• 한국물환경학회지
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• 제36권6호
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• pp.521-534
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• 2020

In this study, the variation of water quality was analyzed for six sites in major tributaries of the Nakdong River Basin. Standard-FDC (Flow Duration Curve) was developed using PM (Percentile Method), one of the statistical FDC estimation methods. The LDC (Load Duration Curve) was obtained using the developed FDC. The current method and the LDC evaluation method were compared and analyzed to evaluate the achievement of TWQ (Target Water Quality). Regarding the monthly flow rate variation, the five sites showed the distribution of the lowest flow rate between May and June, indicating a high probability of dry weathering of the streams. The variation of water quality confirmed the vulnerable timing of flow rate in each site, and it is therefore deemed necessary to plan to reduce T-P and TOC. A comparison and evaluation of TWQ showed that there was a difference between the TWQ values achieved by the two techniques. In addition, the margin ratio to the 50% excess ratio can be found in the LDC evaluation. The results of the LDC evaluation by section and by month showed whether or not the water quality was exceeded by flow conditions, along with the vulnerable sections and timing. Accordingly, it is judged that this method can be used for water quality management in TMDLs (Total Maximum Daily Loads).

• 상하수도학회지
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• 제29권5호
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• pp.551-557
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• 2015

The TMDL (Total Maximum Daily Load) has been used to determine the water quality target. LDC (Load Duration Curve) based on hydrology has been used to support water quality assessments and development of TMDL. Also FDC (Flow Duration Curve) analysis can be used as a general indicator of hydrologic condition. The LDC is developed by multiplying FDC with the numeric water quality target of the factor for the pollutant of concern. Therefore, this study was to create LDC using the stream flow data and numeric water quality target of BOD and T-P in order to evaluate the pollutant load characterization by flow conditions in Heukcheon stream. When it is to be a high-flows condition, BOD and T-P are necessary to manage. BOD and T-P did not satisfy the numeric water quality target for both seasons (spring and summer). In order to meet the numeric water quality target in Heukcheon stream, management of non point source pollutant is much more important than that of point source pollutant control.

• 한국물환경학회지
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• 제29권4호
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• pp.523-530
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• 2013

This study has been carried out to clarify the characteristics of discharge and pollutant loading according to flow conditions at jiseok stream watershed (JSW). A flow rate and pollutant load in the study watershed were estimated by equation of stage-discharge and discharge-loads rating curve. By using the methods above, I've evaluated the water quality (WQ) of the JSW if it is satisfied with the standard target. I've collected the data of BOD and T-P from the JSW every 8 days for the duration of 12 months. And then, I've schematized the data upon the load duration curve and the results showed me that the WQ of JSW was satisfied with the standard target. I've also collected the same data every each day for the duration of 12 months from JSW and have schematized the data again. And the results showed that it also was satisfied with the standard target. To be concluded, I've determined that point pollution sources of JSW gives more significant impacts to the WQ than non-point pollution sources of JSW and hence, as time goes, point pollution sources will keep depriciating the WQ of JSW. Therefore, further efforts will be required to JSW to maintain the WQ.

• 한국물환경학회지
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• 제25권5호
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• pp.792-802
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• 2009

The objective of this study is to construct the watershed management system with link of the non-point sources model and to estimate delivery ratio duration curves for various pollutants. For the total water pollution load management system, non-point source model should be performed with the study of the characteristic about non-point sources and loadings of non-point source and the allotment of pollutant in each area. In this study, daily flow rates and delivered pollutant loads of Nakdong river basin are simulated with modified TANK model and minimum variance unbiased estimator and SWAT model. Based on the simulation results, flow duration curves, load duration curves, and delivery ratio duration curves have been established. Then GIS analysis is performed to obtain several hydrological geomorphic characteristics such as watershed area, stream length, watershed slope and runoff curve number. As a result, the SWAT simulation results show good agreements in terms of discharge, BOD, TN, TP but for more exact simulation should be kept studying about variables and parameters which are needed for simulation. And as a result of the characteristic discharges, pollutants loading with the runoff and delivery ratios, non-point sources effects were higher than point sources effects in the small-scale test bed of Nakdong river basin.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.132-132
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• 2020

유황곡선은 하천유량의 변동성을 함축적으로 나타내고 연간유량 분석방법(calendar-year method)과 전 자료기간유량분석방법(total-period method)을 이용하여 작성하고 분석할 수 있다. 본 연구는 유황곡선 상에서 유역특성인자들을 포함시켜 작성하는 방법을 제시하였고 지형 및 기상학적 인자를 통해 지역화 시킨 유황곡선을 통해 미계측 유역의 유황곡선을 추정할 수 있는 곡선을 개발하고자 한다. 이를 위해 유역의 특성인자자료를 수집하여 독립변수로 설정하였고 다중회귀분석을 실시하여 변수들을 지역화 시켰다. 지역화 시킨 변수들을 유황곡선에 반영하여 대상지역에서 하나의 유황곡선으로 나타내었다. 도출한 유황곡선을 자료가 있는 지역을 미계측유역이라 가정하고 검증하였다. 검증결과 실제자료와 유사하게 나타나는 것을 확인할 수 있었고 이를 통해 미계측 유역의 유출량 자료가 부족한 유역에 대한 예측과 과거 많은 부분이 결측된 유역에 대한 유출량 예측도 가능할 것이라 판단된다. 또한 강우시나리오를 통해 지형인자가 고려된 유황곡선을 이용한 다양한 자료분석을 실시할 수 있을 것이라 판단된다.

