• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.19-26
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• 2023

This research aimed to predict the seepage rate in the base rocks of a concrete face rockfill dam (CFRD) by conducting numerical analysis under various conditions. We examined the relationship between basic grouting and seepage, emphasizing the significance of the permeability coefficient of the grouting material and the rock. Moreover, we observed a decrease in seepage with an increase in the cross-sectional area of the dam. The results of this study provide essential input factors and outcomes of numerical analysis, incorporating various parameters, to inform the design phase. Additionally, our findings offer a dependable approach for calculating a reasonable seepage rate during both operational and maintenance phases.

• Management & Information Systems Review
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• v.36 no.3
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• pp.89-111
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• 2017

The era of today's day is that the era of the black gold age is now approaching the era of the blue gold age. As the importance of water increases, support and policies for the water industry are presented. The water industry is a public service industry but it faces the problem for unbalanced supply between users. One of solutions for solving the problem at hand is the privatization of the public service and it is the most sensitive and focused subject to the issue. Korea is also coming up for the privatization of the water industry. So, one of the privatization operations based on the privatization of the current waterworks law is management contract by the specialized organization and it is in progress to enhance the efficiency of public services. Therefore, this study aims at finding out the local water supply services' efficiency by K-Water using DEA(Data Envelopment Analysis), and productivity analysis by malmquist index on 18 organizations of the implementation of local water supply management contract using the date from 2012 to 2014. According to the result of the DEA, 10 of the 18 organizations were the most efficient during 3 years and malmquist index for analysing the productivity was decreasing. That is because of the leakage ratio and utilization ratio of the raw water and both of them are significant to productivity. As a result, this study differs from the previous studies by analysing efficiency and productivity using DEA and malmquist index to the solution for the problem faced by current water industry.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.4
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• pp.41-54
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• 2021

It is very essential to estimate the water body area using remote exploration for water resource management, analysis and prediction of water disaster damage. Hydrophysical detection using satellites has been mainly performed on large satellites equipped with optical and SAR sensors. However, due to the long repeat cycle, there is a limitation that timely utilization is impossible in the event of a disaster/disaster. With the recent active development of Micro satellites, it has served as an opportunity to overcome the limitations of time resolution centered on existing large satellites. The Micro satellites currently in active operation are ICEYE in Finland and Capella satellites in the United States, and are operated in the form of clusters for earth observation purposes. Due to clustering operation, it has a short revisit cycle and high resolution and has the advantage of being able to observe regardless of weather or day and night with the SAR sensor mounted. In this study, the operation status and characteristics of micro satellites were described, and the water area estimation technology optimized for micro SAR satellite images was applied to the Daecheong Dam basin on the Korean Peninsula. In addition, accuracy verification was performed based on the reference value of the water generated from the optical satellite Sentinel-2 satellite as a reference. In the case of the Capella satellite, the smallest difference in area was shown, and it was confirmed that all three images showed high correlation. Through the results of this study, it was confirmed that despite the low NESZ of Micro satellites, it is possible to estimate the water area, and it is believed that the limitations of water resource/water disaster monitoring using existing large SAR satellites can be overcome.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.993-1003
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• 2023

Due to the increasing greenhouse gas emissions, the global mean temperature has risen by 1.1℃ compared to pre-industrial levels, and significant changes are expected in functioning of water supply systems. In this study, we assessed impacts of climate change and instreamflow management on water supply reliability in the Geum River basin, Korea. We proposed univariate climate response functions, where mean precipitation and potential evaporation were coupled as an explanatory variable, to assess impacts of climate stress on multiple water supply reliabilities. To this end, natural streamflows were generated in the 19 sub-basins with the conceptual GR6J model. Then, the simulated streamflows were input into the Water Evaluation And Planning (WEAP) model. The dynamic optimization by WEAP allowed us to assess water supply reliability against the 2020 water demand projections. Results showed that when minimizing the water shortage of the entire river basin under the 1991-2020 climate, water supply reliability was lowest in the Bocheongcheon among the sub-basins. In a scenario where the priority of instreamflow maintenance is adjusted to be the same as municipal and industrial water use, water supply reliability in the Bocheongcheon, Chogang, and Nonsancheon sub-basins significantly decreased. The stress tests with 325 sets of climate perturbations showed that water supply reliability in the three sub-basins considerably decreased under all the climate stresses, while the sub-basins connected to large infrastructures did not change significantly. When using the 2021-2050 climate projections with the stress test results, water supply reliability in the Geum River basin was expected to generally improve, but if the priority of instreamflow maintenance is increased, water shortage is expected to worsen in geographically isolated sub-basins. Here, we suggest that the climate response function can be established by a single explanatory variable to assess climate change impacts of many sub-basin's performance simultaneously.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.775-784
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• 2023

