• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.1
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• pp.158-168
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• 2007

This study analyzed the reduction efficiency to a debris barrier planed with the Office of Forestry and local provinces among diverse measurements for the diminution of high-density turbid water and soil erosion of Soyang reservoir. As the analysis of soil erosion of Soyang river basin applying rainfall data (2005) and GIS database, soil erosion is estimated as 4,819,494 ton. Also, in the analysis of unit soil erosion, Chugok-, Jaun-, and Ohang stream shows high value comparing with other watersheds. Debris barrier watersheds are extracted as the center of 94 debris barrier points using GIS spatial analysis. As the analysis of soil erosion and sediment delivery ratio (SDR) of debris barrier watershed, the reduction efficiency of soil erosion of debris barrier of 2005 is analyzed as 6.8%, that is 330,203 ton. Also, the reduction efficiency of soil erosion of debris barrier of 2005 increases as 10.5%, that is 506,783 ton, when the locations of debris barrier are changed into the high soil erosion area over 5,000 ton.

• Korean Journal of Ecology and Environment
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• v.51 no.2
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• pp.160-167
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• 2018

The role played by reservoirs in the biogeochemical cycles of elements is a subject of ongoing debate. Recent research has revealed that reservoirs emit significant levels of greenhouse gases. To assess the importance of reservoirs in monsoon climate areas as a source of methane gas into the atmosphere, we investigated variations in organic carbon (OC) input into the reservoir, oxic state changes, and finally the amount of methane emitted (focusing on the ebullition pathway) in Lake Soyang, which is the largest reservoir in South Korea. Total organic carbon (TOC) concentrations were higher during summer after two years of heavy rainfall. The sedimentation rates of particulate organic carbon (POC) and particulate organic nitrogen (PON) were higher in the epilimnion and hypolimnion than the metalimnioin, indicating that autochthonous and allochthonous carbon made separate contributions to the TOC. During stratification, oxygen depletion occurred in the hypolimnion due to the decomposition of organic matter. Under these conditions, $H_2S$ and $CH_4$ can be released from sediment. The methane emissions from the reservoir were much higher than from other natural lakes. However, the temporal and spatial variations of methane ebullition were huge, and were clearly dependent on many factors. Therefore, more research via a well-organized field campaign is needed to investigate methane emissions.

• Korean Journal of Remote Sensing
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• v.34 no.6_1
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• pp.1119-1130
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• 2018

Soyang Lake has been contributing to economic growth by preventing flood damage in the metropolitan area, the water level in the middle to upper flow of lake has been greatly decreased due to the drought in 2015. In order to restore the existing flow rate, Bupyungbo has been built in Bupyeong-ri, Shin Nam-myeon, Inje-gun to cause artificial changes on the sedimentary environment of Bupyeong freshwater region. Therefore, this study intends to confirm the changes of sedimentary environment since Bupyeongbo has been utilized. For this study, we used the Sentinel-2 satellite image data periodically to measure the dimension of water according to the volume of water kept near Bupyung district and analyzed the particle size and the percentage of water content of the sediments through field study. The Sentnel-2 satellite images showed us how the water surface has been changed and that during the period from September 2017 to October 2018, the minimum and maximum area of water surface was observed in June 2018 and in January 2018, respectively. In addition, we find that the smaller being the particle size, the higher having the water content and that there is higher the correlation between the water content and the grain size of the sediment layer. Hereafter, if we will acquire the drone images at Bupyung district, we expect that we will be able to measure the distribution of sediments in the same area according to different time periods and observe various kinds of sediment through field work.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.3
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• pp.303-313
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• 2005

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years $(2000\~2003)$ data at Chuncheon and the probability of prediction is investigated. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for $2\~4$ hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1m/s. Especially, about $42\%$ of foggy day fell on the calm $(0\~0.2\;ms^{-1})$ conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water surface temperature was calculated by using Water Quality River Reservoir System (WQRRS) and then it was used as the surface boundary condition of MM5. The numerical experiment was carried out for 2 days from 1300 LST on 14 October 2003 to 1300 LST on 16 October 2003 and fog was simulated at dawn on 15 and 16 October 2003. Simulated air temperature and dew point temperature indicate the similar tendency to observation and the simulated difference between air temperature and dew point temperature has also the similar tendency within $2^{\circ}C$. Thus, the occurrence of fog is well simulated in the terms of the difference between air temperature and dew point temperature. Horizontal distribution of the difference between air temperature and dew point temperature from the numerical experiment indicates occurrence, dissipation and lasting time of fog at Chuncheon. In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.991-1000
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• 2011

