287-6 A Process-Based Full-Range Model of Soil Water Retention.
See more from this Division: SSSA Division: Soil Physics and Hydrology
See more from this Session: Soil Physics and Hydrology Oral I
Abstract:
The model proposed here recognizes dominant processes in three portions of the range from oven-dryness to saturation. It applies to soil matrix material, exclusive of macropores. The adsorption-dominated dry range is represented by a logarithmic relation used in earlier models. The middle range, of capillary advance/retreat and Haines jumps, is represented by a new adaptation of the lognormal distribution function. The wet range is dominated by trapped air expansion in response to pressure change, as well as a process that increases the sensitivity to changing matric pressure, which may be related in part to a collapse of liquid bridges in response to air expansion. For these the model uses the Boyles’ law inverse-proportionality of trapped air volume and pressure, amplified by an empirical factor to account for the additional process. The model’s eight parameters, though more than in most models, have a strong physical interpretation because they are process-based. Their values therefore can more readily be obtained from fundamental considerations or individual measurements, and have potential for systematic adjustment to account for hysteresis. Another substantial advantage is the physically-plausible treatment of the wet range, which avoids such problems as the blowing-up of derivatives on approach to saturation. This makes the model especially valuable for important but challenging wet-range phenomena such as domain exchange between preferential flow paths and soil matrix.
See more from this Division: SSSA Division: Soil Physics and Hydrology
See more from this Session: Soil Physics and Hydrology Oral I