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Climate change is exacerbating water shortages in upstream basins in the Korean peninsula that lack agricultural water supply systems. The basin investigated in this study requires an extra 208 m3·d−1 of agricultural water during May (the busiest month for agriculture). The purpose of this study was to assess a hybrid-artificial recharge and circulation system, which was composed of a hybrid-recharge source and re-infiltration of pumped water in the field, and to estimate yield capacity by a field injection test and a numerical model. Injecting pretreated stream water for 42 d increased groundwater levels in the recharge basin. Water budget analysis in MODFLOW simulations revealed that injecting water increased groundwater levels as well as stream discharge due to the terrain’s gentle slope. To prevent downstream discharge and maintain groundwater levels after injection, we assumed the installation of an underground barrier at the basin outlet in the model, following which changes in groundwater levels and water balance were simulated. Water level was persistently maintained after a ~31-cm water level rise, and 590 m3·d−1 of water could be supplied from the collector well, which can ease water shortages. Therefore, it is necessary to develop structures to prevent recharged water escape when artificially recharging groundwater in small upstream basins. In upstream areas where reservoirs or water supply conduits are unfeasible, artificial recharge systems could solve water shortages.

국내 설치 운영 중인 지하수 관측정은 계측 센서의 고장 또는 전원 장치의 이상 등으로 결측이 발생하기도 한다. 지하수위 자료를 활용한 수문 평가, 지표수와 지하수의 연계 분석 및 지하수 함양량 산정 등을 위하여 결측 자료의 처리는 필수적이다. 본 연구에서는 가평가평 국가지하수 관측정의 1개월의 지하수위 결측 기간을 채우기 위하여 다변량 ARIMA와 인공신경망 모델인 MLP 및 LSTM을 적용하였으며, RMSE 및 MAE를 활용하여 모델의 정확도를 비교 분석하였다. 자기회귀 특성의 지하수위와 인근의 강우 자료가 입력변수로 사용되는 다변량 ARIMA 및 LSTM 모델이 MLP 모델에 비하여 정확한 것으로 평가되었다. LSTM 모델의 경우, 입력 변수로 사용되는 주변 강우 및 지하수 관측정의 수를 증가하더라도 오차가 거의 줄어들지 않는 것으로 나타났다. LSTM 모델은 훈련 및 검증 자료에 의하여 결정되는 만큼, 지하수위 결측 처리의 일관성을 위해서 입력 변수의 선정 방법에 대한 추가 연구가 수행될 필요가 있다.

Time series of natural groundwater level considering rainfall effects are usually used for the estimation of groundwater recharge, long-term trend analysis, and assessment of interactions between surface water and groundwater along rivers. However, anthropogenic activities, such as groundwater pumping, land excavation, and barrier construction, may induce abnormal changes in water levels. This study aimed to develop a universal long short-term memory (LSTM) model for predicting natural water level variations in a time-series record that has been affected by groundwater abstraction or other anthropogenic factors. This model uses past and present groundwater levels, rainfall and representative principal components of groundwater level time series as input variables. For this purpose, 17 cases of the developed LSTM model were tested using 13 monitoring wells, of which the case with the highest prediction performance was selected. Among the test cases, case 6 was found to achieve the highest performance, with average RMSE and MAE values of 0.061 and 0.027, respectively. The case 6 model used rainfall, groundwater level of monitoring wells, and four main principal components (1–4) as input variables. Also, its optimum window size was found to be 5. The accuracy of the LSTM model was found to be more strongly affected by window size than by input variables. Although the case 6 LSTM model may have errors for some monitoring wells, it has high potential as a universal model that can consistently determine natural groundwater levels in South Korea. This LSTM model makes it universally available for water level prediction, even with long missing periods in groundwater level time series or in the absence of adjacent observations for model input.

