In this study, the effect of tributary width on the turbulence parameters in a trapezoidal main of a channel confluence system is investigated using Numerical Simulations. 3D code is calibrated using the data from experimental tests in the literature. Parameters including streamwise velocity component, Bed Shear stress and water surface variations in the main channel are studied. Results indicate that increasing the tributary width results in the reduction of the area of the recirculation zone in the main channel, decreasing the bed shear stress as well as the depth of the upstream flow.