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| Titel |
Gaining and losing stream reaches have opposite hydraulic conductivity distribution patterns |
| VerfasserIn |
X. Chen, W. Dong, G. Ou, Z. Wang, C. Liu |
| 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. 7 ; Nr. 17, no. 7 (2013-07-09), S.2569-2579 |
| Datensatznummer |
250018924
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| Publikation (Nr.) |
 copernicus.org/hess-17-2569-2013.pdf |
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| Zusammenfassung |
| In gaining streams, groundwater seeps out into the streams. In losing streams,
stream water moves into groundwater systems. The flow moving through the
streambed sediments under these two types of hydrologic conditions is
generally in opposite directions (upward vs. downward). The two opposite
flow mechanisms affect the pore size and fine particle content of
streambeds. Thus it is very likely that the opposite flow conditions affect
the streambed hydraulic conductivity. However, comparisons of the hydraulic
conductivity (K) of streambeds for losing and gaining streams are not well
documented. In this study, we examined the K distribution patterns of
sediments below the channel surface or stream banks for the Platte River and
its tributaries in Nebraska, USA. Two contrasting vertical distribution
patterns were observed from the test sites. In gaining reaches, hydraulic
conductivity of the streambed decreased with the depth of the sediment cores. In
losing reaches, hydraulic conductivity increased with the depth of the
sediment cores. These contrasting patterns in the two types of streams were
mostly attributed to flow directions during stream water and groundwater
exchanges. In losing reaches, downward movement of water brought fine
particle into the otherwise coarse sediment matrix, partially silting the
pores. For gaining reaches, upward flow winnowed fine particles, increasing
the pore spacing in the top parts of streambeds, leading to higher hydraulic
conductivity in shallower parts of streambeds. These flux directions can
impact K values to depths of greater than 5 m. At each study site, in situ
permeameter tests were conducted to measure the K values of the shallow
streambed layer. Statistical analyses indicated that K values from the sites
of losing reaches were significantly different from the K values from the
sites of gaining reaches. |
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