A hybridization of managed aquifer recharge (MAR) with pre-oxidation processes was conducted in this study to investigate changes in dissolved organic matter characteristics and the attenuation of selected trace organic contaminants (TrOCs). Potassium permanganate, chlorine, and ozone treatments were used for pre-oxidation, which effectively attenuated some TrOCs, particularly the combination of MAR with ozone achieved 84-99% attenuation. The pre-oxidation step using potassium permanganate showed high removal of carbamazepine (96%). Moreover, MAR was also combined with nanofiltration (NF) as a multi-barrier concept for the removal of persistent TrOCs after MAR. A short-chain polyfluoroalkyl substance (PFAS) was effectively removed after combining MAR columns with NF membranes. Thus, pre-oxidation coupled with MAR followed by NF could potentially enhance the removal of selected TrOCs.

Artificial recharge is increasingly necessary to ensure sustainable groundwater supplies and meet the needs of a growing population and crop cultivation in the age of climate change. In this study, artificial groundwater recharging using surplus water resources within the local area is considered for a water shortage area during a drought season, Shingok village, Hongsung-gun, South Korea, that lacks water sources. Based on an analysis of the monthly supply and demand with the water budget method, the current water supply is determined to be entirely dependent on groundwater wells, and water shortages occur in May (approximately 6446 m3) when rice planting begins. The surplus groundwater, which is the amount of natural recharge minus the present usage, and stream discharge are sufficient from December to June, so they are considered source waters for artificial recharge. A depth of 6 ~ 19 m is suggested as the main target region for recharge based on the composition of strata and the vertical distribution of the hydraulic conductivity, which was investigated with electric resistivity survey, drilling, and pumping test methods. Considering the permeability of layers, a vertical well, by which water can infiltrate directly into the target strata, is proposed as the main injection structure, and a ditch is also suggested as an auxiliary system to improve the effect of injection over a broad area. In the future, a detailed design for the injection scenario, injection facility, well and ditch arrangements, and pumping facility will be established through numerical modeling, field injection tests, etc. If it is impossible to obtain water from a long distance, an artificial recharge system based on local water sources may be an appropriate method of securing water considering the storage capacity of permeable strata.

This study was conducted to evaluate seasonal groundwater quality due to groundwater pumping and hydrochemical characteristics with groundwater level fluctuations in an agricultural area in Korea. Groundwater levels were observed for about one year using automatic monitoring sensors, and groundwater uses were estimated based on the monitoring data. Groundwater use in the area is closely related to irrigation for rice farming, and rising groundwater levels occur during the pumping, which may be caused by the irrigation water of rice paddies. Hydrochemical analysis results for two separate times (17 July and 1 October 2019) show that the dissolved components in groundwater decreased overall due to dilution, especially at wells in the alluvial aquifer and shallow depth. More than 50% of the samples were classified as CaHCO3 water type, and changes in water type occurred depending on the well location. Water quality changes were small at most wells, but changes at some wells were evident. In addition, the groundwater quality was confirmed to have the effect of saltwater supplied during the 2018 drought by comparison with seawater. According to principal component analysis (PCA), the water quality from July to October was confirmed to have changed due to dilution, and the effect was strong at shallow wells. In the study areas where rice paddy farming is active in summer, irrigation water may be one of the important factors changing the groundwater quality. These results provide a qualitative and quantitative basis for groundwater quality change in agricultural areas, particularly rice paddies areas, along with groundwater level and usage.

Because the mixture of seawater and freshwater in the Gyeongin-Ara Waterway in South Korea can lead to the intrusion of saline water into surrounding aquifers, systematic management through the establishment of a groundwater protection area is required. The analytic hierarchy process (AHP) model is used to delineate this protection area based on two primary factors and five secondary factors related to saline water intrusion. The study area is divided into 987 gridded cells with a unit size of 100 × 100 m, and the final evaluation score for each cell is calculated using the AHP model. Consequently, several artificial neural network models based on a multilayer perceptron are developed using the AHP’s secondary criteria and the evaluation score. Comparing the evaluation scores of ANN and AHP, more than 180 samples are required in the ANN model to insure high R2 between the original and estimated values. The ANN model is more consistent than the AHP model when determining groundwater protection area, because it can be re-constructed due to the changes in some secondary criteria and also changed due to a standardization process. The final evaluation score by the ANN model based on 300 samples, with the highest R2, is calculated and the regions with a score higher than 2.0 are selected as the groundwater protection area, accounting for 15% of the total cells. This area is similar to the range within approximately 200 m of the GA Waterway and also includes some changing sites in hydrogeochemistry and electric conductivity, which is produced by saline water intrusion. If the land-use type, groundwater levels, and some other criteria change at any cell, the ANN model can be re-executed to verify whether the cell belongs to a groundwater protection area. Considering that salinity of groundwater near the waterway can be affected by various factors including well depth, pumping conditions, and groundwater levels, the ANN model, which is a non-linear model, can be more effective for prediction than the AHP model.

