Effect of Temperature on Pressure Head‐Water Content Relationship and Conductivity of Two Soils

Abstract

AbstractA series of experiments was conducted in the laboratory to study the effect of temperature on pressure head‐water content relationship and on hydraulic conductivity as a function of water content and pressure head in two silt loam soils. Hydraulic conductivity was determined as a function of water content and pressure head at constant temperatures of 15, 25, and 35C by steady state and pressure plate outflow methods.The temperature dependence of pressure head‐water content relationship during pressure plate outflow could not be explained on the basis of changes in surface tension of air‐water interfaces alone. Pressure head‐water content relationship under steady state flow conditions was found to be different from that under transient flow conditions during pressure plate outflow. Desorption curves obtained at the three temperatures under steady state flow conditions did not reflect any temperature effects.Results of the steady state experiments were too variable to reflect any temperature dependence of hydraulic conductivity either as a function of water content or as a function of pressure head of soil water. Hydraulic conductivity as a function of soil water content was found to be more temperature dependent than as a function of pressure head of soil water in pressure plate outflow experiments. The increase in hydraulic conductivity at a given water content due to temperature rise is almost entirely accounted for by the decrease in viscosity of water.