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.

The variation of groundwater level in Jeju Island is analyzed with the data of precipitation observed from 48 monitoring post and groundwater level observed from 84 monitoring wells during 2001 to 2009. The groundwater level rises in summer and falls in winter. The rise of groundwater level by precipitation is fast and small in the eastern region and slow and large in the western region. However, the speed of fall during the period of no rain is slower in the eastern region than in the western region. It tells that permeability is greater in the eastern region than in the western region. In this paper, we set up the base level of groundwater and calculate recharge volume between the base level and groundwater surface. During the period, the average recharge volume was 9.83 ×109㎥ and the maximum recharge volume was 2.667 ×1010㎥ after the typhoon Nari. With these volume and the recharge masses obtained by applying the recharge ratio of 46.1%, estimated by Jeju Province (2003), the porous ratio over the whole Jeju Island is 16.8% in average and 4.6% in the case of maximum recharge volume just after typhoon Nari. A large difference in the two ratios is because that it takes time for groundwater permeated through the ground just after rain fall to fill up the empty porous part. Although the porous ratios over the whole Jeju Island obtained in this way has a large error, they give us the advantage to roughly estimate the amount of recharged groundwater mass directly from observing the groundwater level.

To solve a problem of water supply on urban areas, groundwater recharge has to be assessed not only for evaluating the possibility of groundwater development but also for identifying a sustainable aquifer system for water resource development. The assessment of groundwater recharge has been challenged since the land use has been changed constantly. In this study, the groundwater recharge and its ratio were assessed from 1961 to 2007 in Su-yeong-gu, Busan, South Korea by analyzing precipitation, land use, and soil characteristics. For land use analysis, the urbanization change was considered. The land use areas for the residential, agricultural, forest, pasture, bare soil, and water in 1975 occupy 18.6 %, 30.0%, 48.8%, 0.1%, 2.0%, and 0.5% of total area, respectively. The land use ratios were sharply changed from 1980 to 1985; the agricultural area was decreased to 18.3%, and the residential area was increased to 15.0%. From 1995 to 2000, the agricultural area was decreased to 5.5%, and the residential area was increased to 5.4%. The annual averages of precipitation, groundwater recharge, and its ratio were 1509.3 mm, 216.0 mm, and 14.3% respectively. The largest amount of the groundwater recharge showed in 1970 as 408.9 mm, comparing to 2138.1 mm of annual rainfall. Also, the greatest ratio of the groundwater recharge was 19.8% in 1984 with 1492.6 mm of annual rainfall. The lowest amount and ratio of the groundwater recharge were 71.9 mm and 8.0% in 1988, relative to 901.5 mm of annual precipitation. As a result, it is concluded that rainfall has increased, whereas groundwater recharge has decreased between 1961 and 2007.

본 연구에서는 SWAT 모형과 HELP 모형을 이용하여 보청천 유역의 지하수 함양량을 산정하였다. SWAT 모형은 지표수 및 지하수 성분을 모두 고려할 수 있는 물순환 모형이지만, 토양층에 대한 침루과정의 물리적 해석이 미흡하다. 반면에 HELP 모형은 중간유출 및 지하수 유출성분을 모의하지 못하지만, 토양층에서의 비포화흐름을 고려하여 침루과정을 해석할 수 있다. 국내유역에서 함양량 산정을 위해 SWAT 모형은 여러 유역에서 성공적으로 적용되어 왔지만,

Groundwater recharge characteristics in a fractured granite area, Mt. Geumjeong, Korea. was interpreted using bedrock groundwater and wet-land water data. Time series analysis using autocorreclation, cross-correlation and spectral density was conducted for characterizing water level variation and recharge rate in low water and high water seasons. Autocorrelation analysis using water levels resulted in short delay time with weak linearity and memory. Cross-correlation function from cross-correlation analysis was lower in the low water season than the high water season for the bedrock groundwater. The result of water level decline analysis identified groundwater recharge rate of about 11% in the study area.

본 연구에서는 대상유역인 경안천 유역 (유역면적 )에 대한 지하수 함양량 추정을 위해, 완전 분포형 모형인 MIKE SHE를 적용하였다. 모형 입력자료로서 DEM 토지이용도, 정밀토양도 등과 같은 GIS 자료를 구축하고, 기상자료를 이용하여 증발산 입력자료를 생성하였다. 유역 최종 출구점인 경안 수위표 지점에서의 유출자료를 활용하여 모형 보정과 검증을 수행한 결과, 관측치의 경향을 잘 모의하는 것으로 나타났으며, 유역내 운영되고 있는 마평 지하수위 관측

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 Wicheon 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.

현재 우리나라에서 주로 사용되는 지하수 함양량 추정방법은 지하수 감수곡선에 의한 기저유출분리법과 관측공의 자료를 이용한 지하수위 변동법으로 대별된다. 기저유출분리법은 연단위기반의 집중형 개념의 접근법을 사용하며, 지하수위변동곡선해석법은 유역단위의 물수지 개념보다는 국지적인 지하수 관측정의 변화에 주로 의존하고 있다. 한편 지하수 함양량은 기후조건, 토지이용, 관개와 수리지질학적 비균질성에 의해 현저한 시공간적 변동성을 나타내고 있어서 위의 두 가지 방법

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

우리 나라 갈수기의 하천유출은 대부분 지하수에서 공급되는 유출이므로 홍수기 강우량에 의해 침투한 유역의 수분상태에 지배된다. 따라서, 홍수기의 지하수 함양량 추정을 통한 유역 상태 정보를 이용한다면 갈수기 월유출 예측을 만족스럽게 수행할 수 있는 수문학적 환경을 가지고 있다. 본 연구의 목적은 지하수 함양량에 의한 월유출량의 영향을 평가하고, 이를 다중회귀모형의 독립변수로 이용하여 장기 월유출량 예측을 시도하는 것이다. 해당 월의 유출량, 강수량, 선행

지하수 함양량을 추정하기 위한 방법으로 격자기반의 일변 토양수분 추적기법을 모델링하였다. 본 모델은 GRASS-GIS를 이용하여 모델에 필요한 자료들을 준비하고, 모델은 이들을 ASCII 형태로 받아들여 일별 수행결과(유역출구에서의 유출량, 지표유출 분포도, 토양수분 분포도 등)들을 GRASS상에서 도시하여 주는 형태로 구성하였다. 보청천유역의 일부인 이평교 유역()을 대상으로 모델의 적용성을 검토하였다. '95년 및 '96년도의 IHP유역 연구보고서

시계열모형과 시차분포모형을 결합한 동적모형을 이용하여 강우량과 지하수위의 관계를 파악하였다. 시차에 따른 현재 및 과거 강우량과 과거 지하수위를 독립변수로 하여 동적모형을 구성하였다. 지하수위에 미치는 시차에 다른 강우량의 영향을 Almon 다항식으로 분포시켜 시차분포모형의 매개변수를 추정하였다. IHP 대표유역의 방림과 탄부의 지하수위관측소에서 적용된 동적모형은 강우량에 따른 지하수위를 매우 잘 재현해 주고 있으며, 지하 수위의 예측에도 이용할 수 있