In this study, K-CWQI (Korean-Comprehensive Water Quality Index) including five items such as pH, DO, BOD, SS and T-Coli developed by NIER (National Institute of Environmental Research) in 2006 is calculated by using the result of monitoring in the major tributaries of Gumho-River Basin from 2015 to 2016 and reviewed about applicability when evaluating water quality in the basin. The scope of calculated K-CWQI is from 70 to 90 points in five tributaries and water quality of major tributaries of Gumho-River Basin is evaluated above "slightly good grade". The highest value of K-CWQI is 88 points of Palgeacheon on the other hand, the lowest value of K-CWQI is 77 points of Namcheon. Also, the grade evaluated by K-CWQI and BOD is compared in order to apply K-CWQI to assessment of water quality. The results of this comparison are summarized as follows. The degree of agreement between the grade evaluated by K-CWQI and BOD is reached to 93% when including 1st grade difference as well as exact match and the monthly variation of K-CWQI is relatively lower than BOD. Therefore, K-CWQI not only can complement current water quality standard consisting of a single item, but also assess water environment of tributary comprehensively.

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Milyanggang mid-watershed is located in downstream of Nakdong river basin. The pollutants from that watershed have an direct effect on Nakdong river water quality and it's control is important to manage a water quality of Nakdong river. A target year of Milyanggang mid-watershed water environment management plan is 2013. To predict a water quality at downstream of Milyang river, we have investigated and forecasted the pollutant source and it's loading. There are some plan to construction the sewage treatment plants to improve the water quality of Milyang river. Those are considered on predicting water quality. As results, it is shown that the population of Milyanggang mid-watershed is 131,857 and sewerage supply rate is 62.2% and the livestock is 1,775.300 in 2006. It is estimated that the population is 123,921, the sewerage supply rate is 75.5% in 2013. The generated loading of BOD and TP is 40,735 kg/day and 2,872 kg/day in 2006 and discharged loading is 11,818 kg/day and 722 kg/day in 2006 respectively. Discharged loadings were forecasted upward 1.0% of BOD and downward 2.7% of TP by 2013. The results of water quality prediction of Milyanggang 3 site were 1.6 mg/L of BOD and 0.120 mg/L of TP in 2013. It is over the target water quality at that site in 2015 about 6.7% and 20.0% respectively. Consequently, there need another counterplan to reduce the pollutants in that mid-watershed by 2015.

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