Evaluation of water infiltration models in soil textures under different initial water contents

Water infiltration models are very helpful in predicting runoff in the slopes. The accuracy of the models depends on soil types and initial moisture conditions. This study was conducted to three soil textures (loam, sandy loam and sandy clay loam) with four initial soil moisture levels as a completely randomized design. The infiltration rate models consist of the Kostiakov, Kostiakov-Lewis, Horton, Soil Conservation Service of America, Green-Ampt and Philip were fitted to data and their accuracy were assessed using some statistical parameters. Results showed that soil infiltration rate is affected strongly by initial water content in the soils. The highest variation of infiltration rate was found in sandy loam especially in initial times of infiltration. There were obvious variations in final infiltration rate under different initial water content in the soils and the lowest and the highest variation was observed in sandy clay loam and loam , respectively. The Horton’s model was the best equation describing temporal variation of water infiltration in the sols under different initial water contents, so that itappeared the highest determination coefficient and the lowest values of the root mean squares error and the Akaike index. The Green- Ampt’s model appeared the most sensitivity to initial water content and was weakly fitted with observed data. Therefore, the Horton’s model can be used for predicting infiltration rate under different initial water contents in the soils.