• Title/Summary/Keyword: Load Duration Curve(LDC)

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Application of the Load Duration Curve (LDC) to Evaluate the Achievement Rate of Target Water Quality in the Han-River Watersheds (부하지속곡선(Load Duration Curve; LDC)을 이용한 한강수계 오염총량관리 목표수질 평가방법 적용 방안)

  • Kim, Eunkyoung;Ryu, Jichul;Kim, Hongtae;Kim, Yongseok;Shin, Dongseok
    • Journal of Korean Society on Water Environment
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    • v.31 no.6
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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.

Methodology for the Identification of Impaired Waters Using LDC for the Management of Total Maximum Daily Loads (오염부하지속곡선(LDC)을 이용한 수질오염총량관리 단위유역 목표수질 달성여부 평가방법)

  • Park, Jun Dae;Oh, Seung Young
    • Journal of Korean Society on Water Environment
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    • v.28 no.5
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    • pp.693-703
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    • 2012
  • Load Duration Curve(LDC) is a useful tool for analyzing water quality characteristics under various stream flow conditions. This study investigated the methods to identify impaired waterbodies in the assessment of water quality goal attainment by using LDC for the management of Total Maximum Daily Loads (TMDLs). Three methods were proposed. Non-typical regime exclusion method is a method to exclude water quality observations in the non-typical extreme flow conditions in order to minimize the influence of non-ordinary water quality. Flow regime weighted average method is a method to calculate weighted mean water quality instead of arithmetic mean in order to consider water characteristics properly on stream flow regime in addition to the effect of Non-typical regime exclusion method. Load exceeded interval comparison method is a method to compare the intervals between the attained and non-attained load duration periods on the LDC. The assessment of water quality goal attainment can be performed more reasonably and precisely considering water quality variations on stream flow conditions by applying these proposed methods.

Improvement of Water Quality and Streamflow Monitoring to Quantify Point and Nonpoint Source Pollutant Loads (점오염원과 비점오염원 부하량 정량화를 위한 수질 유량 모니터링 개선)

  • Jang, Ju-Hyoung;Lee, Hyung-Jin;Kim, Hyun-Koo;Park, Ji-Hyoung;Kim, Ji-Ho;Rhew, Doug-Hee
    • Journal of Korean Society on Water Environment
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    • v.26 no.5
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    • pp.860-870
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    • 2010
  • Long term monthly monitoring data showed that the water quality of streams flowing into Lake Paldang has been improved by various strategy for water. However, the effect of quality on Lake Paldang is still insufficient because of nonpoint source from watershed. In order to evaluate quantifying methods for pollution source and make a suggestion on improvements, Storm Water Management Model (SWMM) was constructed by using data set from the water quality and streamflow monitoring network in the Kyoungan watershed for Total Maximum Daily Loads (TMDLs). Load duration curve (LDC) based on the result of the Kyoungan watershed SWMM indicated that the water quality criterion on $BOD_5$ was often exceeded in up-stream than down-stream. From flowrate-load correlation curve, SS load significantly increased as streamflow increases. 75.3% of streamflow and 62.1% of $BOD_5$ loads is discharged especially in the zone of high flows, but monitoring data set didn't provide proper information about the conditions and the patterns associated with storm events. Therefore, it is necessary to acquire representative data set for comparing hydrograph and pollutograph through monitoring experimental watershed and to establish methods for quantifying point and nonpoint source pollutant loads.

Application of the Load Duration Curve (LDC) to Evaluate the Achievement Rate of Target Water Quality in the Nakdong River Unit Watersheds (부하지속곡선(LDC ; Load Duration Curve)을 활용한 낙동강수계 오염총량 단위유역 목표수질 평가방법 적용 방안)

  • Jung, Kang-Young;Kim, Hong Tae;Kim, Sang Soo;Kim, Shin;Shin, Dong Seok;Kim, Gyeong Hoon
    • Journal of Environmental Science International
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    • v.26 no.4
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    • pp.433-445
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    • 2017
  • In recent years, the United States has used the Load Duration Curve (LDC) method to identify water pollution problems, considering the size of the pollutant load in the entire stream flow condition to effectively evaluate Total Maximum Daily Loads (TMDLs). A study on the improvement of the target water quality evaluation method was carried out by comparing evaluations of two consecutive years of water quality and LDC data for 41 unit watersheds (14 main streams and 27 tributaries). As a result, the achievement rate of the target water quality evaluation method, according to current regulations, was 68-93%, and that by the LDC method was 82-93%. Evaluating the target water quality using the LDC method results in a reduction in the administrative burden and the total amount of planning as compared to the current method.

