• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.3
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• pp.167-177
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• 2007

We measured the salinity, pH, and concentrations of $^{222}Rn$ and nutrients in groundwater in the southeastern coastal aquifer off Busan from March to September 2005 to evaluate its submarine discharge and geochemical characteristics. Salinity in coastal groundwater increased sharply at 20 m depth and exceeded 25 ppt below 40 m during the study period, indicating that a strong transition zone between fresh groundwater and seawater developed between 20 and 40 m depths. Fresh groundwater in the upper layer of this transition zone was characterized by high pH, $^{222}Rn$, dissolved inorganic nitrogen (DIN), and dissolved inorganic phosphorus (DIP) and low dissolved inorganic silicate (DSi) relative to seawater in the lower layer. In addition, the vertical profiles of the $^{222}Rn$, DIN, and DIP concentrations imply that a strong advective groundwater flow occurs along the interface of fresh groundwater and seawater near 20 m depth. The geochemical constituents in coastal groundwater also showed strong seasonal variation, with the highest concentrations in summer (June 2005) due to the changes of groundwater recharge and sea level. This implies that the input of terrestrial chemical species into the coastal ocean through submarine groundwater discharge (SGD) could change seasonally. To ascertain the seasonal variation of SGD and SGD-driven chemical species fluxes, and associated ecological responses in the coastal ocean, more extensive studies are necessary using various SGD tracers or seepage meters in the future.

• Journal of Soil and Groundwater Environment
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• v.21 no.3
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• pp.64-81
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• 2016

To analyze the influence of various groundwater flow rates (specific discharge) on BHE system with balanced and unbalanced energy loads under assuming same initial temperature (15℃) of ground and groundwater, numerical modeling using FEFLOW was used for this study. When groundwater flow is increased from 1 × 10⁻⁷ to 4 × 10⁻⁷m/s under balanced energy load, the performance of BHE system is improved about 26.7% in summer and 22.7% at winter time in a single BHE case as well as about 12.0~18.6% in summer and 7.6~8.7% in winter time depending on the number of boreholes in the grid, their array type, and bore hole separation in multiple BHE system case. In other words, the performance of BHE system is improved due to lower avT in summer and higher avT in winter time when groundwater flow becomes larger. On the contrary it is decreased owing to higher avT in summer and lower avT in winter time when the numbers of BHEs in an array are increased, Geothermal plume created at down-gradient area by groundwater flow is relatively small in balanced load condition while quite large in unbalanced load condition. Groundwater flow enhances in general the thermal efficiency by transferring heat away from the BHEs. Therefore it is highly required to obtain and to use adequate informations on hydrogeologic characterristics (K, S, hydraulic gradient, seasonal variation of groundwater temperature and water level) along with integrating groundwater flow and also hydrogeothermal properties (thermal conductivity, seasonal variation of ground temperatures etc.) of the relevant area for achieving the optimal design of BHE system.

• Tunnel and Underground Space
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• v.5 no.4
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• pp.347-362
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• 1995

The purpose of this study was that manage effectively the excavation process of the transport tunnel in DONGHAE mine area by investigating the variationof the surface and groundwater flow system around the tunnel and neighbouring villages. Thus, the effect of excavation and water-prrofing process on the water system has been studied through the naked eye survey of the tunnel and the surface outcrop, joint survey, core drilling, the measurement of the surface water quantity, evapotranspiration and precipitation analysis, rock hydraulics approach, the pressure test of boreholes, the variation of the water level, and finally the numerical analysis. From above approachs, we derived the conclusion that the exhaustion of the surface water was not caused by the tunnel excavation on the groundwater system was minimized by effective water proofing process.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.575-584
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• 2019

