Execution Of A Triple Pumping Test And Interpretation By An Inverse Numerical Model

Abstract

The hydraulic parameters of a multi-layered aquifer are deduced with the help of a multiple pumping test. All the observed drawdowns are interpreted simultaneously with an inverse model. It is shown that the vertical hydraulic conductivities of the semi-pervious layers can be deduced with accuracies comparable to those of the horizontal hydraulic conductivities of previous layers. The lithostratigraphic information collected during drilling and geophysical borehole logging can be represented accurately in the numerical model, an axi-symmetric hybrid finite-difference finite-element model. The model starts with the ordinary least squares method. If there are many outliers this method is followed by the biweighted least squares method to reduce their effect on the estimates. The accuracies of the estimates are deduced from their variance-covariance matrix. The method is illustrated by a triple pumping test in the layered groundwater reservoir at the top of the Ieper Group of Flanders (Belgium) and can be considered as a generalized interpretation method of pumping tests.