• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.65-75
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• 2002

The objectives of this study are to analyse model-based soil moisture variations depending on model parameters m and $T_0$ and to evaluate the model performance for the simulation of soil moisture variations by the comparison of observed groundwater levels and model-driven soil moisture amounts and observed and simulated river discharges at the basin outlet. The selected study area is the Pyungchang IHP river basin with outlet at Sanganmi station and the summer flooding events during '94-'98 are used for the analysis. As a result, soil moisture holding capacity is increased according to increase the parameter m that represents effective groundwater depth. This phenomenon is especially dominant when higher m and $T_0$ values are used. The qualitative comparison of computed base flow and observed groundwater level shows that the base flow peaks are reasonably simulated and the decreasing limbs of hydrograph are mainly caused by base flows. It is concluded that TOPMODEL can be used effectively for simulating basin-averaged soil moisture variations in addition to river flow generations.

• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.529-544
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• 2018

Dongrae hot spring belongs to the residual magma type and has a long history of bathing since the Silla dynasty in Korea. Due to long development of hot spring water, it is expected that the amount of hot spring water in Dongrae hot spring has been changed. In this study, long-trem water level data of Dongrae hot spring were examined for recognizing the change of the hot spring. By the fluctuation analysis of the hot spring water level from January 1992 to July 2018, the maximum and minimum annual drawdowns of no. 27 well were 137.70 and 71.60 meters, respectively, with an average drawdown of 103.39 m. On the other hand, the maximum and minimum annual drawdowns of no. 29 well were 137.80 and 71.70 meters, with an average drawdown of 103.49 m. Besides, drawdown rate became bigger in recent years. As a result of analyzing autocorrelation of the two wells, the correlation coefficient ranged from 0.919 to 0.991, showing seasonal groundwater level fluctuation. The cross correlation analysis between water level and precipitation as well as water level and hot spring discharge resulted in the correlation coefficients of -0.280 ~ 0.256 and 0.428 ~ 0.553, respectively. Therefore, using Dongnae hot-spring water level data from 1992 to 2018, the Mann-Kendall test and Sen's test showed that the continuous decline of water level was mainly caused by the pumping of the hot spring water among various reasons.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.403-412
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• 2015

We summarize the status of exploitable groundwater reserves in Korea based on reports of the National Basic Groundwater Plan, and review methods for estimating groundwater recharge rates, as recharge is a key factor in the estimation of exploitable groundwater reserves. We also outline the various methods used to assess exploitable groundwater reserves in previous groundwater investigation reports. Regarding advancements in the estimation of exploitable groundwater, we recommend that enhanced estimation methodologies (e.g., the water balance method and the advanced water table fluctuation method) and sustainable groundwater management concepts be adopted in the near future.

• Journal of Soil and Groundwater Environment
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• v.11 no.2
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• pp.56-67
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• 2006

Trends of variation in groundwater levels, electrical conductivities and water temperatures obtained from the national groundwater monitoring stations (95 shallow and 169 deep wells) of Korea were evaluated. For the analysis, both parametric (linear regression) and non-parametric (Mann-Kendall test, Sen's test) methods were adopted. Results of linear regression analysis indicated that about 50% of the monitoring wells showed increasing trends of groundwater levels, electrical conductivities, and water temperatures and the others showed decreasing trends. However, the non-parametric analyses with monthly median values revealed that $14.8{\sim}20.0%$ of water levels were decreased, $24.2{\sim}36.9%$ of electrical conductivities were increased, and $27.4{\sim}32.5%$ of water temperatures were increased at a confidence level of 99%. Highly proportions of increasing or decreasing trends were unexpected and they resulted from the relatively short term of data collection (maximum 6 years). Meanwhile, the investigation of groundwater around the national groundwater monitoring stations showed that the decreasing or increasing trends of water levels, electrical conductivities, themselves, didn't indicate directly groundwater hazards such as groundwater depletion or groundwater contamination. Both the values and variation rates (slopes) of water level, electrical conductivity and temperature in the longer period are considered simultaneously. This study is the first comprehensive work in analyzing trends of groundwater data obtained from the national groundwater monitoring stations. Based on this study, the periodical and regular analysis of groundwater data is essentially required to grasp the overall variational trend of groundwater resources in the country.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.401-401
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• 2023

