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| Titel |
Mesoscale connectivity through a natural levee |
| VerfasserIn |
A. E. Newman, R. F. Keim |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 2 ; Nr. 17, no. 2 (2013-02-15), S.691-704 |
| Datensatznummer |
250017718
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| Publikation (Nr.) |
 copernicus.org/hess-17-691-2013.pdf |
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| Zusammenfassung |
| Natural levees are potentially locally important zones of
lateral seepage between stream channels and floodplain
backswamps, because their relatively coarser soils provide
pathways of high hydraulic conductivity in an otherwise low
conductivity system. Therefore, understanding the rates and
mechanisms of subsurface exchange of water and solutes through
natural levees may be necessary for understanding
biogeochemical cycling in floodplains. We measured imposed
hydraulic gradients and solute tracers in 19 shallow
monitoring wells within a 580 m3 volume of natural
levee in the Atchafalaya Basin, Louisiana. We modeled
residence time distributions of pressure and tracers using
a simple linear system to quantify spatially variable
transport velocities and infer dominant flow mechanisms at
a mesoscale. The spatial mean velocity of pressure transport
was faster than the mean velocity of tracer transport by two
orders of magnitude (1.7 × 10−2 and
4.6 × 10−4 m s−1, respectively), and
the variance of pressure velocities was less than the variance
of tracer velocities by seven orders of magnitude
(1.4 × 104 min2 and
7.9 × 1011 min2, respectively). Higher
spatial variability of tracer velocities compared to pressure
velocities indicates different functioning mechanisms of mass
versus energy transport and suggests preferential
flow. Effective hydraulic conductivities, which ranged in
magnitude from 10−1 to
103 m d−1, were higher than would be predicted by soil
texture. We conclude that, in this fine-grained system,
preferential flow paths control water and solute exchange
through natural levees. These findings are important for
future studies of water and solute cycling in riverine
wetlands, and rates of exchange may be particularly useful for
modeling water and nutrient budgets in similar systems. |
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