Soil-Water Retention Curve

Abstract

Soil/water retention curve (SWRC) is the relationship between soil/water matric potential and volumetric soil-water content at equilibrium above the reference (zero) level represented by the free water table at atmospheric pressure. SWRC is the basic soil characteristic needed as input data for simulation models. SWRCs have a hysteresis-like character, i.e. this relationship is different for drying and wetting processes. Methods for SWRC measurement are described (pressure method, method of hanging column, psychrometric method, adsorption and desorption methods), as well as methods for their evaluation from measured data. Analytical expressions of the SWRC are presented and evaluations of useful “hydrolimits” like monomolecular water capacity, wilting point, available water capacity and field capacity using SWRC data are described.