Spreadsheet Optimization for Parameter Estimation of Pressure-Saturation Equations Used for Two-Phase Groundwater Flow

摘要

Spreadsheet optimization using a range of nonlinear error functions was utilized for parameter estimation of the two-phase pressure-saturation models developed by van Genuchten, Brutsaert, Russo and Kosugi. The data was obtained from the UNSODA database (US Salinity Laboratory, Riverside, California). Results show that spreadsheet opti-mization is a practical platform for evaluations based on minimizing nonlinear error functions, consequent-ly allowing for a broader mathematical approach to parameter estimation. An error function representing the sum of the squares of errors provided the best fit for a majority of the soils evaluated, although the frac-tional error function provided the best fit for silts and loams. Outcomes indicated that the van Genuchten parameters m and n may also be estimated individually as opposed to following the published relationship of m= 1 - 1.