Similarity in Unlined Irrigation Canal Systems

Data from three irrigation canal systems are examined, and the observed variations in some relevant flow parameters are considered in relation to the conditions which apply in the case of completely similar movable bed channel flows. It can be seen that the canals flow with ripple, dune, or transitional bed regimes, and that the bed material size decreases in a downstream direction in such a way that the ratio of the mean velocity of flow to the fall velocity of the bed material tends to remain constant. It is shown that it is impossible for complete similarity to exist between the flows in real alluvial channels, and accordingly an attempt is made to define conditions of quasisimilarity based on the stage of development of the bed formation.