Alternative estimation of the soil water retention curve based on the arya-paris model

ABSTRACT: The physical and chemical characteristics of a soil determine its hydraulic properties, such as hydraulic conductivity, infiltration, and moisture. Due to the usefulness of a soil's moisture retention characteristic curve, several methodologies have been developed to obtain it. Mathematical models for the prediction of this hydraulic property constitute a type of methodologies that is economical and very affordable. One of the most practical models is the model of Arya and Paris (1981), which, however, requires an adjustment parameter, which limits its applicability in some cases, and, in addition, underestimates the moisture content by not considering the water remaining in the soil menisci. The present study proposes an alternative model based on the model of Arya and Paris, but that attempts to circumvent the disadvantages mentioned above, assuming a pore network formed by conical pores. The predictions of the moisture retention curve of our alternative model were compared with those of the original model through the root mean square error, using experimental data from 100 soils of three different textural classes, taken from the UNSODA database. The results by texture indicate that the alternative model generally produces better estimates for all three textures; however, for 17% of the soils the Arya and Paris model performed better. Keywords: water retention curve, retention, soil, porosity, volume.