• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.67-76
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• 2008

In this study, a combined model of a water-table fluctuation and a soil moisture content model is proposed for the estimation of groundwater recharge rate at a given location. To evaluate the model, groundwater level data from 4 monitoring wells (Pohang Yeonil, Pohang Kibuk, Suncheon Oeseo, Hongcheon Hongcheon) of National Groundwater Monitoring Network from 1996 to 2005 and precipitation data of corresponding years are used. From the proposed methodology, the groundwater recharge rates are estimated to be from 0.5 to 61.4% for Hongcheon Hongcheon, from 1.1 to 27.4% for Pohang Yeonil, from 5.1 to 41.4% for Pohang Kibuk, and from 1.1 to 8.3% for Suncheon Oeseo. The magnitude of variation of the estimated recharge rate depends on the soil type observed near the stations. The groundwater fluctuation model used in this study includes precipitation as a unique source of water-table perturbation and there may exist corollary limitations. To improve the applicability of the proposed method, a capillary-water content constitutive model for unsaturated fractured rock media may be considered. The proposed recharge rate delineation method is physically based and uses minimum numbers of assumptions. The method may be used as a better substitute for the previous tools for delineating recharge rate of a location using water-table fluctuation method and contribute to national groundwater management plan. Further research on the spatial interpolation of the method is under progress.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.43-51
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• 2008

Periodic fluctuation of water levels were analyzed for their causes and effects on groundwater movement. Groundwater levels were monitored from two shallow monitoring wells, G1 and G4, located at a headwater catchment in the Gwangneung Ecohydrological Research Site using pressure transducers with automatic data-loggers by five-minute interval from February to October, 2006. The water table fluctuates on a daily basis with a clear diurnal variation, and the fluctuation amplitude increases with time from the winter to the summer. Results from spectral analysis of water-level data show periodic variations in 24.38 hour and in 12.19 hour, indicating $P_1$ diurnal and $L_2$ semidiurnal tidal components, respectively. The diurnal component of the water level in summer has greater power than that in winter, implying that the water table is affected not only by earth tides, but also by evapotranspiration. Right after rain stops, the power of diurnal component of the water level decreases, indicating that evapotranspiration influences significantly diurnal periodicity. The effects of diurnal and semidiurnal components of the water level range from 0.4 to 4.2 cm and from 0.2 to 0.7 cm, respectively.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.431-444
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• 2020

The relationship between dam construction and water quality has recently come to be considered an important issue. A dam is a physical factor which causes changes to the river system around it. Considering these points, this study was conducted to obtain basic data by analyzing the relationship between water level fluctuations and water quality parameters in the short-term. In terms of methodology, the new construction of the Yeongju Dam (M5) in 2016 was divided into Stage 1 as the lotic system and Stage 2 as the lentic system, with four years in each period, and the water level fluctuations and water quality were analyzed using official data. As a result of this study, M5, a stagnant area in which organic matter and nutrients accumulate, was found to be an important factor in water quality management. In addition, the water level changed rapidly (0.9±0.2 m → 10.9±7.1 m) as the river environment condition was converted from the lotic system to the lentic system. In addition, water quality parameters such as BOD, COD, TOC, and Chl-a significantly changed in the short-term. Further, since the transport of organic matter and nutrients occurred well in the lotic system, sedimentation was expected to be dominant in the lentic system. Therefore, it was determined that when the river flow is blocked, autochthonous organic matter is an important factor for long-term water quality management in the future. This process can increase the trophic state of the water body. As a result of this study, the TSI_KO value was converted from mesotrophic in Stage 1 to eutrophic in Stage 2. Eventually, short-term changes in the river environment will affect not only changes in water level but also changes in water quality. Thus, a comprehensive and strategic approach is needed for long-term water quality management in the future.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.165.2-165.2
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• 2011

Flow with suction to water turbine must be in stable state at small hydraulic power plant. But because of water level fluctuation and water gate effect according to irregular supply of cooling water, it would happen to produce bubble and vortex and finally lead to problems in power-plant system. With utilizing the concept design of double size gate, surface water overflowed the overhead of gate for stable flow at suction. We developed the overflow condition and analyzed the design factor with existed one such as water level(overflow amount) and overhead of water gate(overflow figure). Flow test and CFD simulation say that flow have stable state around suction and 20% of wave reduction effect at surface layer after surface water overflow.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.109-115
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• 1996

The movement of water through a river embankment and its influenced upon the stability of the slope of the embankment are described. The stability of the embankment is depended upon the location of seepage line. As the seepage flow occurs in the embankment, the slope of the embankment loses its stability. Of particular interest is the stability following a rapid change of water level. The variation of seepage line in the embankment model by a fluctuation of water level is discussed. The experimental models were construction with slopes of 1 : 1.5, 1 : 2.0, 1 : 2.5 and the flow velocity was turned from 60cm/sec~90cm/sec. Based on the experimental study, the following conclusions are drawn. 1) When water level is raised, the seepage line of downstream slope Is raised rapidly as flow velocity increases. 2) For the case of permeable layer, the seepage line raised rapidly as compare with impermeable layer when water lever is raised.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.61-70
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• 2010

