Testing steady-state analysis of single-ring and square pressure infiltrometer data

Abstract

Testing reliability of the saturated soil hydraulic conductivity, K s , estimated by applying the steady-state singlering (SR) model to the quasi steady-state infiltration rates obtained with a single-ring pressure infiltrometer (PI) increases confidence in the estimated K s values. Determining a means to estimate K s from infiltration data collected with a square infiltrometer allows the use of sources of different shapes. Using numerically simulated infiltration rates for six homogeneous soils ranging in texture from sand to silty clay loam, this investigation suggested an overall good performance of the SR model, with estimated K s values differing by not more than 25% from the true values for the 90% of the 96 considered runs. Larger errors were generally obtained for the silty clay loam soil. Even in this case, however, a small ring radius (0.038 m), a relatively high initial soil water content (initial effective saturation = 0.4) and a relatively high depth of ponding (0.10 m) allowed the obtainment of accurate predictions of K s (error = 13%) with a run of practically sustainable duration (4 h). The SR model was also usable to analyze quasi steady-state infiltration data collected with a square infiltrometer when infiltration was assumed to occur through a circular source having the same area of the square infiltrometer. With this assumption, the estimates of K s differed from the true values by not more than a practically negligible 16%. The results of this investigation should help better interpret K s values obtained with the PI and also improve the experimental methodology, depending on the soil. Moreover, a wider applicability of the infiltrometer techniques, i.e. not limited to a circular source, can be expected. Soil heterogeneity should be taken into account in the future since heterogeneity is common in the field.

Accuracy of Saturated Soil Hydraulic Conductivity Estimated from Numerically Simulated Single‐Ring Infiltrations

“…Numerically simulated data were used by Reynolds (2013) to assess different borehole infiltration analyses for determining K s in the vadose zone. Bagarello et al (2016) used numerical simulation of a single‐ring infiltration process to test the single‐level, steady‐state analysis developed for the PI (Reynolds and Elrick, 1990).…”

Source shape and data analysis procedure effects on hydraulic conductivity of a sandy-loam soil determined by ponding infiltration runs

“…According to Bagarello et al (2016), Ks can be determined by using the steady-state infiltration data collected by a square infiltrometer and the relationships by Reynolds and Elrick (1990) because it is possible to assume that infiltration occurred through a circular surface having the same area of the surface sampled by the square infiltrometer. In other terms, the equivalent radius, req (L), that replaces r in Eq.…”

The layering of a mountain podzol can strongly affect the distribution of infiltrated water in the soil profile

“…continuity and tortuosity of the porous system, the occurrence of macropores). Direct measurements of K s are therefore irreplaceable, although it is a very difficult task to measure K s properly (Bagarello et al, 2014(Bagarello et al, , 2016Jačka et al, 2014;Reynolds et al, 2000). The coefficient of variation (CV) of measured K s within a single soil layer is often higher than 100%, even at the plot scale (Jačka et al, 2016(Jačka et al, , 2014Webb et al, 2000).…”