Herein, we analyzed the spatial and temporal variation of DO (dissolved oxygen), BOD (biochemical oxygen demand), and COD (Chemical Oxygen Demand) with the monthly mean observed data for 10 years (2008~2017) in the main stream of the Nakdong River. The water quality of the stations declined in a downstream direction, with the BOD and COD showing their highest values at the ST5 station. From the analysis of the correlation of water quality components at 10 stations, the correlation coefficient between the DO and water temperature was more than –0.90, and that between BOD and Chl-a was 0.48~0.85, and that between COD and TOC was more than 0.65 except for the ST5 and ST10 stations. From the regression analysis using data collected from all stations, the water temperature and DO decreased linearly with a coefficient of determination of 0.90, and the Chl-a and BOD could be described by increasing power functions with a coefficient of determination of 0.83. The TOC and COD followed increasing logarithm functions with a coefficient of determination of 0.58. The TOC efficiency at the 10 stations was estimated and the average efficiencies of BOD and COD were 15.5~36.3% and 57.4~89.6%, respectively.

Abstract
 1. 서 론
 2. 재료 및 방법
 3. 결과 및 고찰
  3.1. 수질 성분의 시공간 변동 분석
  3.2. 수질 성분의 상관관계 분석
  3.3. 관측소별 TOC에 대한 BOD와 COD의 분해율 산정
 4. 결 론
 REFERENCE

• 강동환(부경대학교 환경연구소) | Dong-hwan Kang (Environmental Research Institute, Pukyong National University)
• 소윤환(부경대학교 환경연구소) | Yoon Hwan So (Environmental Research Institute, Pukyong National University)
• 박경덕(부경대학교 마린융합디자인협동과정) | Kyeong-deok Park (Interdisciplinary Program of Marine Convergence Design, Pukyong National University)
• 김일규(부경대학교 환경공학과) | Il-kyu Kim (Department of Environmental Engineering, Pukyong National University)
• 김병우(한국수자원공사 K-water연구원) | Byung-Woo Kim (K-water Research Institute, Korea Water Resources Corporation) Corresponding author