Selecting the optimal model of water infiltration into the soil (Case study: Jahad Nasr lands of Khuzestan province)

The process of infiltration is one of the most important components of the hydrological cycle and field water management. The direct measurement of infiltration process is difficult, time spending and expensive. Therefore, infiltration models are used. Kostiakov, Kostiakov-Lewis, Philip, Soil Conservation Service of America, Horton and Overton models infiltration based on double ring results carried out in two wheat and bean fields to the determination of best infiltration model in the Jahad Nasr Khuzestan province. The results showed that the mean infiltration rate in wheat field was 35.47 cm hr-1 in 15.83 percent moisture before first irrigation up to 6.35 cm hr-1 in soil moisture content of 29.20 percent after second irrigation. The average infiltration rate in the bean field with initial moisture was 16.43 percent before the first irrigation from 61.63 to 13.70 cm hr-1 in the soil moisture content of 23.10 percent after the second irrigation. The lowest and highest RMSE for coefficients of cumulative infiltration models in wheat field were obtained from Philip and Horton equations with 1.21 and 3.14 cm with R2 of 0.93 and 0.95 and the bean field was 1.57 and 3.42 cm with R2 of 0.90 and 0.92, respectively. The lowest and highest RMSE of the infiltration rate in the wheat field were obtained Philip and Horton equations with 0.46 and 0.63 cm min-1 and in the bean field were 0.90 and 1.40 cm min-1, respectively. The accuracy rating of the studied models in two fields showed that Kostiakov-Lewis and Horton models have the highest accuracy in the infiltration rate and Kostiakov-Lewis and Phillip models in cumulative infiltration.