Numerical Investigation of Seepage from Earth Canals and Comparison with Field Measurements

The leakage losses from the unlined canals are a major contributor to water losses in the agricultural sector. An understanding of the nature of leakage losses can help to improved water conveyance efficiency and provides solutions to solving water scarcity problems. In this research, numerical simulation was used to study the effective factors on seepage from earth canals. To verify the available information, some of the earthen canals in Zayandehrud irrigation network were used. A number of 246 numerical models including different sections of trapezoidal, rectangular and triangular earthen canals were performed using SEEP/W software. The results showed that, for numerical simulation a width of 15 times the width of the water surface in the canal would be required for the modelling of the left and right lateral boundaries. The comparison of seepage with empirical relationships showed that the empirical relationships show a large error in the seepage estimation, although Moritz's relation with the coefficient of determination 0.373 was better than the rest. Linear and nonlinear multivariate regression relationships provide a suitable match for seepage discharge estimation. Linear relationship was preferable due to small root mean square error (RMSE) and its simplicity. Wetted perimeter has been distinguished effective parameter in seepage from canal, but canal side slope had low effect on seepage. It is suggested that in future studies, the effect of groundwater depth on leakage from the canal should be considered.