In light of the current complex water situation in Egypt, scientists and researchers have to develop alternative plans to provide new quantities of water by paying attention to the constructions and tools that are used in distributing and controlling the flow in open channels. One of the most critical parameters in the analysis of diversion channel flow is the discharge ratio (Qr). It is the primary goal of this research to investigate the effect of changing the bed roughness of the main channel on the discharge of the branch channel (Qb). The bed roughness of the branch channel was kept constant (nb = 0.01), while for the main channel bed roughness was changed to five values (nm = 0.01, 0.016, 0.023, 0.033, and 0.04). The diversion angle of the branch channel was taken as (45˚), which gave a maximum (Qr) as recommended by some researchers. A discharge range from 4.88 to 17.14 L/sec was used, and 35 runs were conducted. From the analysis of the laboratory data, it was found that the discharge ratio (Qr) decreases as the total discharge through the main channel increases. While it increases with the increase of bed roughness ratios (nr). Moreover, at the bed roughness ratios (nr) ranged from 2.20 to 3.0, the difference in the discharge ratio (Qr) is no significant, for all discharge values passing through the main channel. Thus, maintaining a constant flow rate for the branched channel is considered one of the most essential factors in designing these channels, as it is vital in distributing water shares as percentages and in a consistent manner.