“…This equation is the governing equation for fluid movement in unsaturated soil. It is a strongly nonlinear parabolic partial differential equation; therefore, numerical methods usually are applied to solve it (Berardi, Difonzo, Vurro, & Lopez, 2018;Caviedes -Voullième, Garcı, & Murillo, 2013;Gyrya, Lipnikov, Manzini, & Svyatskiy, 2014;Hills, Porro, Hudson, & Wierenga, 1989;Romano, Brunone, & Santini, 1998;Solin & Kuraz, 2011;Wendland & Pizarro, 2010). However, considerable attention should be paid to solving Richards equation to get an accurate discretization and an efficient solver (Jeltsch & Nevanlinna, 1981;Lipnikov, Moulton, & Svyatskiy, 2016;Miller et al, 2013).…”