• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.157-163
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• 1993

The present study focuses on simulating river profile changes downstream of the Daecheong multipurpose dam by using the computer program HEC-6, which was developed by the United States Army Corps of Engineers. The dam locates at the Keum river, a typical alluvial stream, whose bed material is composed mostly of fine and medium sands. The study reveals that after the completion of dam, a 15 km long reach downstream from the regulatory dam was severely degraded by about 2~3 m. No further severe degradation of this reach is expected, however, because the river-bed of this reach has been well armored since then with gravels and cobbles. Some places in the study reach were degraded locally by 2 m, due mainly to the large-scale gravel mining activities in that reach. On the other hand, a 20 km long reach in downstream study reach is aggraded more or less by 0.5~1 m. Calculation by the computer program HEC-6 is close to measurement for the study river reach. According to the results by HEC-6, the study river reach would remain generally stable in the future, except a few places in the mid-upstream where further river-bed degradation of 1~2 m would occur and a few places in the far downstream where local river-bed aggradations of about 0.5 m would occur.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.107-119
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• 1992

A heavy storm hit the central part of the Korean Peninsula especially on the Chungju Dam Basin from the 9th to 12th of September 1990. The Chungju multipurpose dam is the largest water project in Korea completed in 1986. The storm recorded a peak inflow of about $21,000m^3/sec$ at the dam site which is equivalent to 500 to 1000 years recurring frequency according to the designed concept. Extensive hydrological analyses including field investigation were performed to identify the storm. The result of the field investigation showed that 6 gages among the 22 telemetering rain-gages located in the basin were proved to be out-of-normal operation during the storm. The corrected basin average rainfall was estimated to be 458.6 mm ranging from 206 to 665 mm. The correction of the rainfall depth included the adjustment of the rainfall depths of the 6 gages using the Kriging interpolation technique, and adjustment according to the heights of the gage mouths. For the maintenance and operation of the Chungju Dam, new design floods were suggested from the trend analysis which showed that the design flood have to be increased because of the increasing tendency of the annual flood peaks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3469-3476
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• 2015

The Korea Academia-Industrial cooperation Society. The Korea Academia-Industrial cooperation Society. In Korea, the territory has east high west low type and the rainfall is concentrated in the summer season. A nation having these topography and precipitation condition like Korea has to basically needs support of hardware alternatives. However, the right places decrease gradually and the resistance of the public opinion for national water resources policy stiffens gradually. The climate change has an effect in water resources fields and has a close relation. In the present study, therefore, future inflow of Miryang multipurpose dam basin is estimated by using SWAT model applied RCP 4.5 and 8.5 scenarios of "Korea Meteorological Administration" and considering the results, the future direction is purposed to operate the dam. As a result, the rainfall pattern is changed from traditional peak form to flat form. The dam operation rule in accordance with changing precipitation pattern has to be modified from the conventional operation rule and a new plan has to be established to meet a situation.

• 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.56 no.11
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• pp.765-774
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• 2023

Due to climatechange, precipitation variability has increased, leading to more frequentoccurrences of droughts and floods. To establish measures for managing waterresources in response to the increasing uncertainties of climate conditions, itis necessary to understand the variability of natural river discharge and theimpact of reservoir operation modeling considering dam inflow and artificialwater supply. In this study, an integrated rainfall-runoff and reservoiroperation modeling was applied to analyze the water supply reliability andflood risk for a multipurpose dam catchment under climate change conditions. Therainfall-runoff model employed was the modèle du Génie Rural à 4 paramètresJournalier (GR4J) model, and the reservoir operation model used was an R-basedmodel with the structure of HEC-Ressim. Applying the climate change scenariosuntil 2100 to the established integrated model, the changes in water supplyreliability and flood risk of the Happcheon Dam were quantitatively analyzed.The results of the water supply reliability analysis showed that under SSP2-4.5conditions, the water supply reliability was higher than that under SSP5-8.5conditions. Particularly, in the far-future period, the range of flood risk widened,and both SSP2-4.5 and SSP5-8.5 scenarios showed the highest median flood riskvalues. While precipitation and runoff were expected to increase by less than10%, dam-released flood discharge was projected to surge by over 120% comparedto the baseline

• Journal of Korea Water Resources Association
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• v.57 no.7
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• pp.481-491
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• 2024

Recent droughts make hydroelectric power generation (HPG) decreasing. Due to climate change in the future, the frequency and intensity of drought are expected to increase, which will increase uncertainty of HPG in multi-purpose dams. Therefore, it is necessary to estimate the amount of HPG according to climate change scenarios and analyze the effect of drought on the amount of HPG. This study analyzed the future HPG of the Soyanggang Dam and Chungju Dam according to the SSP2-4.5 and SSP5-8.5 scenarios. Regression equations for HPG were developed based on the observed data of power generation discharge and HPG in the past provided by My Water, and future HPGs were estimated according to the SSP scenarios. The effect of drought on the amount of HPG was investigated based on the drought severity calculated using the standardized precipitation index (SPI). In this study, the future SPIs were calculated using precipitation data based on four GCM models (CanESM5, ACCESS-ESM1-5, INM-CM4-8, IPSL-CM6A) provided through the environmental big data platform. Overall results show that climate change had significant effects on the amount of HPG. In the case of Soyanggang Dam, the amount of HPG decreased in the SSP2-4.5 and SSP5-8.5 scenarios. Under the SSP2-4.5 scenario the CanESM model showed a 65% reduction in 2031, and under the SSP5-8.5 scenario the ACCESS-ESM1-5 model showed a 54% reduction in 2029. In the case of Chungju Dam, under the SSP2-4.5 and SSP5-8.5 scenarios the average monthly HPG compared to the reference period showed a decreasing trend except for INM-CM4 model.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.727-739
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• 1998

