A simple model for predicting soil infiltration rate for vertical line source irrigation

Abstract

In this study, HYDRUS-2D was used to simulate the soil infiltration rate of vertical line source irrigation (VLSI) under different soil textures and initial water contents, as well as for different lengths, diameters and buried depths of the line source. The soil texture, diameter and length of the line source are the dominant influential factors of the soil infiltration rate of VLSI, whereas the initial water content and buried depth of the line source are less influential. The variation of soil infiltration rate is in accordance with the Philip model. The model parameters, i.e., sorptivity (S) and steady infiltration rate (A), increase as the diameter (D) and length (L) of line source increases. A power function between S and D and L, and one between A and D and L, were established. The exponential value of the power function was determined based on the HYDRUS simulation results, thereby obtaining a simplified estimation model of the soil infiltration rate of VLSI containing D and L. The effectiveness of the simplified model was verified based on a laboratory experiment and currently available research. The MAE (mean absolute error, MAE) is 0.056-0.348, RMSE (Root mean square error, RMSE) is 0.073-0.442, PBIAS (percentage bias, PBIAS) is 1.642-2.893, and NSE (Nash-Sutcliffe efficiency coefficient, NSE) is close to 1 (NSE≥0.973), indicating that the model has a high accuracy and can therefore be used for estimating the soil infiltration rate of VLSI. The simplified estimation model established in this study has only two undetermined parameters that can be obtained based on only one set of experimental data, simplifying the experimental scheme and improving the work efficiency.