Soil Temperature Change over Time during Infiltration

Abstract

Heat of wetting (HOW) effects release energy during infiltration of water into soil and temperature changes result. We call these changes infiltration transient temperature (ITT). Experiments determined ITT frequently during one‐dimensional infiltration events. We measured ITT in columns of silty clay and loam soils, at several initial water contents, during constant‐rate infiltration. There was a directly increasing, but nonlinear, relationship of ITT to clay content and a decreasing, nonlinear relation to initial water content, ranging from 1°C maximum in loam at 0.04 g g−1 initial water content to 11°C maximum in silty clay at 0.00 g g−1 We compared the resulting experimental temperature profiles to those generated from a one‐dimensional soil water and heat transport model using the relevant initial and boundary conditions. The model‐predicted ITT profiles exhibited the major features of the experimentally measured profiles. Disabling the HOW effect part of the model resulted in a much smaller predicted temperature peak and a subsequent temperature decrease below ambient behind the wetting front. Since experiments and a numerical model have shown ITT to be appreciable, it is important to understand more completely the role of HOW in coupled soil water and heat transport.