Geoscience Reference
In-Depth Information
Fig. 9.2 Patterns of vertical water flow in a porous medium, as a function of the initial water
content. Shown here are two patterns of water infiltration, in two different ''dry'' and ''wet'' soils,
following infiltration of 40 mm of water containing Brilliant Blue FCF as a dye applied to the
ground surface (Flury et al.
1994
). Reproduced by permission of American Geophysical Union.
Flury et al. (
1994
), doi:
10.1029/94WR00871
. Copyright 1994 American Geophysical Union
the scale of an entire geological layer or aquifer. Heterogeneity of natural porous
media is affected by the various features just mentioned (including macropores,
fissures, fractures, roots, and wormholes), as well as by variability in mineral
composition and mineral distribution at greater depth (recall
Chap. 1
). Fracture
networks dominate preferential flows in clay soils. Also, the soil region (top meters
of the subsurface zone) is particularly susceptible to preferential flow caused by
''biopores.''
Notwithstanding the natural heterogeneity of the subsurface, we can usefully
consider ''homogeneous'' (bulk, effective) descriptions for at least some problems,
especially for water flow (but less so for contaminant migration; see
Sect. 10.1
)
.
Therefore, two basic approaches to modeling generally are used to describe and
quantify flow and transport: continuum-based models and pore-network models.
We discuss each of these here.
