Water quality of the Koejong-reservoir was estimated by using the ecological model to evaluate the effects of industrial sewage discharge. State variables consist of POC, DOC, phytoplankton, DIP, DIN, DO and COD. Initial conditions for the compartment are applied to the model based on the observed results. The reproducibility was found to be satisfactory with the relative error ranging between the calculated value and the observed value. Water quality simulation was conducted by applying additional industrial sewage discharge into the Koejong-reservoir. The concentrations of COD, Chl.a, DIP and COD showed fluctuations of a narrow range. The increment percentages of Chl.a, COD and DIP were 26.6%, 20.2% and 18.2%, respectively. In the case of DO, the concentration decreased 4.8%.

Abstract
 1. Introduction
 2. Materials and Methods
  2.1 Modeling system
  2.2 Ecological model
 3. Results and discussion
  3.1 Study area and input data
  3.2 Reproducibility of ecological model
  3.3 Results of simulation
 4. Conclusion
 REFERENCES

• Dong-Myung KIM(Department of Ecological Engineering, Pukyong National University) Corresponding author
• Ji-Won SUK(Department of Ecological Engineering, Pukyong National University)
• Sun-Young KIM(Department of Ecological Engineering, Pukyong National University)
• Sang-Ik SHIN(College of Marine Science, University of South Florida, St. Petersburg)
• Kyong-Joon ROH(Department of Environmental Engineering, Pukyong National University)