NORMAL-DEPTH EQUATIONS FOR IRRIGATION CANALS

Normal depth is an important parameter occurring in the design of irri gation canals. Direct analytic solution of normal-depth problems is no t possible, as the governing equations for the practical canal section s are implicit. The solution requires tedious methods of trial and err or. Tabular and graphical methods also available for solution are subj ect to errors of double interpolation and errors of judgment in readin g the graphs. Furthermore, the methods are based on Manning's equation , which is valid for a hydraulically rough boundary having a narrow ra nge of relative roughness and involves a roughness coefficient having awkward dimensions. Reported herein are explicit equations for normal depth in various irrigation-canal sections.