Ahuja et al. (1984), effective-porosity relations for saturated conductivity.¶
Source¶
Ahuja, L. R., Naney, J. W., Green, R. E., & Nielsen, D. R. (1984). Macroporosity to characterize spatial variability of hydraulic conductivity and effects of land management. Soil Science Society of America Journal, 48, 699-702.
Scope¶
Territory: Chickasha, Oklahoma, and the Wahiawa Plateau, Oahu, Hawaii, USA
Dataset: Undisturbed cores from 15 sites in a 9.6-ha Renfro silt loam watershed and 54 cores from three related Hawaii Oxic soils; the Hawaii study also supplied 35 field measurements of saturated hydraulic conductivity.
Functions¶
calc_ptf_ahuja1984¶
Estimate saturated hydraulic conductivity from total porosity and water content at -33 kPa using user-supplied empirical coefficients.
Status: implemented
Prediction target: Saturated hydraulic conductivity from effective porosity, defined as total porosity minus volumetric water content at -33 kPa.
Models: \(k(h)\) — Saturated hydraulic conductivity
Inputs¶
| Name | Type | Unit | Domain | Description |
|---|---|---|---|---|
total_porosity | number | cm^3/cm^3 | 0 <= value <= 1 | Total porosity; in the experiments it was taken as saturated volumetric water content. |
theta_33 | number | cm^3/cm^3 | 0 <= value <= 1 | Volumetric soil water content at -33 kPa pressure head. |
coefficient_b | number | cm/h | value > 0 | Soil-specific empirical coefficient in the generalized Kozeny-Carman relation. |
exponent_n | number | 1 | value > 0 | Empirical exponent; the paper evaluates values of 4 and 5 for deriving conductivity scaling-factor distributions. |
Outputs¶
| Name | Unit | Domain | Description |
|---|---|---|---|
k_sat | cm/h | value >= 0 | Saturated hydraulic conductivity. |
Note
Effective porosity is total_porosity - theta_33; the paper notes that field capacity is not a precisely defined soil parameter.
Note
Soil-core fitted exponents were near 4, whereas the smaller Hawaii field dataset had a fitted slope of 1.59 over a narrower effective-porosity range.
Warning
The empirical coefficient B varies with soil type; callers must supply a coefficient calibrated for the soil being evaluated.
Warning
Callers must supply the exponent. The paper evaluates both n = 4 and n = 5 and does not select one as a unique transferable value.
Warning
total_porosity must be greater than or equal to theta_33.