Application of a Nonstandard Explicit Integration to Solve Green and Ampt Infiltration Equation

In this technical note, a nonstandard explicit integration algorithm (EIA) developed by Ramos in 2007 is used to solve the Green and Ampt infiltration equation. EIA is a nonlinear one-step method to solve initial-value problems and yields second-order accuracy. The EIA solution is tested using literature data and the estimated cumulative infiltration is compared with measured, an implicit and two explicit solution techniques for dry and wet soil conditions. The EIA solution estimates cumulative infiltration closer to the measured than the other methods and the relative percentage errors ranged from −5.5 to 4% and from −1.9 to 6.5% for dry and wet soil conditions, respectively. The higher values of Nash–Sutcliffe coefficients (closed to 1) in the case of EIA reveal that the model is more efficient than the other methods for both wet and dry soil conditions. Further, the effect of time step size on the EIA solution is tested and found that Ramos’ EIA is a promising tool for solving Green Ampt infiltration equation using small (time) step sizes.