• The Journal of Engineering Geology
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• v.12 no.2
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• pp.215-234
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• 2002

Groundwater Dam is one of the reliable techniques to get huge amount of groundwater abstraction for municipal, agricultural, drinking, industrial water supply system. It can be a major technique to solve water shortage problems when it based on the sufficient watershed, proper topology, and adequate aquifer distribution and pollution control, Groundwater Dam had initiated its construction by RDC(former KARICO) in early eighties in Korea and 4 of it in total were added more until late eighty. However, this technique has shrunken its application due to gradually decreased yield rate after sever years of construction. After we studied several existing sites precisely, we concluded that the main reason of decreasing yield rate was come form engineering roughness on construction in early nineties. Theoretically, the technique itself seemed to be little detectives however, there were a little application in the fields in Korea. With the recent advance in engineering fields, those defects in construction would be no longer obstacle to construct underground wall and the technique could be a one of major ground water production technique in the future. It is essential to study following items thoroughly before select the appropriate site. The topography and the site of the underground wall, aquifer distribution, the specific technique for wall construction to block groundwater flow effectively and strict quality control during construction are critical. The surface and ground water monitoring data should be collected. Sustainability of the Groundwater Dam with huge groundwater abstraction in long term should be based on the long-term water balance analysis for each site. The water quality, environmental effect analysis and maintenance achedule should be also analyzed and planned in prior. It is suggested that the two consecutive underground wall in the coastal area to prevent seawater intrusion beneath a single wall.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.627-638
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• 2023

This study aimed to evaluate the spatial variability of downstream river flow resulting from the operation of the Gimcheon Buhang Dam in the Gamcheon watershed. The dam's effects on flood reduction during the flood season and on increasing streamflow during the dry season-two main functions of multipurpose dams-were quantitatively analyzed. Streamflow data from 2013 to 2021 for the study waterhsed were simulated on a daily basis using SWAT-K (Soil and Water Assessment Tool - Korea) model. Comparison of the simulated and observed values found goodness of fit values of 0.75 or higher for both the coefficient of determination and the Nash-Sutcliffe model efficiency coefficient. The spatial analysis of the dam's effect on flood reduction focused on the annual maximum flood: rates of flood reduction at the four stations ranged from 8.5% to 25.0%. The evaluation of streamflow increase during times of low flow focused on flow duration curves: in particular, compared to the case without an upstream dam, the average low flow at the four sites increased from 33% to 198%.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1195-1205
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• 2018

In the study, the water shortage of Boryeong Dam watershed ($163.6km^2$) was evaluated under future climate change scenario. The Soil and Water Assessment Tool (SWAT) was used considering future dam release derived from multiple linear regression (MLR) analysis. The SWAT was calibrated and verified by using daily observed dam inflow and storage for 12 years (2005 to 2016) with average Nash-Sutcliffe efficiency of 0.59 and 0.91 respectively. The monthly dam release by 12 years MLR showed coefficient of determination ($R^2$) of above 0.57. Among the 27 RCP 4.5 scenarios and 26 RCP 8.5 scenarios of GCM (General Circulation Model), the RCP 8.5 BCC-CSM1-1-M scenario was selected as future extreme drought scenario by analyzing SPI severity, duration, and the longest dry period. The scenario showed -23.6% change of yearly dam storage, and big changes of -34.0% and -24.1% for spring and winter dam storage during 2037~2047 period comparing with 2007~2016 period. Based on Runs theory of analyzing severity and magnitude, the future frequency of 5 to 10 years increased from 3 in 2007~2016 to 5 in 2037~2046 period. When considering the future shortened water shortage return period and the big decreases of winter and spring dam storage, a new dam operation rule from autumn is necessary for future possible water shortage condition.

• Korean Journal of Remote Sensing
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• v.40 no.2
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• pp.229-241
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• 2024

With the advancement of big data processing technology using cloud platforms, access, processing, and analysis of large-volume data such as satellite imagery have recently been significantly improved. In this study, the Change Detection Method, a relatively simple technique for retrieving soil moisture, was applied to the backscattering coefficient values of pre-processed Sentinel-1 synthetic aperture radar (SAR) satellite imagery product based on Google Earth Engine (GEE), one of those platforms, to estimate the surface soil moisture for six observatories within the Yongdam Dam watershed in South Korea for the period of 2015 to 2023, as well as the watershed average. Subsequently, a correlation analysis was conducted between the estimated values and actual measurements, along with an examination of the applicability of GEE. The results revealed that the surface soil moisture estimated for small areas within the soil moisture observatories of the watershed exhibited low correlations ranging from 0.1 to 0.3 for both VH and VV polarizations, likely due to the inherent measurement accuracy of the SAR satellite imagery and variations in data characteristics. However, the surface soil moisture average, which was derived by extracting the average SAR backscattering coefficient values for the entire watershed area and applying moving averages to mitigate data uncertainties and variability, exhibited significantly improved results at the level of 0.5. The results obtained from estimating soil moisture using GEE demonstrate its utility despite limitations in directly conducting desired analyses due to preprocessed SAR data. However, the efficient processing of extensive satellite imagery data allows for the estimation and evaluation of soil moisture over broad ranges, such as long-term watershed averages. This highlights the effectiveness of GEE in handling vast satellite imagery datasets to assess soil moisture. Based on this, it is anticipated that GEE can be effectively utilized to assess long-term variations of soil moisture average in major dam watersheds, in conjunction with soil moisture observation data from various locations across the country in the future.

