Determination of the Intrinsic Conducting Porosity From Infiltration Measurements on a Water Repellent Sandy Soil.

Determination of the conducting porosity in soils is of critical importance to infiltration, movement of water, and transport of solute and pollutants through the soil profile.  Different pore characteristics such as tortuosity, surface roughness, and discontinuity influence the conducting porosity in soil.  As soil water repellency (SWR) is present in all types of soils to a certain extent, the issue of water repellent pores has yet to be addressed.  This study was conducted to determine if SWR affects the conducting porosity in soil.  Tension infiltrometer measurements were taken at five pressure heads (-0.3, -3, -7, -10 and -13 cm) using water and equivalent pressures using 95% ethanol (-0.11, -1.31, -2.64, -3.77 and -4.9 cm) at five randomly selected location in a jack pine (Pinus banksiana) forest stand in North Eastern. Alberta.  The total conducting porosity in soil determined from ethanol infiltration was higher (10^-3) than that determined from water infiltration (10^-4) in all the locations.  The effect of SWR on the conducting porosity is related to the degree of water repellency and the pore diameter it is affecting.  A high degree of repellency in larger pores has more influence on the conducting porosity due to the contribution to the total water flux.  To accurately determine the conducting porosity, SWR must be taken into account.