This document provides an overview of a project studying the effects of subsurface heterogeneity at hillslope scales using the Parflow modeling system. It discusses motivations to better understand upscaling rules when applying distributed hydrological models with heterogeneous parameters. Initial tests are presented examining the impact of soil property variability on soil moisture and discharge dynamics for flat fields and hillslopes. Preliminary results show that state dynamics are well represented by homogeneous models, but heterogeneity increases non-equilibrium and impacts could depend on the ergodic or non-ergodic nature of the domain. Further work is planned to generalize the tests and analyze coarsening effects at the catchment scale.