Full shape of moisture bulb simulating in surface drip irrigation

Simulation of soil moisture distribution and redistribution, as well as knowledge about wetted dimension in drip irrigation can be considered as important criteria for improving the drip irrigation design. The experiments were carried out in a transparent plexy-glass tank (0.5m *1.22m * 3m) using three different soil textures (i.e. medium, heavy and fine). The emitter outflows were considered as 2.4 and 4 lit/hr with irrigation duration equal to 6hr. In this study, nonlinear regression method (i.e. Microsoft Excel Solver tool 2010) based on experimental data was utilized to develop empirical model for estimating the horizontal distribution of the wetting front in surface drip irrigation. Similarly, the radius of wetted bulb (in the distribution and redistribution phase) at different depths was estimated by optimizing the calculated coefficients of equations and finally, the full shape of the wetting pattern was simulated. The results of proposed models based on performance criteria showed that for distribution phase, the values of R2, RMSE and MAE varied between 0.7-0.89, 1.54-3 cm and 1.38-2.6 cm, respectively. Furthermore, for redistribution phase the R2, RMSE and MAE ranges were 0.6-0.92, 2.15-3.93 cm and 1.7-3.67, respectively. The comparison results of measured and simulated data revealed that proposed models can predict the shape of the moisture front in both distribution and redistribution phases with good accuracy.