The Richards model for spontaneous imbibition of a wetting liquid into a porous medium is revisited. Two methods are presented to determine the effective parameter in the Richards equation, i.e. the saturation-dependent moisture transport coefficient D(S), from pore network simulations: The first method employs a quasi-static pore network model (QPNM), whereas the second method uses a dynamic pore network model (DPNM) to estimate D(S) in an inverse approach. The DPNM simulation results serve as a reference to assess the quality of these two parameter estimation methods. It is found that the solution of the Richards equation is very sensitive to D(S), especially when the porous medium is close to fully saturated. While the saturation levels over time obtained from solving the Richards equation with D(S) calculated from the inverse method match well with those from the DPNM, some discrepancy is observed when the QPNM is used to estimate D(S) instead. (C) 2019 Elsevier Ltd. All rights reserved.