The groundwater level (GWL) is an important subsoil condition for the design of foundation. GWL tends to fluctuate often with seasonal variation, which may cause unexpected, additional settlements with some reductions in the safety margin of foundation. In this study, the effects of fluctuating GWL on the load carrying and settlement behavior of footing were investigated and quantified. A series of model load tests were conducted for various GWL and soil conditions using a hydraulically-controlled chamber system. Changes in load level and rising and falling GWL fluctuation cycle were considered in the tests. Settlements during GWL rise were greater than those during GWL fall. The depth of the GWL influence zone ($\underline{d}_{w,inf}$) varied in the range of 0.3 to 1.5 times footing width and became shallower as GWL continued to fluctuate. Design equations for estimating GWL-induced settlements for footings were proposed. The GWL fluctuation cycle, load level and soil density were considered in the proposed method. Changes in settlement and factor of safety with GWL fluctuation were discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2277-2284
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• 2013

In this study, a groundwater table fluctuation method is suggested to predict groundwater level by means of groundwater table fluctuation due to recharge and discharge under unsteady condition. This model analyzes groundwater variation characteristics by using reaction factor related with groundwater flow and specific yield related with recharge. For the test of this model, measured groundwater level at JD Yongdam 1 and JW Konghang for 5 years (2006-2010) were used. At JD Yongdam 1, the estimated specific yield was 0.023, and the estimated reaction factor was 0.039. At JW Konghang, the estimated specific yield was 0.009 and the estimated reaction factor was 0.028, respectively. This model can estimate recharge and saturated parameters, thus it is expected that this model would be the proper tool for checking the parameter of hydrologic model and percolation features.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.439-449
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• 2019

To prevent the drying-out of streams and to make effective use of stream water and groundwater, it is necessary to evaluate the impact of groundwater pumping on nearby streams. To this end, stream depletion due to groundwater pumping should be investigated in terms of various hydraulic characteristics of the aquifer and stream. This study used the Baalousha analytical solution, which accounts for stream-stage variation over time, to analyze stream depletion due to groundwater pumping for cases where the stream level decreases exponentially and recovers after the decrease. For conditions such as an aquifer transmissivity of 10~100 ㎡ d^-1, storage coefficient 0.05~0.3, streambed hydraulic conductance 0.1~1.0 m d^-1, stream-well distance 100~500 m, and stage recession coefficient 0.1~1.0 d^-1, the contribution of stream water (the dimensionless ratio of stream water reduction rate to groundwater pumping rate) was analyzed in cases where stream level change was considered. Considering the effect of stream-stage recession, the contribution of stream water is greatly reduced and is less affected by the stream-depletion factor, which is a function of the stream-to-well distance and hydraulic diffusivity. However, there is no significant difference in stream depletion under constant- and variable-stage recovery after recession. These results indicate that stream level control can distribute the relative impacts on stream water and aquifer storage during groundwater pumping

• Journal of Radiation Protection and Research
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• v.37 no.3
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• pp.149-158
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• 2012

In this paper, we measured the variations of radon concentrations in groundwater using low-level Liquid Scintillation Counter (LSC), an instrument for analyzing the alpha and beta radionuclides at its 10 sites around the Kumjung-Gu, north-western of Busan. Optimization of Pulse Shape Analyzer (PSA) to determinate the highest value of figure of merit (FM) was decided using Quantulus 1200 LSC with radium-226 source, the optimal PSA level was shown in the range of 100 to 110. The results show that the Minimum Detectable Activity (MDA) of radon concentrations is 0.61 $Bq{\cdot}L^{-1}$ for 20 minutes in PSA level. We find that the average radon concentration in groundwater is high in granitic rock area and low in volcanic rock area. (Biotite granite : 191.39 $Bq{\cdot}L^{-1}$, Micro graphic granite : 141.88 $Bq{\cdot}L^{-1}$, Adamellite : 92.94 $Bq{\cdot}L^{-1}$, Andesite (volcanic) : 35.35 $Bq{\cdot}L^{-1}$). No significant seasonal variation pattern is observed from the long-term variation analysis from 10 selected sites. We have not seen the significant correlation of radon concentration to groundwater temperature, atmospheric temperature, atmospheric pressure and rainfall. The concentration variation is probably caused by more complex factors and processes.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.3
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• pp.103-115
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• 2003

