Unsaturated retention, conductivity and hysteresis
Unsaturated water content θ and conductivity K depend on pressure head ψ and the medium's pore structure.
Key knowledge
Unsaturated water content θ and conductivity K depend on pressure head ψ and the medium's pore structure. A specified retention branch gives moisture capacity C(ψ)=dθ/dψ. Wetting and drying can follow different branches, so one pressure head may correspond to different water contents. Conductivity and retention are required constitutive data rather than consequences of Darcy's law alone.
Values and equations
C(ψ)=dθ/dψ
- θ
- volumetric water content 1
- ψ
- water pressure head relative to the specified air pressure m
- C
- specific moisture capacity for the chosen branch m⁻¹
Conditions and scope
- θ is water volume per bulk volume; ψ is water pressure relative to the stated air pressure divided by ρ_wg. Use a consistent branch, temperature and material-state calibration.
- Hysteresis, air entrapment, evolving pores and preferential macropore flow can invalidate a single-valued local equilibrium relation. Saturated elastic storage is not automatically the derivative of unsaturated retention.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read actual§2.6 characteristic curves/hysteresis and§2.10 equation2.65 defining specific moisture capacity; no uninspected fitted van-Genuchten parameters or universal soil curve adopted.
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Entry details
Permanent link to this entry ↗- Record identity
- uni-earth-soil-water-retention
- Revision
- core.1
- Structured reference record
- University core expansion