Evaluation and Comparison of the Distribution Efficiency of Canals and Semi-Elliptical Channels in Irrigation Networks of Khuzestan Province

Irrigation canals, as one of the most important structures of irrigation networks, have a significant role in reducing seepage losses and increasing the water conveyance efficiency. This research was conducted from 2016 to 2018 in irrigation networks of Khuzestan province. In this research, in order to determine the distribution efficiency, the input-output flow method was used with the use of a propeller velocity meter. To have a rational comparison between canals with different dimensions and capacities, the ratio of losses to inlet discharge per kilometer of canal reach has been considered as an evaluating parameter. In total, 26 concrete trapezoidal canal reaches and 17 semi-elliptical prefabricated channel reaches have been studied. The studied canal reaches were located in Omidieh, Andimeshk, Gotvand, Behbahan, Hamidieh, Dezful, Shoosh, Shooshtar, Ramshir, Ahvaz, Bavi and Shadegan, counties of Khuzestan province. Results showed that distribution network efficiency changes from 38.9% to 99.7% for both canals and semi-elliptical channels. The seepage losses per kilometer of canal length varied from 20.92 to 12454.10 m3/day. Maximum and minimum values of seepage losses relative to inlet discharge for concrete trapezoidal reaches were 0.35% and 61.76%, respectively. In prefabricated channels, the average length of studied reaches, conveyance efficiency and seepage losses per kilometer of channel were 978 m, 84.3%, 2133.11 m3/day and 17.18%, respectively. Using t-test method for concrete trapezoidal canals and semi-elliptical channels showed that the amount of seepage losses per kilometer of canal length in a trapezoidal concrete channel with a value of 1920.05 m3/day has no significant differences compared to prefabricated channel with a value of 2133.11 m3/day. The calculation of Pearson correlation coefficients showed that any increase or decrease in the parameters of the discharge and velocity, as well as the amount of time interval, does not lead to significant changes in the process of conveyance efficiency.