This study examines groundwater movement system analysis and movement forecast algorithm using finite element method. The target is Cheongha-myeon area, Bukgu, Pohang-city which has many difficulties in water supply during drought period. From the comparison of the differences between obtained values by WINFlOW model and observed values, it is thought that groundwater head distribution under steady flow is reflected well at the level of reliability Groundwater movement of study area shows stable pattern from western watershed to eastern coastal area while flow path is dense and steep in the center of the coastal area. The results of particle tracing for each well show a comparatively straight line from the western boundary side to the observation position at the upper area of the well, and are analyzed as it diffuses according to getting closer to the coast at the lower area of the well. The result of effect circle examination attendant on pumping amount in study area shows variation tendency that groundwater head decreases at the side and the lower area more than at the upper area of the well when groundwater flows from west to east(coast). As mentioned above, satisfactory results of groundwater movement analysis using WINFlOW model, two dimensional groundwater movement analysis model, are obtained through the great decrease of physical uncertainty of groundwater movement system.

• Journal of the Korean earth science society
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• v.28 no.4
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• pp.478-490
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• 2007

With groundwater data of seawater intrusion monitoring network in coastal areas of Korea's main land, we analyzed types of seawater intrusion through the coastal aquifer. The data including groundwater level, temperature and electrical conductivity obtained from 45 monitoring wells at 25 watershed regions were evaluated. Based on statistical analysis, correlation analysis and variation type analysis, groundwater levels were mainly affected by rainfall and artificial pumping. About 78% of the monitoring wells showed average temperature higher than $15^{\circ}C$ and about 58% of them showed minimum variations less than $0.2^{\circ}C$. Electrical conductivities showed a large magnitude of variation and irregular characteristics compared with groundwater levels and temperatures. Average electrical conductivities lower than $2,000\;{\mu}S/cm$ were observed at 28 monitoring wells while those of higher than $10,000\;{\mu}S/cm$ were done at 9 monitoring wells. From the cross-correlation analysis, groundwater levels were mostly affected by precipitation while temperature and electrical conductivity showed very low correlation. Meanwhile tidal variations strongly affected the groundwater levels comparing to precipitation. We classified the long-term monitoring data according to variation types such as constant process, linear trend, cyclic variation, impulse, step function and ramp. Impulse type was dominant for variations of groundwater level, which was largely affected by rainfall or artificial pumping, the constant process was dominant for temperature. Compared with groundwater level and temperature, electrical conductivities showed various types like linear trend, step function and ramp. According to the discrepancy of variation characteristics for monitoring data at each well in the same region, periodical analysis of monitoring data is essentially required.

• Journal of Environmental Science International
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• v.14 no.4
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• pp.405-412
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• 2005

Groundwater in Jeju Island, flowing through main stream, is spring water from underground. To set a fixed quantity of groundwater flowing from surface in a hydrological view, 4 downstream (Woedo stream, Gangjung stream, Yeonwoe stream and Ongpo stream) were selected to calculate the characteristic of baseflow and the base-flow discharge through the data on tachometry. There were 11 to 14 level peak caused by runoff, mostly occurred during monsoon season. Also, duration of runoff was 15 to 25 hours, well reflecting the characteristic of inclined, short stream length in Jeju Island and pervious hydrogeographical feature. In case of Gangjung stream, Yeonwoe stream and Ongpo stream, variation of stream water level by baseflow rose above during summer, which was closely linked to the distribution of seasonal precipitation. From autumn to spring, water level fell below while that of Woedo stream remained the same all year round. Data on the water level observed in Woedo stream and Gangjung stream in every single minutes was applied to weir formula(equation of Oki and Govinda Rao) to calculate baseflow discharge. Also, using the data on current and water level calculated in Ongpo stream and Yeonwoe stream, water level-water flow rating was applied to assess base flow discharge.