Simulation of Soil Moisture Profile in Drip Irrigation with HYDRUS-2D Model

Drip irrigation management requires proper information on the horizontal and vertical distribution of moisture in the soil of the root zone. In this study, soil moisture distribution was simulated up to 72 hours after drip irrigation by coefficients of soil water characteristic curve with three different methods in the Hydrus-2D model. These methods were included estimating the soil water characteristic curve of inverse solution methods with soil water characteristic curve data (IS1), inverse solution with soil moisture data after irrigation (IS2), and Rosetta. To determine the accuracy of the simulated moisture values with the measured values, RMSE and R2 were used. The results showed that RMSE and R2 for estimating the soil water characteristic curve in IS1, IS2, and Rosetta methods were obtained 0.008 and 0.999, 0.153 and 0.958, 0.125 and 0.977, respectively. The accuracy of IS1 methods depended on the information of the soil water characteristic curve, Rosetta depended on some early soil properties, and IS2 depended on soil moisture after irrigation. Average RMSE and R2 in the simulation of horizontal moisture distribution for IS1, IS2, and Rosetta were obtained 4.6 and 0.9941, 2.8 and 0.9951, 5.5, and 0.9905, respectively. Also, the mean of these statistics in simulating the vertical distribution of moisture for the mentioned methods were 4.6 and 0.9830, 4.4 and 0.9928, 5.4 and 0.9932, respectively. Finally, the use of IS1 method was recommended due to the shorter time and cost of simulations and the possibility of performing it before the design of the drip irrigation system.