초록
The results of investigation on the water quality of the unit watersheds in the Yeongsang/Seomjin River indicate that $BOD_5$, SS, T-P decrease in most of the unit watersheds. However, $COD_{Mn}$ and T-N increase since the Total Maximum Daily Loads (TMDLs). It is thought that $COD_{Mn}$, which is included non-biodegradable matters, is difficult to decrease only using by conventional biological treatment facilities and T-N is affected by non-point source, etc. The results of assessment on 3 years $BOD_5$ indicate that most of the unit watersheds were being improved except Yeongbon A, Seombon C and Yocheon B. In addition, it was found that T-P were also being improved except Yocheon B and Hwangryeong A. Consequently, water qualities of the unit watersheds have been improved in many cases since the TMDLs.