SOIL-WATER DIFFUSIVITY ESTIMATES FROM ONE-DIMENSIONAL ABSORPTION EXPERIMENTS

A method to estimate soil water diffusivity from experimental absorpti on data was explored. The purpose was to directly match measured sorpt ion curves (water content vs. distance or the Boltzmann transform vari able) to scaled forms of the solutions and thus provide consistent hyd raulic properties. Evaluation of such parameters is critical to predic tion of water and solute transport within the vadose zone. The method is relevant to several, if not most, of the commonly used hydraulic fu nctional relationships. Generally, the results gave two independent re lationships of the parameters. An example was considered and calculati ons performed for three alternative models. The best choice of each mo del was easily found and the evaluated parameters were shown to be con sistent. The soil water diffusivities were compared for the estimated parametric relationships. Individual models provide alternative shapes for the diffusivity function, but tend to converge for the wetter ran ge of water contents.