Spatial Variability of Steady‐State Infiltration Rates as a Stochastic Process

Abstract

Steady‐state infiltration rates were measured in a field plot with infiltrometers of 5‐, 25‐, and 127‐cm inside diameter. Measurements were made with the three ringsizes along five parallel transects, spaced 125 cm apart. The infiltrometers were placed adjacent to each other along each transect (i.e., one hundred twenty‐five 5‐cm rings, twenty‐five 25‐cm rings, and five 127‐cm rings per transect). Infiltration rates were found to be lognormally distributed for all ringsizes and autocorrelated for the 5‐cm ringsize. The 5‐cm data showed that a large fraction of the water infiltrated through a small fraction of the plot area. Autocorrelation functions were determined and power spectrums computed. A first‐order autoregressive process was found to describe the 5‐cm data, and variances of samples composited along a transect agreed with sample variances. The variances for the 25‐ and 127‐cm infiltrometers were compared with sample variances, assuming a simple two‐dimensional autocovariance function. Agreement was found for the 127‐cm rings, but not for the 25‐cm rings.

Infiltration into soils: Conceptual approaches and solutions

“…In most of the cases, the field saturated hydraulic conductivity K s was lognormally distributed [Reynolds and Elrick, 1985;White and Sully, 1992;Russo et al, 1997]. However, steady-state infiltration fluxes and soil surface water content distributed either normally or lognormally [Vieira et al, 1981;Sisson and Wierenga, 1981;Loague and Gander, 1990;Kutilek et al, 1993;Cosh et al, 2004]. Several studies have dealt with modeling the effect of spatial variability of soil hydraulic properties on infiltration [Smith and Hebbert, 1979;Warrick and Nielsen, 1980;Dagan and Bresler, 1983;Sivapalan and Wood, 1986;Milly and Eagleson, 1988;Woolhiser et al, 1996;Assouline and Mualem, 2002;Govindaraju et al, 2006].…”

Heterogeneity of Infiltration Rates in Alluvial Floodplains as Measured with a Berm Infiltration Technique

“…Germann (1981, 1982) suggest an REV for macropore porosity that would occur at a length scale of two to three orders of magnitude higher than an REV for the micropore porosity. Increasing the diameter of double ring infiltrometers has been found to reduce the variability of measured infiltration rates (Sisson and Wierenga, 1981;Lai and Ren (2007). However, whether double ring infiltration can be scaled up to the plot or field scale has not been well established.…”

Berm Method for Quantification of Infiltration at the Plot Scale in High Conductivity Soils

“…It is unknown how well point measurements of infiltration can be extrapolated to the plot or field scale. Sisson and Wierenga (1981) studied the effect of increasing the double ring infiltrometer diameter (up to 127 cm) on steady-state infiltration and reported increasing variability with smaller ring sizes. Lai and Ren (2007) also found that larger double ring infiltrometers (>80 cm) were necessary to reduce variability in measured infiltration rates.…”