• 한국수자원학회논문집
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• 제54권spc1호
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• pp.1183-1193
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• 2021

Low flow는 하천수의 공급관리 및 계획, 관개용수 등 다양한 분야에 영향을 미친다. 이러한 유황곡선을 산정하기 위해서는 30년 이상의 충분한 기간의 유량자료의 확보가 필수적이다. 하지만 국가하천 단위 이하의 하천의 경우 장기간의 유량자료가 없거나 중간에 일정기간 동안 결측된 관측소가 있어 하천별 유황 곡선을 산정하기에 한계가 있다. 이에 과거에는 미계측 유역의 유황을 예측하기 위해 다중회귀분석(Multiple Regression Analysis), ARIMA 모형 등 통계학적 기반의 기법들을 사용하였지만, 최근에는 머신러닝, 딥러닝 모형의 수요가 증가하고 있다. 이에 본 연구에서는 최신 패러다임에 맞는 머신러닝 기법인 DNN기법을 제시한다. DNN기법은 ANN기법의 단점인 학습과정에서 최적 매개변수 값을 찾기 어렵고, 학습시간이 느린 단점을 보완한 방법이다. 따라서 본연구에서는 DNN 모형을 이용하여 미계측 유역에 적용 가능한 유황곡선을 산정하고자 한다. 먼저, 유황곡선에 영향을 미치는 인자들을 수집하고 인자들 간의 다중공선성 분석을 통해 통계적으로 유의한 변수를 선정하여, 머신러닝 모형에 입력자료를 구축하였다. 통계적 검증을 통해 머신러닝 기법의 효용성을 검토하였다.

• 한국물환경학회지
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• 제30권1호
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• pp.60-67
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• 2014

In this study, four methods for calculation of continuous daily flow was suggested using short-term or partial recording station of streamflow including missing data. Using these methods, standard flows at the outlet of unit/small basins for the management of total maximum daily loads (TMDLs) in Namgang dam basin were estimated from full-period flow duration curve (FDC). Four methods of extension are described, and their properties are explored. The methods are regression (REG), regression plus noise (RPN), and maintenance of variance extension types 1 and 2 (MOVE.1, MOVE.2). In these methods, the continuous daily flow was calculated using extension equation based on correlation analysis, after conducting the correlation analysis between historic record of streamflow and long-term recording station (a base station). Finally the best optimal method was selected as the MOVE.2, and the standard flows in the abundant, ordinary, low and drought flow estimated from FDC was evaluated using MOVE.2 in unit/small basins.

• 환경영향평가
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• 제28권1호
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• pp.35-48
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• 2019

장기간 유량측정과 수질분석은 수질오염총량관리제도 유역의 목표수질과 허용 부하량을 결정하기 위하여 필요하다. 목표수질 달성여부를 평가하는데 사용되는 부하지속곡선은 유량과 수질간의 관계를 설명하고, 유량조건별 오염부하량 특성을 평가한다. 경안천의 부하지속곡선은 경안천 목표수질과 2006년부터 2015년까지 연평균 8일 간격으로 측정한 유량자료를 이용한 유량지속곡선에 의해서 작성되었다. 연구결과 경안천은 갈수량 구간에서 목표수질을 초과하여 점오염원에 대한 관리가 필요한 것으로 분석되었다. 또한, 연중 3월에서 6월 사이의 기간 동안에만 목표수질을 초과하는 것으로 나타나 이 기간 동안 경안천의 목표수질을 달성하기 위한 체계적인 유역 관리가 필요한 것으로 판단된다.

• 한국물환경학회지
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• 제31권6호
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• pp.732-738
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• 2015

Water quality in four major river basin in Korea was managed with Total Maximum Daily Load (TMDL) System. The unit watershed in TMDL system has been evaluated with Target Water Quality (TWQ) assessment using average water quality, without considering its volume of water quantity. As results, although unit watershed are obtained its TWQ, its allocated loads were not satisfied and vice versa. To solve these problems, a number of TWQ assessments with using Load Duration Curve (LDC) have been studied at other watersheds. The purpose of this study was to evaluate achievement of TWQ with Flow Duration Curve (FDC) and Load Duration Curve(LDC) at 26 unit watersheds in Han river basin. The results showed that achievement rates in TWQ assessment with current method and with LDC were 50~56 % and 69~73%, respectively. Because of increasing about 20% of achievement rates with using LDC, the number of exceeded unit watershed at Han river Basin was decreased about 4~6 unit watersheds.

• 한국지리정보학회지
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• 제24권3호
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• pp.41-57
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• 2021

본 연구는 대청호 상류에 있는 서화천 유역을 대상으로 SWAT(Soil and Watershed Assessment Tool) 모형을 이용한 수질 관리 대책 적용 및 부하지속곡선(LDC, Load Duration Curve)을 이용한 대책의 효율을 평가하였다. 수질 관리 대책으로는 인공습지, 방치 축분 저감, 비닐하우스 유출량 저감, 생태하천 복원, LID(Low Impact Development) 기술 적용, 점오염원 관리를 적용하였다. 적용된 기술은 부하지속곡선을 통해 유황별 목표 수질 초과율 및 부하량 저감 정도를 이용하여 수질 개선대책의 효율을 평가하였다. 부하지속곡선은 SWAT를 이용하여 장기 유량지속곡선(FDC, Flow Duration Curve)을 만들고 목표 수질을 곱하여 작성하였으며 목표 수질은 서화천 하류에 있는 옥천천 수질 관측지점의 10년간 자료를 사용하여 60분위에 해당하는 값을 목표 수질로 설정하였다. 본 연구를 통하여 여러 가지 수질 대책을 SWAT 모형을 통해 적용 가능성을 확인할 수 있으며 부하지속곡선을 통하여 유황에 따른 시기별 적용 가능성을 검토할 수 있었다.