Analyzing the Effects of Irrigation on the Sensitivity and Estimability of Soil Hydraulic Parameters

Abstract

Parameter estimation is a significant aspect of modeling flow through porous media. To avoid any nonuniqueness issues in parameters estimation, it is important to have a deep understanding of the information content and reliability of the available data. In this study, sensitivity and estimability analyses were conducted to compare the outcomes of two successive irrigation events. Water flow through soil was simulated using HYDRUS-2D for two successive irrigation periods. Sensitivity coefficients were evaluated to quantify the sensitivity of pressure head, water content, and cumulative fluxes to five crucial soil hydraulic parameters (namely, θs, θr, n, Ks, and α). The estimability analysis is further extended to determine the correlation among these parameters. Results show that sensitivity of pressure head, water content, and cumulative fluxes to the parameters is higher after the first irrigation event in comparison to the second one. The parameters were also found to be more estimable during the first irrigation event. The pressure head was proved to contain the best information content, followed by water content data. It was also inferred that cumulative fluxes data are not suitable to estimate parameters individually. Out of the five parameters, θs was found to be the most sensitive and estimable parameter, while θr comes out to be the least sensitive and estimable parameter. This study helps in estimating the information content of the available data and identifying the most estimable parameters with the least correlation.