The construction of a new barrage, the Gangjeong–Koryeong Barrage, in the Nakdong River and related sluice-gate operation has resulted in higher river-water and groundwater levels in the fl...

A strategy to transport freshwater mixed with seawater in the Gyeongin-Ara Waterway was established to improve and maintain the water quality. Saline water in a canal can cause its spread into the surrounding aquifer and therefore a groundwater monitoring system is essential to detect this phenomenon. Thirty-four monitoring wells were proposed based on the distribution of the chloride concentration estimated with a numerical model, and 29 wells were finally constructed as close to the proposed sites as possible. Multi-depth monitoring sensors were installed at 11 wells to measure the vertical spread of saline water. Principal component analysis and a comparison of actual measurements and model-estimated values for electric conductivity showed that the locations of the monitoring wells were appropriate for detecting the salinity spreading in groundwater.

본 연구에서는 기계학습 기법인 인공신경망(ANN)과 지지벡터기계(SVM) 기반 지하수위 시계열 예측모델을 개발하고 이를 국가지하수관측망 216개소 지하수위 자료에 적용하였다. 시계열 예측 모델 적용의 목적은 결측 및 이상 자료를 보정하고 지하수위 자료에 포함된 양수 및 하천수위 변동 영향을 제거하여 강우에 의한 지하수위 변동 모의에의 적용성을 평가하는 것이다. 먼저 각 관측소에 대해 1일 직접예측 모델을 구성한 뒤 이를 이용한 반복예측 모델을 구성하고 각 모델의 예측 및 모의 능력을 검토하였다. 시계열 예측 모델 적용 결과 결측, 이상 자료, 양수 및 하천수위 영향을 효과적으로 보정하고 강우에 의한 지하수의 변동 패턴을 모의하는 것으로 나타났다. 오차지표 분석 결과 ANN 모델이 SVM 모델보다 다소 높은 직접예측능력을 보여주지만 반복예측모델에 대한 안정성은 SVM이 높은 것을 알 수 있다. 또한 본 연구에서는 이용된 연구자료에 대한 ANN, SVM 기반 시계열 모델 적용 시 적절한 모델 파라미터 값의 범위를 제시하였다. 본 연구에서 적용한 방법론과 결과는 지하수관측망 수위 자료 이상값을 탐지하는데 이용되어 지하수관측망을 효과적으로 관리하는데 활용될 수 있다. 또한 강우에 의한 지하수위 변동을 모의함으로써 지하수위 변동법을 적용하여 지하수 함양률을 산정하는 등 지하수 자원을 관리하는데 활용될 수 있을 것으로 기대한다.

The construction of a river barrage can increase groundwater levels upstream of the barrage during the rainy season. Analytical and statistical approaches were applied to evaluate the relationship between groundwater and river water at the Changnyeong–Haman river barrage in Korea using time series data of water level and electrical conductivity from June 2011 to September 2014. An artificial neural network based time series model was designed to filter out the effect of rainfall from the groundwater level data in the study area. Aquifer diffusivity and river resistance were estimated from the analytical solution of a one‐dimensional unit step response function by using the filtered groundwater level data. River resistance increased in response to groundwater level fluctuations. Cross‐correlation analyses between the groundwater and the river water showed that the lag time increased during the observation period for both the water level and the electrical conductivity while the cross‐correlation function declined for the same period. The results indicated that a constant river stage maintained at the river barrage can weaken the hydrologic stress and reduce the exchange of material between the river and the adjacent aquifer because of the deposition of fine sediment on the river bottom and walls. Copyright © 2016 John Wiley & Sons, Ltd.

