A. Behrangi - MSc Graduate, Sharif University of Technology, Civil Engineer, SABIR Co.
S.M. Borghei - Associate Professor, Civil Engineering Department, SUT
A.R. Daemi - General Director ofWater Planning Bureau, Ministry of Energy, Iran

Hydraulics of open-channel junction concerns many disciplines in engineering such as; river engineering, environmental hydraulics, sedimentation and scouring problems. Although,ample study are available in this field but, due to many parameters involved, more studies are needed. Among the variables, different channel width ratio (branch to main) and connection geometry (sharp and non-sharp) have been less studied. In this paper, experimental results of these two matters are of main interest. The results show that a non-sharp edge junction reduces dramatically the separation zone dimensions. Also, the separation shape index cannot be assumed constant for all situations contrary to previous suggestions. A new relation for separation zone dimension with inflow angle (instead of junction angle which has been suggested by previous works) is introduced which has resulted a better correlation with present data.