Improving Hydraulic Conductivity Estimates from Minidisk Infiltrometer Measurements for Soils with Wide Pore‐Size Distributions

Abstract

Disk infiltrometers are established as standard devices for measuring soil surface hydraulic properties. This study explored the validity of a semiempirical approach that is used to obtain estimates of the near‐saturated hydraulic conductivity from disk infiltrometer data. The approach was compared with two other estimation expressions. The analysis was based on three‐dimensional numerical modeling of the infiltration process, i.e., on synthetic data. The results of the validation procedure showed that the original expression performed best among the compared methods, but still failed for fine‐textured soils and the selected Cambisols. This is due to the overwhelming importance of lateral soil water movement by capillarity, which is not adequately addressed by any of the models. The study showed that improved estimates, specifically for fine‐textured soils and Cambisols and for small infiltrometer radii (minidisks), can be obtained by extending the original approach. This is achieved primarily (i) by using the modified van Genuchten parameterization of soil hydraulic functions instead of the original one, and (ii) by including a more representative set of soils in the objective function when optimizing the estimation formula.

Rainfall pattern effects on crusting, infiltration and erodibility in some South African soils with various texture and mineralogy

“…This instrument allows water to infiltrate while under tension to prevent the filling of the macropores. Therefore, the resultant hydraulic conductivity is characteristic of the soil matrix, and is less spatially variable (Dohnal et al, 2010;Decagon Devices, 2007). For most soils, water flow in macropores is eliminated when the suction is kept at 0.02 m. However, sandy and clay soils require higher and lower suction, respectively (Decagon Devices, 2007).…”

“…The value of A was then computed using Eq. (3) (Dohnal et al, 2010). (3) where: n and α were the Van Genuchten parameters.…”

On parameterization of heat conduction in coupled soil water and heat flow modelling

“…The soil water retention curves were measured for 100-ccm samples taken at 4 depths below the surface (15,30,45, and 60 cm) using the pressure plate method. The unsaturated hydraulic conductivity for the pressure head of -3 cm was determined using in-situ minidiskinfiltrometer measurements and the empirical relationship proposed by Dohnal et al (2010). The presence and character of the preferential flow were demonstrated by means of a dye tracer applied during an in-situ ponded infiltration experiment (Císlerová 2005).…”

New automatic minidisk infiltrometer: design and testing

“…Dimensionless empirical coefficients A 1 and A 2 in the equation (7) and (8) can be calculated for van Genuchten model parameters of the retention curve of a given soil in accordance with Zhang's method modification published by Dohnal et al (2010): [ ]…”