• Journal of Environmental Science International
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• v.23 no.4
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• pp.615-623
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• 2014

The groundwater level varies according to the characteristics and composite materials of aquifer. In this study, specific yield and reaction factor which are the major two hydrogeological parameters in the WTF(Water Table Fluctuation) method were estimated and analyzed spatial characteristics. 8 groundwater level stations which have enough measuring period and high correlation with rainfall in the Hancheon watershed were used. The results showed that specific yield was randomly distributed and reaction factor showed inverse trend with altitude. If the enough data were collected, reaction factor according to altitude in ungauged points could be estimated by using these parameter characteristics.

• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.87-93
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• 2010

The change of water level in reservoirs is an important factor causing failure of bank slopes, i.e. landslide. The water level of Three Gorges reservoir in China fluctuate between 145 m and 175 m, as a matter of flood control. During its normal operational state, the rate of water level fluctuation is supposed to range from 0.67 m/d to 3.0 m/d. Majiagou slope is located on the left bank of Zhaxi River, 2.1 km up from the outlet. Zhaxi River is a tributary of the Yangtze River within the Three Gorges area, of which the water level changes with the reservoir. At the back of Majiagou slope, a 20 m long and 3~10 cm wide fissure developed just after the reservoir water level rose from 95 m to 135 m in 2003. This big fissure was a full suggestion of potential failure of this slope. In this study, the pore water pressure files obtained from seepage analysis were used to evaluate the change in factor of safety (FS) with reservoir water level. Slope stability analyses then were carried out, with fully specified slip surface and limit equilibrium method. In the limit equilibrium analysis, the contribution of negative pore water pressure to shear strength was considered by the use of Fredlund's shear strength equation for unsaturated soils. On the base of the analyses, the change of FS with reservoir water level was interpreted in detail. It was found that FS against bank slopes decreases with the rise of the reservoir water level and increases with the drawdown of the reservoir water level. The most dangerous state was when the reservoir water level stays at the highest for a long time.

• Journal of Environmental Science International
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• v.3 no.4
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• pp.333-348
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• 1994

The groundwater levels at 11 sites and the vertical variations o( the water Quality at 1 site were measured to study the characteristic of the groundwater level fluctuation of Cheju Island. The results of the measurements for the groundwater levels were as follows; In the eastern part, inculding Kimnyong, Jongdal and Sungsan, a sinusoidal fluctuation of groundwater levels occurred in response to oceanic tides. The tidal effect on the groundwater level was reduced depending upon the distance from seashore. But time lag showed that the trend is reversed. However, in the Samyang, Kosan and Shinhyo areas show that the groundwater level was directly influenced by the amount of precipitation. Especially, Shinhyo area which southern part in Cheju was affected the most and show upper parabasal groundwater level. In Susan- I which eastern part in Cheju, well rovealed that water Quality changed with the period of a tide. Salinity at the lim, bellow the natural groundwater level, was approched to the brackish groundwater(1000ppm).

• Journal of Environmental Science International
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• v.26 no.10
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• pp.1135-1146
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• 2017

At riverbank filtration sites, groundwater levels of alluvial aquifers near rivers are sensitive to variation in river discharge and pumping quantities. In this study, the groundwater level fluctuation, pumping quantity, and streamflow rate at the site of a riverbank filtration plant, which produces drinking water, in the lower Nakdong River basin, South Korea were interrelated. The relationship between drawdown ratio and river discharge was very strong with a correlation coefficient of 0.96, showing a greater drawdown ratio in the wet season than in the dry season. Autocorrelation and cross-correlation were carried out to characterize groundwater level fluctuation. Autoregressive model analysis of groundwater water level fluctuation led to efficient estimation and prediction of pumping for riverbank filtration in relation to river discharge rates, using simple inputs of river discharge and pumping data, without the need for numerical models that require data regarding several aquifer properties and hydrologic parameters.

• Journal of Industrial Technology
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• v.30 no.B
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• pp.83-89
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• 2010

Generally, the accuracy of the prediction of flood elevation is difficult to identify due to the sedimentation on a river bed, earth and sand being moved by flow, and localized torrential downpours caused by climate change. It is also because of natural and artificial influences on rivers. To predict river floodings successfully, more precise and reliable flood elevation prediction system is needed, in which the concentration time of downstream is numerically interpreted through analyzing and utilizing the watermark of the upper region. Therefore, this research analyzed the prediction methods of the changes in water levels, which use the watermarks of the upper region. The watermarks which impacts the spot being predicted of flood was selected through floodgate analysis and correlation analysis. With the selected watermarks, a statistically reliable regression equation was yielded.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.28-31
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• 2002

The water level fluctuation (WLF) method is a conventional method for quantifying groundwater recharge by multiplying the specific yield to the water level rise. A 2-D unconfined flow model with a time series of the recharge rate is developed. It is used for elucidating the errors of the WLF method which is implicitly based on the tank model where the horizontal flow in the saturated zone is ignored. Simulations show that the recharge estimated by the WLF method is underestimated for the observation well near the discharge boundary. This is due to the fact that the hydraulic stress resulting from the recharge is rapidly dissipating by the horizontal flow near the discharge boundary Simulations also reveal that the recharge was significantly underestimated with increase in the hydraulic conductivity and the recharge duration, and decrease in the specific yield.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.1
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• pp.33-41
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• 1999

Time-lag and amplitudes of the fluctuation of groundwater level are used to determine hydraulic parameters around Han River. The groundwater level at observation wells fluctuates between highest and lowest responding to the Han River level. The factors affecting the groundwater fluctuation are examined. The transmisivity of the Han River alluvium calculated from the measured water table fluctuations measured ranges from 9.39${\times}$10$^1$to 4.02${\times}$10$^3$㎡/day. Based on the hydrogeological data along the river sides, the flow characteristics of groundwater for water level fluctuations were simulated using a ground water flow model MODFLOW.

• 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.

• Geotechnical Engineering
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• v.12 no.6
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• pp.65-78
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• 1996

The Chungpyung Dam is a 16 yearn old rock-fill dam for a Pumped storage hydro-Power plant, located in the middle of the Korean Peninsula. Since the dam is subjected to the daily water level fluctuation, such as rapid drawdown and refill, thus inducing a structural impact on the behavior of dam body, it draws attention of many engineering concerns. Traditionally, steady-state analysis was employed to investigate the seepage in the dam body, but in this study the seepage analysis was numerically performed by 2-D FEM thansient analysis. As a boundary condition for an analysis, the water level fluctuation was incorporated to simulate the daily change. As a res41t, the various seepage phenomena such as hydraulic gradient, seepage vector, and pore water pressure distribution were quantified at the corresponding time of interest as the water level rises and recedes. The seepage flux was also estimated and compared with the measured data which were both acceptable considering design criteria. The result proves that there is no sign of hazardous sources contributing to the possibility of piping, internal erosion and excess leakage through the dam body.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.68-71
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• 2006

Seasonal fluctuation of groundwater level by pumping amount and stream discharge at the riverbank filtrate site adjacent to the Nakdong River in Daesan-Myeon was characterized. Groundwater level fluctuation shows increase in wet season (June, July, August and September) and decrease in dry season (the other months). Seasonal variation of pumping amount shows similar trend to the groundwater fluctuation due to higher consumption of potable water in summer. The relation of specific capacity, Nakdong River and pumping quantity was analyzed. The logarithmic relationship between specific capacity and the stream discharge gives high correlation coefficient, 0.96. This fact indicates that the increase of stream discharge rate reduces the rate of drawdown in the pumping area in wet season.