Temperature Dependence of Soil Hydraulic Properties

Abstract

AbstractThe study of soil water movement under nonisothermal conditions requires knowledge of the hydraulic properties as a function of temperature. A dual‐energy gamma system was used to investigate temperature effects on the water retention curve and the hydraulic conductivity function of a Norfolk sandy loam soil (Typic Paleudults). These hydraulic properties were determined from simultaneous measurements of soil water pressure head, volumetric water content, and soil temperature at 13 measurement points along a lucite flow cell during transient drainage conditions while maintaining a temperature gradient. It was concluded that temperature influences water retention more than can be explained by surface tension changes of pure water only. Entrapped air was not considered to be the primary cause of the larger temperature effect. The influence of temperature on measured hydraulic conductivities was close to predictions from viscosity changes for most of the measurement points. Deviations from predicted hydraulic conductivity values were attributed to thermal vapor flow. Temperature had little or no effect when the hydraulic conductivity was plotted vs. soil water pressure head.