• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.415-420
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• 2017

유량자료는 연속적으로 관측하기가 쉽지 않을 뿐 아니라 모든 관측소에서 매년 적정한 유량자료를 생산하는 것 또한 매우 어려운 실정이다. 이에 따라 미계측 유역에 대한 유량 산정을 위해 많은 연구가 진행되고 있다. 영국의 "Low Flow Studies report(Institute of Hydrology, 1980)"에서는 갈수량 산정과 관련하여 기저유량비(Base Flow Index, BFI)를 사용하는 것을 추천하였다. 국내에서는 이와 관련한 적용 사례가 없기 때문에 본 연구에서는 BFI를 적용하여 미계측 유역의 갈수량을 산정하고자 하였다. 대상유역은 낙동강 권역의 22개 지점을 대상으로 실시하였으며, 기저유량비 및 평균 갈수량과 유역 및 수문인자들의 상관분석을 수행하였다. 분석을 통하여 기저유량비는 토양군 C와 지하수위를 독립변수로, 평균 갈수량은 기저유량비, 유역면적, 강수량을 독립변수로 선정하여 회귀분석을 실시하였다. 그 결과 개발한 기저유량비 지역회귀모형의 상대오차는 -26.5%(기계2)~57.2%(구영)의 범위로 분포하였고, 절대오차의 평균은 17.2%로 산정되었다. 평균 갈수량 지역회귀모형은 상대오차가 -38.4%(도천)~184.4%(길안)의 범위에서 분포하고 있으며, 절대오차의 평균은 47.3%이다. 그러나 소토, 기계2, 길안 지점을 제외하면 절대오차는 30.6%이다. 상대오차는 다소 부정적이지만 기존에 개발된 지역회귀모형으로 평균 갈수량을 산정한 결과와 비교하면 상대적으로 양호한 것으로 판단된다. 사용한 자료의 기간이 6년으로 통계적인 결과로 보기에는 다소 미흡한 측면이 있지만, 유역인자로서 BFI가 미계측 유역의 갈수량 특성을 설명할 수 있는 우수한 인자라고 판단하였다.

• Korean Journal of Environment and Ecology
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• v.16 no.3
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• pp.239-248
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• 2002

This study was conducted to investigate the hydrological characteristics of groundwater level change and rainfall-runoff processes at the Moojechi Bog located in Mt. Jeungjok, Ulsan. The average runoff rate of bog was 0.58 which is similar to that of general mountainous watershed. In the short term hydrograph, runoff was increased slowly and It took a long time to arrive peak flow. After that time, the decreasing pattern of runoff was slower than that of general mountainous watershed. In case of the long term water budget, the Moojechi Bog had a abundant base flow and runoff was continued in spite of non rainfall period. The groundwater level was arrived peak flow immediately after rain stop but was decreased very slowly until the next rain. The change pattern of long term groundwater level was very similar to that of the amount of rain and discharge. The higher rainfall intensity was, the lower slope of recession curve on the groundwater level was and the longer rainfall duration was, the longer peak flow was. Judging from these results, Moojechi bog could be evaluated to have a constant groundwater level.

• The Journal of Engineering Geology
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• v.30 no.3
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• pp.303-314
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• 2020

Bottled water companies submit monthly hydrologic data including periodical environmental effects investigation, daily water production capacity, water production, water level, water chemistry (pH, EC, temperature) per hour and strictly manage groundwater by periodical analyses. Thus few problems concerning drawdown due to excess intake of groundwater take place. Nevertheless, bottled water companies are imprinted as a contribution to civil affairs resulted regarding groundwater near the companies. Therefore, a new method is required during water balance analysis in environmental effects evaluation, which should be compatible with the evaluation by hydrologic experts as well more accessible to non-experts. In this study, water level of surface water and recharge rate in subcatchment where water production wells are located were measured and monthly baseflow rates were separated from normal streams. Besides, recharge properties of groundwater and surface water in the same catchment area were estimated using analyses of oxygen and hydrogen isotopes in groundwater (production well), surface water, and rainfall.

