Comparison of soil-water hysteresis models

Abstract

Four methods for calculating the hysteretic differential soil-water capacity, dϑdP, are described and compared. The methods included three procedures used in earlier studies and a fourth method that uses the slope of the soil-water characteristic. The methods were chosen because they are easy to use and require only the main hysteresis curves of the soil-water characteristic to generate all higher-order curves. Two methods, the Point and Slope methods, showed considerable pumping when the soil-water pressure was cycled between − 36 and − 25 cm for a typical soil. These methods would not be satisfactory when numerous wetting-drying cycles are to be modeled. None of the methods was consistently better than the others for simulating primary wetting or drying curves for three test soils. Also, each method performed equally well when used as part of a numerical model for simulating hysteretic flow. However, because of the simplicity of use and limited storage requirements, the Linear method appears to be the method of choice for calculating the hysteretic differential soil-water capacity for most modeling applications.