ABSTRACT
Soil hydraulic properties should be directly measured whenever possible, as they are critically
important to the transport and storage of water and solutes (see other chapters in the Section Soil
Water Analysis), and they are highly variable in space and time. However, direct measurement is
not always feasible, due to restrictive budgets, insufficient time, and substantial difficulty
associated with certain measurements, such as the dry end of the unsaturated hydraulic con-
ductivity relationship. In these situations, the only practical option may be to estimate soil
hydraulic properties from more easily measured parameters, such as texture, bulk density,
porosity, and soil water desorption-imbibition relationships. Although the prudence of estimat-
ing soil hydraulic properties has been questioned (particularly when predicting or modeling
water-solute movement; Philip 1991; Addiscott 1993; Passioura 1996), it can nonetheless
provide insights that would otherwise be difficult to achieve; and it also allows extrapolation
beyond the specific soil conditions under which measurements must be conducted.
