Determination of Hydraulic Properties in Sloping Landscapes from Tension and Double-Ring Infiltrometers

Abstract

The majority of landscapes, natural or cultivated, are nonlevel. However, specifically designed instruments are not available for estimation of soil hydraulic properties in sloping landscapes. The objective of this study is to examine if tension and double-ring infiltrometers are suitable for determination of soil hydraulic properties on sloping soil surfaces. A field experiment was conducted in a silt loam soil (Typic Haplustolls) in Saskatchewan, Canada to explore the usefulness of tension and double-ring infiltrometers for the determination of soil hydraulic properties in sloping landscapes. Soil surfaces were created to represent four treatments, 0 (level), 7, 15, and 20% slopes. For each treatment, water infiltration rates were measured using a double-ring infiltrometer and a tension infiltrometer at −3, −6, −10, −13, −17, and −22 cm water pressure heads. In addition, three-dimensional computer simulation studies were performed for a tension infiltrometer with various disc diameters and water pressure heads for different surface slopes. Steady-state infiltration rate, field-saturated hydraulic conductivity, unsaturated hydraulic conductivity as a function of water pressure head, macroscopic capillary length parameter, and water-conducting macro- and mesoporosity were compared for different surface slopes. These parameters were not significantly different (p < 0.05) between level and sloping lands. Experimental and numerical results of this study suggest that both tension and double-ring infiltrometers are suitable for characterization of surface soil hydraulic properties in landscapes with slopes up to 20%.