• 한국환경과학회지
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• 제15권3호
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• pp.253-260
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• 2006

Groundwater recharge from precipitation is affected by the infiltration from ground surface and the movement of soil water. Groundwater recharge is directly related to the groundwater amount and flow in aquifers, and baseflow to rivers. Determining groundwater recharge rate for a given watershed is a prerequisite to estimate sustainable groundwater resources. The estimation of groundwater recharge rate were carried out for three subwatersheds in the Wicheon watershed and two subwatersheds in the Pyungchang River basin and for the period 1990-2000, using the NRCS-CN method and the baseflow separation method. The recharge rate estimates were compared to each other. The result of estimation by the NRCS-CN method shows the average annual recharge rate 15.4-17.0% in the Wicheon watershed and 26.4-26.8% in the Pyungchang River basin. The average annual recharge rates calculated by the baseflow separation method ranged 15.1-21.1% in the W icheon watershed, and 25.2-33.4% in the Pyungchang River basin. The average annual recharge rates calculated by the NRCS-CN method is less variable than the baseflow separation method. However, the average annual recharge rates obtained from the two methods are not very different, except NO. 6 subwatershed in Pyungchang River basin.

• 한국환경과학회지
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• 제16권5호
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• pp.561-569
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• 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.

• 한국수자원학회논문집
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• 제37권5호
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• pp.397-406
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• 2004

어떤 특정 지역의 지하수 개발량을 적적히 파악하기 위해서는 지하수함양량의 산정이 필요하다. 경상북도에 위치한 위천 유역내의 소유역에 대하여 지하수 함양량을 산정하였다. 기저유출분리법과 SCS-CN방법을 이용하여 갈수년과 풍수년이 존재하는 1992년∼1997년간의 년 평균 지하수 함양량을 추정하였다. 기저유출분리법을 이용하여 추정한 결과, 연평균 지하수 함양률이 11.9%∼18.7%로 변화하였으며 계산기간 중의 년 평균 강수에 의한 지하수 함양량은 141.6mm로 지하수함양률은 14.5%이었다. SCS-CN방법을 이용하여 추정한 결과, 연평균 지하수 함양균이 7.9%∼20.9%로 변화하였으며 계산기간 중의 년 평균 강수에 의한 피하수 함양량은 147.4mm 로 지하수 함양률은 15.1%이었다. 두 방법으로 산정한 갈수년과 풍수년이 존재하는 장기간 동안의 년 평균 강수에 의한 지하수 함양량은 지하수 개발에 유용하게 사용할 수 있음을 나타낸다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 추계학술발표회
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• pp.88-91
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• 2001

The purpose of this study is to localize the recharge rate into the national scale, calculated by use of the groundwater level from the 123 monitoring stations. The soil type, land use type, and bedrocks are selected for the influential factors over recharge rate. The main hypothesis is that the recharge rate can be expressed by the sum of the weighted averages of recharge rates of each factors. The optimized weights of soil type, land-use time and bedrocks from 119 stations are 0.80, 0.18 and 0.02 respectively. So this study offers that localization is available from the recharge rates calculated by groundwater level monitoring results.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권6호
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• pp.22-35
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• 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.

• 한국물환경학회지
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• 제28권5호
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• pp.743-753
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• 2012

The hydrologic models, capable of simulating groundwater recharge for long-term period and effects on it of crops management in the agricultural areas, have been used to compute groundwater recharge in the agricultural fields. Among these models, the Soil and Water Assessment Tool (SWAT) has been widely used because it could interpret hydrologic conditions for the long time considering effects of weather condition, land uses, and soil. However the SWAT model couldn't represent the spatial information of Hydrologic Response Unit (HRU), the SWAT HRU mapping module was developed in 2010. With this capability, it is possible to assume and analyze spatio-temporal groundwater recharge. In this study, groundwater recharge of rate for various crops in the Mandae stream watershed was estimated using SWAT HRU Mapping module, which can simulate spato-temporal recharge rate. As a result of this study, Coefficient of determination ($R^2$) and Nash-Sutcliffe model efficiency (NSE) for flow calibration were 0.80 and 0.72, respectively, and monthly groundwater recharge of Mandae watershed in Haean-myeon was 381.24 mm/year. It was 28% of total precipitation in 2009. Groundwater recharge rate was 73.54 mm/month and 73.58 mm/month for July and August 2009, which is approximately 18 times of groundwater recharge rate for December 2009. The groundwater recharges for each month through the year were varying. The groundwater recharge was smaller in the spring and winter seasons, relatively. So, it is necessary to enforce proper management of groundwater recharge during droughty season. Also, the SWAT HRU Mapping module could show the result of groundwater recharge as a GIS map and analyze spatio-temporal groundwater recharge. So, this method, proposed in this study, would be quite useful to make groundwater management plans at agriculture-dominant watershed.

