Wetting is defined as the process leading to increase in water content of an unsaturated soil upon ingress of water. Drying is defined as the process leading to reduction in water content and degree of saturation of a soil due to evaporation or evapotranspiration.

Where does wetting and drying occur?

Wetting and drying is common along coastlines. Clay-rich rocks are prone to expand when they are wet and contract when they dry. This results in cracks which are vulnerable to both freeze-thaw and salt crystallisation.

How alternate wetting and drying works?

This is Alternate Wetting and Drying (AWD), whereby the soil is not kept continuously flooded. Instead, it is allowed to drain for a period of one or more days after the ponded water has disappeared, before being re-flooded (Lampayan, Rejesus, Singleton, & Bouman, 2015).