at nearby and downstream reaches. In particular, the applicability of the Stream Depletion Factor (SDF) and Stream Bed Factor (SBF), which are widely used for evaluating the degree of streamflow depletion due to groundwater pumping, was evaluated. The simulated results demonstrated that the streamflow depletion rate divided by the pumping rate significantly differ depending on well locations and distance between well and stream, showing a wide range of values from below 20% to above 90%. From the simulated results, it was found out that the SDF or the SBF can be a partial referred value but not an absolute criterion in determining whether a pumping well has a great impact on streamflow depletion or not.

• Journal of Korea Water Resources Association
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• v.40 no.6 s.179
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• pp.431-446
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• 2007

Groundwater flow in a basin is greatly affected by many hydrogeological and hydrological characteristics of the basin. A groundwater flow model for the Kap-cheon basin ($area=648.3km^2$) in the Geum river basin was established using MODFLOW by fully considering major features obtained from observed data of 438 wells and 24 streams. Furthermore, spatial groundwater recharge distribution was estimated employing accurately calibrated watershed model developed using SWAT, a physically semi-distributed hydrological model. Model calibration using observed groundwater head data at 86 observation wells yielded the deterministic coefficient of 0.99 and the water budget discrepancy of 0.57%, indicating that the model well represented the regional groundwater flow in the Kap-cheon basin. Model simulation results showed that groundwater flow in the basin was strongly influenced by such factors as topological features, aquifer characteristics and streams. The streams in mountainous areas were found to alternate gaining and losing steams, while the streams in the vicinity of the mid-stream and down-stream, especially near the junction of Kap-cheon and Yudeong-cheon, areas were mostly appeared as gaining streams. Analysis of water budget showed that streams in mountainous areas except for the mid-stream and up-stream of Yudeong-cheon were mostly fed by groundwater recharge while the streams in the mid and down-stream areas were supplied from groundwater inflows from adjacent sub-basins. Hence, it was concluded that the interactions between surface water-groundwater in the Kap-cheon basin would be strongly inter-connected with not only streams but also groundwater flow system itself.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.209-212
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• 2006

Using sulfur sotope analysis of dissolved sulfate in surface water, we have investigated the source of sulfate in order to identify the abandoned metallic mines, which have the potential of heavy metal contamination within watershed. The range of the sulfur isotope values for dissolved sulfate in stream waters (DD-1 and 2) are similar to those of sulfides from the Dunjun mine, which suggests that oxidation of sulfides is the principal source of $SO_4^{2-}$ in these stream waters. Also, heavier sulfur isotopes in waters near Baekjun and Hamchang mines imply the possibility of contamination in waters by these metallic mines.

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.557-566
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• 2018

Pohang earthquake (Main shock magnitude = 5.4) occurred in Southeastern region of South Korea in November 15, 2017. Groundwater levels of 6 monitoring wells with 5 minutes interval measurements located in that region and stream water levels of 4 stations located along the Hyeongsan-gang stream are used for the analysis of earthquake induced effects. Four groundwater monitoring wells show a short-term decrease of groundwater level after a main shock and one well does an increase and the maximum change is about 42.0 cm. Especially, groundwater levels at two monitoring wells near the epicenter are consistently maintained after a decrease. There is little relationship between earthquake magnitude or a distance to epicenter and changing amount of groundwater level and it may be due to the inhomogeneity of geologic material and unconsolidated sediments distribution. The changes in permeability of fractured zone and groundwater levels occasionally cause changes in stream flow rate, and water level of the Hyeongsan-gang stream in the study area decreases just after the earthquake and increases again up to the normal level and next shows an more gentle decreasing slope. Total increasing flow rates at S1 (upstream site) and S4 (downstream site) stations are about $12,096m^3$ and $116,640m^3$, respectively, during the increasing period.

• Journal of Korea Water Resources Association
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• v.55 no.7
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• pp.481-494
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• 2022

This study proposed a evaluation of the monthly vulnerable period for groundwater level management in the Miho stream watershed and a technique for evaluating the vulnerable period for future groundwater level management using LSTM. Observation data from groundwater level and precipitation observation stations in the Miho stream watershed were collected, LSTM was constructed, predicted values for precipitation and groundwater levels from 2020 to 2022 were calculated, and future groundwater management was evaluated when vulnerable. In order to evaluate the vulnerable period of groundwater level management, the correlation between groundwater level and precipitation was considered, and weights were calculated to consider changes caused by climate change. As a result of the evaluation, the Miho stream watershed showed high vulnerability to underground water management in February, March, and June, and especially near the Cheonan Susin observation well, the vulnerability index for groundwater level management is expected to deteriorate in the future. The results of this study are expected to contribute to the evaluation of the vulnerable period of groundwater level management and the derivation of preemptive countermeasures to the problem of groundwater resources in the basin by presenting future prediction techniques using LSTM.

