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| Titel |
Reliability of in-stream retention metrics |
| VerfasserIn |
Jevgenijs Savickis, Mattia Zaramella, Andrea Marion |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132891
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| Publikation (Nr.) |
 EGU/EGU2016-13438.pdf |
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| Zusammenfassung |
| The temporary solute retention within transient storage zones (TSZs) has been shown to have
a large effect on the transport of solute. This retention can significantly increase the overall
in-stream residence time and as consequence increase the contact time of solute with
aquatic interfaces (biota, sediment) and living species. An important question that
arises is whether the currently available metrics adequately represent retention
mechanism. This work attempts to investigate the reliability of two existing measures, the
hydrological retention factor (Rh) and the fraction of median travel time due to
transient storage zone (Fmed200). For this purpose, five conservative tracer tests
were conducted in four European streams with distinct morphological, sediment
composition, vegetation and hydraulic characteristics. The obtained breakthrough
curves (BTCs) were used to derive storage zone parameters (storage zone area,
storage zone exchange coefficient and mean residence time), which then were used
for comparison and in the metric expressions. The storage zone parameters were
computed using a single TSZ model OTIS-P and a multiple TSZ model STIR. The
STIR model was applied to BTCs as an additional tool to separate TSZs into short
timescale (ST) and long timescale (LT). The study results reveal correlation between
Fmed200 and LT residence time T2 values, where the streams with the lowest Fmed200
(0.01-0.96) have the smallest long timescale storage zones T2 values, ranging from
912 s to 1402 s. The findings also demonstrate an influence of discharge rate on
both retention metrics. The greatest Fmed200 (6.19) and Rh (0.938) values are
calculated for the streams with low discharge rates (0.08-0.10 m3s−1) and a relatively
high ST storage zone residence times T1 (159 s to 351 s). Results show that the
Fmed200 and Rh metrics are strongly affected by the short timescale transient storage
zones, whereas the LT storage zones (hyporheic) effects are not taken into account. |
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