• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.331-347
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• 2023

The downstream submergence damages caused during the flood season in 2020, around the Yongdam-dam and five other sites, were analyzed using related dam management data. Hourly- and daily-data were collected from public national websites and to conduct various analyses, such as autocorrelation, partial-correlation, stationary test, trend test, Granger causality, Rescaled analysis, and principal statistical analysis, to find the cause of the catastrophic damages in 2020. The damage surrounding the Yongdam-dam in 2020 was confirmed to be caused by mis-management of the flood season water level. A similar pattern was found downstream of the Namgang- and Hapcheon-dams, however the damage caused via discharges from these dams in same year is uncertain. Conversely, a different pattern from that of the Yongdam-dam was seen in the areas downstream of Sumjingang- and Daecheongdams, in which the management of the flood season water level appeared appropriate and hence, the damages is assumed to have occurred via the increase in the absolute discharge amount from the dams and flood control capacity leakage of the downstream river. Because of the non-stationarity of the management data, we adapted the wavelet transform analysis to observe the behaviors of the dam management data in detail. Based on the results, an increasing trend in the discharge amount was observed from the dams after the year 2000, which may serve as a warning about similar trends in the future. Therefore, additional and continuous research on downstream safety against dam discharges is necessary.

• Journal of Korea Water Resources Association
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• v.47 no.2
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• pp.195-206
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• 2014

In this study, a performance evaluation method of water supply for a multi-purpose dam based on deficitsupply method and reservoir storage is presented. The method is applied to 16 multi-purpose dams and water supply performance is evaluated. As a result, 6 dams (Soyanggang, Chungju, Hoengseong, Andong, Imha, and Hapcheon dam) have highest performance and 2 dams (Sumjingang and Buan dam) have relatively low performance. Particularly, Buan dam is the most vulnerable in the analysis results of reliability, resiliency, and vulnerability. Therefore, measures to improve the performance of water supply are needed in Buan multi-purpose dam.

• Journal of Korea Water Resources Association
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• v.54 no.2
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• pp.135-144
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• 2021

This paper attempted to find implications for water resource management and water quality improvement by analyzing the causal relationship among discharge, water temperature and pollution index, which were expected to have a great effect on water quality with the rise of water temperature and precipitation change as the warming effect in recent years. For this purpose, the unit root test, cointegration test, and Granger causal test were carried out for 10 multi-purpose dams in Korean major water systems using time series data on discharge, water temperature, BOD, COD and DO. It was analyzed that the fluctuation of water temperature affected the pollution index more than the fluctuation of discharge volume. Also, Hapcheon dam and Chungju dam were the best water quality management dams based on the high causal relationship between water quality and discharge. The second rank was Daecheong dam. The third-ranking group were Yongdam and Andong dam, whose causal relationships between water quality and discharge were low. The last group were the remaining five dams.

• Journal of Korean Society on Water Environment
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• v.36 no.3
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• pp.229-244
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• 2020

Hydrologic models, as a useful tool for understanding the hydrologic phenomena in the watershed, have become more complex with the increase of computer performance. The hydrologic model, with complex configurations and powerful performance, facilitates a broader understanding of the effects of climate and soil in hydrologic partitioning. However, the more complex the model is, the more effort and time is required to drive the model, and the more parameters it uses, the less accessible to the user and less applicable to the ungauged watershed. Rather, a parsimonious hydrologic model may be effective in hydrologic modeling of the ungauged watershed. Thus, a semi-distributed hydrologic partitioning model was developed with minimal composition and number of parameters to improve applicability. In this study, the validity and performance of the proposed model were confirmed by applying it to the Namgang Dam, Andong Dam, Hapcheon Dam, and Milyang Dam watersheds among the Nakdong River watersheds. From the results of the application, it was confirmed that despite the simple model structure, the hydrologic partitioning process of the watershed can be modeled relatively well through three vertical layers comprising the surface layer, the soil layer, and the aquifer. Additionally, discussions were conducted on antecedent soil moisture conditions widely applied to stormwater estimation using the soil moisture data simulated by the proposed model.

