We investigate the Japan's Master Plan of Comprehensive Sewerage System (JMPS) and Lake Biwa basin sewerage and suggest future development direction of the Watershed Sewerage System Maintenance Plan in Korea enforced on February 2, 2013. The JMPS is designed for compliance with the environmental standard for water quality under the Environmental Policy Act. The effluent standards applied in the master plan of Lake Biwa's Sewerage Plan for the Lake Biwa is tougher than the national standards. Therefore the Lake Biwa Baisn Sewerage System was the first in Japan to adopt facilities that perform advanced treatment for nitrogen and phosphorus removal. BOD, SS, T-N and T-P concentrations of discharge water of sewage are 0.9, 0.6, 5.5, 0.06 mg/L, respectively. Especially removal efficiency for BOD is 99.5 percent. It is necessary to study the diversification of the evaluation criteria, cost minimization approach, subsidy system improvement, economic concept of discharge load adjustment system and establishment of basin sewerage concept for the development of the basin sewerage plan in Korea.

ab s t r ac tTo improve the water quality of the four major rivers in Korea, Ministry of Environment of Korea (MOE) has introduced the Total Maximum Daily Loads (TMDLs) management system since 2002 and BOD was selected as one of the target materials during the first period (2004)(2005)(2006)(2007)(2008)(2009)(2010). For an effective watershed management, it is necessary to have one or more quantitative measures that can be used to evaluate the relationship between pollutant sources and their impacts on water quality. Such measurable quantities are termed water quality indicators. Once an indicator is selected, target values for that indicator must be established to distinguish between the impaired and unimpaired state of the water-body. Various factors such as available data, application, management conditions and cost will be considered for the selection of an appropriate watershed management indicator. This paper introduces various factors required for choosing target water quality indicators and establishes reasonable target values during the second TMDLs period (2010)(2011)(2012)(2013)(2014)(2015).

The current Total Pollution Load Control (TPLC) sets the Target Water Quality (TWQ) by utilizing the delivery ratio, unit loads, and water quality modeling, it also allocates the watershed's permitted discharge load. Currently, common target pollutants of every unit watershed in TPLC are BOD and T-P. This study has reviewed the 1th and 2th of TWQ setting process for the Nakdong River 3th TWQ setting in Total Pollution Load Control (TPLC). As a result of review, 1th and 2th were divided into one management basin (mulgeum) for setting management goals. However, 3th was divided into six management basins (mulgeum, gnagjeong, geumho river, nam river, miryang river, end of nakdong river). The principle of management goal setting were to achieve the objective criteria of Medium Areas for the linkage of the water environment management policy. And Anti-Degredation (principle of preventing deterioration) were applied to the 3th TWQ. Also, additional indicators were considered in accordance with the reduction scenarios for the final management goals.

ab s t r ac tThe delivery ratio of pollutant loads can be defined as the ratio of the discharged pollutant load delivered to the point of interest divided by the mass of pollutants generated at the source. Assessing delivery ratios is important to watershed management planning for Total maximum daily load because delivery ratios can indicate the characteristic pollutants of a watershed. To estimate exact delivery ratios, monitoring data of water quality and flow for the duration of flow are required. However, time, cost, and labor constraints mean that such data sets are often incomplete, and additional monitoring efforts are needed to supplement data. Watershed-scale models that are properly calibrated and verified can provide estimates of water flow and quality to fill gaps in data. In this study, model outputs were used to calculate the delivery ratio. The results demonstrate the usefulness of the watershed-model method for estimating the delivery ratio. Construction of a nationwide watershed model for South Korea and the model outputs for target water quality station will be useful for local governments. The watershed model used in this study adequately simulated watershed characteristics and is recommended for use in estimating delivery ratios to support TMDL management.

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