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The impact of medium architecture of alluvial settings on non-Fickian transport

Advances in Water Resources

By:
, , and
DOI: 10.1016/j.advwatres.2013.01.004

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Abstract

The influence of heterogeneous architecture of alluvial aquifers on non-Fickian transport is explored using the Monte Carlo approach. More than two thousand high-resolution hydrofacies models representing seven groups of alluvial settings are built to test the effects of varying facies proportions, mean length and its anisotropy ratio, juxtapositional tendencies, and sub-facies heterogeneity. Results show that the volumetric fraction (P(Z)) of floodplain layers classified by their thicknesses Z controls the non-Fickian tailing of tracer transport at late times. A simple quantitative relationship SBTC≈SP(Z)/2-1 is built based on a multi-rate mass transfer analysis, where SBTC is the slope of the power-law portion of tracer breakthrough curve, and SP(Z) denotes the slope of the power-law portion of the distribution of P(Z) which can be measured, e.g., in core logs. At early times, the mean length of hydrofacies affects the non-Fickian tailing by controlling the channeling of flow in high-permeability non-floodplain materials and the sequestration in surrounding low-permeability floodplain layers. The competition between channeling and sequestration generates complex pre-asymptotic features, including sublinear growth of plume mean displacement, superlinear growth of plume variance, and skewed mass distribution. Those observations of the influence of medium heterogeneity on tracer transport at early and late times may lead to development of nonlocal transport models that can be parameterized using measurable aquifer characteristics.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The impact of medium architecture of alluvial settings on non-Fickian transport
Series title:
Advances in Water Resources
DOI:
10.1016/j.advwatres.2013.01.004
Volume
54
Year Published:
2013
Language:
English
Publisher:
Elsevier
Contributing office(s):
Branch of Regional Research-Western Region
Description:
22 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Advances in Water Resources
First page:
78
Last page:
99
Number of Pages:
22