• Journal of Korea Water Resources Association
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• v.37 no.5
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• pp.397-406
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• 2004

It is necessary to estimate the groundwater recharge rate properly to evaluate the reasonable development amount of groundwater in a specific site. A small basin in Wicheon River Basin located in the Province of Kyungsangbuk-Do is selected to calculate the groundwater recharge rate. Average annual groundwater recharge rates are calculated from 1992 to 1997 because wet and draught year are contained during this period. In the calculation, baseflow separation method and SCS-CN method are applied to this area. As a result of estimation by baseflow separation method, the value of groundwater recharge ratio is varied between 11.9% and 18.7%. The average annual recharge rate is 14.5%. The average annual recharge rate calculated by SCS-CN method is varied between 7.9% and 20.9%. The average annual recharge rate in the calculation period is 15.1%. The results show that the average annual recharge amount from infiltration in the study basin is 141.6mm and 147.4mm in each estimation method. It appears that the average annual recharge amount calculated for the long period containing wet and draught year by the two methods is useful for groundwater development.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.305-312
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• 2011

Because groundwater recharge shows spatial-temporal variability due to climatic conditions, it is necessary to investigate land use and hydrogeological heterogeneity, and estimate the spatial variability in the daily recharge rate based on an integrated surface-groundwater model. The integrated SWAT-MODFLOW model was applied to compute physically based daily groundwater recharge in the Jincheon region. The temporal variations in estimated recharge were calibrated using the observed groundwater head at several National Groundwater Monitoring Stations and at automatic groundwater-monitoring sites constructed during the Basic Groundwater Investigation Project (2009-2010). For the whole Mihocheon watershed, including the Jincheon region, the average groundwater recharge rate is estimated to be 20.8% of the total rainfall amount, which is in good agreement with the analytically estimated recharge rate. The proposed methodology will be a useful tool in the management of groundwater in Korea.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.2
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• pp.57-65
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• 1998

Recently, many researchers have studied on the estimation of groundwater storage and its usable amount in Korea. Those studies were, however, mostly on the groundwater recharge amount over the nation or for the large extent of areas. On the other hand, it has been also needed to study on the regional recharge rate for the planning of groundwater management or for the assessment of groundwater development impacts. In this paper, two practical methods for the estimation of regional groundwater recharge have been studied and proposed, which are $\circled1$ the estimation of the groundwater recharge due to the SCS-CN infiltration method, and $\circled2$ the estimation of groundwater recharge ratio by analyzing groundwater level hydrographs.

• 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 Environmental Science International
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• v.23 no.4
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• pp.625-635
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• 2014

Temporal variation of groundwater levels in Jeju Island reveals time-delaying and dispersive process of recharge, mainly caused by the hydrogeological feature that thickness of the unsaturated zone is highly variable. Most groundwater flow models have limitations on delineating temporal variation of recharge, although it is a major component of the groundwater flow system. A new mathematical model was developed to generate time series of recharge from precipitation data. The model uses a convolution technique to simulate the time-delaying and dispersive process of recharge. The vertical velocity and the dispersivity are two parameters determining the time series of recharge for a given thickness of the unsaturated zone. The model determines two parameters by correlating the generated recharge time series with measured groundwater levels. The model was applied to observation wells of Jeju Island, and revealed distinctive variations of recharge depending on location of wells. The suggested model demonstrated capability of the convolution method in dealing with recharge undergoing the time-delaying and dispersive process. Therefore, it can be used in many groundwater flow models for generating a time series of recharge.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.113-114
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• 2004

In order to classify the groundwater recharge characteristics in an urban area, a time series analysis of groundwater level data was performed. For this study, the daily groundwater level data from 35 monitoring wells were collected for 3 years (Fig. 1). The use of the cross-correlation function (CCF), one of the time series analysis, showed both the close relationship between rainfall and groundwater level change and the lag time (delay time) of groundwater level fluctuation after a rainfall event. Based on the result of CCF, monitored wells were classified into two major groups. Group I wells (n=10) showed a fast response of groundwater level change to rainfall event, with a delay time of maximum correlation between rainfall and groundwater level near 1 to 7 days. On the other hand, the delay time of 17-68 days was observed from Group II wells (n=25) (Fig. 1). The fast response in Group I wells is possibly caused by the change of hydraulic pressure of bedrock aquifer due to the rainfall recharge, rather than the direct response to rainfall recharge.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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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.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.351-356
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• 2002

Groundwater recharge rate was estimated by applying the groundwater level fluctuation method utilizing Theis (1937) approach with specific yield estimation technique of Shevenell (1996) and the temperature method using observed data from National Groundwater Observation Stations. Results based on analysis of water level observation data of 10 alluvium wells reveal that the recharge rates for 5 wells of Kum river area range 3.7~25.0% and those for 5 wells of Nakdong river area range 3.6~21.7%. Results obtained from the temperature method based on water temperature data indicated that the upward flow resulted from evapotranspiration is dominant for 4 wells of the Kum river area and 5 wells of the Nakdong river area. The other wells showed the downward flow which is related to groundwater recharge in these areas.

• Journal of Soil and Groundwater Environment
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• v.6 no.1
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• pp.33-43
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• 2001

A calculation technique which estimates natural recharge using groundwater level change was proposed and prepared with the existing techniques using groundwater recession curve during dry days. As a part of estimating natural groundwater recharge nation wide, the reliable data from the national groundwater monitoring network were used and the methodology was applied to the three sites which have enough data (Chungju, Jinju and Kwangju). For this study, seasonal variation of groundwater level change, an analysis of lagging time on groundwater level and cumulative precipitation, and a comparative study for groundwater recharge were conducted.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.515-522
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• 2013

To investigate groundwater variation characteristics in the Hancheon watershed, Jeju Island, an integrated hydrologic component analysis was carried out. For this purpose, SWAT-MODFLOW which is an integrated surface-groundwater model was applied to the watershed for continuous watershed hydrologic analysis as well as groundwater modeling. First, ephemeral stream characteristics of Hancheon watershed can be clearly simulated which is unlikely to be shown by a general watershed hydrologic model. Second, the temporally varied groundwater recharge can be properly obtained from SWAT and then spatially distributed groundwater recharge can be made by MODFLOW. Finally, the groundwater level variation was simulated with distributed groundwater pumping data. Since accurate recharge as well as abstraction can be reflected into the groundwater modeling, more realistic hydrologic component analysis and groundwater modeling could be possible.