The relationship between discharge (Q) and suspended sediment (SS) concentration often is used for the estimation of inflow SS concentration in reservoir turbidity modeling in the absence of actual measurements. The power function, SS=aQb, is the most commonly used empirical relation to determine the SS load assuming the SS flux is controlled by variations of discharge. However, Q-SS relation typically is site specific and can vary depending on the season of the year. In addition, the relation sometimes shows hysteresis during rising limb and falling limb for an event hydrograph. The objective of this study was to examine the hysteresis of Q-SS relationships through continuous field measurements during flood events at inflow rivers of Yongdam Reservoir and Soyang Reservoir, and to analyze its effect on the bias of SS load estimation. The results confirmed that Q-SS relations display a high degree of scatter and clock-wise hysteresis during flood events, and higher SS concentrations were observed during rising limb than falling limb at the same discharge. The hysteresis caused significant bias and underestimation of SS loading to the reservoirs when the power function is used, which is important consideration in turbidity modeling for the reservoirs. As an alternative of Q-SS relation, turbidity-SS relation is suggested. The turbidity-SS relations showed less variations and dramatically reduced the bias with observed SS loading. Therefore, a real-time monitoring of inflow turbidity is necessary to better estimate of SS influx to the reservoirs and enhance the reliability of reservoir turbidity modeling.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1658-1662
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• 2009

최근 들어 기후 변화로 인한 이상 강우 현상과 기록적인 집중 강우로 탁수 발생의 빈도와 강도가 증가하고, 탁수의 장기간 하류 방류로 인해 경제적인 피해가 발생할 뿐만 아니라 환경적으로도 중요한 문제로 대두되고 있다. 저수지로 유입된 탁수의 시공간적 분포 예측 결과의 신뢰도는 탁수 밀도류 해석의 정확도에 가장 큰 영향을 받으므로 유입 하천수의 밀도 거동에 대한 정확한 해석이 필요하다. 따라서 탁수의 거동해석은 수리 및 수질의 연동 모의(Coupled modeling)가 필수적이다. 본 연구의 목적은 수리 및 수질의 연동 해석이 가능한 2차원 횡 방향 평균 모형(CE-QUAL-W2)을 소양호에 구축하고, 기록적인 강우 사상을 보인 2006년 수문조건에서의 모형의 적용성과 한계점을 평가하는데 있다. 구축한 소양호 탁수 예측 모델을 2006년 탁수사상에 적용한 결과, 홍수 사상으로 이중 첨두 유량이 발생한 후 저수지 내에서 중층 밀도류와 바닥밀도류의 두 가지 밀도류 형태가 혼재하여 진행되는 현상이 적절히 모의되었다. 하지만, 저수지내에서 측정한 탁수 수괴(plume)의 시공간적 수직분포(profiles)는 모의결과와 다소 편차를 보였으며, 특히 저수지 바닥 인근에서 모델은 실측값을 과대평가 하였다. 오차의 원인은 모델 입력 자료의 불확실성과 수치모델의 불확실성으로 판단된다. 따라서 향후 탁수 거동 모델링과정의 불확실성을 최소화하고 모의결과의 신뢰도를 개선하기 위해서 극한탁수 사상에서 발생하는 수리학적 현상과 SS 입자 동력학에 대한 이론적 연구와 입력 자료의 정확한 산정을 위한 현장 실험이 필요하다.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.72-72
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• 2018

