• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.247-254
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• 2012

Soil and Water Assessment Tool (SWAT) model has been widely used in estimation of flow and water quality at various watersheds worldwide, and it has an auto-calibration tool that could calibrate the flow and water quality data automatically from thousands of simulations. However, only continuous measured day flow/water quality data could be used in the current SWAT auto-calibration tool. Therefore, 8-day interval flow and water quality data measured nationwide by Korean Ministry of Environment (MOE) could not be used in SWAT auto-calibration even though long-term flow and water quality data in the Korean Total Maximum Daily Load (TMDL) watersheds available. In this study, current SWAT auto-calibration was modified to calibrate flow and water quality using 8-day interval flow and water quality data. As a result of this study, the Nash and Sutcliffe Efficiency (NSE) values for flow estimation using auto-calibration are 0.77 (calibration period) and 0.68 (validation period), and NSE value for water quality (T-P load) estimation (using the 8-day interval water quality data) is 0.80. The enhanced SWAT auto-calibration could be used in the estimation of continuous flow and water quality data at the outlet of TMDL watersheds and ungaged point of watersheds. In the next study, the enhanced SWAT auto-calibration will be integrated with Web based Load Duration Curve (LDC) system, and it could be suggested as methods of appraisal of TMDL in South Korea.

• Journal of Korean Society on Water Environment
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• v.32 no.2
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• pp.149-162
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• 2016

In recent years, there has been demand for precise estimations of pollutant loads on nationwide scale for the development of appropriate site specific (watershed specific) policies to reduce the negative impact of pollutant loads. River flow data and water quality data that were previously collected by various research institutes and universities for specific research purposes for a limited period was utilized in this study. However, only TMDL 8-day interval flow and water quality data were available in national scale. Three watersheds were selected and pollutant loads were calculated by two methods i.e., Numeric Integration (NI) method and Soil and Water Assessment Tool (SWAT). Subsequently, the results were compared to determine the appropriate method for monitoring nonpoint source networks nationwide. The SWAT model was calibrated and its estimated daily flow data were used in the NI method with estimated sediment data for 8-day monitoring data for three watersheds. The results indicated that the quantity of pollutant loads estimated with the NI and SWAT are different to some degrees especially during the summer season for all the three study watersheds. Thus, more frequent sampling of water quality is needed for nonpoint source pollutant estimation.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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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.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.689-698
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• 2011

In South Korea, Total Maximum Daily Load (TMDL) has been enforced since 2004 to restore and manage water quality in the watersheds. However, the appraisal of TMDL in South Korea has lots of weaknesses to establish the plan for recovery of water quality because it just evaluates the target water quality during the particular flow duration interval. In the United States, Load Duration Curve (LDC) method bas been widely used in the TMDL to evaluate the water quality and pollutant loads considering variation of stream flow. In a recent study, web-based Load Duration Curve system was developed to create the LDC automatically and provide the convenience of use. In this study, web-based Load Duration Curve system was applied in the Gapyeongcheon watershed using the daily flow and 8-day interval water quality data, and Q-L Rating Curve was used to evaluate the water quality and pollutant load in the watershed, also. As a result of study, water quality and pollutant load in Gapyeongcheon watershed were met with water quality standard and allocated load in the all flow durations. Web-based Load Duration Curve system could be applied to the appraisal of South Korean TMDL because it can be used to judge the impaired flow duration and build up the plan of load reduction, and it could enhance the publicity. But, web-based Load Duration Curve system should be enhanced through addition of load assessment tools such as Q-L rating curve to evaluate water quality and pollutant load objectively.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.620-627
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• 2007

In this study a general analysis method for watersheds with the entire runoff conditions and corresponding water quality is proposed and its applicability based on the currently available information is investigated. Using the 8-day-interval data set of runoff and water quality observed by Nakdong River Environment Research Center, the flow duration curve and discharge-load relation curve for each unit watershed are established, then the load duration curve is finally constructed. This paper discusses how the load duration curve can be used in the assessment of TMDL. The entire Nakdong river watershed is also divided into prior managing areas of point sources or non-point sources in a way of general management. It is thought that LDC can be a great tool for visualizing overall probabilities of current water quality and thus for the TMDL management.

• Journal of Environmental Impact Assessment
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• v.28 no.1
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• pp.35-48
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• 2019

Long term flow measurement and water quality analysis data need to determine the target and allowable load for each basin in Total Water Pollution Load Management System (TWPLMS). The Load Duration Curve (LDC) is analyzed the relationship between flow data and water quality, and evaluates the pollutant load characterization by flow conditions. LDC of Kyeongancheon is created by the Flow Duration Curve (FDC) that was analyzed 8-day interval measured flow data from 2006 to 2015 and numeric water quality target in Kyeongancheon. As a result of this study, it is necessary to manage the point source pollutant because the numeric water quality target is not satisfied in the low flows. Also the numeric water quality target has been exceed for four months from March to June of the year and continuous and systematic watershed management is required to satisfy the numeric water quality target.