Simulation of the advance Velocity of the Wetting Front in pulse Drip Irrigation Systems by nonlinear regression model

In this study, experiments were carried out in a transparent plexy-glass tank (0.5m*1m*3m) using three different soil textures (fine, heavy and medium). The drippers were installed at 3 different soil depths (surface, 15cm and 30cm). The emitter outflows were considered 2.4, 4 and 6 lit/hr. Also, these experiments were carried out for two continuous and pulse irrigation systems. In pulse irrigation, the pulse cycles were considered 30-30, 20-40 and 40-20 min. In this research, using nonlinear regression model, empirical models were developed to predict the advance velocity of the moisture front at different directions. The parameters of suggested model include emitter discharge, saturated hydraulic conductivity, application time, soil bulk density, emitter installation depth, initial soil moisture content, the ratio of irrigation time to complete period of each cycle and the proportions of sand, silt and clay in the soil. The results of comparison between measured and simulated values of advance velocity indicated that these models were acceptable accuracy in estimating the advance velocity of the wetting front in different directions. The values of the mean absolute error (MAE) and the root mean square error (RMSE) ranged 0.031-0.108 and 0.067-0.275 cm/min, respectively.