Using sparse polynomial chaos expansions for the global sensitivity analysis of groundwater lifetime expectancy in a multi-layered hydrogeological model

Authors

Deman, G., Konakli, K., Sudret, B., Kerrou, J., Perrochet, P. and Benabderrahmane, H.

Abstract

The present study makes use of polynomial chaos expansions to compute Sobol’ indices in the frame of a global sensitivity analysis of hydro-dispersive parameters in a synthetic multi-layered hydrogeological model. The model introduced in this paper is a simplified vertical cross-section of a segment of the subsurface of the Paris Basin. This 15-layer numerical model is aimed at exploring the behavior of groundwater and solute fluxes when accounting for uncertain advective and dispersive parameters. Applying conservative ranges, the uncertainty in the input variables is propagated upon the mean lifetime expectancy of water molecules departing from a specific location within a highly confining layer situated in the middle of the numerical model. The sensitivity analysis indicates that the variability in the mean lifetime expectancy can be sufficiently explained by the uncertainty in the petrofacies, i.e. the sets of porosity and hydraulic conductivity, of only a few layers of the model.