Water Quality Characteristics Evaluation by Flow Conditions Using Load Duration Curve - in Youngbon A Watershed - (부하지속곡선을 이용한 유량 조건별 수질특성 평가 - 영본A 유역을 대상으로 -)

  • Park, Jinhwan;Kim, Kapsoon;Jung, Jaewoon;Hwang, Kyungsup;Moon, Myungjin;Ham, Sangin;Lim, Byungjin
    • Journal of Environmental Impact Assessment
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    • v.22 no.4
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    • pp.319-327
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    • 2013
  • This study was conducted to identify runoff characteristics of pollutants using flow duration curve(FDC) and load duration curve(LDC) in Youngbon A watershed during 2009~2011. A flow rate and pollutant load in the study watershed were estimated by equation of stage-discharge and discharge-loads rating curve. From these methods, BOD, T-N, and T-P have evaluated whether water quality standards would have attained. Results showed that BOD loads of about 50% plotted above the LDC, while T-N and T-P loads of about 50% plotted below the curve. It means that BOD of about 50% have exceeded the water quality criteria, while T-N and T-P of about 50% have complied with the water quality standards. Meanwhile, BOD, TN and T-P loads plotted above the LDC of low flows, implying that they were more affected by point pollution sources than nonpoint pollution sources in the study watershed.

Application of the Load Duration Curve (LDC) to Evaluate the Rate of Achievement of Target Water Quality in the Youngsan · Tamjin River Watersheds (부하지속곡선(LDC)을 이용한 영산강 · 탐진강수계 오염총량관리 목표수질 평가방법 적용 방안)

  • Cheong, Eunjeong;Kim, Hongtae;Kim, Yongseok;Shin, Dongseok
    • Journal of Korean Society on Water Environment
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    • v.32 no.4
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    • pp.349-356
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    • 2016
  • Total Maximum Daily Loads (TMDLs) System has been used to improve water quality in the Youngsan·Tamjin river basin since 2004. The Basic Policy of TMDLs sets up the standard flow based on the average dry condition or mid-range flow during the last 10 years. However, Target Water Quality (TWQ) assessment on TMDLs has been used to evaluate water quality through eight-day intervals over 36 times a year. The results for allocation evaluation and target water quality evaluation were different from each other in the same unit watershed during the first period. In order to improve the evaluation method, researchers applied Load Duration Curve (LDC) to evaluate water quality in nine unit watersheds of the Youngsan·Tamjin river basin. The results showed that achievement rates of TWQ assessment with the current method and LDC were 67~100% and 78~100%, respectively. Approximately 11% of the achievement rates with use of LDC were higher than those with use of the current method. In conclusion, it is necessary to review the application of the LDC method in all Four Major River Watersheds.

A Study on Selection Method of Management Watershed for Total Pollution Load Control at Tributary (지류총량관리를 위한 관리유역 선정 방법에 관한 연구)

  • Hwang, Ha Sun;Lee, Sung Jun;Ryu, Jichul;Park, Ji Hyung;Kim, Yong Seok;Ahn, Ki Hong
    • Journal of Korean Society on Water Environment
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    • v.32 no.6
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    • pp.528-536
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    • 2016
  • The purpose of Total Pollution Load Control at Tributary is to obtain maximum improvement effect of water quality through finding the most impaired section of water-body and establishing the proper control measure of pollutant load. This study was implemented to determine the optimal management of reach, period, condition, watershed, and pollution source and propose appropriate reduction practices using the Load duration curve (LDC) and field monitoring data. With the data of measurement, LDC analysis shows that the most impaired condition is reach V (G4~G5), E group (flow exceedance percentile 90~100%) and winter season. For this reason, winter season and low flow condition should be preferentially considered to restore water quality. The result of pollution analysis for the priority reach and period shows that agricultural nonpoint source loads from onion and garlic culture are most polluting. Therefore, it is concluded that agricultural reuse of surface effluent (storm-water runoff with non-point sources) and low impact farming that includes reducing fertilization and controlling the height of drainage outlet are efficient water quality management for this study watershed.

