Estimating Van Genuchten Diffusivity Parameter of Undisturbed Soils in Oklahoma

Reliable estimates of soil water diffusivity are critical for describing and predicting water movement in unsaturated soils. Moisture diffusion through unsaturated soils is governed by the total suction gradient within the soil profile, with moisture moving from regions of low total suctions to regions of high total suctions. As a result, soil water diffusivity is regarded as one of the most fundamental soil hydraulic parameters, and precise acquisition and parameterization of diffusivity are critical in understanding soil moisture dynamics and soil hydrology. The study's objective is to establish a well-documented foundation for assessing soil suction variations within the so-called moisture active zone or vadose zone. The study utilized a supervised method for estimating soil diffusivity at 5 cm below the ground surface using Oklahoma Mesonet matric suction measurements. The study presents a set of equations for estimating van Genuchten diffusivity in Oklahoma soils. The study's findings show that the prediction model produced results comparable to those obtained by the one-step pressure outflow procedure.