DefinePK

Abstract

Richards’ equation was used to govern water infiltration into the unsaturated soil. Haverkamp’s hydraulic properties were used to govern the matric pressure head and hydraulic conductivity relations. Sobol’ variance-based method as a global sensitivity analysis tool was coded to study sensitivity and uncertainty values of input parameters. The same input parameters uncertainty values used in Sobol’ variance-based method could be subjected to an inverse method to search for a set of globally optimized input parameters. Therefore, a simple Genetic Algorithm, i.e. an inverse method, was coded and used to improve the current framework for the uncertainty analysis. A simple significant digit approximation method was developed, applied on the input parameters, and the generated uncertainty parameter values were found to cause 15.4 % of error, which could be reduced if the number of input parameter significant digit used in the simulation were increased. The simple Genetic Algorithm was able to search for a set of globally optimized input parameters at a low population size, i.e. 50, on three cases tested and also was found able to handle noise data. Data points at the lower and upper plains of the water infiltration front are necessary for the inverse method.