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| Titel |
Longitudinal dispersion in natural channels: 2. The roles of shear flow dispersion and dead zones in the River Severn, U.K. |
| VerfasserIn |
P. M. Davis, T. C. Atkinson, T. M. L. Wigley |
| 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 ; 4, no. 3 ; Nr. 4, no. 3, S.355-371 |
| Datensatznummer |
250001744
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| Publikation (Nr.) |
 copernicus.org/hess-4-355-2000.pdf |
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| Zusammenfassung |
| The classical one-dimensional advection-diffusion equation (ADE) gives an
inadequate description of tracer cloud evolution in the River Severn, U.K. A
solute transport model incorporating the effects of tracer storage in dead zones
is presented in which the channel is conceived as being divided into two
parallel regions. The bulk flow region occurs in the central part. Its
longitudinal dispersive properties are described by the ADE. Adjacent to this,
an additional cross-sectional area is defined in which tracer can be stored
temporarily in regions of slowly moving water called dead zones. Exchange
between the two regions follows a first order rate equation. Applying the model
to the River Severn shows that a dispersing cloud’s evolution occurs in two
distinct stages with a rapid transitional phase. Initially, shear-dispersion is
dominant while the tracer particles mix fully over the bulk flow. Once this has
occurred, dead zone storage accounts well for the non-Fickian evolution of the
cloud. After the transitional phase the dead zone storage mechanism clearly
dominates over shear-dispersion. Overall, the combined shear flow dispersion –
dead zone model (D-DZM) provides a much better, physically consistent
description of the tracer cloud’s evolution than the simple classical ADE
approach can do alone.
Keywords: Channels; dispersion; dead
zones; tracers; River Severn |
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