Discussion of 'Estimation of the Longitudinal Dispersion Coefficient Using the Velocity Profile in Natural Streams' by II Won Seo and Kyong Oh Baek

摘要

The authors began this paper with the statement, "When a one-dimensional model is used for predicting the concentration variation of pollutants in natural streams, the selection of a proper dispersion coefficient is considered the most important task." The discussers have been involved in numerous projects that included water quality modeling of rivers, and in our personal experience, in no case was the estimation of the dispersion coefficient considered the most important task. Usually the dispersion coefficient was adjusted as one of many calibration parameters to help match the water-quality data. Often the lack of spatial water quality data meant that once a dispersion value was selected it was not further adjusted, as other parameters were much more sensitive in the calculation. The discussers and others have found that for steady-state water quality models the dispersion coefficient is among the least sensitive of parameters (e.g., Himesh et al. 2000).