Mc. Goncalves et al., PEDO-TRANSFER FUNCTIONS FOR ESTIMATING UNSATURATED HYDRAULIC-PROPERTIES OF PORTUGUESE SOILS, European journal of soil science, 48(3), 1997, pp. 387-400
The measurement of unsaturated soil hydraulic properties is expensive
and time consuming. These properties are hence frequently predicted wi
th so-called pedo-transfer functions (PTFs) using basic soil propertie
s (e.g. particle-size distribution, organic matter content and bulk de
nsity). In this study PTFs are developed by regression between hydraul
ic data and basic soil properties. Parameters are quantified for: (i)
the retention model of van Genuchten using 80 soil profiles with a tot
al of 230 retention curves, and (ii) the conductivity model of Gardner
using 20 soil profiles and 129 hydraulic conductivity curves. The pro
files represent the main soil families in Portugal, ranging from coars
e sands to heavy clays. The PTFs derived from data for all soils provi
de a fairly poor description of the hydraulic parameters because of th
e heterogeneity of the profiles. The description of several parameters
is improved by using PTFs that are developed for more homogeneous soi
ls grouped according to their particle-size distribution. A further im
provement is achieved by including the water contents at 2.5 cm, 100 c
m, and 15 000 cm water suctions in the retention PTFs, or the saturate
d hydraulic conductivities in the conductivity PTFs.