S. H. Sadeghi - Department of Water Engineering, College of Agriculture, Isfahan University of Technology, Isfahan ۸۴۱۵۶-۸۳۱۱۱, Islamic Republic of Iran.
S. F. Mousavi - Department of Water Engineering, College of Agriculture, Isfahan University of Technology, Isfahan ۸۴۱۵۶-۸۳۱۱۱, Islamic Republic of Iran.
S. H. R. Sadeghi - College of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor ۴۶۴۱۷-۷۶۴۸۹, Islamic Republic of Iran.
M. Abdolali - Department of Statistics, College of Mathematical Sciences, Isfahan University of Technology, Isfahan

Factor  is introduced for direct head loss calculation and sizing in dual-diameter laterals of sprinkler and trickle irrigation systems when the Hazen-Williams equation is to be applied. Application of this factor prevents trial and error and uses fewer head-loss equations in calculating the total friction loss and designing dual-diameter laterals. The proposed factor is a function of total number of outlets on the lateral, number of outlets on the smaller-diameter section of the pipe and ratio of smaller diameter to the larger diameter pipe. By solving two practical examples, the advantage of this factor over other approaches was shown. It was also demonstrated that design of lateral sizing by the given equations is simpler, easier and more accurate than the previous methods.

Correction factor, Friction loss, Irrigation systems, Tapered lateral pipe