• 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 Korean Society on Water Environment
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• v.21 no.4
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• pp.360-367
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• 2005

We have performed to analyze the trophic state resulting of Lake Yongdam as a result of water quality and nutrient concentration. Lake Yongdam is artifitial multi-purpose Dam resulting from the floods of 2001. The water quality of Lake Yongdam may affect the status of the Geum river basin including the Daecheong reservoir. It is necessary to understand the trophic state to assess water quality until stability after flooding. Water quality was surveyed using depth and hydraulic condition analysis. Further density flow was estimated for stratification and trophic state of Lake Yongdam by chlorophyll ${\alpha}$ concentration (2001~2004). And Environmental factors on chlorophyll ${\alpha}$ concentration were analyzed statistically. Trophic state was evaluated as the oligotrophic state at the main stream of the reservoir and eutrophic state at the upper stream in 2001, but evaluated as eutrophic state in 2002 and 2003 by TSI of Aizaki. From the results of multiple regression analysis using stepwise method, chlorophyll ${\alpha}$ concentration was shown to be very significant when nutrient concentration is high upon initial filling of the Dam. Chlorophyll ${\alpha}$ concentration varied according to sample site, season and year. Concentration were high in the upper stream of Lake Yongdam 4, algae bloom in these watershed were affected by location and high nutrient levels in the summer season which have in turn increased phytoplankton bloom into the reservoir.

• Journal of Korea Water Resources Association
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• v.38 no.1
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• pp.25-35
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• 2005

Nowaday the amount of water resource to generate the hydro-power energy has decreased as that of the water supply has increased. In case that the national market of the energy will be in free competition, the energy producer need to suggest the amount of the optimal supply with the hydrological reliability for a deal. In this study the optimal reservoir operation was performed by the linear programming and the optimal reliabilities of inflows and the power supply were obtained by the one dimensional search technique to estimate the energy with the optimal inflow reliability which the power system of the Yongdam multipurpose dam in Geum river can produce. And the main results were presented.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.3
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• pp.13-22
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• 2008

The objective of this study is to evaluate the applicability of extracted PRMS input parameters by KGIS-Hydrology over Yongdam-Dam watershed. KGIS-Hydrology is a system for automatic extraction and analysis of watershed characteristic data. Input parameters of PRMS were generated from GIS data (DEM, soil, forest type, etc.) using KGIS-Hydrology. Multi-temporal meteorological data from Jangsu station of KMA (Korea Meteorological Administration) were used for all simulation periods. Input parameters of PRMS were optimized using observed runoff data of Yongdam-Dam station (1966-2001) and validated using observed runoff data of Yongdam-Dam station (2002-2006, Yongdam-Dam watershed). The results showed that the simulated flows were much closed to the observed flows of Yongdam-Dam (2002-2006) and Donghyang (2001-2004) station by 0.49~0.83 and 0.57~0.75 model efficiencies, respectively.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.647-659
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• 2003

The purpose of this study is to evaluate hydrological applicability of spatially observed rainfall distribution data by the TRMM/PR (Tropical Rainfall Measuring Mission / Precipitation Radar). For this study, firstly, TRMM/PR data (Y) of the Yongdam-Dam Watershed (930.38$km^2$) was extracted and secondly, TRMM/PR data and the rainfall data (X) by AWS (Automatic Weather Station) were compared by executing a correlation analysis. As a result, the regression equations were deduced as two parts (under 60mm/day : Y = 18.55X-0.53, over 60mm/day : Y = 3.11X+51.16). SCS runoff analysis was conducted using 7 rainfall events in 1999 for Yongdam-Dam watershed and the Cheon-Cheon subwatershed for the revised TRMM/PR data. TRMM/PR data showed relative errors ranging from 19.6％ ti 45.6％, and from 11.3％ to 38.9％ for Cheon-Cheon subwatershed and Yongdam-Dam watershed, respectively, AWS data showed relative errors ranging from 0.5％ to 12.8％, and from -1.6％ to -10.3％, for Cheon-Cheon subwatershed and Yongdam-Dam watershed, respectively. Futher researches are necessary to evaluate the relationship between TRMM/PR data and AWS data for practical hydrological applications.

