Estimation of Soil Hydraulic Parameters Using Inverse Method Based on Specific Liquid-Vapor Interfacial Area Around the Soil Particles

For the simulation of soil water flux, the relationships between the soil hydraulic conductivity, water content and pressure head are required. The relationship between soil water content ( with soil pressure head [h( ] and hydraulic conductivity [K( )] are usually obtained by fitting experimental equations. Describing these relationships, the experimental equations such as van Genuchten (van Genuchten, 1980) have been used. Zand-Parsa and Sepaskhah, (2004) proposed a new method for prediction of the soil hydraulic conductivity function [K( ) based on specific liquid-vapor interfacial area around the soil particles and Zand-Parsa (2006) improved this method for a more straightforward and efficient numerical technique for prediction of function.
The different equations of h ( and K ( ) have three to five soil hydraulic parameters, which vary considerably in different soil groups. For measurements of the soil hydraulic parameters, laboratory and field methods are time consuming and require excessive financial costs; hence, inverse methods have been used by many researchers. Estimation of the soil hydraulic parameters with using the inverse method is usually less costly and time-consuming than the direct methods, especially for in situ characterization of large sites. Soil hydraulic parameters can be predicted using the inverse method, which are the combination of the numerical model with an iteration algorithm, and genetic algorithm for parameter estimation values (Kamali and Zand-Parsa (2016); Mahbod and Zand-Parsa (2010). For a given initial and boundary conditions and soil hydrauic parameters, Richards’ equation can be solved with numerical methods.
In this study, soil hydraulic parameters were estimated by inverse method based on the soil-water characteristic curve of van Genuchten (1980) method, the function of soil hydraulic conductivity- water content obtained by the method of liquid- vapor interfacial area around the soil particles (Zand-Parsa, 2006).