• Journal of Korea Water Resources Association
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• v.44 no.12
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• pp.915-928
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• 2011

The main purpose of this study is to understand the effects of hydroclimatic factors on annual actual evapotranspiration and to suggest the multiple linear regression (MLR) equations for the estimation of annual actual evapotranspiration from watershed. To accomplish this study purpose, 5 dam watersheds (Goesan dam, Seomjingang dam, Soyanggang dam, Andong dam, Hapcheon dam) were selected as study watersheds and annual actual evapotranspiration was estimated based on annual water balance analysis from each watershed. The estimated annual actual evapotranspiration from water balance analysis was used to evaluate the MLR equations. Furthermore, the possibility of the estimation of actual evapotranspiration using potential evapotranspiration equations (Penman equation, FAO P-M equation, Makkink equation, Preistley-Taylor equation, Hargreaves equation) was evaluated. It has turned out that it is not appropriate to use potential evapotranspiration for the estimation of actual evapotranspiration because the correlation between actual evapotranspiration and potential evapotranspiration is very low. The comparison of MLR equations with current actual evapotranspiration equations indicates that MLR equations can be used for the estimation of annual actual evapotranspiration. Furthermore, it has turned out that the effects of hydroclimatic factors on annual actual evapotranspiration from dam watersheds are different in each watershed; however, for all watersheds in common precipitation has turned out to be the most important climatic factor affecting on the estimation of annual actual evapotranspiration.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.283-289
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• 2018

In our study, we collected data from a 100 kW floating photovoltaic (PV) system installed in Gyeongnam Hapcheon Dam and observed correlations between the power generation of the floating PV system and the irradiance, water temperature, humidity, ambient temperature, wind speed, and module temperature. Firstly, there was little correlation between the water temperature and power generation. Secondly, the ambient temperature, wind speed, and humidity all showed greater correlations with power generation. Finally, the power generation was very highly correlated with the irradiance and module temperature. In conclusion, the power generation of the floating PV system is related individually to environmental factors.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.155-155
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• 2017

최근 우리나라는 기후변화의 영향으로 다목적댐 저수율이 예년에 비해 크게 줄어들어 정상적인 용수공급에 어려움을 겪고 있다. 지구온난화로 인한 기후변화의 가속화는 가뭄의 강도와 발생 빈도를 증가시켜 정상적인 용수공급은 앞으로 더욱 어려워질 것으로 예상된다. 이에 따라 기후변화에 대처할 수 있는 용수공급 방안이 필요할 것으로 판단된다. 본 연구에서는 기후변화에 따른 합천댐의 용수공급능력 분석을 위해 CMIP5 GCM 기후변화 시나리오에 따른 합천댐의 용수공급 능력을 분석하였다. 용수공급능력을 향상시킬 수 있는 비구조적 대안으로 다목적댐의 용수공급 조정기준 및 다목적댐의 비상용량을 활용하였다. 기후변화에 따른 분석기간은 21세기 초기(2011-2040년, 30년), 21세기 중기(2041-2070년, 30년), 21세기 후기(2071-2099년, 29년)로 설정하였다. 저수지 모의운영을 위해 저수지 모의운영 프로그램인 HEC-ResSim을 이용하였다. 또한 용수공급 능력을 평가하기 위한 지표로 용수공급의 신뢰도와 회복도, 취약도 등을 산정하고 그 결과를 비교 분석하였다.

• ALGAE
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• v.17 no.2
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• pp.105-115
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• 2002

