Application of the SWAP model to simulate water–salt transport under deficit irrigation with saline water

The agro-hydrological Soil–Water–Atmosphere–Plant (SWAP) model was calibrated and validated to simulate water–salt transport based on field experiments in an arid region of China. The simulation results show lower soil water content but higher salt concentration under deficit irrigation. Soil water and salinity below 95 cm at 80% evapotranspiration (ETcETc) treatments and 65 cm at 60% ETcETc treatments were hardly affected by irrigation. With deficit irrigation, the maximum water uptake and salt accumulated layer moved upward. The SWAP model was also used to predict long-term deficit irrigation with saline water. The salinization process reached equilibrium after utilization of saline water for a few years. In summary, the numerical model proves to be a useful tool for studying water–salt transport under different scenarios and for evaluating irrigation practices for a long period.