Hydraulic properties determine the soil water content and its transport in the soil. They are provided in most current climate models as empirical formulas by functions of the soil texture. Such is not realistic if the soil contains a substantial amount of macropores. A two-mode soil pore size distribution is incorporated into a land surface model to provide more accurate estimation of hydraulic properties of well-aggregated soils. The pore-size distribution for soils with heterogeneous pore systems is regarded as a linear combination of two simple (uni-mode) distributions, thus the macropores can be isolated as an component of the size distribution. The matric potential and the unsaturated hydraulic conductivity are derived from this distribution. Using an observational dataset at a tropical forest site with aggregated soils, the treatment is found to significantly improve the simulation of its soil moisture and surface water fluxes.