• 한국수자원학회논문집
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• 제47권11호
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• pp.997-1005
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• 2014

본 연구에서는 연 최저 유입량과 연 최대 부족량 자료를 이용하여 수문학적 가뭄을 평가하였고, 수자원 시설의 계획 및 관리에 이용할 수 있도록 물 부족량-지속기간-빈도 곡선을 제안하였다. 연 최저 유입량 분석결과, 대부분의 지속기간에서 1989년, 1996년 수문학적 가뭄의 재현기간이 가장 길었다. 연 최대 부족량 분석결과, 비교적 짧은 지속기간인 60일, 90일 부족량의 재현기간은 1982년에서 약 35년으로 가장 길게 나타났으며, 길게 지속되었던 수문학적 가뭄은 1995년으로 재현기간은 약 20년이었다. 가뭄은 크기와 함께 지속기간도 주요한 변수이지만 연 최저 유입량을 이용한 방법은 지속기간을 구분하지 못한다는 단점이 확인되었다.

• 한국수자원학회논문집
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• 제45권10호
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• pp.969-981
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• 2012

본 연구에서는 서로 다른 ENSO(El Ni$\tilde{n}$o Southern Oscillation) 형태에 따른 한강유역의 연최대홍수량과 저유량의 정량적 변화 및 발생시점의 변화를 분석하였다. 경향성 분석결과, 연최대유출의 경우 한강 전체 유역면적의 48.3%가 통계적으로 유의한 증가패턴을 보였으며, 연최대 유출의 발생시기는 한강 서부유역에서 늦어지고, 동부유역에서는 빨라지는 경향이 있음을 확인하였다. 또한 7일 저유량의 경우, 24개 중권역중 6개 유역(전체 면적의 26.0%)에서 통계적으로 유의한 감소경향을 보였으며, 저유량의 발생시기는 한강중상류 유역에서 빨라지는 경향이 있음을 확인하였다. CT(Cold tongue)/WP(Warm-pool) El Ni$\tilde{n}$o 시기에 연최대유출의 발생시점의 차이는 크지 않으나, CT El Ni$\tilde{n}$o 시기에는 전체유역의 89.0%에서 연최대유출량이 평년보다 작게 나타났다. 또한, 7일 저유량의 발생시점은 WP El Ni$\tilde{n}$o 시기에 평균적으로 약 17일 정도 빠르며, CT El Ni$\tilde{n}$o (WP El Ni$\tilde{n}$o)시기에는 전체 유역의 72.7%(20.0%)에서 통계적으로 유의한 증가(감소)패턴을 보이는 것으로 분석되었다. 본 연구는 서로 다른 형태의 CT/WP El Ni$\tilde{n}$o가 한강 유역 수자원의 양과 발생시점의 변화에 민감하게 영향을 미치고 있음을 확인하였으며, 향후 다양한 형태의 ENSO에 따른 수문변량의 변화에 대한 진단연구를 통하여 장기적인 수자원관리 및 예측을 위한 기초 자료로 활용이 가능하리라 사료된다.

• 한국물환경학회지
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• 제28권2호
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• pp.224-231
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• 2012

It is necessary to develop flow duration curve (FDC) on each unit watershed in order to analyze flow conditions in the stream for the management of Total Maximum Daily Loads (TMDLs). This study investigated a simple method to develop FDC for the general use of the curve. A simple equation for daily flow estimation was derived from the regression analysis between the 8-day interval flow data of a unit watershed and the daily flow monitoring data of an adjacent upstream region. FDC can be prepared with the calculation of daily flow by the equation for each unit watershed. An annual and a full-period FDC were drawn for each unit watershed in Guem river basin. Standard flow such as low and ordinary flow can be obtained from the annual FDC. Major percentile of flow such as 10, 25, 50, 75 or 90% can be obtained from the full-period FDC. It is considered that this simple method of developing FDC can be utilized more widely for the calculation of standard flow and the assessment of water quality in the process of TMDLs.

