New Method for Determining Water‐Conducting Macro‐ and Mesoporosity from Tension Infiltrometer

Abstract

Characterization of water‐conducting porosity at and near saturation is required in understanding rainfall and snowmelt infiltration and runoff as well as chemical transport in soil. There are methods available to quantify water‐conducting porosity in situ, but with serious limitations. The objective of this paper was to present a general equation for water‐conducting porosity based on ponded‐ and tension‐infiltration measurements. Some analytical solutions are developed for specific unsaturated hydraulic conductivity functions such as the Gardner's exponential and rational power models, Brooks and Corey model, and van Genuchten–Mualem model. Tension infiltrometer measurements were taken at six different pressure heads between −0.3 to −2.2 kPa and double‐ring infiltrometer measurements at a pressure head of 0.35 kPa. The analytical solutions were compared with numerical solutions and existing methods for calculation of water‐conducting porosity. Both the analytical and numerical solutions can reliably determine the water‐conducting porosity of surface soils in situ within the practical pressure head range of the tension infiltrometer. Our method gave consistent water‐conducting porosity, regardless of the width of pressure head ranges. The existing methods overestimated water‐conducting macroporosity by a factor of greater than two and overestimated total water‐conducting porosity by a factor of >10 for measurements taken at large pressure head intervals compared with that of our method. Combining with hydraulic parameter estimation from tension infiltrometer measurements, our method may reduce the number of tension infiltration measurements required to calculate water‐conducting porosity.

Stabilization of soil hydraulic properties under a long term no-till system

“…This introduces an inconsistency, however, because K in equation 2 relates to the range of pore sizes participating in water transmission, whereas equivalent r, equation 1, relates to the maximum pore size for water storage (Bodhinayake et al, 2004). Reynolds et al (1995) proposed using the flow-weighted mean pore radius R 0 (L), which represents an effective equivalent mean pore radius that is conducting water at a certain supply pressure head, and it has been used to characterize temporal and tillage-induced changes in water-conducting macropores (Messing & Jarvis, 1993;Reynolds et al, 1995;Sauer et al, 1990;Schwen et al, 2011).…”

“…Watson & Luxmoore (1986) calculated the water-conducting porosities using the minimum equivalent pore radius r in the range (Equation 1). However, this introduces an inconsistency because K in equation 2 relates to the range of pore sizes participating in water transmission, whereas the equivalent r relates to the maximum pore size for water storage (Bodhinayake et al, 2004). As stated by Reynolds et al (1995), R 0 , compared to storage-based C, better Table 1.…”

“…The tension disc infiltrometer is a valuable tool for understanding water movement through macropores and the soil matrix near saturation (Watson & Luxmoore, 1986;Logsdon & Jaynes 1993;Moret & Arrúe, 2007), and for studying the effects of different practices on soil surface hydraulic properties (Malone et al, 2003;Moret & Arrúe, 2007). This device allows estimation of K from saturation to a few centimeters of suction head (Angulo-Jaramillo et al, 2000;Soracco, 2009) and quantification of the role of macropores during infiltration (Bodhinayake et al, 2004). This technique requires only minimal disturbance of the soil.…”

Advances in Canadian Peatland Hydrology, 2003-2007

“…extended the applicability of the Guelph permeameter method to peat soils underlain by an impermeable boundary, such as bedrock or permafrost, with a new set of shape factors determined by numerical simulation. Other researchers have focussed on alternative means of in-situ measurement of peat permeability, including water tracing (Weiler and Naef, 2003;Quinton and Gray, 2003), and tension infiltrometer measurements at successive pressure heads (Bodhinayake et al, 2004). Carey et al (2007) measured the water conducting porosity of organic soils for different pore radii ranges using the method proposed by Bodhinayake et al (2004) and compared these values to active pore size distributions from laboratory thin sections and pressure plate analysis.…”

Effects of Compaction Due to Machinery Traffic on Soil Pore Configuration

“…The tension disc infiltrometer is a valuable tool for understanding water movement through macropores and the soil matrix under near saturation conditions (Watson and Luxmoore, 1986;Logsdon and Jaynes, 1993;Moret and Arrúe, 2007). This device allows estimation of K from saturation to a few centimeters of suction head (Angulo-Jaramillo et al, 2000) and quantification of the role of macropores during infiltration (Bodhinayake et al, 2004;Soracco et al, 2012). This technique requires only minimal soil disturbance.…”