A quasi 3D hydrodynamical model of the Dogger aquifer in the Paris area has been established through a finite difference scheme. The model has appeared able to describe some real charateristics of the Dogger (piezometry, transmittivity, salt, helium and Carbon 14 distributions). A discordance between Darcy speeds derived from the hydrodynamical model (0.15 m/y) and localized dilution findings (15-17 m/y) is shown. It could be explained by an interference phenomenon in the measuring wells or a flow-thermal transfer-salt transfer coupling phenomenon that had not been taken into account in the model. Results indicate that the first hypothesis should be the good one.