Abbas Parsaie, Amir Hamzeh Haghiabi
Study on the river water quality is a main part of environmental engineering. Longitudinal dispersion coefficient ( DL ) is one of the main important parameters in the river water quality studies. Several parameters such as hydraulically and morphological rivers are affective on the DL , whereas the mount effectiveness of some of them such as riverbed form cannot be measured. So, researchers proposed that the DL is proportional to the flow velocity, channel width, river flow depth, and shear velocity. Defining the most influence parameters on the DL leads to develop an optimal structure for empirical formulas and soft computing techniques which will be propose for estimation of DL .In this paper the principle component analysis (PCA) was used to define the most affective parameters on the DL . The PCA results indicated that the width of the river, flow depth, and flow velocity are the most important parameters on the DL . Evaluating the performance of empirical formulas with considering the PCA results showed that the Tavakollizadeh and Kashefipur formula is accurate among the empirical formulas.