• Journal of Environmental Science International
• /
• v.16 no.5
• /
• pp.561-569
• /
• 2007

This study used SCS-CN method to estimate the real recharge of the study area which is one of the most reasonable techniques to estimate groundwater recharge when there is no available runoff data in a watershed. From the results of tile real recharge analysis for the study area using SCS-CN method, it was analyzed that the year 1994 when the drought was severe shotted the lowest recharge of 106.3mm with recharge rate of 12.4%, and the highest recharge of 285.6mm with recharge rate of 21.8% occurred in 1990. Yearly average recharge of 213.2mm was obtained, and tile average recharge rate was 16.9%/year. KOG-FLOW model which has powerful post process functions consists of setting environments for input parameters in Korean language, and help function is added to each input data. Detailed information for each parameter is displayed when the icon is placed on the input parameters, and geologic boundaries or initial head data for each layer can be set easily on work sheet. The relative errors (R. E.) for each model's observed values and calculated values are $0.156{\sim}0.432$ in case of KOG-FLOW, and $0.451{\sim}1.175$ in case of WINFLOW, therefore it is known that KOG-FLOW model developed in this study produced results compared to observed head values.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.986-990
• /
• 2009

Using artificial rainfall simulator, the soil loss, which is deemed as most cause of muddy water problem among Non-point source(NPS) pollutant, was studied by the analysis of direct runoff flow, groundwater runoff, and groundwater storage properties concerned with rainfall intensity, slope of area, and land cover. The direct runoff showed increasing tendency in both straw covered and bared boxes which are 5%, 10%, and 20% sloped respectively. Also the direct runoff volume from straw covered surface boxes were much lower than bared surface boxes. It's deemed as that the infiltration capacity of straw covered surface boxes were increased, because the surface sealing by fine material of soil surface didn't occurred due to the straw covering. Under the same rainfall intensity and slope condition, 2.4 ${\sim}$ 8.2 times of sediment yield were occurred from bared surface boxes more than straw covered surface boxes. The volume of infiltrated were increased due to straw cover, the direct runoff flow were decreased with decreasing of tractive force in surface. To understand of relationship the rate of direct runoff flow, groundwater runoff, and groundwater storage by the rainfall intensity, slope, and land cover, the statistical test was performed. It shows good relationship between most of factors, expect between the rate of groundwater storage and rainfall intensity.

• Journal of Soil and Groundwater Environment
• /
• v.21 no.6
• /
• pp.22-35
• /
• 2016

Global climate change could have an impact on hydrological process of a watershed and result in problems with future water supply by influencing the recharge process into the aquifer. This study aims to assess the change of groundwater recharge rate by climate change and to predict the sustainability of groundwater resource in Pyoseon watershed, Jeju Island. For the prediction, the groundwater recharge rate of the study area was estimated based on two future climate scenarios (RCP 4.5, RCP 8.5) by using the Soil Water Balance (SWB) computer code. The calculated groundwater recharge rate was used for groundwater flow simulation and the change of groundwater level according to the climate change was predicted using a numerical simulation program (FEFLOW 6.1). The average recharge rate from 2020 to 2100 was predicted to decrease by 10~12% compared to the current situation (1990~2015) while the evapotranspiration and the direct runoff rate would increase at both climate scenarios. The decrease in groundwater recharge rate due to the climate change results in the decline of groundwater level. In some monitoring wells, the predicted mean groundwater level at the year of the lowest water level was estimated to be lower by 60~70 m than the current situation. The model also predicted that temporal fluctuation of groundwater recharge, runoff and evapotranspiration would become more severe as a result of climate change, making the sustainable management of water resource more challenging in the future. Our study results demonstrate that the future availability of water resources highly depends on climate change. Thus, intensive studies on climate changes and water resources should be performed based on the sufficient data, advanced climate change scenarios, and improved modeling methodology.

• Water for future
• /
• v.27 no.1
• /
• pp.79-88
• /
• 1994

This study was conducted to analyse groundwater flow in the Bugok hot spring area using the MODFLOW model which can simulate three dimensional groundwater flow both in confined and unconfined aquifers. Based on this study the following conclusions were obtained: 1) The hydraulic conductivity and the specific storage of the aquifer were 0.0135 m/day and 0.020, respectively, and the model-predicted groundwater elevation agreed well with the observed one. 2) Simulation results showed that the groundwater level declines at the end of the one-year simulation period when the annual recharge rate is small and the annual pumping rate high, which is the worst combination. Except that combination, the groundwater level does not decline at the end of one-year simulation period indication the pumping rates used were allowable. 3) The safe yield depends upon the magnitudes of the recharge and pumping rates. The pumping rate should not produce excess decline of groundwater level around April when the water level is the lowest in a year.

