Evaluation and determination of infiltration models parameters in Oshtorinan plain

Using infiltration models for modeling surface and subsurface flow as well as designing and evaluation of irrigation systems is necessary. Since the parameters used in these equations are highly dependent on the soil types and surface conditions، field tests is a necessary tool for determination of these parameters. Several infiltration models have been proposed for this purpose that are mostly empirical، semi-empirical or theoretical in nature. In order to select an appropriate model for various field conditions، field tests are required. In this study، several empirical infiltration models were compared with one another and with the Philip exact infiltration equation which was obtained by simplifying the numerical solution of general flow equation in porous media. Required data for selecting appropriate model were taken from Oshtorinan plain، Lorestan، Iran to predict cumulative infiltrationvalues. In this area surface soils are dominantly clay. Infiltration tests were conducted in three locations with clay texture، using double rings infiltrometers. Parameters of four infiltration models (Kostiakov،SCS، Philip، Kostiakov-Lowis) were determined. Model evaluation was performed by comparing relative error. The results of this analysis indicated that the Kostiakov model with a mean relative error of 0. 8 was the most appropriate model for estimating cumulative infiltration in the studied area.