Simulation of Soil Water Distribution by HYDRUS- 1D Under Subsurface and Surface Drip Irrigation Systems in Wheat Cultivation Using the Results of ET-HS Model

Water distribution and soil moisture changes are necessary to design the irrigation system that are costly and time consumer. This study aimed to estimate the performance of HYDRUS-1D model to estimate the distribution of soil moisture in the surface and subsurface drip irrigated in wheat cultivation using ET-HS model to estimate water demand in the arid region. A field experiment was conducted with three depth of emitter installation (0-15 and 30 cm) and moisture measurement at six soil depths (10 to 60 cm) with four repetitions for two consecutive years in arid and semi-arid areas of Isfahan. For this reason, Soil moisture was measured using soil moisture detector device (Diviner 2000) every day. Simulated and field data were compared on the basis of statistical indicators. The results showed that except in 0-10 cm with coefficient of determination (R2 = 0.74), other layers have high R2 value and best fit was at a depth of 10-20 (R2=0.93). The root mean square error (RMSE) index values were low except in the surface layer (0-10) with 0 and 30 cm depth of emitter. Highest and lowest values of coefficient of residual mass (CRM) was 0.008 and -0.0046, respectively. Based on aforementioned results of the evaluation, the model can be used for optimal management of irrigation in arid and semi-arid.