With the increasing trend of extreme rainfall that exceeds the design frequency of man-made structures due to extreme weather, it is necessary to review the safety of agricultural reservoirs designed in the past. However, there are no local government-managed reservoirs (13,685) that can be discharged in an emergency, except for reservoirs over a certain size under the jurisdiction of the Korea Rural Affairs Corporation. In this case, it is important to quickly deploy a mobile siphon to the site for preliminary discharge, and this study evaluated the applicability of a mobile siphon with a diameter of 200 mm, a minimum water level difference of 6 m, 420 (m²/h), and 10,000 (m²/day), which can perform both preliminary and emergency discharge functions, to the Yugum Reservoir in Gyeongju City. The test bed, Yugum Reservoir, is a facility that was completed in 1945 and has been in use for about 78 years. According to the hydrological stability analysis, the lowest height of the current dam crest section is 27.15 (EL.m), which is 0.29m lower than the reviewed flood level of 27.44 (EL.m), indicating that there is a possibility of lunar flow through the embankment, and the headroom is insufficient by 1.72 m, so it was reviewed as not securing hydrological safety. The water level-volume curve was arbitrarily derived because it was difficult to clearly establish the water level-flow relationship curve of the reservoir since the water level-flow measurement was not carried out regularly, and based on the derived curve, the algorithm for operating small and medium-sized old reservoirs was developed to consider the pre-discharge time, the amount of spillway discharge, and to predict the reservoir lunar flow time according to the flood volume by frequency, thereby securing evacuation time in advance and reducing the risk of collapse. Based on one row of 200 mm diameter mobile siphons, the optimal pre-discharge time to secure evacuation time (about 1 hour) while maintaining 80% of the upper limit water level (about 30,000 m²) during a 30-year flood was analyzed to be 12 hours earlier. If the pre-discharge technology utilizing siphons for small and medium-sized old reservoirs and the algorithm for reservoir operation are implemented in advance in case of abnormal weather and the decision-making of managers is supported, it is possible to secure the safety of residents in the risk area of reservoir collapse, resolve the anxiety of residents through the establishment of a support system for evacuating residents, and reduce risk factors by providing risk avoidance measures in the event of a reservoir risk situation.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.363-375
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• 2024

Waterbody change detection using satellite images has recently been carried out in various regions in South Korea, utilizing multiple types of sensors. This study utilizes optical satellite images from Landsat and Sentinel-2 based on Google Earth Engine (GEE) to analyze long-term surface water area changes in four monitored small and medium-sized water supply dams and agricultural reservoirs in South Korea. The analysis covers 19 years for the water supply dams and 27 years for the agricultural reservoirs. By employing image analysis methods such as normalized difference water index, Canny Edge Detection, and Otsu'sthresholding for waterbody detection, the study reliably extracted water surface areas, allowing for clear annual changes in waterbodies to be observed. When comparing the time series data of surface water areas derived from satellite images to actual measured water levels, a high correlation coefficient above 0.8 was found for the water supply dams. However, the agricultural reservoirs showed a lower correlation, between 0.5 and 0.7, attributed to the characteristics of agricultural reservoir management and the inadequacy of comparative data rather than the satellite image analysis itself. The analysis also revealed several inconsistencies in the results for smaller reservoirs, indicating the need for further studies on these reservoirs. The changes in surface water area, calculated using GEE, provide valuable spatial information on waterbody changes across the entire watershed, which cannot be identified solely by measuring water levels. This highlights the usefulness of efficiently processing extensive long-term satellite imagery data. Based on these findings, it is expected that future research could apply this method to a larger number of dam reservoirs with varying sizes,shapes, and monitoring statuses, potentially yielding additional insights into different reservoir groups.

