In this study the estimation method for stream hydraulic characteristics which is served as the input data
set for running QualKo water quality model is investigated. The conventional approach for estimating such hydraulic
parameters is to use the data set from the last cross section in each reach. However, it is shown that in order to
represent correctly flow velocity profiles or the travel time in streams, hydraulic parameters of QualKo model should
be estimated with all cross section data set within the corresponding reach. In addition, the unsuitable estimation of
hydraulic parameters at some reaches has influence on the water quality predictions at the corresponding reaches,
and the errors of water quality predictions are propagated toward the downstream without any error attenuation.