Developing a novel method for estimating parameters of Kostiakov–Lewis infiltration equation

In this study, the volume balance equation and Elliott and Walker’s two-point method were employed to estimate the Kostiakov–Lewis (KL) infiltration equation parameters. The volume balance equation has a maximum point, whose location (distance) is a function of two parameters, r (constant parameter in advance equation) and f o . (final infiltration rate). If the length of the field is less than the distance of maximum point, then parameters of the infiltration equation obtained by the two-point method will have appropriate values. Otherwise, the values of infiltration parameters would depend on the values of r and f o , and there would be a possibility of their values being inappropriate. In this method, the soil texture of the field is assumed to be homogeneous; so, the relationship between r and f o is ignored, which may render the two-point method unsuitable in heterogeneous soils. By investigating the effect of soil heterogeneity on the values of r and f o , it was found that in the two-point method, point information is used for the estimation of parameters of the KL infiltration and that there is no clear relationship between these two points. As a result, a novel method was developed in this study to estimate the KL infiltration equation parameters and applied in three irrigation fields. The infiltration parameters obtained by the proposed method had appropriate values. The infiltration depth computed with the use of parameters so obtained was in close agreement with observed infiltration depth. Thus, the proposed method is potentially useful for estimating the KL infiltration equation parameters.