우리나라의 대형 저수지에 담수된 수체는 여름에 온도가 높은 표수층과 온도가 낮은 심수층, 그리고 두 층 사이에서 온도가 크게 변화되는 변온층으로 나뉘게 된다. 여름 홍수기에 상류 하천에서 저수지로 유입되는 부유사는 큰 밀도를 가지기 때문에 저수지의 바닥을 타고 하층 밀도류의 형태로 저수지 하류로 전파된다. 그러나 밀도류가 성층화된 저수지의 변온층에 도달하면 심수층과 변온층 하층의 낮은 온도로 인해 발생하는 수체의 큰 밀도로 하층으로 더 침투하지 못하고 변온층이나 심수층 상층에서 남아 하류에 중층밀도류의 형태로 전파된다. 대량의 탁수를 하류에 방류하면 하류 수질에 문제가 발생되며 저수시키면 댐 수질 및 심수층 생물체의 태양광 차단 문제가 발생되므로 저수지에서 밀도류의 조절은 대형 저수지 운영에 매우 중요한 사항이다. 따라서 본 연구의 목적은 층적분 모형을 사용하여 대형 저수지에서 발생하는 중층밀도류의 전파 및 선택취수시설을 이용한 밀도류의 차단과 방류에 대해 수치모의하는 것이다. 이를 위하여 중층 밀도류를 수치모의하기 위한 1차원 수치모형을 제시하였으며 소양강댐 상류 소양호에 적용하여 적용성을 검토하고 밀도류의 전파 및 방류에 대해 분석하였다.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.342-349
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• 2000

This paper demonstrates the influence of intensity of the monsoon on morpho-hydrological fluctuations in Taechung Reservoir during 1993${\sim}$1994. During the study, hydrological variables including rainfall, inflow, and discharge volume showed distinct contrast between 1993 and 1994. Interannaul differences in rainfall occurred during the monsoon in July${\sim}$August monsoon and influenced inflow, discharge, and water residence time (WRT). Total inflow in 1993 was four times greater than that of 1994, and summer inflow in 1993 was 8 times greater than summer 1994. Annual Mean WRT was 93.2 d in 1993 vs. 158.6 d in 1994 and the largest differences occurred between monsoons of 1993 and 1994. Morphometric variables reflected the interannual contrasts of hydrology, so that in 1993 surface area, total volume, shoreline development, and mean depth increased consistently from premonsoon to postmonsoon and over this same period in 1994 they decreased. This outcome indicates that the area of shallow littoral zones in 1993 was greater than in 1994. Also, the drainage area to surface area (D/L) at 80 m MSL was 60.7 which was much greater than values in Soyang and Andong reservoirs and natural lakes world-wide. The morpho-hydrodynamic conditions seemed to influence in-reservoir nutrient concentration which is one of the most important factors regulating the eutrophication processes. I believe, under the maximum hydrodynamic fluctuations in Korean waterbodies during the monsoon, applications of mass balance models to man-made lakes for assessments of external loading should be considered because the models can be used under the seasonally stable inflow and water residence time.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.227-234
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• 2013

The vertical shaft of a selective intake structure, which is constructed in a large reservoir, is required to be impermeable and to employ a grouting technology to prevent water inflow from the reservoir or surrounding ground. In this study, groundwater inflow is estimated using a numerical model for two cases (i.e., grouting or non-grouting cases at the exterior of a vertical shaft) and compared with data measured during an excavation at the construction site of a selective intake structure in the Soyang reservoir, Korea. Groundwater inflow is estimated to range from 444 to 754 $m^3/d$ in the case of non-grouting and from 58 to 95 $m^3/d$ in the case of grouting. The groundwater inflow measured in a vertical shaft, which ranges from 30 to 100 $m^3/d$, is similar to the simulated amount. It is recommended that before the excavation of a shaft, water inflow is estimated using a numerical model and a grouting test to ensure excavation stability and improve excavation efficiency.

• Journal of Korea Water Resources Association
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• v.42 no.2
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• pp.161-168
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• 2009

The purpose of this study is to evaluate the variation of probability flood according to the flow regulation by multi-purpose dams (Soyang and Chungju) in the Han-river basin, Korea. SWAT-K (Soil and Water Assessment Tool-Korea) was used in order to generate regulated and unregulated daily streamflows upstream of Paldang dam. Simulated flow regulated by the Soyang and Chungju dams was calibrated by comparison with the observed inflow data at Paldang reservoir. Generally the ratio of flood flows to daily streamflows is known to decrease with drainage area in a watershed. Regulated and unregulated flood flows were obtained from the relationship between flood flows and daily streamflows. Extreme Type-I distribution was applied for flood frequency analysis and L-moment method was used for parameter estimation. This is a novel approach capable of understanding the variation in flood frequency with dam operation for the relatively large watershed scale, and this will helps improve the applicability of daily stream flow data for use in flood control as well as in water utilization.