Drying-memory effects and texture-dependent salinity responses revealed by full-range measurements of soil hydraulic properties

Accurate soil hydraulic properties (SHP) are essential for groundwater modeling with Richards’ equation. In coastal soils affected by sea-level rise, SHP shift in response to changing salinity and repeated wetting-drying cycles, yet the combined effects of soil salinity and drying memory remain poorly quantified. We conducted a controlled laboratory study to investigate these interactions across the full moisture range in three soils of different textures (sand, sandy loam, and silt loam). Soils were saturated with artificial seawater at three salinity levels, 0, 15, and 30 dS m⁻¹. SHP were measured using HYPROP evaporation experiments and WP4C dewpoint potentiometry over repeated drying cycles. Salinity induced strong, texture-dependent responses. Although salinity imposed a limited influence on the water retention behavior of the sandy silt loam, it resulted in a pronounced increase in unsaturated hydraulic conductivity, consistent with salt-driven flocculation and pore-domain reorganization. Across all textures, SHP exhibited non-linear dependencies on salinity, texture, and drying memory. Model fitting of the measured data showed that the Peters-Durner-Iden (PDI) model outperformed the van Genuchten model, due to its explicit representation of adsorptive water and film flow. The resulting dataset provides a mechanistic foundation for next-generation SHP models that incorporate dynamic soil structure and texture-specific coupling between matric and osmotic effects.