• Journal of Korean Society on Water Environment
• /
• v.21 no.6
• /
• pp.609-616
• /
• 2005

A high ammonia nitrogen ($NH_3-N$) concentration has been recursively observed every winter season in Geum River, which hindered chemical treatment processes at a water treatment plant. A flushing discharge from Daecheong Dam was often considered to dilute $NH_3-N$, but information on the quantitative effect of flushing on the downstream water quality was limited. In this study, the impact of a short-term reservoir flushing on the downstream water quality was investigated through field experiments and unsteady water quality modeling. On November 22, 2003, the reservoir discharge was increased from $30m^3/sec$ to $200m^3/sec$ within 6 hours for the purpose of the experiment. The results showed that flushing flow tends to reduce downstream $NH_3-N$ concentrations considerably, but the effectiveness was limited by flushing amount and time. An unsteady river water quality model was applied to simulate the changes of nitrogen concentrations in response to reservoir flushing. The model showed very good performance in predicting the travel time of flushing flow and the effect of flushing discharge on the reduction of downstream $NH_3-N$ concentrations at Maepo and Geumnam site, but a significant discrepancy was observed at Gongju site.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.389-389
• /
• 2011

과거의 무분별한 수자원 개발에 따른 자연환경파괴로 인해 점차 대규모 다목적댐의 건설과 같은 신규 수자원 개발이 쉽지 않은 상황이지만, 여전히 댐은 유한의 수자원을 적극적으로 확보하기 위한 가장 대표적인 방법으로서, 안정적인 용수 확보를 통한 물부족의 해소와 효율적인 운영을 통한 홍수와 가뭄 피해 예방을 위해 중요한 역할을 해오고 있다. 댐의 건설로 인해 하류측 본류에서는 과거와 같은 유량의 극심한 계절적인 편차는 감소되었으며, 가뭄이나 홍수에 대한 피해 규모도 저감되었다고 볼 수 있다. 댐 건설에 따른 수문학적 변화에 대한 분석은 실제 댐 건설 전후의 장기적인 관측자료를 비교하는 것이 가장 정확한 방법이나, 대부분 관측자료가 전무하거나 충분하지 못하기 때문에 일반적으로 모델링을 통해 장기간의 유출자료를 추정한 후 이를 기반으로 그 영향을 평가하고 있다. 모델링 방법으로는 과거부터 오랫동안 국내 수자원 해석 및 계획에 폭넓게 활용되고 있는 TANK 모형을 비롯하여, SSARR, NWS-PC, TOPMODEL, HSPF, PRMS, SLURP, SWAT, MIKE-SHE 등 다양한 모형들이 적용되고 있다. 이 중에서 SWAT은 유역의 수문 수질의 시공간적인 해석 및 관리, 그리고 미래 유역환경변화에 따른 영향 평가 등을 위해 국내는 물론 국제적으로도 많이 적용되고 있는 모형이다. 본 연구에서는 SWAT 모형을 국내 유역 특성에 적합하도록 개선한 SWAT-K 모형을 이용하여, 금강유역에서의 대청댐 및 용담댐의 운영과 인위적인 용수 이용에 따른 유출량, 증발산량 및 지하수 함양량 등의 수문성분의 변화를 분석하였다. 대청댐의 건설과 유역내 용수 이용으로 인해 하류측 공주지점에서의 유출량은 자연상태에 비해 증가하는 것으로 나타났으며, 지하수 함양량과 증발산량은 감소하는 것으로 분석되었다.

• Journal of Korean Society on Water Environment
• /
• v.28 no.3
• /
• pp.359-366
• /
• 2012

Accurate predictions about the water quality of a river have great importance in identifying in-stream flow and water supply requirements and solving relevant environmental problems. In this study, the effect of water release from upstream dam on the downstream water quality has been investigated by applying a hydological model combined with QUAL2E to Geum River basin. The ESP (Ensemble Stream Prediction) method, which has been validated and verified by lots of researchers, was used to predict reservoir and tributary inflow. The input parameters for a combined model to predict both hydrological characteristics and water quality were identified and optimized. In order to verify the model performance, the simulated result at Gongju station, located at the downstream from Daecheong Dam, has been compared with measured data in 2008. As a result, it was found that the proposed model simulates well the values of BOD, T-N, and T-P with an acceptable reliability.

• Journal of Korea Water Resources Association
• /
• v.56 no.1
• /
• pp.11-21
• /
• 2023

This study suggests the drought resilience index as S-day as a means of preparing for the recent extreme drought, allowing for the actual operational identification of each drought countermeasure's priority as well as the vulnerability of water resource facilities to drought. Although each dam's drought measures are unique in this case, the representative examples include adjusting the water supply, linking the functioning of various facilities, and considering emergency capacity. Here, 15 multipurpose dams and water supply dams in Korea were inspected. Under the return period of 20-year drought, most of dams showed stable by adjusting the water supply overall. The measures, however, did not seem to be able to resist a multi-year drought lasting more than two years. Besides, Hoengseong and Anodong-Imha Dam only lasted a year under the 100-year drought return period with other measures. Without the deployment of drought mitigation strategies, it is expected that the Hoengseong Dam, Andong-Imha Dam, Gunwi Dam, Unmun Dam, Daecheong Dam, and Juam Dam would not be able to meet the all water demand for a year under the 20-year drought condition. The ideal capacity for each drought measure was then suggested. Additionally, by increasing or decreasing the current supply contract by 10% in order to account for demand changes resulting from socio-economic instability, the drought response capacity of all 15 dams was re-evaluated. By lowering the supply contract amount by 10%, it was possible to endure a severe drought.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1B
• /
• pp.55-64
• /
• 2008

The evidence of changes in the climate system is obvious in the world. Nevertheless, at the current techniques for flood frequency analysis, the flood distribution can not reflect climate change or long-term climate cycles. Using a linear regression and a Mann-Kendall test, trends in annual maximum precipitation and flood data for several major gauging sites were evaluated. Moreover, this research considered incorporating flood trends by climate change effects in flood frequency analyses. For five rainfall gauging sites (Seoul, Incheon, Ulleungdo, Jeonju, and Gangneung), upward trends were observed in all gauged annual maximum precipitation records but they were not statistically significant. For three streamflow gauging sites (Andong Dam, Soyanggang Dam, and Daecheong Dam), upward trends were also observed in all gauged annual maximum flood records, but only the flood at Andong Dam was statistically significant. A log-normal trend model was introduced to reflect the observed linear trends in annual maximum flood series and applied to estimate flood frequency and risk for Andong Dam and Soyanggang Dam. As results, when the target year was 2005, 50-year floods of the log-normal trend model were 41% and 21% larger then those of a log-normal model for Andong Dam and Soyanggang Dam, respectively. Moreover, the estimated floods of the log-normal trend model increases as the target year increases.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.937-941
• /
• 2006

본 연구에서는 비상여수로와 같은 치수능력 증대를 위한 구조물의 이수적 측면의 활용성에 대해 검토하였다. 이를 위해 대청댐 유역을 대상으로 홍수기와 비홍수기로 구분하여 수문분석을 실시하고, 대청댐 하류부 무피해 방류량을 산정하였으며, 저수지 모의운영을 통하여 비홍수기 운영수위인 상시만수위와 홍수기 운영수위인 제한수위를 검토하였다. 본 연구 결과 비홍수기 상시만수위와 홍수기 제한수위를 가변적으로 운용하여 다목적댐의 이수능력을 증대시킬 수 있는 것으로 분석되었다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1596-1600
• /
• 2006

자연적인 하천은 하도 상황의 변경, 유역 토지이용의 변화, 댐과 저수지, 하천 골재채취의 영향 등 여러가지 요인에 의해 하상변동이 발생하게 된다. 본 연구에서는 금강 대청댐 하류구간의 실측자료를 토대로 장기하상변동 모의를 하여 예측된 결과와 실측단면을 비교하였으며, 실측단면이 장기하상변동 모의결과보다 상당히 저하된 것으로 분석되었다. 또한 금강의 측량자료를 수집하여 비교분석한 결과 시간이 경과함에 따라 금강의 하상이 지속적으로 저하되는 것으로 나타났으며, 대청댐 하류의 하상고는 대청댐 상류보다 저하폭이 상당히 큰 것으로 나타났다. 원인분석 결과 대청댐 건설로 인한 유사차단으로 인하여 대청댐 하류의 하상고는 지속적으로 저하되는 것으로 판단되었으며, 주요원인으로 금강의 골재채취가 금강하류 하상변동에서 상당히 큰 영향을 미치는 것으로 분석되었다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.303-303
• /
• 2011

효율적인 수자원 관리를 위해서는 미래 수문자료의 예측치에 대한 구간을 추정하여 미래에 관측될 자료에 대한 정보를 얻는 문제는 어렵지만 중요한 부분에 해당한다. 특히 중장기 유량예측은 입력변수의 불확실성이 크므로 확률론적 방법을 적용한 예측이 유리하다. 본 연구에서는 SSARR 모형을 이용하여 현재 유역의 상태에 과거에 재현되었던 강우를 결합한 앙상블 유출시나리오를 생성하였다. 그리고 대청댐 월 유입량에 대한 확률론적 예측방안을 제시하기위하여 과거 시나리오의 관측 ESP(Ensemble Streamflow Prediction)확률 및 Croley방법, PDF-Ratio방법을 한국의 기상예측정보 실정에 맞는 가중치 부여방안으로 적용하여 분석하였다. 2010년도 상반기를 기준으로 각 분석 기법별 정확성을 검증한 결과 Croley, PDF-Ratio 등 기상전망을 가중치로 부여한 확률론적 예측기법의 효용성을 확인하였다.

• Journal of Korea Water Resources Association
• /
• v.42 no.1
• /
• pp.1-8
• /
• 2009

In this study, based on the major activities which might have affected the ecological system of the Geum River, a conceptual model was proposed to guide scenario development for the eco-hydrological river evaluation. Also, an analysis method employing a set of models consisting, with other supporting programs, of KModSim for watershed network analysis and RAP for ecosystem analysis was developed for eco-hydrological river assessment. Then, hydrological analyses with various scenarios were conducted to examine the flow regime changes expected from the construction and operation of the Youngdam Multipurpose Dam (YMD) and Daecheong Multipurpose Dam (DMD) in the Geum River basin. The results indicated that the "Percentile 10" values for 10% exceeding time were decreased by 20.5% and 8.0% at Sutong downstream of YMD and Gongju downstream of DMD, respectively, while "Percentile 90" values for 90% exceeding time were increased by 56.3% and 340.8% at Sutong and Gongju, respectively, resulting in the reduction of the high flow variability typical for unregulated rivers in Korea. The results of eco-hydrological analyses will be presented in the following papers.

• Journal of Korean Society on Water Environment
• /
• v.21 no.4
• /
• pp.360-367
• /
• 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.