• Journal of Environmental Impact Assessment
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• v.33 no.5
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• pp.214-227
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• 2024

Domestic multipurpose dams are operated to secure reservoir capacity during the summer rainy season, supplying domestic water and maintaining environmental flow in downstream rivers during low-flow periods. This operational approach affects the water quality of downstream rivers. The aim of this study is to evaluate the impact of monthly planned discharge from Youngju Dam on the downstream tributaries, NaeseongCheon and the main stream of the Nakdong River. To achieve this, hydrodynamic and water quality modeling was conducted using the CE-QUAL-W2 model to simulate travel times and changes in water quality parameters. The Time Lagged Cross Correlation (TLCC) method was adapted to analyze the correlation between water quality at Youngju Dam and representative points in the downstream NaeseongCheon and Nakdong River, taking into account the travel time of the dam discharge. The analysis revealed a significant water quality correlation between the discharge from Youngju Dam and the NaeseongCheon monitoring point (Point 5), with correlation coefficients ranging from 0.382 to 0.777. However, the correlation coefficients for water quality between Youngju Dam and the main stream of the Nakdong River ranged from -0.528 to 0.317, indicating either a very weak or negative correlation. This suggests that there is no significant correlation between the water quality of Youngju Dam and the Nakdong River main stream. The findings indicate that the main objective of constructing Youngju Dam to improve the water quality of the Nakdong River main stream may not have substantial practical effectiveness. Therefore, it is essential to review the dam's operational plans with a focus on improving the water quality of NaeseongCheon, which is directly affected by the dam, and to conduct further research in this area.