Calibration and Reliability in Groundwater
Modelling: Credibility of Modelling
(Proceedings of ModelCARE 2007 Conference, held in
Denmark, September 2007). IAHS Publ. 320, 2008, 262-266.
A new approach for the stochastic inversion of flow and transport data:
application to the macrodispersion experiment (MADE-2) site
C. LLOPIS-ALBERT & J. E. CAPILLA
Institute for Water and Environmental
Engineering, Technical University of Valencia, Camino de Vera s/n.,
46022 Valencia, Spain
Abstract A large-scale natural-gradient tracer
experiment conducted in a highly heterogeneous aquifer at the Macrodispersion
Experiment (MADE-2) site on Columbus Air Force Base in Mississippi, USA, is
simulated using a new 3-D stochastic inverse modelling technique for the
construction of transmissivity (T) fields in a non-multiGaussian framework,
which is based on the gradual deformation method. The method, as presented in
this study, can adopt any random function model defined by the local
conditional cumulative density functions (ccdfs) and the spatial structure is determined by the probability fields.
Moreover, it is also able to include secondary data
obtained from expert judgment or from geophysical surveys. The method has succeeded where many
other investigations have failed. The new methodology implements a dual-domain
mass transfer approach that, together with conditioning to T data, transient pressures (p) and concentration (c) data, in a non-multiGaussian
approach, has allowed the reproduction of the heavy tailing of the tracer plume
as observed in the field. This also illustrates the importance of preferential
flow paths on the anomalous tracer plume spreading at the MADE site. Besides,
an uncertainty assessment of contaminant transport has been carried out using
the Monte Carlo method with the aid of the stochastic models.
Key words stochastic inversion; gradual deformation; geostatistics; mass transport; tracer test; secondary data; non-multiGaussian; backward-in-time probabilities