• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5B
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• pp.459-466
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• 2011

In this study, the resources investigations of small hydropower generation were carried out for the five proposed sites in northern Gyeong-buk area. They consisted of the discharge measurements, rating-curve, flow duration curves, electricity generation, and economic analysis, respectively. The basic data were suggested to select the optimal small hydropower sites in northern Gyeong-buk area. The sites for Yecheon Gun and Munsu Myeon as a result are the best proposed ones using economic analysis. We considered, however, that the finacial benefit for small hydropower development may be small under 500 kW facility. The optimal proposed site over 500 kW facility was suggested as Yeongyang Gun in this study.

• Journal of Korea Water Resources Association
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• v.47 no.2
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• pp.107-117
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• 2014

Hancheon reservoir, which is located upstream of Jeju city, has been built for flood mitigation after Typhoon Nari, 2007. To verify flood mitigating effect of the this reservoir on the downstream area, runoff analysis based on the measured data (two stream discharge monitoring stations and inflow data to the reservoir) is carried out during torrential rain followed by typhoon Dainmu, 2010. The stream water level was recorded as 3.14 m for the peak at the down gradient station. The stream water level under the assumption of absence of Hancheon reservoir is calculated as 4.16 m using the estimated rating curve, stream water propagation velocity, and the bypassed volume of water to the reservoir. This result shows that clear effect of reservoir operation which is capable of mitigating peak discharge in the downstream area.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.932-932
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• 2012

하천의 유량은 우리나라 수자원의 주요 구성원이므로 그 자료는 수자원 분야의 기초자료로서 매우 중요한 역할을 한다. 하천의 유량을 알기 위한 연속적인 측정은 많은 비용과 인력 등으로 의해 현실적으로 어려운 일이다. 따라서 하천 수위와 측정된 유의 관계를 도시한 수위-유량관계곡선식(Stage-Discharge Rating Curve)으로 통상 유량을 산정하고 있다. 수위-유량곡선은 하천의 수자원의 계획 및 관리, 홍수예보, 수리시설물의 설계 등에 이용되고 있다. 그러나 하류에 보와 같은 구조물이 존재하는 경우 단순 수위-유량관계곡선식으로 유량을 환산하는 경우, 배수영향으로 인해 환산유량은 실제유량과 큰 차이가 나게 된다. 본 연구에서는 배수영향이 있는 곳의 동일수위에서 유량변화의 가장 큰 요인인 수면경사임을 착안하여 동일 수위에 대한 실제 현장의 수면경사와 유량관계 분석을 통해 수위-하강고-유량 관계를 정량적으로 파악하여 환산유량 편차를 줄이고자 하였다. 현장 지점은 창녕 합천보와 함안 창녕보 사이에 위치한 적포교 지점으로서 보의 수문개폐여부에 따른 수위-하강고-유량관계 분석을 통해 유량을 환산하고 현재 운영되고 있는 자동유량 측정치와 비교하였다. 단순 수위-유량곡선을 통해 환산한 유량 값과 하강고를 고려한 환산유량을 자동유량 측정치와 비교한 결과 각각 39.85%와 5.04%의 표준오차를 보여, 보다 정확한 환산유량 값을 구할 수 있었다. 따라서, 본 연구결과는 하류 보등 시설물이나 본류흐름 등에 의한 배수영향을 받는 지점에서의 환산유량을 기존보다 정확히 산정할 수 있는 방법을 제시하였다는데 그 의의가 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.370-370
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• 2023