• Journal of Korea Water Resources Association
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• v.51 no.2
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• pp.99-107
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• 2018

This study was to evaluate the stream depletion due to groundwater pumping from 17 wells near the Anseongcheon upper stream using the Baalousha's analytical solution (2012) which directly considers stream width and streambed hydraulic conductivity. The input hydraulic values of aquifer and streambed were obtained from the pumping tests and seepage experiments. The estimated streamflow depletion rates divided by pumping rate (dimensionless stream depletion) showed a range from 0.23 to 0.89 for 5 year pumping. In particular, the results revealed that the groundwater pumping has insignificant effects on streamflow when the stream depletion factor (SDF) is higher than 1,000 with values of dimensionless stream depletion lower than 0.4. A more simple Hunt's solution (1999) also applied to the same wells, and the results showed that the difference between the dimensionless stream depletions calculated by using both solutions could be negligible. From the comparison of the Baalousha's solution (2012) with the Hunt's solution (1999) with total 3,000 cases of simulations with combinations of various aquifer and stream properties, the stream-well distance should be more longer than stream width for reducing the discrepancy between both solutions.

• Journal of Korean Society of Forest Science
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• v.96 no.5
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• pp.561-566
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• 2007

This study was conducted to clarify runoff production processes in forested catchment through hydrograph separation using three-component mixing model based on the End Member Mixing Analysis (EMMA) model. The study area is located in the coniferous-forested experimental catchment, Gwangneung Gyeonggido near Seoul, Korea (N 37 45', E 127 09'). This catchment is covered by Pinus Korainensis and Abies holophylla planted at stocking rate of 3,000 trees $ha^{-1}$ in 1976. Thinning and pruning were carried out two times in the spring of 1996 and 2004 respectively. We monitored 8 successive events during the periods from June 15 to September 15, 2005. Throughfall, soil water and groundwater were sampled by the bulk sampler. Stream water was sampled every 2-hour through ISCO automatic sampler for 48 hours. The geochemical tracers were determined in the result of principal components analysis. The concentrations of $SO_4{^{2-}$ and $Na^+$ for stream water almost were distributed within the bivariate plot of the end members; throughfall, soil water and groundwater. Average contributions of throughfall, soil water and groundwater on producing stream flow for 8 events were 17%, 25% and 58% respectively. The amount of antecedent precipitation (AAP) plays an important role in determining which end members prevail during the event. It was found that ground water contributed more to produce storm runoff in the event of a small AAP compared with the event of a large AAP. On the other hand, rain water showed opposite tendency to ground water. Rain water in storm runoff may be produced by saturation overland flow occurring in the areas where soil moisture content is near saturation. AAP controls the producing mechanism for storm runoff whether surface or subsurface flow prevails.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.589-601
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• 2008

The variation of groundwater level near the Shingok weir has been analyzed. To consider the soil inhomogeneity, coefficient of effective permeability was computed to be 0.313 m/day in the horizontal direction, and 0.0423 m/day in vertical direction. Anisotropic ratio is 7.19. The river water level drawdown (caused by the removing of the weir) causes the groundwater level drawdown, and 3 months are required for the new steady condition. and groundwater flows from Han river toward Gulpo stream before the removing of the weir, but when the weir removed, the flow direction changes. The groundwater level falls maximum 30 cm in the areas under the influence of Han river, but, in the areas near Kulpo stream, groundwater level falls about 10 cm. The amount of groundwater use in the study area was investigated to be $52m^3/day$ and in this condition, groundwater level falls maximum 1m (before or after the removing of Shingok weir). therefore, the variation of groundwater level caused by the removing of Shingok weir is less than that caused by the usual use of groundwater.

• Journal of Korea Water Resources Association
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• v.48 no.9
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• pp.769-779
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• 2015

The streamflow depletion due to groundwater pumping from deep aquifer near the Juksan stream has been simulated, in this study, by using the surface water and groundwater integrated model, SWAT-ODFLOW in order to analyze the relationship between the stream depletion and hydraulic properties of aquifer and streambed, and to spatially assess the streamflow depletion. The simulated results showed that the streamflow depletion rate divided by the pumping rate for each well location ranges from 10% to 90% with reflecting the various well-stream distance, transmissivity, storativity, and streambed hydraulic conductance. In particular, the streamflow depletion exceeds about 50% of pumping rate for conditions with transmissivity higher than $10m^2/day$ or storage coefficient lower than 0.1. The simulated results in the form of spatial maps indicated that the spatially averaged percent depletion of streamflow is about 53.6% for five years of pumping which is lower than that for shallow aquifer pumping by 12.9%. From the spatially distributed stream depletion, it was found that higher and more rapid stream depletion to pumping occurs near middle-downstream reach.