Simplified determination and sensitivity analysis of soil-moisture retention curves and hydraulic conductivity

Abstract

A simple algorithm is presented that estimates the parameters contained in the Van Genuchten analytical soil-moisture characteristic curves. No graphical estimations are involved and convergence is rapid. The values obtained from the simple algorithm are introduced as starting values in a Newton-Raphson minimization procedure which yields more accurate evaluations of the parameters. The very good approximation offered by the simple algorithm is responsible for the small number of subsequent Newton-Raphson iterations. Based on the final results of the minimization scheme an analytical sensitivity analysis is carried out with respect to changes induced in the basic parameter “residual water content”. Soils with a wide range of hydraulic properties were subjected to the above analysis. It is demonstrated that for lower water contents the sensitivity of the hydraulic conductivity becomes by 2–5 orders of magnitude larger than it is for higher ones.