• Economic and Environmental Geology
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• v.53 no.5
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• pp.619-629
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• 2020

The National Groundwater Monitoring Network (NGMN) in South Korea has been implemented in alluvial/ bedrock aquifers for efficient management of groundwater resources. In this study, aquifer types were reclassified with unconfined and confined aquifers based on water-level fluctuation and water quality characteristics. Principal component analysis (PCA) of water-level data from paired monitoring wells of alluvial/bedrock aquifers results in the principal components of both aquifers showing similar water-level fluctuation pattern. There was no significant difference in the rate of water-level rises responding to precipitations and in the NO₃-N concentrations between the alluvial and bedrock aquifers. In contrast, in the results classified with the hydrogeological type, the principal components of water level were different between unconfined and confined conditions. The water-level rises to precipitation events were estimated to be 4.6 (R²=0.8) in the unconfined and 2.1 (R²=0.4) in the confined aquifers, respectively, indicating less impact of precipitation recharge to the confined aquifer. The confined aquifers have the average NO₃-N concentration below 3 mg/L, implying the natural background level protected from the sources at surface. In summary, reclassification of aquifers into hydrogeological types clearly shows the differences between unconfined and confined aquifers in the water-level fluctuation pattern and NO₃-N concentrations. The hydrogeologic condition of aquifer could improve groundwater resource management by providing critical information on groundwater quantity through recharge estimation and quality for protection from potential contamination sources.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1793-1797
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• 2007

한강 "수변구역"에서 비점오염물질의 공공수역 유입을 억제하기 위한 다양한 방법들 중에서 보편적이고 자연친화적인 방법은 다양한 생물의 서식공간이며, 동시에 본류로 유입되는 과정에서 수질을 정화시키는 수질개선 공간인 수변완충구역, 또는 지대를 설정하여 관리하는 것이다. 그러나 이러한 수변완충지대 효과 분석 및 설정에 관한 연구는 국내에서 아직 수행되지 않았다. 본 연구의 목적은 수변구역의 자정능력을 높이는 것은 물론 그 밖의 하천 연안에서 비점오염물질의 차단과 처리능력을 증진시키고 수변 생태계의 서식처 보전 및 복원을 위해서 수변완충지대의 수질정화 기술개발과 생물다양성을 창출하는 수변완충지대 조성 기법을 개발하는데 있다. 본 연구에서는 기존 수변완충지의 추가적인 조성과 보완, 시험완충지 생태구조 및 기능 기초조사, 시험완충지 오염부하 저감효과의 실험 및 분석, 수변완충지대 설치 구상 등의 연구를 수행하였다. 수행 지역은 한강수계 지역으로 남한강 수변인 경기도 양평군 병산리에서 실시하였으며, 잔디와 갈대, 갯버들, 혼합지역, 자연그대로의 상태(대조지역)의 5 구역으로 구분하였고, 깊이별로 샘플을 채취하여 유입수와 표면유출, 하부유출을 비교해 보았다. 연구 결과, 5 가지 구역 중 잔디 구역의 SS, T-N, T-P, TOC의 제거 효율이 각각 76.7%, 85.2%, 97.6%, 83.3%로 가장 좋은 오염물질 제거 효율을 보였으며, 깊이 별 분석에서는 표면유출에서 하부유출로 갈수록 월등한 효율을 보였다. 따라서 본 연구를 통하여 비점오염원에 대한 한강수계의 수자원 보호 효과를 기대할 수 있고, 수변완충지대의 조성, 유지관리기술의 개발을 통한 수변완충지대의 계획과 설계에 직접적인 기여를 할 수 있으며, 수변구역에 설치 가능한 Riparian Buffer Zone의 중요성과 효율성을 알려 현재 하상 저니 준설 및 폭기 위주의 사업에서 생태 공학적 복원을 적극 고려한 정화사업으로 확대 추진하고자 한다.해결책을 얻어내는 상호보완적인 결과를 추구한다. 그가 디자인하는 작품은 전형적인 이미지를 내포하지 않는다. 즉 그의 작품은 기존의 가치와 이념적인 것은 배제하고, 창의적인 개념을 도출하였다.형모서리는 건물 특화 성격이 강하므로 불가피할 경우 소형 액센트 광고 위치를 미리 벽면으로 할애하는 것이 경관 및 입면계획에 유리한 것으로 분석되었다. 불확실도 해석모형 등의 새로운 기능을 추가하여 제시하였다. 모든 입출력자료는 프로젝트 단위별로 운영되어 data의 관리가 손쉽도록 하였으며 결과를 DB에 저장하여 다른 모형에서도 적용할 수 있도록 하였다. 그리고 HyGIS-HMS 및 HyGIS-RAS 모형에서 강우-유출-하도 수리해석-범람해석 등이 일괄되게 하나의 시스템 내에서 구현될 수 있도록 하였다. 따라서 HyGIS와 통합된 수리, 수문모형은 국내 하천 및 유역에 적합한 시스템으로서 향후 HydroInformatics 구현을 염두에 둔 특화된 국내 수자원 분야 소프트웨어의 개발에 기본 토대를 제공할 것으로 판단된다.았다. 또한 저자들의 임상병리학적 연구결과가 다른 문헌에서 보고된 소아 신증후군의 연구결과와 큰 차이를 보이지 않음을 알 수 있었다. 자극에 차이가 있지 않나 추측되며 이에 관한 추후 연구가 요망된다. 총대장통과시간의 단축은 결장 분절 모두에서 줄어들어 나타났으나 좌측결장 통과시간의 감소 및 이로 인한 이 부위의 통과시간 비율의 저하가 가장 주요하였다. 이러한 결과는 차가운 생수 섭취가 주로 결장 근위부를 자극하는 효과를 발휘하는 것이 아닌가 해석된다. 이와 같은 연구결과를 통해 생다시마를 주원료로 개발된 생다시마차와 생다시마 음료가 만성 기능성 변비 증세를 개선하는 효능이 잠재적으로 있음을 확인하였다. 그러나 생약제재의 변비약 수준으로 변비 개선 효능을 증대하기 위해서는 재료 배합비의 개선이나 대장 운동기능을 향상시키는 유효성분의 보강 등이 필요하다는 점도 알 수 있었다.더불어 산화물질 해독에 관여하는