터널이나 폐기물저장소와 같은 지하 구조물 또는 지표에서부터 상당한 깊이로 설계되거나 건설되는 구조물을 계획하거나 건축할 때 구조물의 안전성에 영향을 주는 수많은 요인 중에 간과할 수 없는 것이 바로 지하수이다. 뿐만 아니라 지상 혹은 지하에서 오염이 발생하여 오염물질이 지중환경으로 유입되는 경우, 지하수 거동은 오염물의 이송·확산에 지대한 요인으로 작용한다. 최근에는 지구온난화와 같은 유례없는 기후변화를 경험하고 있고, 따라서 수자원으로써 지하수의 역할이 더욱 중요해지고 있다. 지하수의 저류와 거동은 지하매질의 특성에 지배되고 있지만, 지표 아래 자리잡고 있는 매질의 특성을 정확히 파악하기란 매우 힘들고, 따라서 지하수 거동을 해석함에 항상 불확실성이 존재한다. 전통적으로 지하매질의 특성을 이해하기 위해 다양한 지구물리탐사를 수행하여 왔고, 더욱 직접적인 관찰을 위해 시추를 수행하여, 시료를 수집·관찰하고, 시추공에서의 다양한 현장수리실험을 통해 수리특성을 알고자 하였다. 하지만 그동안의 다양한 노력에도 불구하고, 지하매질 및 지하수 거동에 대한 불확실성은 여전히 줄어들지 않고, 오히려 증가하고 있다. 따라서, 본 연구에서는 지하수 거동을 결정짓는 지하매질의 수리특성에 대한 불확실성을 정량화하기 위한 도구로써, 매개변수 보정법의 하나인 Pilot Point Method(PPM)을 소개하고자 한다. 우물 또는 관측정을 통해 관측되는 지하수의 수위는 지하매질의 특성을 반영하고 있으며, 인간이 가장 쉽게 취득할 수 있는 지하 정보에 해당한다. 지하수 수위를 이용하여 수치모형의 매개변수를 보정하게 되며, 이 때 PPM이 적용된다. Pilot points의 공간적인 분포에 따라 다양한 보정 결과가 산출될 수 있으며, 다양한 결과들을 통해 변동계수를 산정한 후 수리특성의 불확실성이 높은 지역을 나타낼 수 있다. 본 연구를 통해 얻은 결과는 물리탐사 또는 시추 작업을 위한 위치 선정의 기초자료로 활용될 수 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.71-84
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• 1985

Using a saturated-unsaturated transient flow equation the change of hydraulic heads within a dike due to tidal fluctuation is investigated in this study. The calculation is done by the use of a software computer program called FLUMP, which is based on a FEM technique and useful to the analyses of unsaturated flow problems. Some of the program has been supplemented in this study for the application to the rise of a tide. It is assumed that a dike is composed of two materials, that the tide rises and falls with a constant amplitude of 10 meters, and that water tables are located at 0m, 5m, and lam from the minimum tidal level. For these conditions the hydraulic heads are calculated for 8 cycles(96 hours) of tidal changes. It is known from the analysis that the hydraulic heads change with tidal level in some extent and that the amplitudes of the head varies depending on the location within the dike: the maximum amplitude shows near the toe of the dike, the amplitude decreases with increasing distance from the upstream face, and beyond a certain location the heads are unaffected by the tidal differences. Assuming that the dike has been completed in a moment the hydraulic heads are nearly stabilized in 96 hours towards some constant values corresponding to a specified water table.