The prediction of long-term groundwater level fluctuations is necessary to effectively manage groundwater resources and to assess the effects of changes in rainfall patterns on groundwater resources. In the present study, a weighted error function approach was utilised to improve the performance of artificial neural network (ANN)- and support vector machine (SVM)-based recursive prediction models for the long-term prediction of groundwater levels in response to rainfall. The developed time series models were applied to groundwater level data from 5 groundwater-monitoring stations in South Korea. The results demonstrated that the weighted error function approach can improve the stability and accuracy of recursive prediction models, especially for ANN models. The comparison of the model performance showed that the recursive prediction performance of the SVM was superior to the performance of the ANN in this case study. ANN- and SVM-based long-term groundwater level prediction models were developed.We proposed a weighting factor approach for recursive prediction models.The method can enhance the performance of the long-term groundwater level prediction model.

The construction of river barrages has led to an increase in groundwater (GW) levels (WL_G) near the upstream regions of these barrages, particularly in the wet season. Statistical approaches were applied in this study to examine the relationships between WL_G and river water (RW) level (WL_R), and electrical conductivity of groundwater (EC_G) and electrical conductivity of river water (EC_R) in the Changnyeong–Haman river barrage area located downstream of the Nakdong River for the period June 2011–January 2014. Our finding suggested that the WL_G increased and the concentrations of most chemical constituents in the GW decreased in the study area owing to the construction of the barrage. However, long-term operation of the barrage is expected to trigger a decrease in the RW–GW interaction resulting from the clogging of the bed and the wall of the river, which would in turn increase GW contamination. Copyright © 2016 John Wiley & Sons, Ltd.

Large barrages have been constructed on the main rivers in South Korea to store water and mitigate fluvial flooding damage. However, the increase in water levels behind the barrages can potentially lead to a rise in groundwater levels in the riversides. The purpose of this study was to describe the effect of a barrage on groundwater levels and to test the applicability of a numerical model to groundwater inundation in this context. The Shincheon–Baekcheon catchment is characterised mainly by agricultural land use and includes significant greenhouse cultivation. Its two zones, which are lower A and upper B basins, mainly yield fine- and coarse-grained deposits, respectively. Trend and distribution analyses of manual and automatic measurements of groundwater levels indicated that: (1) the groundwater levels generally increased as the river water levels rose after the river was dammed; (2) the significant correlation between groundwater and river water levels could lead to reductions in the groundwater levels if the barrage gates were opened as a control measure; and (3) the lowering of high groundwater levels during dry seasons is important for preventing soil wetting in the riversides.

Intelligeo Co. LtdReceived 2 June 2015; received in revised form 13 June 2015; accepted 15 June 2015강변여과수의 수평집수정 시공시 불균질성 지층에 의한 굴착 지연 등은 전체 굴착 공정에 영향을 미칠 수 있다. 본 연구에서는 안성천 지역에서 시공 중인 수평집수정의 굴착 과정에서 심도별로 취득된 입도분석 자료, 균등계수, 곡률계수를 활용하여 실제 굴착 속도를 추정하는 방안을 제시하였다. 균등계수와 곡률계수를 입력인자로 사용한 회귀식을 도출한후 타 수평집수정에 적용한 결과, 조립질이면서 분급이 양호한 지층에 추정식이 잘 맞는 것으로 나타났다. 본 연구 결과는 중소규모의 하천을 대상으로 개발된 만큼, 향후 대하천 주변의 굴착 정보를 활용하여 추정식을 보완한다면 보다 정확한 설계 및 효율적인 시공 관리가 가능할 것이다.주요어: 강변여과수 , 수평집수정 , 입도분석 , 균등계수 , 곡률계수Delays in horizontal well drilling when encountering heterogeneous sediments can have negative effects on theconstruction process at a riverbank filtration site. Grain size analysis, including calculation of the coefficient of uni-formity and the coefficient of curvature, was conducted on soil samples collected at each drilling depth during theprocess of drilling horizontal wells. These results were then used to develop a linear equation for estimating drill-ing velocity using the coefficient of uniformity and the coefficient of curvature as inputs. Testing of the linear equa-tion in other horizontal wells indicates that the equation is most appropriate for coarse-sand-sized and well-sortedsediment. Because this study was conducted in a region with small- to medium-sized streams, more data are neededfrom larger rivers to modify the general equation. Our results will provide better estimates of drilling velocity, inturn enabling more detailed design and more effective construction management at riverbank filtration sites.Key words: riverbank filtration, horizontal well, grain size analysis, coefficient of uniformity, coefficient of cur-vature