• 한국지반환경공학회 논문집
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• 제9권7호
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• pp.73-85
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• 2008

우리나라에는 1995년부터 전국에 지하수 관측소를 설치하여 2005년에 320개소를 완료하였으며, 일 4회 지하수위 자료가 자동 측정되고 있다. 지하수 수위 강하곡선법으로 산정한 관측 지점에서의 지하수 함양율 자료의 평균값을 유역 평균 함양율로 사용하는 것은 대표성이 결여되어 있기 때문에 한계가 있다. 따라서, 본 연구에서는 지하수위 미계측 지역을 대상으로 지하수 함양율을 추정할 수 있도록 223개 관측 지점의 특성 인자와 지하수 함양율과의 관계를 통계적 기법을 활용하여 분석하고 이를 토대로 회귀모형을 구축하였다. 본 연구에서는 군집분석을 통하여 분석대상 관측정을 선정하고, 분산분석을 통하여 지하수 함양량 추정에 필요한 4가지 인자(대상 지점 인근하천의 규모, 하천까지 거리, 지형 경사도, 암석 성인)를 추출하였으며, 이들 인자에 대한 각 관측지점의 특성 자료를 수집하여 회귀 모형에 적합시킨 결과 미계측 지역의 지하수 함양율 추정이 가능한 것으로 평가되었다.

• 한국환경과학회지
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• 제24권4호
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• pp.495-504
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• 2015

To estimate water balance of Pyosun watershed in Jeju Island, a three-dimensional finite difference model MODFLOW was applied. Moreover, the accuracy of groundwater flow modeling was evaluated through the comparison of the recharge rate by flow modeling and the existing one from water balance model. The modeling result under the steady-state condition indicates that groundwater flow direction was from Mt. Halla to the South Sea and groundwater gradient was gradually lowered depending on the elevation. Annual recharge rate by the groundwater flow modeling in Pyosun watershed was calculated to 236 million $m^3/year$ and it was found to be very low as compared to the recharge rate 238 million $m^3/year$ by the existing water balance model. Therefore, groundwater flow modeling turned out to be useful to estimate the recharge rate in Pyosun watershed and it would be available to make groundwater management policy for watershed in the future.

• 한국환경과학회지
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• 제13권12호
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• pp.1033-1039
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• 2004

The methodology developed by Soil Conservation Service for determination of runoff value from precipitation is applied to estimate the precipitation recharge in the Pyungchang river basin. Two small areas of the basin are selected for this study. The CN values are determined by considering the type of soil, soil cover and land use with the digital map of 1:25,000. Forest covers more than $94{\%}$ of the study area.. The CN values for the study area vary between 47 in the forest area and 94 in the bare soil under AMC 2 condition. The precipitation recharge rate is calculated for the year when the precipitation data is available since 1990. To obtain the infiltration rate, the index of CN and five day antecedent moisture conditions are applied to each precipitation event during the study period. As a result of estimation, the value of precipitation recharge ratio in the study area vary between $15.2{\%}\;and\;35.7{\%}$ for the total precipitation of the year. The average annual precipitation recharge rate is $26.4{\%}\;and\;26.8{\%}$, meaning 377.9mm/year and 397.5mm/year in each basin.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.574-578
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• 2003

There are so many methods to estimate the groundwater recharge. These methods can be categorized into four groups. First groupis related to the water balance analysis, second group is concerned with baseflow/springflow recession, and third group is interested in some types of tracers; environmental tracers and/or temperature profile. The limitation of these types of methods is that the estimated results of recharge are presented in the form of an average over some time period. Forth group has a little different approach. They use the time series data of hydraulic head and specific yield evaluated from field test, and the results of estimation are described in the sequential form. But their approach has a serious problem. The estimated results in forth typeof methods are generally underestimated because they cannot consider the discharge phase of water table fluctuation coupled with the recharge phase. Ketchum el. at. (2000) proposed calibrated method, considering recharge- and discharge-coupled water table fluctuation. But the dischargeis considered just as the areal average with discharge rate. On the other hand, there are many methods to estimate the source wavelet with observed data set in geophysics/signal processing and geophysical methods are rarely applied to the estimation of groundwater recharge. The purpose this study is the evaluation of the applicability of one of the geophysical method in the estimation of sequential recharge rate. The applied geophysical method is called minimum entropy deconvolution (MED). For this purpose, numerical modeling with linearized Boussinesq equation was applied. Using the synthesized hydraulic head through the numerical modeling, the relative sequenceof recharge is calculated inversely. Estimated results are very concordant with the applied recharge sequence. Cross-correlations between applied recharge sequence and the estimated results are above 0.985 in all study cases. Through the numerical test, the availability of MED in the estimation of the recharge sequence to groundwater was investigated