• Journal of the Korean GEO-environmental Society
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• v.15 no.6
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• pp.5-15
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• 2014

This study is to quantitatively evaluate the impact on surrounding groundwater of waterway tunnel excavation and cofferdam construction in which A-dam and B-dam, so prediction of groundwater fluctuation and tunnel lining installation was studied. As a result, drawdown of groundwater level during tunnel excavation and cofferdam construction occurred about 3.58 m in the tunnel shaft. The initial condition of groundwater level recovered by up to 90 % was simulated after the completed the construction of the tunnel and lining installation. Groundwater inflow in the tunnel evaluated was analyzed to have exceeding water design criteria of the tunnel. The groundwater inflow is reduced to maximum $0.006m^3/min/km$ after lining installation done in the tunnel, so effect of lining installation was evaluated as 93 % or more. Drawdown of about 0.04~0.31 m occurs in the houses and temples analysis of groundwater system of the surrounding area from construction. Drawdown has occurred nearly by considering annual groundwater level fluctuation of National Groundwater Observation Network.

• Geotechnical Engineering
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• v.8 no.1
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• pp.81-102
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• 1992

Landslides on hillside slopes with shallow soil cover over a sloping bedrock are frequently caused by increases in porewater pressures following of heavy rainfall and it is one of the most important factors of assessing the risk of landslide to predict the groundwater level fluctuations in hillslopes. This paper presents the comparative study of three unsaturated flow models developed by Sloan et al., Reddi, L.N., and Thomas, H.A., Jr., respectively, which are used to predict the increase of groundwater levels in hillside slopes. The parametric study for each of models is also presented. The Kinematic Storage Model(KSM) developed by Sloan et at. is utilized to predict the saturated groundwater flow. They are applied to the two sites in Korea so as to examine the possibility of use in the groundwater flow model. The results show that two unsaturated models developed by Sloan et al. and Reddi, L. N. are largely affected by the uncertain parameters like saturated permeability and saturated water content : the abed model has the potential of use in unsaturated flow model with the optimal estimates of model parameters utilizing available optimization techniques. And it is also found that the KSM must be modified to account for the time delay effect in the saturated zone. The results of this paper are able to be utilized in developing the predictive model of groan dwater level fluctuations in a hillslope.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.65-74
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• 2005

National groundwater monitoring stations have been managed throughout the country by Korea Water Resources Corporation (KOWACO) in order to monitor variations in quantity and quality of groundwater resources. A multi-sensor installed in each monitoring station well measures groundwater level, water temperature and electrical conductivity every six hours and the logged data are automatically transmitted to a host computer in KOWACO. Meanwhile despite regular station inspection and replacement of deteriorate or broken devices, abnormal values or outliers often occur due to intrinsic limitations of automatic monitoring and transmission. Thus prompt recognition and measures to these values are essentially required to reduce disturbance and missing period of the data. In this study, time and frequency of outlier occurrence were analyzed for the water level data obtained from national groundwater monitoring stations within the Han river basin in 2000. The analysis results indicated that the most prominent patterns of the outliers were rapid decline for water level, no variation for temperature and steep decline for electrical conductivity. This study provided a sample criterion for determining the outlier for each parameter.

• Journal of Korea Water Resources Association
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• v.38 no.7 s.156
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• pp.517-526
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• 2005

In Korea, the methods of estimating groundwater recharge can categorized into two groups. One is baseflow separation method by means of groundurater recession curve, the other is water level fluctuation method by using the data from groundwater monitoring wells. Baseflow separation method is based on annual recharge and lumped concept, and water-table fluctuation method is largely dependent on monitoring wells rather than water budget in watershed. However, groundwater recharge rate shows the spatial-temporal variability due to climatic condition, land use and hydrogeological heterogeneity, these methods have various limits to deal with these characteristics. For this purpose, the method of estimating daily recharge rate with spatial variability based on distributed rainfall-runoff model is suggested in this study. Instead of representative recharge rate of large watershed, the subdivided recharge rate with heterogeneous characteristics can be computed in daily base. The estimated daily recharge rate is an advanced quantity reflecting the heterogeneity of hydrogeology, climatic condition, land use as well as physical behaviour of water in soil layers. Therefore, the newly suggested method could be expected to enhance existing methods.