• Journal of Korea Water Resources Association
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• v.55 no.3
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• pp.205-215
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• 2022

Amidst the global climate crisis, dam operation policies formulated under the stationary climate assumption could lead to unsatisfactory water management. In this work, we assessed status-quo performance of the Yongdam Dam in Korea under various climatic stresses in flood risk reduction and water supply reliability for 2021-2040. To this end, we employed a decision-centric framework equipped with a stochastic weather generator, a conceptual streamflow model, and a machine-learning reservoir operation rule. By imposing 294 climate perturbations to dam release simulations, we found that the current operation rule of the Yongdam dam could redundantly secure water storage, while inefficiently enhancing the supply reliability. On the other hand, flood risks were likely to increase substantially due to rising mean and variability of daily precipitation. Here, we argue that the current operation rules of the Yongdam Dam seem to be overly focused on securing water storage, and thus need to be adjusted to efficiently improve supply reliability and reduce flood risks in downstream areas.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.199-211
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• 2010

The objectives for this study were to evaluate spatial and temporal characteristics of water quality, based on long-term water quality monitoring data during 1993~2008. We found that physico-chemical and ecological conditions in the Daecheong Reservoir (DR) were modified by the construction of upper dam (i.e., Yongdam Reservoir). total phosphorus (TP), Secchi depth (SD), and chlorophyll-a (CHL) in the DR showed significant longitudinal decreases along the headwater-to-the downlake, indicating a large spatial variation, and this gradient was more intensified during the high-flow season (monsoon). Nutrient-rich water containing high nitrogen and phosphorus in the monsoon season (July~August) passed through the reservoir as a density current in the metalimnetic depth, and also high suspended solids increased in the metalimnetic depth, especially during the monsoon. According to the deviation analysis of Trophic State Index (TSI), >50% of TSI (CHL)-TSI (SD) and TSI (CHL)-TSI (TP) values were negatives, so that inorganic suspended solids (non-votatile solids) influenced the underwater light regime against phytoplankton growth. Also, ratios of CHL:TP after the dam construction evidently increased, compared to the values before the upper dam constructions, indicating a greater yield of phytoplankton in the unit phosphorus. Overall data showed that ecological and functional changes in Daecheong Reservoir occurred after the construction of upper dam (Yongdam Reservoir).

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.499-502
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• 2003

Using the daily water balance model of the Keum River Barrage Dam, water supply capacity was analyzed. The scenario of reservoir inflow was selected to case with Daechung dam, case with no dam, case with Yongdam dams. Runoffs in 12 sub watersheds were simulated by the DAWAST model considered return flows.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.737-739
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• 1998

This presentation describes an experiment to intergrated control, protection and measurement system configulation at KOWACO's Yongdam hydro-power station currently constructed by discrete electronic and electromechenical devices. The experiment is designed to exploit existing microcomputer technologies, digital signal processors, m/w&fiber optic communications. The theory of operation and advantages of the intergrated approach are discussed.

• Journal of Korea Water Resources Association
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• v.46 no.5
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• pp.505-517
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• 2013

In this study, water supply for Geum River Basin was calculated by regulating the future water supply of Dam with the future expected discharges. HadGEM2-AO, which is the climate change prediction model that KMA (Korea Meteorological Administration) recently introduced was used for this study. The data of weather stations within the Geum River basin was extracted with the new Greenhouse Gas RCP scenario. The runoff of Geum river basin was simulated using the ArcSWAT for the 1988~2010 period. After validating the model, the similarity of results between simulation and observation at the Yongdam Dam and Daecheong Dam was 92.25% and 95.40%, respectively, which shows a good agreement with observed data. As the result of analysis for the discharges, the discharges would increase 47.76% under the RCP4.5 scenario and 36.52% under the RCP8.5 scenario. Water balance analysis was conducted by the KModSim for predicting the water supply under the runoff variation. We analyzed the volume of water intake with national standard of water supply 95% by Dam Operation Manual. By the analysis under RCP4.5 scenario, $9.41m^3/s$, $24.82m^3/s$ of additional water supply is available on Yongdam Dam and Daecheong Dam. By the analysis under the RCP8.5 scenario, $6.48m^3/s$, $21.08m^3/s$ of additional water supply is available on Yongdam Dam and Daecheong Dam.