Microflowmeter–tension disc infiltrometer: Part II – Hydraulic properties estimation from transient infiltration rate analysis

SummaryMeasurements of soil sorptivity (S0) and hydraulic conductivity (K0) are of paramount importance for many soil-related studies involving disciplines such as agriculture, forestry and hydrology. In the last two decades, the disc infiltrometer has become a very popular instrument for estimations of soil hydraulic properties. The previous paper in this series presented a new design of disc infiltrometer that directly estimates the transient flow of infiltration rate curves. The objective of this paper is to present a simple procedure for estimating K0 and S0 from the linearisation of the transient infiltration rate curve with respect to the inverse of the square root of time (IRC). The technique was tested in the laboratory on 1D sand columns and 1D and 3D 2-mm sieved loam soil columns and validated under field conditions on three different soil surfaces. The estimated K0 and S0 were subsequently compared to the corresponding values calculated with the Vandervaere et al. (2000) technique, which calculates the soil hydraulic parameters from the linearisation of the differential cumulative infiltration curve with respect to the square root of time (DCI). The results showed that the IRC method, with more significant linearised models and higher values of the coefficient of determination, allows more accurate estimation of K0 and S0 than the DCI technique. Field experiments demonstrate that the IRC procedure also makes it possible to detect and eliminate the effect of the sand contact layer commonly used in the disc infiltrometry technique. Comparison between the measured and the modelled cumulative infiltration curves for the K0 and S0 values estimated by the DCI and IRC methods in all the 1D and 3D laboratory experiments and field measurements shows that the IRC technique allowed better fittings between measured and modelled cumulative infiltration curves, which indicates better estimations of the soil hydraulic properties.

► A new procedure (IRC) to estimate the K0 and S0 soil properties is presented.
► IRC uses the transient infiltration rate measured with a microflowmeter–infiltrometer.
► IRC was compared to the standard Vandervaere et al. (2000) technique (DCI).
► The IRC method allows more significant linearised models, with higher R2 values.
► Estimates of K0 and S0 with IRC were more accurate than those obtained with DCI.