Field Determinations of Soil Hydraulic Properties for Statistical Analyses
1980
Russo, David | Bresler, Eshel
A procedure for repetitive determinations of soil hydraulic properties is based on the assumption that the functional relationships between soil water content (θ) and soil water pressure head (h), and between the hydraulic conductivity (K) and h, can be expressed mathematically. The parameters in the mathematical expression are: saturated hydraulic conductivity (Kₛ) and water content (θₛ), residual (or irreducible) water content (θᵣ), water entry value of h (hw), and the parameters η and β, characterizing the pore size distribution of the soil. Values of Kₛ and hw are measured by the air-entry permeameter of H. Bouwer. The parameters η and β were calculated with measured values of Kₛ, hw, θₛ, θᵣ, and the sorptivity, S, as measured by C. Dirksen's method. The variability in the determination of the K(θ) function is evaluated in the field, from 30 measurements of each of the six parameters made in a single 2 by 2 m site. This variability is smaller than the variability of K(θ) as calculated from a simulation of a transient drainage. The K(h) and θ(h) functions are rapidly obtained and thus suitable for performing large numbers of measurements for the determination of the probability density functions (and joint probability density functions) of the soil hydraulic conductivity, K(θ), and soil water retentivity, h(θ), functions.
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