Watershed Modeling Application for Receiving Water Quality Management in Nakdong River Basin (낙동강 유역의 수질관리를 위한 유역모델링 적용 연구)

  • Jang, Jae-Ho;Ahn, Jong-Ho
    • Journal of Korean Society on Water Environment
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    • v.28 no.3
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    • pp.409-417
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    • 2012
  • SWAT model was applied for the Nakdong River Basin to characterize water quality variability and assess the feasibility of using the load duration curve to water quality management. The basin was divided into 67 sub-basins considering various watershed environment, and rainfall runoff and pollutant loading were simulated based on 6 year measurements of meteo-hydrological data, discharge data of treatment plants, and water quality data (SS, T-N and T-P). The results demonstrate that non-point source loads during wet season increase by 80 ~ 95% of total loads. Although the rate of water flow governs the amount of SS that is transported to the main streams, nutrient concentrations are highly elevated during dry season by being concentrated. This phenomenon is more pronounced in the lower basin, receiving large amounts of urban point source discharges such as treated sewages. Also, the load duration curves (LDC) demonstrate dominant source problems based on the load exceedances, showing that SS concentrations are associated with the rainy season and nutrients, such as T-P, may be more concentrated at low flow and more diluted at higher flow. Overall, the LDC method could be used conveniently to assess watershed characteristics and pollutant loads in watershed scale.

Analysis of Load Duration Curve Difference using 8 Day and Extended Daily Flow (8일 유량 및 일유량 자료를 이용한 오염부하지속곡선의 변화 분석)

  • Kwon, Pilju;Ryu, Jichul;Kim, Hongtae;Lim, Kyoung Jae
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.166-166
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    • 2017
  • 현재 우리나라에서 많은 연구에 활용되고 있는 오염부하지속곡선(Load duration curve, LDC)은 단일 기준유량의 문제점을 개선하기 위해 전체 유량 범위를 고려한 수질오염총량관리제(Total Maximum Daily Loads, TMDL) 평가 기법으로 개발되었다(Choi et al., 2012). LDC를 이용해 목표수질 달성여부를 분석하기 위해서는 일유량자료를 바탕으로 유량지속곡선(Flow Duration Curve, FDC)의 작성이 선행되어야 하는데(Park and Oh, 2012), 365일 연속적으로 측정된 실측 자료를 이용하는 것이 가장 확실하고 정확한 방법이다. 그러나 현재 환경부에서는 총량관리 단위유역에서 8일 간격으로 실측 유량 및 수질 측정이 이루어지고 있고, 특히 주로 비강우 시에 측정이 이루어지고 있는 실정이기 때문에 고유량에 대한 모니터링 자료가 부족한 실정이다. 이 같은 이유로 많은 연구에서 불연속적인 평균 8일 간격 유량을 그대로 사용하거나 일유량자료를 확보하기 위해 다양한 방법을 이용하고 있다. 그러나 이러한 유량자료의 변동은 유랑지속곡선에 변화를 주고 결과적으로는 LDC를 이용한 목표수질 달성여부를 판단함에 있어 불확실성이 있다. 이에 본 연구의 목적은 환경부 총량측정망 8일유량자료와 이와 연계성이 있는 국토교통부 하천유량 측정망 일유량자료를 이용하여 각각의 LDC를 작성하고, 이러한 일유량과 8일유량 사용이 LDC를 이용하여 목표수질에 대한 오염부하 특성분석에 어떠한 영향을 미치는지 유량 조건별로 차이를 비교분석하는 데 있다.

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Development of Desktop-Based LDC Evaluation System for Effectiveness TMDLs (효과적인 오염총량관리를 위한 데스크탑 기반의 LDC 평가 시스템 개발)

  • Ryu, Jichul;Hwang, Ha-Sun;Lee, Sung-Jun;Kim, Eun Kyoung;Kim, Yong Seok;Kum, Donghyuk;Lim, Kyoung Jae;Jung, Younghun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.58 no.4
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    • pp.67-74
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    • 2016
  • Load Duration Curve (LDC) can be used as a method for load management of point and non-point pollution source because the LDC easily assesses the water quality corresponding to hydrological changes in a watershed. Recently, the application of LDC to total pollution load management is a growing interest in Korea. In this regard, A desktop-based LDC assessment system was developed in this study to provide convenience to users in water quality evaluation. The developed system can simply produce the LDC by using streamflow and water quality data involved in its database. Also, The system can quantitatively inform the success or failure of the achievement for a target water quality at monthly scale. Furthermore, seasonal water quality and point/non-point pollution load in a watershed can be estimated by this system. We expect that the developed system will contribute to establish local and national policies regarding water management and total pollution load management because of its advantages such as the pollution tracking investigation and the analysis of water quality and pollution loading amount in an ungauged watershed.