Abstract:The wetting pattern is difficult to observe during the vertical line source irrigation. Knowledge of the dimensions of wetted soil around the emitter under irrigation is essential to design of cost-effective and efficient vertical line source irrigation systems. Based on the HYDRUS-2D model, a mathematical model of soil water movement in vertical line source irrigation was established. And 81 scenarios were set up to simulate the changing process of wetted soil under different soil textures, initial water content, line source length, diameter and depth conditions. The dimensions of wetted soil were mainly affected by soil texture, the thicker the soil texture was, the faster the wetted front was moved, and the length, diameter and buried depth of line source had little influence on it. The migration process of soil wetting front was in accordance with the power function relationship. The power function index was changed little in the horizontal and vertical upward directions, but it was increased with the saturated hydraulic conductivity (Ks) in the vertical downward direction. The power function coefficient was increased with the increase of Ks. An empirical model for predicting the wetted soil dimensions under vertical line source irrigation containing Ks was proposed, the model reliability was verified by using experimental data. MAE and RMSE were close to 0, PBIAS was between -4% and 9%, and NSE was not less than 0.929, indicating that the prediction effect was good. The model can be estimated only by Ks, and the experimental design was simple. The possibility of predicting the soil wetting front migration distance under vertical line source irrigation by soil physical parameters was initially realized.
