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| Titel |
A Critical Analysis of the Concept of Scale Dependent Macrodispersivity |
| VerfasserIn |
Alraune Zech, Sabine Attinger, Vladimir Cvetkovic, Gedeon Dagan, Peter Dietrich, Aldo Fiori, Yoram Rubin, Georg Teutsch |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113763
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| Publikation (Nr.) |
 EGU/EGU2015-14924.pdf |
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| Zusammenfassung |
| Transport by groundwater occurs over the different scales encountered by moving solute
plumes. Spreading of plumes is often quantified by the longitudinal macrodispersivity αL
(half the rate of change of the second spatial moment divided by the mean velocity). It was
found that generally αL is scale dependent, increasing with the travel distance L of the plume
centroid, stabilizing eventually at a constant value (Fickian regime).
It was surmised in the literature that αL scales up with travel distance L following a
universal scaling law. Attempts to define the scaling law were sursued by several authors
(Arya et al, 1988, Neuman, 1990, Xu and Eckstein, 1995, Schulze-Makuch, 2005), by fitting
a regression line in the log-log representation of results from an ensemble of field experiment,
primarily those experiments included by the compendium of experiments summarized by
Gelhar et al, 1992.
Despite concerns raised about universality of scaling laws (e.g., Gelhar, 1992, Anderson,
1991), such relationships are being employed by practitioners for modeling multiscale
transport (e.g., Fetter, 1999), because they, presumably, offer a convenient prediction tool,
with no need for detailed site characterization. Several attempts were made to provide
theoretical justifications for the existence of a universal scaling law (e.g. Neuman, 1990 and
2010, Hunt et al, 2011).
Our study revisited the concept of universal scaling through detailed analyses of field data
(including the most recent tracer tests reported in the literature), coupled with a thorough
re-evaluation of the reliability of the reported αL values. Our investigation concludes that
transport, and particularly αL, is formation-specific, and that modeling of transport cannot be
relegated to a universal scaling law. Instead, transport requires characterization of aquifer
properties, e.g. spatial distribution of hydraulic conductivity, and the use of adequate models. |
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