Effective Unsaturated Hydraulic Conductivity of Multilayer Soil Profiles.

Steady-state evaporation from a water table has been extensively studied for both homogeneous and layered porous media. For layered media it is of interest to find an equivalent homogeneous medium and define "effective" (or upscaled) hydraulic properties. In this study the effective unsaturated hydraulic conductivity of multilayer media exhibiting a Miller and Miller type heterogeneity structure has been evaluated based on numerical simulations. Different scenarios of layered systems with normally and lognormally distributed scaling factors were assumed. Results of the numerical simulations showed a positive correlation between the slope of the effective hydraulic conductivity curve (on logarithmic scale) for each layer and the scaling factor assigned to that layer. Obtained results further indicated that effective unsaturated hydraulic conductivity overall falls between the harmonic and geometric means of the hydraulic conductivities of individual considered layers.