Determination of Hydraulic Conductivity Using a Tension Infiltrometer

Abstract

A new procedure is presented for in situ determination of saturated and near‐saturated hydraulic conductivity [Kfs and K(ψ), respectively] from a sequence of steady infiltration measurements made at several tensions on a single infiltration surface. The method applies to tension infiltration from either a surface disk or from within a ring inserted a small distance into the soil. The analysis employs a modification of Wooding's solution for infiltration from a shallow pond, combined with numerically determined shape factors that account for the interaction effects between flow geometry and soil properties. The method is found, via numerical simulations, to have an overall accuracy within about ± 7%, regardless of whether the predicted K(ψ) function is flat with an indistinct air‐entry value, steep with a distinct air‐entry value, or very steep with no air‐entry value. Some important practical features of the method are that it does not require measurement of the often‐difficult square‐root‐of‐time infiltration behavior, no special considerations are required regarding the thickness of the contact layer, it minimizes the effect of local spatial heterogeneity by using only one infiltration surface per set of K(ψ) measurements, it avoids the use of potentially unstable simultaneous‐equations solution procedures, and it can be applied to tension infiltration from both disk and ring infiltrometers.

Inverse estimation of soil hydraulic properties under oil palm trees

“…These results are significant in that they, if combined with the fact that stemflow rainfall rates are much higher than the throughfall rates, cause much higher local infiltration rates near the trees stem areas than in areas away from the trees, including open areas. Wooding's (1968) analytical solution, implemented here using a combination of the approaches of Ankeny et al (1991) and Reynolds and Elrick (1991), proved to be very effective in estimating unsaturated hydraulic conductivities. Numerical inversion of the tension disc infiltrometer data provided a relatively simple, yet reliable alternative method for determining the water retention and hydraulic conductivity curves of near saturated soils.…”

“…(2). In our study we used the simplified approach followed by Ankeny et al (1991) and Reynolds and Elrick (1991). Ankeny et al (1991) assumed that A = K(h) / ϕ(h) is constant within an interval between h i and h i + 1 .…”

“…The infiltration rate data for both the stemflow and throughfall areas were used in the equations proposed by Ankeny et al (1991) and Reynolds and Elrick (1991) as discussed earlier, to determine the unsaturated hydraulic conductivity. The approach of Ankeny et al (1991) was used to calculate the unsaturated hydraulic conductivity from the steady state infiltration rates at two different tensions, while the approach of Reynolds and Elrick (1991) provided a piecewise exponential function for the hydraulic conductivity to yield estimates midway between two applied tensions.…”

“…The approach of Ankeny et al (1991) was used to calculate the unsaturated hydraulic conductivity from the steady state infiltration rates at two different tensions, while the approach of Reynolds and Elrick (1991) provided a piecewise exponential function for the hydraulic conductivity to yield estimates midway between two applied tensions. Fig.…”

Impacts of interrelated biotic and abiotic processes during the past 125000 years of landscape evolution in the Northern Mojave Desert, Nevada, USA

“…The tension infiltrometer (TI) method (Ankeny et al, 1988;Reynolds and Elrick, 1991) was used to determine the hydraulic properties of the surface soil. Two paired undercanopy and intercanopy locations were identified at each site in undisturbed areas adjacent to the flora transects.…”