Assessing a Semi-Empirical Model Performance to Predict the Wetting Patterns in Subsurface Drip Irrigation

Due to the complexity of soil water distribution, proposed models in the literature can not provide accurate predictions of wetting patterns beneath Subsurface Drip Irrigation (SDI) laterals. In this study, a semi-empirical model using easily accessible data of the SDI system and soil hydrodynamic properties is proposed to predict the wetting patterns in both distribution and redistribution phases. The aforementioned model has been developed based on a novel approach that integrates the governing equations of lateral hydraulics with empirical equations obtained through dimensional analysis. To develop the model and evaluate its performance, three 16-mm drip line pipes with 0.2, 0.4, and 0.5 m emitter spacing, and 2–5 l/h discharge were placed at 0.20 m depth in a soil box filled with clay loam soil. Water was applied for 3 hours at 50, 100, and 150 kPa operating pressures, and the wetting pattern’s geometries were measured in each lateral after 1, 2, 3, and 24 h. Subsequently, the model’s performance was assessed and compared with that of three other models. RMSE, MAE, NSE and RSR statistical indexes of the wetting depth were 0.001–0.002 m, 0.004–0.009 m, 0.816–0.961 and 0.195–0.429, respectively, whereas those associated with the wetting width were 0.001–0.003 m, 0.005–0.016 m, 0.632–0.959 and 0.202–0.607, respectively. These values yielded the lowest error when compared with the corresponding obtained from other well-known models. Consequently, our specialized model was successful in wetting pattern prediction beneath the lateral as a line source.