evaluation and determination of the coefficients of infiltration models in marvdasht region, fars province

infiltration process plays an important role in water cycle of the nature. conducting field experiments is necessary to determine the coefficients of infiltration equations due to the dependence of these coefficients to the soil type, soil surface conditions and the amount of initial soil moisture content. this study has been carried out in a field located in islamic azad university, marvdasht branch, fars province. with regard to various initial amounts of soil moisture content and clay loam soil texture of the study area, permeability tests including double rings and single ring methods were conducted in 8 points as well as the coefficients of philippe and kostiakov models were determined to estimate the coefficients of infiltration models and to determine a proper model to forecast cumulative infiltration values. results of the evaluation shows that, kostiakov model has more proper operation in estimating the amount of infiltration compared with philippe model, and coefficients of the studied models (kostiakov and philippe models) vary with soil moisture variation. these variations in some cases are high and for some others are low. variations trend also is not fully compatible with soil moisture conten