Determination of seepage loss in earthen channels supplied by Hamoon channel in Dorodzan irrigation and drainage network.

Irrigation channels, which are parts of rainwater catchment systems, have been used for water supply in agriculture for a long time. Seepage loss in irrigation channels is one of the farmers' concerns. Seepage loss, especially in earthen channels, can be noticeable. Different equations have been developed to estimate seepage loss amount in irrigation channels. However, the accuracy of the equations can be determined only by seepage loss measurement. In this research, three earthen channels of the "Dorodzan" irrigation and drainage network were selected. These earthen channels are Abadeh Ramjerd, Zargaran, and Hasan Abad, which are supplied by the "Hamoon" channel. By conducting field experiments, the amount of seepage loss along some reaches of these channels was measured, and conveyance efficiency was determined. Also, the accuracy of different equations for the estimation of seepage loss was evaluated. The results show that the seepage loss rate in each kilometer length of the channel in Abadeh Ramjerd, Zargaran, and Hasan Abad is 4.56% and 10.6, and 19.19%, respectively. To evaluate the accuracy of different equations for estimation of seepage loss in the mentioned earthen channels, the Mean Average of Absolute Error (MARE) statistical criterion was utilized. The outcomes show that under channel conditions, the accuracy of each equation for estimation seepage loss was different. It means that among several equations to estimate seepage loss, in Abadeh Ramjerd channel, the equation developed by Etcheverry, in  Zargaran channel Moritz's equation, and in Hasanabad channel, Offengeden's Equation has more accuracy than other equations. The MARE values for the best seepage loss estimator in Abadeh Ramjerd, Hasan Abad, and Zargaran were 0.168, 0.397, and 0.319, respectively.