In case of groundwater recharge estimation using water table fluctuation method, specific yield affects the accuracy and confidence level of recharge rate. Nevertheless, there have been few studies on the method for the accurate estimation of specific yield in Korea. Specific yield estimated from the relationship between rainfall and groundwater levels is reasonable compared to the other methods. However, lots of factors such as artificial pumping, evapotranspiration by the plants, and a sudden increase in water levels by a heavy rainfall can affect the pattern of groundwater levels' fluctuation and make an over-estimated or under-estimated specific yield. This study obtained a reasonable specific yield by using a daily or 12 hourly average of rainfall and groundwater levels measured in a dry season.

• Journal of KSNVE
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• v.6 no.5
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• pp.671-677
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• 1996

This paper presents the analytical method for predicting turbulence- induced noise in the multilayered cylinder composed of an outer hose, an inner fluid and an internal core. It is assumed that an infinite axisymmetric cylinder is located horizontally in water with free stream velocity and the turbulent boundary layer (TBL) surrounding the outer hose is fully developed and homogeneous. The transfer function at the core surface due to the propagation of the pressure fluctuation within the TBL is formulated using the linearized Navier-Stockes equation for solid and fluid. In the estimation of the energy spectrum of wall pressure fluctuation, the empirical formula proposed by Strawderman based on the Corcos model is used. A general algorithm for the calculation of the pressure level at the surface of a core, that is, turbulence- induced noise, is presented. Through the detailed numerical simulation, it is found that the major noise mechanism is the propagation of the bulge wave along hose.

• Journal of the Korean Geosynthetics Society
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• v.20 no.1
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• pp.45-55
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• 2021

In this study, the behavioral characteristics of the fill dam were analyzed during water level fluctuations through a numerical analysis model, and the reservoir safety management plan was prepared. The variation in plastic deviatoric strain, horizontal displacement, stress path, pore water pressure, etc., due to elevation of water level in the upper and lower sides of shell and core were analyzed using numerical analysis software, viz. GTS NX and LIQCA. The analysis results manifest that as the water level in the dam body increases rapidly, the pore water pressure and displacement also increase quickly. It was found that the elevation of the water level causes an increase in pore water pressure in the dam body as well as an increase in the saturation of the dam body and decreased effective stress. It is considered that this type of dam behavior can be the cause of the reduction of strength and stiffness of the dam. Also, it is assumed that the accumulated plastic deviatoric strain due to the deformation of the dam body caused by water infiltration causes an increase in displacement. Based on these experimental results and the results of analyses of the existing reservoir safety diagnosis techniques, an improvement plan for dam safety diagnosis and evaluation criteria was proposed, and these results can be used as primary data while revising dam safety diagnosis guidelines.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2007.04a
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• pp.85-88
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• 2007

Sea level fluctuation present a direct influence to those who live near the coast. The importance of monitoring sea level is evident. Therefore, various techniques have been employed for sea level measurements such as the coastal water level gauges, satellite altimetry and GPS buoy. Especially, GPS buoys have been used to measure water levels, atmospheric parameter and other physical conditions in sea, tide correction, the altimeter range calibration, ocean environment. In this paper, we will mainly concentrate on the kinematic technique for GPS buoy to measure the sea level. A test was carried out to test the method proposed in this paper, which made use of a GPS buoy equipped to monitor the sea level in Busan. We have executed to analysis about applications of GPS buoy.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.158-167
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• 1999

In parallel flow condition, to estimate the stability of the extended embankment constructed on a permeable foundation ground, a laboratory model test was performed due to extended materials and water level increasing velocity of a flood period. A laboratory model test was peformed for different permeability coefficients ($K_1=2.0{\times}10^{-5}cm/sec,\;K_2=1.5{\times}10^{-4}cm/sec,\;K_3=2.3{\times}10^{-3}cm/sec$) using seepage. The fluctuation of water level occurring to an extended embankment was analyzed by laboratory model tests as vary the increasing velocity of water level with 0.6cm/min, 1.2cm/min, 2.4cm/min respectively. In analysis results, the increase of water level into embankment occurs rapidly because seepage water moving along with a permeable soil flow into embankment. The larger the permeability coefficient of an extended part is the longer initial seepage distance, and the exit point of downstream slope is gradually increased and then shows unstable seepage behavior as occurring partial collapse. As the increasing velocity of water level increase, the initial seepage line is formed low, and the discharge increases. Therefore, the embankment extended by a lower permeable soil than existing embankment shows stable seepage behavior because an existing embankment plays a role as filter for an extended part.