• 한국관개배수논문집
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• 제16권1호
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• pp.94-99
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• 2009

• 한국환경과학회지
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• 제26권8호
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• pp.939-953
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• 2017

For the development of flow duration curves for the management of 41 Total Maximum Daily Load (TMDL) units of the Nakdong River basin, first, an equation for estimating daily flow rates as well as the level of correlation (correlation and determination coefficients) was extrapolated through regression analysis of discrete (Ministry of Environment) and continuous (Ministry of Land, Infrastructure and Transportation) measurement data. The equation derived from the analysis was used to estimate daily flow rates in order to develop flow duration curves for each TMDL unit. By using the equation, the annual flow duration curves and flow curves, for the entire period and for each TMDL unit of the basin, were developed to be demonstrated in this research. Standard flow rates (abundant-, ordinary-, low- and drought flows) for major flow duration periods were calculated based on the annual flow duration curves. Then, the flow rates, based on percentile ranks of exceedance probabilities (5, 25, 50, 75, and 95%), were calculated according to the flow duration curves for the entire period and are suggested in this research. These results can be used for feasibility assessment of the set values of primary and secondary standard flow rates for each river system, which are derived from complicated models. In addition, they will also be useful for the process of implementing TMDL management, including evaluation of the target level of water purity based on load duration curves.

• Korean Journal of Hydrosciences
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• 제4권
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• pp.51-63
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• 1993

This study is to verify the applicability of statistical models in predicting flood frequency at the stage gaging stations of which the flow is under natural condition in the Han River basin. The results of the study show that the statistical flood frequency models were proven to be fairly reasonable to apply in practice, and also were compared with sampling variance to calibrate the statistical efficiency of the estimators of the T year floods Q(T) by two different flood frequency models. As a result, it was showed that for return periods greater than about T = 10 years the annual exceedance series estimators of Q(T) has smaller sampling variance than the annual maximum series estimators. It was showed that for the range of return periods the partial duration series estimators of !(T) has smaller sampling variance than the annual maximum series estimate only if the POT model contains at least 2N(N : record length) items or more in order to estimate Q(T) more efficiently than the ANNMAX model.

• 한국해양학회지
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• 제19권2호
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• pp.210-216
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• 1984

5년간의 시간별 풍속 자료를 이용하여 연안 표층풍의 일변화가 분석되었다. 특히 내륙으로 부는 바람 (onshore flow)이 지배적인 계절에는 야간 최대풍의 최대 출현 빈도가 자정에 나타났다. 연평균 남풍 계열을 갖는 야간 최대풍은 북풍 계열 보다 약 3배이상의 출현을 보여준다. 중림의 대기 안정도가 연안에 지배적이므로 바람이 해양에서 내륙으로 불 경우는 (offshore flow) 상승된 전선역전층과 지표역전층에 의해 형성된 전단력(shear flow)이 연안경계층으로 전이되어 야간 연안 최대표층풍이 형성된다.

• 한국물환경학회지
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• 제26권2호
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• pp.279-288
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• 2010

The water quality variations or changes are closely relevant to the characteristics of unit watersheds and have an effect on the attainment of their water quality goal. This study was conducted to analyze the water quality distribution and its change patterns of unit watersheds in Nakdong river basin. It revealed that 25 unit watersheds out of 41 showed the normality in water quality. Most of unit watersheds had a considerable variation in water quality, especially in the season of spring and summer but a little in terms of flow rate. Annual relative differences in water quality ranged from 13.0 to 26.6% with the maximum of 75%. 28 unit watersheds (62%) had the tendency to decrease in water quality as the flow rate increased while 13 (38%) to increase. The extension of standard flow led to considerable differences in water quality depending on its ranges, which meant uncertainties might be included in the process of TMDL development. It is suggested that annual average flow rate should be chosen as a standard flow in the area where the water quality change has little relation to the flow rate.

