Predictions of water flow and transport processes in soils subjected to structural changes such as compaction of tilled agricultural lands, or newly constructed landfills and other waste isolation designs, rely on accurate description of soil unsaturated hydraulic conductivity. Recent studies have documented the critical role of aggregate contact characteristics on water flow rates and pathways in unsaturated aggregated soils. We developed an analytical model for aggregate contact size evolution as a basis to predict effects of compression on unsaturated hydraulic conductivity of aggregated soil. Equating normal stress on the inter-aggregate contacts to soil matrix yield stress at stress equilibrium enables to predict inter-aggregate contact size as a function of stress conditions and soil matrix rheological properties. The hydrologic component of the model predicts unsaturated hydraulic conductivity of a pack of idealized aggregates (spheres) based on contact size and saturation conditions under prescribed applied load. Model calculations will be compared with recent measurements of hydraulic conductivity and contact area for pairs of aggregates.