수자원이란 인간의 생활이나 경제활동 및 자연환경 유지 등을 하는데 이용할 수 있는 자원으로서의 물을 말하며 효율적인 수자원의 활용을 위해서는 수문조사가 필수적이라고 할 수 있다. 수문조사는 강수량, 수위, 유량, 유사량, 증발산량, 토양수분량을 측정, 조사, 분석하는 것이라고 할 수 있으며 이 중 유량은 강우-유출 관계 규명, 이수, 치수 등을 위해 높은 정확도의 관측자료가 필요하다. 그러나 하천유량은 장기간 연속적으로 관측하는 것이 어려우므로 특성 횟수의 유량조사를 통해 수위-유량관계곡선식(Rating curve)을 개발하여 수위로부터 연속적인 유량을 산정하여 활용하고 있어 이를 개선하기 위해 전자파표면유속계를 활용한 자동유량측정장치를 개발하였으며 측정자료 분석 및 알고리즘 고도화를 통해 신뢰도 높은 유량을 산정하고자 하였다. 운동하는 물체에 의하여 산란된 전자파의 주파수가 변하게 되는 현상을 도플러 효과라고 하며 이때의 주파수의 변화량을 도플러 주파수라고 한다. 전자파표면유속계는 하천 수면으로 전자파를 발사한 후 물 표면에서 반사되는 전자파의 도플러 효과를 이용하여 표면유속을 측정하는 것으로 전자파표면유속계를 교량 상류 방향으로 고정시켜 설치하였으며 측정된 자료는 유량관측 시스템에서 저장, 관리되고 물리적, 통계적 방법이 적용된 알고리즘을 통해 유량을 산정한다. 산정된 유량의 정확도 확보를 위해 바람 영향, 최적 환산계수 재산정, 통계분석 등을 통해 시스템의 유량산정 알고리즘 개선 방안을 도출하였으며 개선된 알고리즘이 적용된 유량은 NSE(Nash Sutcliffe Efficiency), PBIAS(Percent Bias), RSR(RMSE-observations standard edviation ratio)을 통해 평가하였다. 바람 영향은 유량 관측 고도화 매뉴얼(일본 토목연구소)의 경험식과 현장에서 관측된 풍향·풍속을 활용하여 분석하였으나 개선효과가 미미한 것으로 나타났으며 자동으로 관측된 유량자료에 포함된 무작위적인 변화량을 감소시키기 위해 경향성 분석을 병행하여 이동평균 방법을 적용하였다. 또한 ADCP 등을 활용한 유량측정성과와 수위-유량관계곡선식과의 비교·분석을 통해 수위별 최적 환산계수를 산정하여 유량산정 알고리즘에 적용한 결과 NSE는 0.980, PBIAS는 1.580, RSR은 0.142로 모두 Very Good(높은 상관성)으로 분석되어 유량자료의 정확도를 확보하였다.

• Journal of Korean Society on Water Environment
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• v.37 no.4
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• pp.249-262
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• 2021

This study investigated the pollution characteristics of the main pollution zone in the Hwangguji watershed and the influence of the tributary on the main stream. The characteristics of the main pollution zone, including, the water quality index (WQI), stream rating, load duration curve (LDC), delivery load density (DLD), and contribution of the tributary to the mainstream, were evaluated by time-series visual heatmap. The WQI of the mainstream of Hwangguji was lowered to the poor (IV) level from the inflow point of Suwon stream (SW) and the LDC excess rate in the T-P was higher than that of BOD₅, especially for the wet season, suggesting that management of non-point source with T-P is preferred. The contribution (%) of the tributaries in the upstream section of Hwangguji watershed were BOD₅ 14.54%, TOC 15.67%, T-N 5.43%, and T-P 6.97%. In particular, the Suwon sewage treatment plant located in the mainstream showed a high contribution of BOD₅ (64.40%) and T-P (53.54%), respectively, due to the high discharge rate (6.019 m³/sec). Meanwhile, Sammi and Gal stream have a large impact on the mainstream with high DLD and poor WQI. Thus, both streams were considered as pollution hot spots. These results provide useful basic data for preparing more effective water quality improvement and management plans in the watershed.

• 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 Korean Society of Forest Science
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• v.89 no.5
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• pp.564-575
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• 2000

This study was carried out to reveal characteristics of long-term runoff by using HYCYMODEL in a small forested watershed. From May to September in 1998 and in 1999, the fitness of HYCYMODEL and runoff characteristics were estimated by HYCYMODEL using rainfall and discharge at the experimental watershed. The function of stage and discharge in the experimental watershed was determined as following equation $Q=11.148H^{2.5867}$($R^2=0.9956$). From May to September in 1998 and in 1999, the runoff rates were 57.7% in 1998 and 87.1% in 1999 at the experimental watershed. The discharge was assumed to be increased because of rainfall intensity difference and thinning. By applicability test, the HYCYMODEL showed good estimation of runoff by optimized fifteen parameters. Comparing runoff characteristics before and after thinning by calculating through HYCYMODEL, direct runoff and base runoff increased 4%, 7%, respectively as evapotranspiration decreased 11%. Parameters $D_{50}$ and $K_h$, which were related to the direct run, and a parameter $K_u$, which was related to the baseflow, were assumed to indicate that forest was changed by the effect of thinning and weathering process of bed rock.

