U. Shani et R. Gordinkatz, SOIL HYDRAULIC MODELS SELECTION BASED ON IN-SITU MEASUREMENTS, Journal of irrigation and drainage engineering, 124(6), 1998, pp. 285-289
Soil hydraulic properties are usually expressed as functional relation
ships between the soil hydraulic conductivity and water content or mat
ric potential, and between the matric potential and water content. Bot
h functions are highly nonlinear, and direct in-situ measurements are
time consuming and involve considerable uncertainty. Therefore, method
s based on soil hydraulic models, i.e., functions chosen a priori and
containing parameters estimated from measurements, are of interest. Th
e most widely used models are those of Gardner in 1958, Russo in 1988,
Brooks and Corey in 1964, and van Genuchten in 1980. For such models,
an equation is derived that relates the developed expression for the
first moment, M, of the diffusivity function with a combination of mea
sured parameters: saturated hydraulic conductivity, capillary length,
saturation and residual water content, and soil sorptivity. The M expr
essions are derived for the three models in the form of explicit funct
ions of their parameters. Three overlapping M ranges are determined wh
ere the selection of a respective model is preferable.