Prediction of Chlorophyll-a Changes due to Weir
Constructions in the Nakdong River Using EFDC-WASP
Modelling

Seo, Dongil; Kim, Minae; Ahn, Jong Ho

doi:2012.17.2.95

Environmental Engineering Research 2012;17(2): 95-102. DOI: https://doi.org/10.4491/eer.2012.17.2.095

Prediction of Chlorophyll-a Changes due to Weir Constructions in the Nakdong River Using EFDC-WASP Modelling

Dongil Seo¹^†, Minae Kim¹, and Jong Ho Ahn²

¹Department of Environmental Engineering, Chungnam National University, Daejeon 305-764, Korea
²Division of Water and Environment, Korea Environment Institute, Seoul 122-706, Korea

Corresponding Author: Dongil Seo ,Tel: +82-42-821-6679, Fax: +82-42-822-5610, Email: seodi@cnu.ac.kr

Received: January 21, 2012; Accepted: May 18, 2012.

ABSTRACT

To evaluate the effect of the 4 major rivers restoration project in the Nakdong River to water quality of the river, the Environmental Fluid Dynamics Code (EFDC) and Water Quality Analysis Simulation Program (WASP), are applied in series. Results showed overall decrease in biochemical oxygen demand (BOD₅) concentrations and increase in chlorophyll-a concentrations, while total nitrogen and total phosphorous concentrations did not show significant changes, relatively. Decrease in BOD₅ concentrations seems to be influenced by an increased hydraulic residence time, which may allow more time for the degradation of organic material. Changes in Chlorophyll-a (Chl-a) concentration, due to the project were more significant for the upper stream areas that show relatively low Chl-a concentration ranges (less than 20 g/L). After the introduction of the Geumho River in the middle part of the Nakdong River, rapid growth of phytoplankton was observed. However, in this middle part of the Nakdong River, the ratio of Chl-a concentration change are less significant, compared to the upper stream areas, due to the project. In the lower stream area, Chl-a concentration decreased after the project. This seems to be resulted from the decreased light availability, due to increased depth, while the nutrient concentrations have been high enough to support phytoplankton growth.