The main objectives o reservoir optimal operation can be described as follows : maximization of the benefits through optimal allocation of the limited water resources for various purpose; minimization of t도 costs by the flood damage in potential damaging regions and risk of dam failure, etc. through safe drainage of a bulky volume of excessive water by a proper reservoir operation. Reviewing the past research works related to reservoir operation, we can find that the study on the matter of the former has been extensively carried out in last decades rather than the matter of the latter. This study is focused on developing a methodology of optimal reservoir operation for flood control, and a case study is performed on the Chungju multipurpose reservoir in Korea. The final goal of the study is to establish a reservoir optimal operation system which can search optimal policy to compromise two conflicting objectives: downstream flood damage and dam safety-upstream flood damage. In order to reach the final goal of the study, the following items were studied : (1)validation of hydrological data using HYMOS: (2)establishment of a downstream flood routing model coupling a rainfall-runoff model and SOBEK system for 1-D hydrodynamic flood routing; (3)replication of a flood damage estimation model by a neural network; (4)development of an integrated reservoir optimization module for an optimal operation policy.

• The Journal of the Korea Contents Association
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• v.7 no.3
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• pp.140-151
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• 2007

In this study, we attempted to develop a watershed runoff index subject to main control points by dividing the Geum River basin into 14 sub-basins. The Yongdam multipurpose dam Daecheong multipurpose dam and Gongju gage station were selected to serve as the main control points of the Geum River basin, and the observed flow of each control point was calculated by the discharge rating curve, whereas the simulated flow was estimated using the Rainfall Runoff Forecasting System (RRFS), user-interfaced software developed by the Korea Water Corporation, based on the Streamflow Synthesis and Reservoir Regulation (SSARR) model developed by the US Army Corps of Engineers. This study consisted of the daily unit observed flow and the simulated flow of the accumulated moving average flow by daily, 5-days, 10-days, monthly, quarterly and annually, and normal monthly/annually flow. We also performed flow duration analysis for each of the accumulated moving average and the normal monthly/annually flows by unit period, and abundant flow, ordinary flow, low flow and drought flow estimated by each flow duration analysis were utilized as watershed runoff index by main control points. Further, as we determined the current flow by unit period and the normal monthly/annually flow through the drought and flood flow analysis subject to each flow we were able to develop the watershed runoff index in a system that can be used to determine the abundance and scarcity of the flow at the corresponding point.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.16-27
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• 2019

Alteration in the flow regime of rivers are caused by natural climate change and the changes in anthropogenic hydrological environment due to dam construction. These changes in flow regime cause serious changes not only in the fresh water ecosystems of the rivers but also in the physical structures and fish habitats of the streams. In this study, the alteration in the hydrological characteristics of the Gam river basin due to Buhang dam construction and the changes in ecological health condition, water quality, and river cross-section were analyzed. As a result of analysis by indicators of hydrologic alteration (IHA) to quantitatively change the flow regime of Gam river, HA (Hydrologic Alteration) is more than ±1 and various changes have occurred in the river ecosystem after Buhang dam construction. In addition, ecological health condition and water quality showed different response for each element, and in the case of riverbeds and channel cross-sections, the degradation of channel bed was obviously monitored after dam construction. The results of this study are expected to be used as an efficient method for evaluating changes in stream ecosystems caused by stream regime changes.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.8
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• pp.635-640
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• 2009

After 1960s, in accordance with getting bigger in changing range of annual rain precipitation, those dams were built in order to prevent any drought and flood through the regulation of flux. In case of such dam, when it reaches to some definite pondage, for its regulation of water volume, numerous volume of water in the reservoir should be discharged by opening the floodgate, at this time a severe damage can be occurred to those lives and properties of the residents and tourists at the river or riverside. Accordingly, despite the sounding alarm broadcasting for prevention and notice such damage could be clearly travelled to those people without influence by the discharging noise or other neighboring environmental factor, since it was only empirically installed without any peculiar research until now, the alarm broadcasting could not effectively travel, and the travelling distance also could not known correctly. On such point of view, this Study has ever grasped the characteristics by frequencies and its sound pressure level about the discharge noise and the alarm broadcasting of Daechung Dam, one of multipurpose dams through the measurement and analysis by distances, and based on this, also has ever presupposed the proper location of additional alarm broadcasting spot using a simulation program named Cadna-A.