• 한국농공학회지
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• 제16권4호
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• pp.3600-3610
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• 1974

Experimental work of batch-type dryer was conducted to develop its optimurm operating conditions by analyzing the major factors which affect the drying performance. A laboratory batch-type dryer was constructed and tested for various levels of heated-air rates, and depths of grain deposit. Tong-il rice variety having the initial moisture content of approximaely 23 per cent in wet basis was used for the experiment. The criteria selected for establishing the optimum operating condition were the drying performance rate, the thermal efficiency, and the operational cost of the dryer. The results of the study are summarized as follows: 1. The performance rate of dryer for a specific operating condition was defined as total amount of material dried per hour when the moisture content of grains in the upperlayer reaches to 16 per cent in wet basis. The optimum operating conditions as viewed in the rate of drying performance could be justified by functional realtionship between the depth of grain deposit and air flow rate. In other words, there was a definite depth of grain deposit for a given air-rate which make the dryer performance maximum. The optimum grain depth for the batch-type dryer with 3.3㎡ loading area and with the attached axial fan was about 35cm. 2. The thermal efficiency for the dryer was evaluated by the ratio of the latent heat required to evaporate the grain moisture to the heat input required to raise the ambient air-temperature to 40 degree centigrade. The optimum operating condition as viewed in term of thermal efficiency analyzed was that grater depth and lower air flow-rate may be desirable. This condition is contracted with the optimum condition as viewed by the dryer performance rate. 3. The annual operating cost of batch-type dryer was analyzed for different annual hour of use and for different operation condition. The optimum condition as viewed in terms of operating cost was almost identical to one as viewed in terms of dryer performance rate. Therefore, the most economical use of batch-type dryer for the same annual operating hours can be obtained when the dryer operated in the condition of maximum dryer performance rate. Increasing the annual operating hour may be desirable to cut down the dryer operation cost, since the annual hour of dryer use is much sensitive to the operating cost than any peractical conditions of dryer operation. 4. The most desirable operational condition as justified by combining all the criteria, dryer performance rate, thermal efficiency and annual operating cost, could be concluded to operate the dryer in the condition of maximum performance rate. The condition in general is identical to the lowest operation cost for a given annual operating hour.

• Water Engineering Research
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• 제6권2호
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• pp.39-48
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• 2005

The Brazos River is one of the longest rivers contained entirely in the state of Texas, flowing over 700 miles from northwest Texas to the Gulf of Mexico. Today, the Brazos River Authority and Texas Commission on Environmental Quality interest in drought protection plan, waterpower project, and allowing the appropriation of water system-wide and water right within the Brazos River Basin to meet water needs of customers like farmers and local civilians in the future. Especially, this purpose of this paper primarily intended to provide the data for the engineering guidelines and make easily geological mapping tool. In the Brazos River basin, many stream-flow gage station sites are not working, and they can not provide stream-flow data sets enough for development of the Probable Maximum Flood (PMF) for use in the evaluation of proposed and existing dams and other impounding structures. Integrated GIS-Spatial Interpolation (GIS-SI) tool are composed of two parts; (1) extended GIS technique (new making interface for hydrological regionalization parameters plus classical GIS mapping skills), (2) Spatial Interpolation technique using weighting factors from kriging method. They are obtained from the relationship among location and elevation of geological watershed and existing stream-flow datasets. GIS-SI technique is easily used to compute parameters which get drainage areas, mean daily/monthly/annual precipitation, and weighted values. Also, they are independent variables of multiple linear regressions for simulation at un gaged stream-flow sites. In this study, GIS-SI technique is applied to the Brazos river basin in Texas. By assuming the ungaged flow at the sites of Palo Pinto, Bryan and Needville, the simulated daily/monthly/annual time series are compared with observed time series. The simulated daily/monthly/annual time series are highly correlated with and well fitted to the observed times series.