Determination of Soil Hydraulic Properties from Infiltration Data Using Various Methods

In the present study, the determination of soil saturated hydraulic conductivity (K-s) and soil sorptivity (S) from one-dimensional vertical infiltration data of eight different soils were investigated using three methodologies. Specifically, the nonlinear optimization procedure with the help of the Excel Solver application using six different two-parameter infiltration equations, as described by Valiantzas, Haverkamp et al. (complete, two and three approximate expansions), Talsma and Parlange and Green and Ampt; the linearization method of cumulative infiltration data by Valiantzas and the method of Latorre et al. were used. The results showed that, in almost all cases, the relative errors in the prediction of S were smaller than those of K-s. The nonlinear optimization procedure using the Valiantzas equation gave the best prediction of S and K-s, with relative errors up to -12.49% and 13.61%, respectively. The two-term approximate expansion of Haverkamp gave the highest relative errors in both S and K-s. The various forms of the Haverkamp equation (complete and three approximate expansion), as well as the Latorre method, gave good predictions of S and K-s in fine-textured soils. In all forms of the Haverkamp equation, when parameter beta was considered as an additional adjustment parameter, no improvement in the prediction of the S and K-s values was achieved, so the constant value beta = 0.6 was proposed. The relative errors in the prediction of S and K-s resulting from the linearization method of the cumulative infiltration data were similar to those of the Valiantzas equation by the nonlinear optimization procedure. The accuracy in estimating the S and K-s parameters from each equation depends on its infiltration time validity and the soil type.