This is conducted to observe underground temperature and to analyze its change affected by climate condition and soil infiltration in the mountainous area, Yesan region, Chungcheong-namdo province. Additionally, underground temperature change is also simulated using air temperature and soil thermal properties with a numerical model. Soil temperature monitoring data acquired from each depth, 20 cm, 50 cm, and 100 cm, indicates that the data within 50 cm in depth shows peak-shaped big fluctuation directly affected by air temperature and it at 100 cm has open-shaped small fluctuation. Underground temperature variation, a difference between high and low values, during monitoring period is weakly proportional to hydraulic conductivity of the sediment and it is assumed that water plays a part in delivering air temperature in soil. The underground temperature estimated by a numerical model is very similar to the observed data with an average value of 0.99 cross-correlation coefficient. From the result of this study, the aquifer unsaturated hydraulic conductivity of the soil and the groundwater recharge is likely to be able to estimate with underground temperature profile calculated using a numerical model.

Global climate change causes a high variability in precipitation and surface temperature increase in the world. Global climate models (GCMs) are effectively used to predict climate change at a global scale. In contrast, regional climate models (RCMs) can more efficiently predict climate change scenarios for a small territory such as South Korea. We estimated the groundwater level change in four drainage basins (the Han River, Nakdong River, Geum River, and Yeongsan-Sumjin River basins) in South Korea over the period 2000–2012, and then predicted the groundwater level change from 2000 to 2100 using a water budget model, considering RCMs with RCP 4.5 and RCP 8.5 scenarios. A distinct trend in the groundwater levels of each drainage basin was detected via the inversely close relationship with precipitation patterns of the drainage basin, showing a decrease in the groundwater level in relation to the increasing precipitation trend of the RCM scenarios. It is also proposed that the precipitation amount during the dry season more dominantly affects groundwater recharge than during the wet season.

The aim of the Four Major Rivers Restoration Project (4MRRP) was to mitigate flood damage by controlling surface water levels via the construction of large barrages along the main rivers of South Korea. The increase in surface water levels behind such barrages can lead to a rise in groundwater levels upstream, which may increase the likelihood of flooding after heavy rainfall or during non-pumping periods. A total of 900 groundwater monitoring sites, comprising 446 automatic and 454 manual stations, are proposed on the low-lying plains alongside the rivers based upon the following criteria: groundwater flow directions, topography (determined using GIS analysis), the desire for equal spacing of monitoring wells, economic efficiency, field accessibility, and cost. A numerical model (MODFLOW) is used to estimate future groundwater flow directions and the area likely to be affected by a rise in surface water levels after barrage construction. Since 2011, 137 automatic monitoring wells have been constructed, and recent time series data show that groundwater levels are closely linked to surface water levels, and increased rapidly for the first 1–2 years after barrage construction. Groundwater monitoring wells will be essential for assessing the depth to groundwater, forecasting the extent of any potential flooding, and developing countermeasures such as drainage system.