• Journal of Korea Water Resources Association
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• v.47 no.6
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• pp.501-511
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• 2014

The effects of initial conditions and input values of the rainfall-runoff model were studied in the applications of a lumped concept model for flood event data extension. For the initial conditions of the rainfall-runoff model, baseflow effects and spatial distributions of saturation points ($R_{sa}$) for the storage function methods (SFM) were analyzed. In addition, researches on the effects of rainfall data conditions as input values for the rainfall-runoff model were performed. The Chungju Dam watershed was selected and divided into 3 catchments including smaller size of 22 sub-catchments. The observed discharge and inflow amounts at Yeongwol 1, Chungju Dam, and Yeongwol 2 water level stations were individually operated as criteria for flood data extension in 30 flood events from 1993 to 2009. Direct and base flow were distinguished from a stream flow. In order to test capability of flood data extension, obtained base flow was applied to the rainfall-runoff model for three water level stations. When base flow was adopted in the model, the Nash-Sutcliffe Efficiency(NSE) was increased. The numbers of over satisfaction for model performance (>0.5) were increased over 10%. Saturation points ($R_{sa}$) which strongly influence the runoff amount when rainfall starts were optimized based on the runoff amount at three water level stations. The sizes of saturation points for three locations were similar which means saturation point size is not depending on the runoff amount. The effects of rainfall information for flood runoff were tested at 2002ev1 and 2008ev1. When increased the amount of rainfall information, the runoff simulations were closer to the simulations with full of rainfall information. However, the size of improvement was not substantial on rainfall-runoff simulations in terms of the size of total amount of rainfall.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.314-314
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• 2021

홍수(floods)는 인간의 생명과 재산에 큰 피해를 발생시키는 자연재해 중 하나로 최근 지구 온난화와 기후 변화로 인하여 홍수 발생 빈도와 강도가 증가하고 있다. 때문에, 홍수 발생 시 정확한 홍수량 산정을 위하여 유역 내 지표수 및 지하수 흐름 분석을 통하여 전반적인 물 순환의 이해가 필수적이다. 이에 본 연구는 지표수-지하수 연계 모형을 활용하여 홍수 발생 시 미호천 유역에서 지하수가 하천 유량에 미치는 영향을 분석한다. 본 연구는 Hydrological-Ecological Integrated watershed-scale Flow (HEIFLOW) 모형을 적용하여, 국내 유역 특성을 고려하여 시간단위 홍수 사상 분석을 수행한다. 모형 구축을 위하여 2013년과 2014년도의 미호천내의 7개 기상 및 강우관측소, 1개의 수위 관측소의 정보를 활용하여 지표수 모형을 구축하며, 같은 기간의 지하수 모형 구축을 위해 7개의 국가 지하수 관측망의 지하수 수위 자료와 유역의 수문지질도(Hydrogeological map)의 정보를 활용한다. 미호천 유역 내 HEIFLOW 모형의 홍수 모의 결과 산정된 하천 유량은 관측 유량과 0.79 R²의 우수한 모의 성능을 나타내고 있으며, 지하 수위 모의 역시 지하수 수위 변동을 적절하게 모의한다. 또한, 미호천 유역의 하류 지역은 하천으로 유출되는 지하수가 하천의 기저 유량에 상당한 영향을 미치는 것으로 나타나며 홍수 시에는 지하수 유출의 증가로 인한 급격한 첨두 홍수량의 상승을 보인다. 이와 같은 결과는 홍수 모의 시 지표면 유출 분석에 초점을 두고 있는 홍수 국내의 홍수량 산정 방법에 지하수의 거동 및 하천 유량에 미치는 영향을 정량적인 정보를 제공할 수 있을 것으로 판단되며, 추후 국내 홍수량 산정의 새로운 방법의 하나로 활용될 가능성을 보여준다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.75-87
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• 2007

Groundwater recharge rates were estimated and compared in a headwater catchment at the Gwangneung Supersite using three different methods: water-table fluctuation (WTF), mass balance, and hydrograph separation techniques. Data were obtained during the rainy season from June to September 2005. Two different WTF methods estimated the groundwater recharge rate as 25.9% and 23.6%. The mass balance calculation of chloride ions indicated recharge rates of 13.4% on average. Baseflow separation using chloride ion as a tracer from six storm hydrographs produced a 14.0% net baseflow rate on average. Because of the implicit assumption of a long-term steady state without storage change, recharge rates calculated by mass balance and hydrograph separation were smaller than those done with WTF methods, which include the amount of increased storage due to the water-level rise. Subsequently, the WTF method is superior to others in the estimation of groundwater recharge rate to comprehend the dynamic characteristics of the hydrologic cycle.