• Water Engineering Research
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• v.1 no.1
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• pp.25-37
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• 2000

This study presents some results of a preliminary study for the coupled precipitation and river flow prediction system. The model system in based on three numerical models, Mesoscale Atmospheric Simulation model for generating atmospheric variables. Soil-Plant-Snow model for computing interactions within soil-canopy-snow system as well as the energy and water exchange between the atmosphere and underlying surfaces, and TOPMODEL for simulating stream flow, subsurface flow, and water tabled depth in an watershed. The selected study area is the 2,703 $\alpha_4$ $\km_2$ Soyang River basin with outlet at Soyang dam site. In addition to providing the results of rainfall and stream flow predictions, some results of DEM and GIS application are presented. It is obvious that the accurate river flow predictions are highly dependant on the accurate predictation predictions.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.37-48
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• 2011

Recently, the social and environmental functions of nature river are important due to the increase of expectation for river restoration. So it should be considered the effect of vegetation affecting the conveyance capacity and hydraulic resistance. However, it has not yet proposed a objective standard and modeling method to estimate the effect of conveyance capacity according to vegetaion distribution in the watercourse such as water level or velocity. Therefore, this study simulates the variations of water level and velocity using 3-dimensional hydrodynamic model, EFDC, to consider a conveyance capacity in downstream of the Soyang Reservoir. The simulation results were validated using statistical index such as F-test and T-test. As results, the water level rises about 0.01 to 0.47m and velocity difference are about -0.95m/s to 0.23m/s.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.582-594
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• 2012

A simple ecohydorlogic model that simulates hydrologic components and vegetation dynamics simultaneously based on equations of soil water dynamics and vegetation's growth and mortality is discussed. In order to simulate ungauged watersheds, the proposed model is calibrated with indirected estimated observation data set; 1) empirically estimated annual vaporization, 2) monthly surface runoff estimated by NRCS-CN method, and 3) vegetation fraction estimated by SPOT/VEGETATION NDVI. In order to check whether the model is performed well with indirectly estimated data or not, four upper dam watersheds (Andong, Habcheon, Namgang, Milyang) in Nakdong River watershed are selected, and the model is verified.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1817-1821
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• 2006

본 연구에서는 미농무성 농업연구소에서 개발된 준 분포형 장기유출모형인 SWAT 모형을 활용하여 융설모의에 따른 유출 및 수문성분의 영향을 분석하고자 하는데 그 목적이 있다. 대상유역은 충주댐 상류유역을 선정하였다. 표고에 따른 온도, 강수변화를 고려하기 위해 대상유역을 4개의 표고밴드로 구성하였으며, 12개 기상관측소 자료를 이용하여 표고에 따른 온도, 강수변화율을 산정하였다. 모의결과 융설을 고려한 결과가 융설을 모의하지 않은 결과보다 관측유량과 비교해 우수한 결과가 나타났으며, 각 수문성분별로도 상당한 차이가 있는 것으로 나타났다. 따라서 장기유출해석 시 융설영향의 고려가 중요한 요소가 될 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.987-991
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• 2006

본 연구에서는 유역의 비점오염물질의 거동을 해석할 수 있는 분포형 모델링 기법으로서 SWAT 모형을 선정하고, 충주댐 유역에 대해 모형 입력자료 및 물리적 매개변수 자료를 구축하였다. 구축된 모형을 이용하여 각 하도구간별 오염원에 따른 오염부하량 발생량을 비교한 결과, 산림지로 구성된 대부분의 상류부 소유역에서 점오염원에 의한 부하량이 매우 작게 나타났으며, 총 오염부하량도 상대적으로 작게 나타났다. 다만, 상류유역 중에서 유역면적이 상대적으로 넓고 유역내 밭의 비율이 높은 송천 유역의 경우는 오염부하량이 다소 높게 나타났다. 그리고 제천시를 포함하고 있는 도시지역인 8번 유역에서는 점오염원에 의한 부하량이 비점오염원에 의한 부하량보다 높게 나타났으며, 유역 전체로는 총질소의 경우 14%, 총인의 경우 23% 정도가 점원에 의한 오염부하량으로 나타났다. 이상의 결과로부터 각 하도구간별로 오염원에 따른 오염부하량을 비교함으로써 대상유역에서의 점오염원과 비점오염원에 의한 부하량의 영향을 검토할 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.47-51
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• 2009

증발산량을 산정하는 것은 자연현상과 인문현상을 이해하는 것의 기초가 된다. 이에, 최근 증발산량을 추정하는 많은 연구가 진행되고 있는 가운데 원격탐사 기법을 이용하는 것이 효과적인 것으로 알려지고 있다. 본 연구에서 소개할 SEBAL (Surface Energy Balance Algorithm for Land) (Bastiaanssen, 1995) 모형은 Landsat이나 NOAA 또는 MODIS 같은 원격탐사 위성으로부터 획득한 디지털 이미지 데이터(위성영상)를 이용하여, 지표에서 일어나는 증발산과 기타의 에너지 교환을 계산하는 이미지-프로세싱 모델이다. 우리나라 대상 유역에 위성영상을 사용하여 증발산량을 추정하는 SEBAL 모형의 적용 가능성을 검토하여, 유역 내 증발산량 분포의 시공간적 특성을 분석하고자 하였다. 연구 대상 지역은 유역 면적 약 6661.1km2의 충주댐 유역으로, Terra MODIS 위성영상을 이용하였다. SEBAL 증발산량의 평가를 위해 Penman-Monteith 공식에 의해 계산된 증발산량을 이용하여 비교하였으며, 그 결과 오차가 허용 가능한 10% 이내로 나타났다.