• Journal of Environmental Science International
• /
• v.24 no.12
• /
• pp.1691-1703
• /
• 2015

When constructing tunnels, it is important to understand structural, geological and hydrogeological conditions. Geumgeong tunnel that has been constructed in Mt. Geumjeong for the Gyeongbu express railway induced rapid drawdown of groundwater in the tunnel construction area and surroundings. This study aimed to analyze groundwater flow system and baseflow using long-term monitoring and groundwater flow modeling around Geumgeong tunnel. Field hydraulic tests were carried out in order to estimate hydraulic conductivity, transmissivity, and storativity in the study area. Following the formula of Turc and groundwater flow modeling, the annual evapotranspiration and recharge rate including baseflow were estimated as 48% and 23% compared to annual precipitation, respectively. According to the transient modeling for 12 years after tunnel excavation, baseflow was estimated as $9,796-9,402m^3/day$ with a decreasing tendency.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.459-462
• /
• 2004

This study assesses groundwater vulnerability to contaminants in 12 administrative districts of the city of Changwon, using DRASTIC technique. DRASTIC was originally applied to situations in which the contamination sources are at the ground surface, and the contaminants flow into the groundwater with infiltration of rainfall. However, groundwater contamination in urban areas can also be related to excessive pumping resulting in a lowering of the water level. The correlation coefficient between minimum DRASTIC indices and the degree of poor water quality for 10 districts is low as 0.40. The correlation coefficients between minimum DRASTIC indices and the groundwater discharge rate, and between minimum DRASTIC indices and well density per unit area are 0.70 and 0.87, respectively. Thus, to evaluate the potential of groundwater contamination in urban areas, it is necessary to consider other factors such as groundwater withdrawal rate and well density per unit area with ratings and weights as well as the existing six DRASTIC factors.

• The Journal of Engineering Geology
• /
• v.16 no.3 s.49
• /
• pp.293-300
• /
• 2006

The groundwater movement in the west costal landfill area was analyzed by measuring N value by Standard Penetration Test, coefficient of permeability by falling head method, linear structure analysis by Digital Elevation Method, groundwater flow direction and rate by flowmeter logging due to tidal variation in the each borehole. The coefficients of permeability of the weathered zone and of the marine deposit showed similar values although some values of weathered zone show smaller values than those of the marine deposit. The major groundwater flow and rate in the marine deposit observed as east-west direction due to tidal variation, but on the other hand it was observed as N45E in weathered zone which is the major direction of the linear structures in the area. 2 hours delayed changes of the groundwater flow direction was observed during the 24 hours observation, and it seems to be a travel time of the tidal wave which cause the continuous change of the hydaulic gradient of the groundwater.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.09a
• /
• pp.89-92
• /
• 2004

The influence of a single fracture intersection on density-driven immiscible flow is compared between wetting (water into air) and nonwetting (Trichloroethylene into water) flows. At low supply rates, the intersection acted as a hysteretic gate to pulsed flow of the wetting phase, but had minimal influence on nonwetting phase flow. For both cases, increasing the supply rate led to the formation of continuous fluid tendrils that crossed the intersection without interruption. The wetting experiment returned to pulsed flow as the supply rate was decreased, while the nonwetting experiment maintained a continuous flow structure. Results suggest a fundamental difference between wetting and nonwetting phase flows in fracture network.

• The Journal of Engineering Geology
• /
• v.28 no.4
• /
• pp.529-540
• /
• 2018

Sand dam is a flow barrier commonly built on small or medium size sandy rivers to accumulate sand and store excess water for later use or increase the water table. The effectiveness of sand dam in increasing the water table and the amount of extractable groundwater is tested using numerical models. Two models are developed to test the hypothesis. The first model is to simulate the groundwater flow in a pseudo-natural aquifer system with the hydraulically connected river. The second model, a modified version of the first model, is constructed with a sand dam, which raises the riverbed by 2 m. In both models, the effect of groundwater abstraction is tested by varying the pumping rate. As the model results show the groundwater after the construction of the sand dam has increased significantly and the amount of extractable groundwater is also increased by many folds. Most importantly, in the second model, unlike the pseudo-natural aquifer system, the groundwater abstraction does not have a significant effect on the water table.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2012.05a
• /
• pp.26-26
• /
• 2012

The Kurobe river, which runs through eastern Toyama Prefecture is one of the most famous rivers for wild water because of its steep slope in the range from 1/5 to 1/120. This river forms an alluvial fan in the range up to 13 kilometers from the sea. In this region, significant seepage flow occurs and thus the stream sometimes been intermitted. Moreover, the amount of seepage flow seems to vary with the groundwater level of the region. To keep the river environment healthy for flora and fauna, especially to conserve good condition for spawning of fishes, an appropriate environmental flow should be maintained in the river. To achieve this target, controlling of the upstream reservoir has to be studied in depth. One of the major problems to decide the amount of water to be released from the reservoir to maintain the environmental flow is to estimate the amount of water leaked into the groundwater from the river. This phenomenon is affected by the river flow rate as well as the groundwater level in the alluvial fan and the conditions vary in space and time. Thus, a grid-based hydrological cycle analysis model NK-GHM has been applied to clarify the hydrological cycle componentsin this area including seepage/discharge from/to the river. The model was tested by comparing with river flow rate, groundwater levels and other observations and found that the model described those observations well. Consequently, the seepage from the Kurobe river was found significant but it was also found that the groundwater in this region has been preserved by the recharge from the irrigation water supply into paddy fields in the alluvial fan.