Simulation of long-term effect of surface and subsurface strip irrigation on salt distribution with HYDRUS-2D

Long-term studies of the effects of the use of irrigation systems, in addition to being time consuming, impose high costs on the researcher. On the other hand, environmental and non-uniform changes in long-term data collection can affect the accuracy of the experiment. The use of numerical models and long-term experimental simulations based on calibrated parameters for a short-term experiment can be an effective aid in such research. In this study, the main purpose was to simulate the long-term effect of surface and subsurface strip irrigation on salt accumulation in soil profiles using the HYDRUS-2D model. Firstly, the model was calibrated using volumetric moisture data and measured electrical conductivity, Then, to ensure that the model provides logical results, the model was validated using data that were not used in the calibration step. The RMSE (Root Mean Square Error) and NRMSE (Normalized Root Mean Square Error) statistical indices were used to assess the validity of the model. The results of ten years of simulation for surface irrigation showed that the electrical conductivity of soil layers increased on average from 1 dS / m to 9 dS / m. Also, the EC of soil layers for the subsurface system has increased from 0.73 dS / m to 5.5 dS / m on average over five years. Due to the lack of effective leaching for both systems, accumulated salt is much more at soil surface and decreasing by depth. Based on the results, soil leaching at out-season time is necessary and salt removing from root zone is highly recommended to preserve salinity balance and sustainability in farming.