Korea Water Resources CorporationReceived 28 July 2014; received in revised form 11 August 2014; accepted 13 August 20141993년 지하수법 제정 이후 정책은 지하수 보전관리를 우선하고 보조수원으로 제한적으로 활용하는데 초점을 두어왔으나, 최근 인구 증가, 물 수요 증가, 균등 분배 및 기후 변화 등으로 지하수댐, 강변여과 등의 개발 정책을 중요시 하게 되었다. 인구의 증가, 물 환경의 변화 및 위해성 증가 등은 물 산업이 급격히 증가하는 요인으로 작용하여 왔으며 물산업의 투자 규모는 지속 증가할 것으로 전망되고 있다. 그 동안 국내 지하수 시장은 일반 개인 관정 개발과 먹는샘물이 주도해 왔으나, 최근에는 지질학 기원의 차별화된 지하수 특성을 활용한 신규 사업 영역(건강, 의학 등)으로 확대되고 있다. 향후 지하수 분야가 물 산업 클러스터 내의 핵심으로 자리 잡고 정보통신기술 및 의학 등과 연계한 연구 및 기술 개발을 적극 추진하여 공공 지하수 개발, 지하수 활용의 다변화 등이 적극 추진되어야 할 것이다.주요어 : 물 산업, 지하수 산업, 물 위해성, 먹는 샘물Since the establishment of the Groundwater Act in Korea in 1993, the national policy on groundwater has focusedon the preservation and management of groundwater, which should be used only as a subsidiary water resource.However, population growth, increased water demand, climate change, and the need for uniform water distributionhave brought changes to groundwater policy, and have led to the prioritization of development projects such asgroundwater dams and river bank filtration. Population growth, changes to the water environment, and increasedwater risks have all played a role in triggering rapid growth within the water industry; the size of the investment inwater resources will also continue to increase worldwide. Until now, private wells and bottled mineral water have ledthe groundwater industry in South Korea. However, a new area of the groundwater industry, which includes thehealth and medical sciences, employs groundwater properties derived from regional geology, and is growing. Thisrequires the advancement of groundwater research and technical development connected with ICT (Information andCommunication Technology) and medical science, and that the public development of groundwater and its variousapplications is expanded through locating groundwater in the core of the water industry cluster.Key words : water industry, groundwater industry, water risk, bottled mineral water

It is important to predict the groundwater level fluctuation for effective management of groundwater monitoring system and groundwater resources. In the present study, three different time series models for the prediction of groundwater level in response to rainfall were built, those are transfer function noise model (TFNM), artificial neural network (ANN), and adaptive neuro fuzzy interference system (ANFIS). The models were applied to time series data of Boen, Cheolsan, and Hongcheon stations in National Groundwater Monitoring Network. The result shows that the model performance of ANN and ANFIS was higher than that of TFNM for the present case study. As lead time increased, prediction accuracy decreased with underestimation of peak values. The performance of the three models at Boen station was worst especially for TFNM, where the correlation between rainfall and groundwater data was lowest and the groundwater extraction is expected on account of agricultural activities. The sensitivity analysis for the input structure showed that ANFIS was most sensitive to input data combinations. It is expected that the time series model approach and results of the present study are meaningful and useful for the effective management of monitoring stations and groundwater resources.

지하수 , 지하댐, 유효공극률 , 유황곡선 , 대체 수자원This paper aims to calculate the increase in groundwater quantity following groundwater dam construction, and toassess its impact on surface water. In the study area of Osib-cheon, Yeongdeok, we estimated groundwater quantity,groundwater level, and effective porosity, and examined surface water fluctuations with respect to the increasedgroundwater quantity based on the flow duration. The results reveal that the increased groundwater quantity was atmost 91,746 m

K-water Institute, Korea Water Resources Corporation근래 들어 환경에 대한 관심이 높아지면서 지표수 개발 여건은 불리해지고 있으며, 또한 양질의 수자원에 대한 욕구는 점차 증가함에 따라 정부는 지하수 개발 정책을 도모하게 되었다. 이와 같은 개발 정책을 추진하기 위해서는 보다 정확한 지하수 개발가능량과 지하수 이용량 파악이 중요하다. 본 연구에서는 양질의 지하수 이용량 자료를 확보하기 위해 전국(5개 도의 32개 시군)을 대상으로 수년간 모니터링을 실시하고, 통계분석을 통해 합리적인 지하수 이용량 산정방법을 제시하였다.생활용 지하수의 경우 전국을 도시지역, 도농복합지역, 농촌지역으로 구분하고, 지하수 용도를 가정용, 공동주택용, 간이상수도용, 학교용, 일반용 등 5가지로 분류하였다. 농업용 지하수의 경우 전국을 강수량에 따라 평균 강수량지역, 평균 강수량 미만지역, 평균 강수량 초과지역으로 구분하고, 지하수 용도를 전작용, 답작용, 원예용, 축산용-육우, 축산용-양돈, 축산용-양계로 분류하였다. 이로부터 모니터링 자료에 대한 군집분석과 회귀분석을 통해 지역별-용도별 지하수 이용량 추정식을 제시하였다. 향후 본 연구에서 제시한 기준을 적용하여 국가 지하수 이용량 통계의 신뢰도가 크게 향상될 것으로 기대된다.주요어