Influences of vrious environmental factors on the eutrophication of Nakdong River were analyzed statistically using water samples collected from 1 January, 1999, to 30 September, 2001 at Namji area. The relationships between the concentration of chlorophyll α (eutrophication index) and environmental factors and were analyzed to develop a statistical model which can predict the status of eutrophication. The concentation of chlorophyll α ranged from 66.2 mg · $m^{-3}$ to 70.8 mg · $m^{-3}$ during dry winter season and the average concentration during this study period was 35.5 mg · $m^{-3}$ Namji area of Nakdong River was in the hypereutrohic stage in terms of water quality. Stephanodiscus sp. and Aulacoseria granulata var. angustissima were dominant species during the witnter to spring time and summer to autumn period, respectively. Based on the correlation analysis and the analysis of variance between chlorophyll α concentration and environmental factors, significantly high positive relationships were found in the order of BOD> pH> COD > KMnO₄ consumption > DO > conductivity > alkalinity. In contrast to these factors, significantly negrative relationships were found as in the order of $PO₄^{3-}-P$ >water level>the rate of Namgang-dam discharge > NH₃-N> the rate of Andong-dam discharge> the rate of Hapchoen-dam discharge. Based on the factors analysis of environmental factors on the concentration of chlorophyll α, we obtained five factors as follows. The first factor included water level, pH, turbiditiy, conductivity, alkalinity and the rate of Namgang-dam discharge. The second factor included water temperature DO, NH₄+-N, NO₃- -N. The third factor included KMnO₄ consumption COD and BOD. The fourth factor included the rate of Andong-dam discharge, the rate of Hapcheon-dam discharge, and the rate of Imha-dam discharge. The final factor included T-N T-P and $PO₄^{3-}-P$ > concentration. We derived two statistica models that can predict the occurrence of eutrophication based on the factors by factor analysis, using regression analysis. The first model is the stepwise regression model whose independent variables are the factors produced by factor analysis : chl α (mg · $m^{-3}$ = 42.923+(18.637 factor 3) + (-17.147 factor 1) + (-12.095 factor 5) + (-4.828 factor 4). The second model is the alternative stepwise regression model whose independent variables are the sums of the standardized main component variables:chl α (mg · $m^{-3}$ = 37.295+(7.326 Zfactor 3) + (-2.704 Zfactor 1)+(-2.341 Zfactor 5).

• Journal of the Korean Institute of Landscape Architecture
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• v.51 no.2
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• pp.131-142
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• 2023

Solar power facilities to reduce carbon emissions are continuously being installed in forests, farmland, city, and on water. However, research on visual preferences and the psychological impact on observers after installing solar power facilities is insufficient. Therefore, in this study, shooting was conducted according to the viewing distance of the near, middle, and distant views of Hapcheon Dam, Korea's largest floating photovoltaic power plant. The acquired images were edited using Photoshop to compare the presence or absence of floating photovoltaic power generation facilities. In addition, psychological changes and visual preferences were analyzed through an EEG test and questionnaire among 50 participants. The results are summarized, as follows. First, the installation of water photovoltaic power generation facilities has a passive impact on the subjects' psychological changes and visual preference. Second, the psychological changes due to the installation of water photovoltaic power generation facilities were judged to affect almost all research subjects, regardless of nationality, gender, or universisty major. Third, the visual preference for installing the water photovoltaic power generation facility is low, which can be interpreted as the water photovoltaic power generation facility negatively affecting the "friendliness" and "naturalness" of the landscape. In addition, this change in visual preference was found to differ depending on the gender and universiity major of the subjects. Fourth, the psychological change and visual preference of the floating photovoltaic power generation facility according to the viewing distance, found that the close range had a higher effect than the middle and distant ranges.

• Journal of Environmental Impact Assessment
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• v.32 no.6
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• pp.473-487
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• 2023

Korea's multi-purpose dams, which were constructed in the 1970s and 1980s, have a single outlet located near the bottom for hydropower generation. Problems such as freezing damage to crops due to cold water discharge and an increase the foggy days have been raised downstream of some dams. In this study, we analyzed the effect of water intake depth on the reservoir's water temperature stratification structure and outflow temperature targeting Hapcheon Reservoir, where hypolimnetic withdrawal is drawn via a fixed depth outlet. Using AEM3D, a three-dimensional hydrodynamic water quality model, the vertical water temperature distribution of Hapcheon Reservoir was reproduced and the seasonal water temperature stratification structure was analyzed. Simulation periods were wet and dry year to compare and analyze changes in water temperature stratification according to hydrological conditions. In addition, by applying the intake depth change scenario, the effect of water intake depth on the thermal structure was analyzed. As a result of the simulation, it was analyzed that if the hypolimnetic withdrawal is changed to epilimnetic withdrawal, the formation location of the thermocline will decrease by 6.5 m in the wet year and 6.8 m in the dry year, resulting in a shallower water depth. Additionally, the water stability indices, Schmidt Stability Index (SSI) and Buoyancy frequency (N²), were found to increase, resulting in an increase in thermal stratification strength. Changing higher withdrawal elevations, the annual average discharge water temperature increases by 3.5℃ in the wet year and by 5.0℃ in the dry year, which reduces the influence of the downstream river. However, the volume of the low-water temperature layer and the strength of the water temperature stratification within the lake increase, so the water intake depth is a major factor in dam operation for future water quality management.