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Calibration and Reliability in Groundwater Modelling: From Uncertainty to Decision Making (Proceedings of ModelCARE’2005, The Hague, The Netherlands, June 2005). IAHS Publ. 304, 2006. pp.227–233.

A composite medium approach for probabilistic modelling of contaminant travel time distribution to a pumping well in a heterogeneous aquifer

M. Riva¹, L. Guadagnini¹, A. Guadagnini¹, E. Martac² & T. ptak³

1 Politecnico di Milano, D.I.I.A.R., Piazza Leonardo da Vinci 32, I-20133 Milano, Italy

monica.riva@polimi.it

2 Universität Tübingen, Tübinger Grundwasserforschungsinstitut TGF, Institut für Geowissenschaften, D- 72076 Tübingen, Germany

3 Geosciences Centre (GZG), University of Göttingen, Goldschmidtstrasse 3, D-37077 Göttingen, Germany

Abstract We analyse the probabilistic nature of the time of travel of conservative solutes to a pumping well operating within a heterogeneous aquifer. The latter is modelled as a three-dimensional, doubly stochastic composite medium, where distributions of geological materials and hydraulic properties are uncertain. The problem is tackled within a numerical Monte Carlo framework. We study the importance of uncertain facies geometry and uncertain hydraulic conductivity and porosity on predictions of solute time of travel to the pumping well by focusing on two special cases in which: (1) the facies distribution is random, but the hydraulic properties of each material are fixed, and (2) both facies geometry and material properties vary.

Keywords capture zones; composite media; heterogeneity; uncertainty estimation; well fields