hysteresis: phenomenon and modeling in soil- water relationship

hysteresis has been widely recognized in the soil water relationship. in this paper, a detailed review of hysteresis was performed in relation to its models. so far, different models have been suggested to describe hysteresis in the water retention curve (wrc) that could be categorized into two main groups: conceptual and empirical models. the models in the first group are based on the domain theory of capillary hysteresis and those in the second group rely on the analysis of observed wrc shape and properties. conceptual models include the independent and dependent domain theories and the parlange's model, while empirical models consist of the interpolation, linear, slope and scaling – down models. different results of studies carried out by several researchers showed that the parlange model, that uses the concept of rational extrapolation, was the best model to predict hysteresis of the wrc.