 Matric potential hysteresis arises from differences in wetting behaviour causing dry medium to re-wet; that is, it depends on the saturation history of the porous medium.Hysteretic behaviour means that, for example, at a matric potential (Ψm) of , the volumetric water content (θ) of a fine sandy soil matrix could be anything between 8% to 25%.Tensiometers are directly influenced by this type of hysteresis.