ABSTRACT
The two frequently encountered phenomena in soils-thermal and hydraulic-involving movement of water in the soil in response to thermal-and hydraulic-driven processes, produce changes in soil water content and porewater chemistry. Correspondingly, there will also be changes in solute content and advective-diffusive transfer of solutes in the soil. In hydraulicdriven processes, water content increases and/or decreases are the direct result of movement of water from one location to another under water content gradients, or movement of water from a water source under hydraulic gradients. In thermal-driven processes, water content changes are due to two different mechanisms occurring simultaneously: (a) water transfer (liquid water and vapour) in response to temperature gradients, thereby creating water content gradients, and (b) water movement because of the water content gradients. These two mechanisms of water movement have been termed as heat-mass simultaneous movement processes or heat-mass coupling phenomena by de Vries (1958). In this chapter, we will be concerned with hydraulic properties in relation to hydraulic-driven processes, and thermal and hydraulic properties of soils in heat-mass coupling phenomena.