• Journal of Soil and Groundwater Environment
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• v.7 no.3
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• pp.45-59
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• 2002

This study is objected to demonstrate the spatial variability of the ground-water recharge by classifying the types of ground-water hydrographs and assessing the recharge ratio(the ratio of the rise of ground-water level to cumulative precipitation) of each type using the National Ground-water Monitoring network data. A total of 5 types were identified by factor analysis on the ground-water hydrographs nationwide. The recharge ratio of each type were estimated to be 6.5% (TYPE I), 4.1 % (TYPE II), 9.2%(TYPE III), 5.8 %(TYPE IV), 15.3 %(TYPE V) in the confidence level of 95.44% and 6% variation was estimated site by site even in the same type. The recharges of Han, Nakdong, Keum, Youngsan·Seomjin river basins were estimated as 10.0 %, 6.1 %, 8.3 %. and 6.6 % respectively. These results were consistent with the results of the existing baseflow method.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.382-385
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• 2002

부산 금정산 일대의 평균 수리전도도는 1E-6m/sec ~ 1E--8m/sec차수의 범위로 시험공별로 차이를 보이고 있다. 이 지역에서 지표면의 해발고도(X)에 따른 지하수위(Y)의 상관식 Y =1.00024*X - 3.26725 으로부터 지하수위를 추정하였다. 이 지역에 내린 총 강수량은 함양지역(24,524,131$m^2$)에 연평균강수량(1477.5mm)를 곱한 값(36,234,404㎥/yr)이고, 총 함양량은 기저유출량까지 합한 양(9,073,254㎥/yr)이다 증발산량은 강수량의 약 49%이므로 17,754,858㎥/yr이다. 온천수 사용량은 2,500㎥/day이고, 산성마을의 지하수 사용량은 1,000㎥/day으로 보면, 인위적인 양수량은 1,095,000㎥/yr(강수량의 3%)가 된다. 3차원 지하수유동 모델링 소프트웨어인 GMS package의 MODFLOW를 사용하여 분석한 결과, 금정터널 예정 구간(9.99km)에서의 최대 유출량은 99,200㎥/day이다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.589-601
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• 2008

The variation of groundwater level near the Shingok weir has been analyzed. To consider the soil inhomogeneity, coefficient of effective permeability was computed to be 0.313 m/day in the horizontal direction, and 0.0423 m/day in vertical direction. Anisotropic ratio is 7.19. The river water level drawdown (caused by the removing of the weir) causes the groundwater level drawdown, and 3 months are required for the new steady condition. and groundwater flows from Han river toward Gulpo stream before the removing of the weir, but when the weir removed, the flow direction changes. The groundwater level falls maximum 30 cm in the areas under the influence of Han river, but, in the areas near Kulpo stream, groundwater level falls about 10 cm. The amount of groundwater use in the study area was investigated to be $52m^3/day$ and in this condition, groundwater level falls maximum 1m (before or after the removing of Shingok weir). therefore, the variation of groundwater level caused by the removing of Shingok weir is less than that caused by the usual use of groundwater.

• The Journal of Engineering Geology
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• v.23 no.2
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• pp.137-147
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• 2013

For the effective management of groundwater resources, it is necessary to predict groundwater level fluctuations in response to rainfall events. In the present study, time series models using artificial neural networks (ANNs) and support vector machines (SVMs) have been developed and applied to groundwater level data from the Gasan, Shingwang, and Cheongseong stations of the National Groundwater Monitoring Network. We designed four types of model according to input structure and compared their performances. The results show that the rainfall input model is not effective, especially for the prediction of groundwater recession behavior; however, the rainfall-groundwater input model is effective for the entire prediction stage, yielding a high model accuracy. Recursive prediction models were also effective, yielding correlation coefficients of 0.75-0.95 with observed values. The prediction errors were highest for Shingwang station, where the cross-correlation coefficient is lowest among the stations. Overall, the model performance of SVM models was slightly higher than that of ANN models for all cases. Assessment of the model parameter uncertainty of the recursive prediction models, using the ratio of errors in the validation stage to that in the calibration stage, showed that the range of the ratio is much narrower for the SVM models than for the ANN models, which implies that the SVM models are more stable and effective for the present case studies.