• Journal of Korea Water Resources Association
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• v.56 no.5
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• pp.311-323
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• 2023

In order to reduce disaster damage by localized heavy rains, floods, and urban inundation, it is important to know in advance whether natural disasters occur. Currently, heavy rain watch and heavy rain warning by the criteria of the Korea Meteorological Administration are being issued in Korea. However, since this one criterion is applied to the whole country, we can not clearly recognize heavy rain damage for a specific region in advance. Therefore, in this paper, we tried to reset the current criteria for a special weather report which considers the regional characteristics and to predict the damage caused by rainfall after 1 hour. The study area was selected as Gyeonggi-province, where has more frequent heavy rain damage than other regions. Then, the rainfall inducing disaster or hazard-triggering rainfall was set by utilizing hourly rainfall and heavy rain damage data, considering the local characteristics. The heavy rain damage prediction model was developed by a decision tree model and a random forest model, which are machine learning technique and by rainfall inducing disaster and rainfall data. In addition, long short-term memory and deep neural network models were used for predicting rainfall after 1 hour. The predicted rainfall by a developed prediction model was applied to the trained classification model and we predicted whether the rain damage after 1 hour will be occurred or not and we called this as 1ST-Model. The 1ST-Model can be used for preventing and preparing heavy rain disaster and it is judged to be of great contribution in reducing damage caused by heavy rain.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.11-22
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• 2009

Long-term rainfall-runoff modeling is a key element in the Earth's hydrological cycle, and associated with many different aspects such as dam design, drought management, river management flow, reservoir management for water supply, water right permission or coordinate, water quality prediction. In this regard, hydrologists have used the hydrologic models for design criteria, water resources assessment, planning and management as a main tool. Most of rainfall-runoff studies, however, were not carefully performed in terms of considering reservoir effects. In particular, the downstream where is severely affected by reservoir was poorly dealt in modeling rainfall-runoff process. Moreover, the effects can considerably affect overall the rainfallrunoff process. An objective of this study, thus, is to evaluate the impact of reservoir operation on rainfall-runoff process. The proposed approach is applied to Anseong watershed, where is in a mixed rural/urban setting of the area and in Korea, and has been experienced by flood damage due to heavy rainfall. It has been greatly paid attention to the agricultural reservoirs in terms of flood protection in Korea. To further investigate the reservoir effects, a comprehensive assessment for the results are discussed. Results of simulations that included reservoir in the model showed the effect of storage appeared in spring and autumn when rainfall was not concentrated. In periods of heavy rainfall, however, downstream runoff increased in simulations that do not consider reservoir factor. Flow duration curve showed that changes in streamflow depending upon the presence or absence of reservoir factor were particularly noticeable in ninety-five day flow and low flow.