HR: 14:55h
AN: H13H-06    [Abstracts]
TI: Effective Dispersion in Heterogeneous Media: Comparison between Experiments, Inverse Modeling, and First-Order Theory
AU: * Cirpka, O A
EM: Olaf.Cirpka@EAWAG.CH
AF: Swiss Federal Institute for Environmental Science and Technology (EAWAG), \"Uberlandstr. 133, D\"ubendorf, 8600 Switzerland
AU: Nowak, W
EM: Wolfgang.Nowak@IWS.Uni-Stuttgart.DE
AF: Universit\"at Stuttgart Institut f\"ur Wasserbau, Pfaffenwaldring 61, Stuttgart, 70550 Germany
AU: Jose, S C
EM: Surabhin.Jose@IWS.Uni-Stuttgart.DE
AF: Universit\"at Stuttgart Institut f\"ur Wasserbau, Pfaffenwaldring 61, Stuttgart, 70550 Germany
AU: Rahman, M A
EM: Arifur.Rahman@IWS.Uni-Stuttgart.DE
AF: Universit\"at Stuttgart Institut f\"ur Wasserbau, Pfaffenwaldring 61, Stuttgart, 70550 Germany
AB: Effective dispersion is a measure to characterize dilution and solute mixing in heterogeneous aquifers. Here, we compoute the longitudinal effective dispersion coefficient from the second central temporal moment of a breakthrough curve observed at a point. Standard macrodispersion coefficients, by contrast, describe the spread of concentration observed over the entire cross-section of the domain. We have performed conservative tracer tests in a 14m long sandbox filled heterogeneously with four different types of sands. The filling pattern mimics natural sediments, including larger-scale structures created by the different sand types, and micro-structures within the sand lenses created by the sedimentation applied in the filling procedure. We characterize point-related breakthrough curves and curves averaged over all probes within a measurement plane by their temporal moments. The observed effective dispersion is about 2/3 of the standard macrodispersion. We have fitted the semi-analytical expressions for the second central moments of Dentz et al. (2000) and Fiori and Dagan (2000) to the data, finding good qualitative agreement with physically reasonable parameters. The data were also used to identify the distribution of the conductivity field and the field of an apparent scalar dispersion coefficient by geostatistical inversing. The major patterns of conductivity could be identified, and the dispersion coefficient identified was in the order of local transverse dispersion coefficients. The latter indicates that most of the heterogeneity could be resolved in the inversing procedure.
DE: 3260 Inverse theory
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1869 Stochastic processes
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting