Diffusion experiments cannot be performed at the formation scale because of time constraints. However, profiles of natural tracers (Section 4.6) offer an opportunity to test the applicability of transport properties derived in the laboratory on small samples. For instance, the observed profiles of stable water isotopes and of Cl in porewater in the Benken borehole have been modelled based on several assumptions. The following conclusions were drawn (Gimmi et al. 2007, Gimmi & Waber 2004): (1) No signature of advection could be detected in the profile shapes; the development of the profiles is dominated by molecular diffusion. (2) Using laboratory-derived diffusion coefficients adjusted for the higher in-situ temperature, an evolution time for the signature towards the Keuper aquifer consistent with the palaeo-hydrogeological history could be obtained. Thus, laboratory-derived diffusion coefficients are relevant also at the formation scale. Similar conclusions were drawn from a broad study that compared profiles of several natural tracers at various sites in several countries including the Mont Terri rock laboratory (Mazurek et al. 2011) and from the recent modelling of profiles of e.g. stable water isotopes obtained in the three siting regions (Section 4.6). There, porosities and diffusion coefficients that vary with depth according to the measured laboratory parameters and the measured temperature trend for each site were used. This led to a good match with the measured tracer profiles for plausible timing of events (with respect to the palaeo-hydrogeological evolution) in each aquifer.