Currently, surface irrigation is the most common method of irrigation in the country, but due to its low efficiency, water losses in this type of system are significant. Therefore, proper management of water consumption, proper design, and increasing the efficiency of surface irrigation is very important. For proper surface irrigation design, knowledge of soil water infiltration's characteristics is necessary. In this study, Manning’s roughness coefficient and coefficients of the Kostiakov-Lewis' infiltration equation were optimized by simulating the advance phase using a numerical solution of the Saint-Vanant's equations and comparing it with the real results. Also, infiltration simulation and prediction of the Kostyakov-Lewis' infiltration equation coefficients were performed using the complete hydrodynamics model, the Richards’ equation, the HYDRUS-1D,2D software, and combining the hydrodynamics model with the other methods mentioned. To eva‎luate the accuracy of the methods, two series of field data for furrow irrigation were used, the first series was related to the Isfahan University of Technology and the second series was related to the Tabriz University. The accuracy criteria of the methods was a comparison between the computational infiltration volume with each method and the actual infiltration volume. The results showed that the combination of the hydrodynamics model with the HYDRUS-1D software and the numerical solution of the Richards’ equation increased the infiltration volume error, but for the HYDRUS-2D software, this combination reduced the error so that the best method for predicting the Kostiakov-Lewis' infiltration equation coefficients was the method of Hydro-HYDRUS-2D with NRMSE equal to 13.2%, and the method of Hydro- Richards with NRMSE equal to 31.4% had the most error. The results also showed higher accuracy of the HYDRUS-2D software with NRMSE equal to 13.8% compared to the hydrodynamics model with NRMSE equal to 29.7% in estimating the infiltration equation's coefficients. The results of the t-test at the of level 5% also showed that the infiltration's volume error estimated using the methods of Hydro-HYDRUS2D in comparison with Hydro-Richards (t(16)=-2.365), HYDRUS-2D in comparison with Richards (t(16)=-2.260), Hydro-HYDRUS2D in comparison with Richards (t(16)=-2.250) and HYDRUS-2D in comparison with Hydro-Richards (t(16)=-2.371) was significantly less but there was no significant difference between the estimated infiltration's volume error with other methods.

محمد شايان نژاد

سعيد اسلاميان، شمس الله ايوبي