Evaluation of some infiltration models and hydraulic parameters

The evaluation of infiltration characteristics and some parameters of infiltration models such as sorptivity and final steady infiltration rate in soils are important in agriculture. The aim of this study was to evaluate some of the most common models used to estimate final soil infiltration rate. The equality of final infiltration rate with saturated hydraulic conductivity (K(s)) was also tested. Moreover, values of the estimated sorptivity from the Philip's model were compared to estimates by selected pedotransfer functions (PTFs). The infiltration experiments used the double-ring method on soils with two different land uses in the Taleghan watershed of Tehran province, Iran, from September to October, 2007. The infiltration models of Kostiakov-Lewis, Philip two-term and Horton were fitted to observed infiltration data. Some parameters of the models and the coefficient of determination goodness of fit were estimated using MATLAB software. The results showed that, based on comparing measured and model-estimated infiltration rate using root mean squared error (RMSE), Horton's model gave the best prediction of final infiltration rate in the experimental area. Laboratory measured K(s) values gave significant differences and higher values than estimated final infiltration rates from the selected models. The estimated final infiltration rate was not equal to laboratory measured K(s) values in the study area. Moreover, the estimated sorptivity factor by Philip's model was significantly different to those estimated by selected PTFs. It is suggested that the applicability of PTFs is limited to specific, similar conditions.