Climate change has resulted in a gradual increase in the surface temperature and significantly variable precipitation in different regions of the world. Linear regression of the groundwater levels in Korea between 2000 and 2010 revealed a decreasing trend with a slope of −29.2 mm/yr; −29.6 mm/yr in the wet season and −32.0 mm/yr in the dry season. Mann-Kendall and Sen’s tests were carried out using the groundwater levels and groundwater temperatures at 78 locations in South Korea between 2000 and 2010. The groundwater levels showed a trend in ~50% of the 78 groundwater level datasets, of which ~70% exhibited a decreasing trend at the 95% confidence level. This decreasing trend in the groundwater levels appears to be related to a change in the precipitation in South Korea because more abundant rainfall in the wet season each year does not contribute significantly to groundwater recharge, whereas less rainfall that occurs in the dry season can cause a decrease in the groundwater level. Linear regression of the groundwater temperatures revealed a slope of 0.1006 °C/yr between 2000 and 2010 with a gentler slope (0.08 °C/yr) in summer (June–September), showing that the increase in surface temperature has an impact on increasing the groundwater temperature. In this situation of climate change in Korea, the paradigm of groundwater management strategy needs to be altered properly.

/d의 지하수가 수직구내로 유입되는 것으로 예상되었으며, 실제 그라우팅을 거친 후 굴착 3과정에서 배출된 지하수량을 측정한 결과 30~100 m/d의 범위를 보여 예측 수량과 유사한 것으로 나타났다. 수직구의 작업 안정성 확보 및 원활한 공정을 위해서는 수치모델을 활용한 그라우팅 효과의 사전 평가가 필요하며 이를 근거로 그라우팅 시공을 선행한 후 굴착이 진행되는 것이 필요하다.주요어 : 선택취수설비 , 굴착, 그라우팅 , 지하수 유입량, 수치모델The vertical shaft of a selective intake structure, which is constructed in a large reservoir, is required to be imper-meable and to employ a grouting technology to prevent water inflow from the reservoir or surrounding ground. Inthis study, groundwater inflow is estimated using a numerical model for two cases (i.e., grouting or non-groutingcases at the exterior of a vertical shaft) and compared with data measured during an excavation at the constructionsite of a selective intake structure in the Soyang reservoir, Korea. Groundwater inflow is estimated to range from444 to 754 m

A geological barrier such as a mountain ridge surrounding a large reservoir generally plays some part in preventing water leakage from the reservoir, but water flows out naturally according to the hydraulic gradient because the reservoir water level is typically higher than that outside. The hydrogeological, geochemical, and isotopic properties of water in the Daechung Dam area were analysed to characterize the source and the phenomenon of the groundwater flowing through the geological barrier. Our geochemical analysis showed that the concentrations of anions and cations tended to increase, due to the longer residence time of the water, as the distance between the sampling site and reservoir increased. Elevation differences (calculated using oxygen and hydrogen isotopes) between the highest and lowest sampling sites ranged between 350 and 420 m based on the altitude effect on isotope concentration, but the actual difference was only 35 m. These results, including analysis of the rate of water seepage from the reservoir (ca. 2.3% to 14.4% of natural recharge), indicate the possibility that groundwater in the study area originated from reservoir water that was derived from upstream water and rainfall in the high mountainous area of the upper watershed. Copyright © 2013 John Wiley & Sons, Ltd.