• Journal of Korea Water Resources Association
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• v.45 no.11
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• pp.1107-1119
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• 2012

The objectives of this study are to develop the flow nomograph for real-time flood forecasting and to assess its applicability in restored Cheonggye stream. The Cheonggye stream basin has the high impermeability and short concentration time and complicated hydrological characteristics. Therefore, the flood prediction method using runoff model is ineffective due to the limit of forecast. Flow nomograph which is able to forecast flood only with rainfall information. To set the forecast criteria of flow nomograph at selected flood forecast points and calculated criterion flood water level for each point, and in order to reflect various flood events set up simulated rainfall scenario and calculated rainfall intensity and rainfall duration time for each condition of rainfall. Besides, using a rating curve, determined scope of flood discharge following criterion flood water level and using SWMM model calculated flood discharge for each forecasting point. Using rainfall information following rainfall scenario calculated above and flood discharge following criterion flood water level developed flow nomograph and evaluated it by applying it to real flood event. As a result of performing this study, the applicability of flow nomograph to the basin of Cheonggye stream appeared to be high. In the future, it is reckoned to have high applicability as a method of prediction of flood of urban stream basin like Cheonggye stream.

• Korean Journal of Environmental Agriculture
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• v.30 no.3
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• pp.268-274
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• 2011

BACKGROUND: A large scale of sediment load delivered from watershed causes substantial waterway damages and water quality degradation. Controlling sediment loading requires the knowledge of the soil erosion and sedimentation. The various factors such as watershed size, slope, climate, land use may affect sediment delivery processes. Traditionally sediment delivery ratio prediction equations have been developed by relating watershed characteristics to measured sediment yield divided by predicted gross erosion. However, sediment prediction equations have been developed for only a few regions because of limited sediment data. Besides, little research has been done on the prediction of sediment delivery ratio for asia monsoon period in mountainous watershed. METHODS AND RESULTS: In this study Tank model was expanded and applied for estimating sediment yield to Oship River of east coast. The rainfall-runoff in 2006 was verified using the Tank model and we derived good result between observed and calculated discharge in 2009 at the same conditions. In relation to sediment yield, the sediment delivery rate of 2006 was very high than 2009 regardless of methods for estimating sediment load. It was thought to be affected by heavy rainfall due to the typhoon. CONCLUSION(s): For estimating sediment volume from watershed, long-term monitoring data on discharge and sediment is needed. This model will be able to apply to predict discharge and sediment yield simultaneously in ungauged area. This approach is more effective and less expensive method than the traditional method which needs a lot of data collection.

• Journal of Korean Society of Disaster and Security
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• v.13 no.4
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• pp.65-74
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• 2020

Continuous and accurate instrument of river water usage is needed for sustainable river water management. Although the instrument methods applicable to each point of use of river water are different, more precise direct instrument methods are required at the point of major open channel. Users of river water should select appropriate direct instrument methods to measure usage, but there is a lack of standards and verification research. In this study, the H-Q rating curve method, ultrasonic method, and microwave method were applied directly to the test basin in the upper basin of Mangyeong river, and the accuracy of measurement data was evaluated by comparing absolute error between discharge data calculated by instrument method. When comparing the calculated discharge of point units, the ultrasonic method showed the best results of the actual measurement. Through continuous instrument, the sum of the daily and monthly units was compared, and the ultrasonic and microwave methods were shown to be highly accurate. Based on the results of this study, it is hoped that the appropriate direct measurement method can be selected according to the importance of the river water use facility, considering that the ultrasonic method and the microwave method are relatively costly compared to the water level-flow relationship method.