توانایی مدل HYDRUS-2D در شبیه‌‌سازی توزیع رطوبت در خاک تحت سیستم آبیاری قطره‌ای زیرسطحی

Knowing about the way water is distributed in the soil is essential for designing and managing the Subsurface Drip Irrigation systems (SDI). Since carrying out experiments to recognize the form of moisture distribution in the soil is too complicated and time-consuming, using numerical simulations can be an efficient, effective substitute method to design these systems. One of these models is HYDRUS-2D, which is able to simulate the movement of water, heat and solute in saturated and unsaturated conditions in soil. This research aims to figure out the extent to which the HYDRUS-2D model is able to estimate wetting pattern in soil around a dripper. The simulations’ findings were compared to the data gathered from the field, including SDI system in different irrigation times, and 72 hours after irrigation. Moreover, the rates of error were measured for all points and distances from the dripper in all times of irrigation and also beyond that. The results indicated that the model can simulate the changes, trend similar to what happened in the soil profile. However, it estimated the rate of soil moisture with higher errors in those points in which the wetting took place, with the maximum error rate being RMSE= 0.05 per every 1.5 hours after irrigation starting point in the depth of 30 centimeters where dripper is placed. Also, with an increase in the irrigation time, and soil moisture evening which resulted from redistribution of moisture, the model resulted in better estimations. 72 hours after finishing the irrigation, the estimates were closer to real figures with an average error estimate of RMSE= 0.002.