Diversion channels are used in irrigation networks and many of water resource projects. Due to the diversion of a portion of the water, a ratio of the main flow streamlines is deflected to the diversion channel (on the diversion side).The ratio of dividing streamlines increases from the surface to the bottom due to the high momentum of the flow upper layers, which resists its diversion. This negatively affects the quality of diversion water, as the largest proportion of it comes from the high sediment concentration of the lower layers. In this study, the effect of changing the sharp edge of the diversion channel entrance to a circular edge (at upstream, downstream or both sides) on the behavior of dividing streamlines. The study considered five different percentages of the diversion discharge ratio (between 7.5% and 30% of the total discharge) with five different diameters of the circular edge. The results indicated that there is a noticeable improvement of the dividing streamlines uniformity along the flow depth when using the upstream and downstream circular edge, as well as when using large diameter of the upstream circular edge only. In addition, increasing the discharge ratio reduces the regularity of the flow lines.