Evaluation of HYDRUS 2D Software to Estimate StoredWater and Wetting Pattern of Surface Drip Irrigation

Characteristics of a produced soil wetting front by a point source plays considerable role in the efficiency of drip irrigation. The Shape of wetting pattern depends on various factors such as soil texture and layers, soil structure and emitter discharge. The purposes of this study include evaluation of wetting front advancement and comparison of HYDRUS 2D model simulations of surface drip irrigation with measured data on the field and estimating the depth of stored water in soil layers. In this study, a drip irrigation using T-Tape method was carried out on a sandy loam soil at four different irrigation times (2, 4, 8 and 24 hour).Volumetric water content of soil samples were measured by gravimetric method. Evaluation of the simulated and measured soil water content was performed by using adjusted coefficient of correlation (R2), relative error (RE) and normalized root mean square errors (NRMSE) values. Based on the results, the NRMSE value for water content of soil profile with radial distances of zero and 10 (cm) from the dripper location, was calculated in the range of 10 to 15 and 7 to 14 percent, respectively. Also, the RE and average R2 values for the same water content were calculated in the range of 8 to 16 and 7 to 13 percent and 0.96 and 0.95, respectively. The results indicated that the HYDRUS 2D model could predict the soil water content with appropriate precision. Also, three scenarios including 1-double discharge increment (Q2), 2- soil bulk density increment (S1) and 3- soil bulk density reduction (S2), were evaluated for investigating the amount of water stored in the soil profile. The results showed that the effect of soil bulk density parameter (S1 and S2) on the amount of stored water depth is greater than the impact of discharge (Q2). So as a reduction of 5% in bulk density, on average, increased the stored water depth in the soil profile the rate of 69.85 percent, while this enhancement for the 2-fold increase in the discharge scenario was 41.91 percent.