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| Titel |
Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients |
| VerfasserIn |
S. Krause, T. Blume, N. J. Cassidy |
| 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 ; 16, no. 6 ; Nr. 16, no. 6 (2012-06-29), S.1775-1792 |
| Datensatznummer |
250013333
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| Publikation (Nr.) |
 copernicus.org/hess-16-1775-2012.pdf |
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| Zusammenfassung |
This paper investigates the patterns and controls of aquifer–river exchange
in a fast-flowing lowland river by the conjunctive use of streambed
temperature anomalies identified with Fibre-optic Distributed Temperature
Sensing (FO-DTS) and observations of vertical hydraulic gradients (VHG).
FO-DTS temperature traces along this lowland river reach reveal discrete
patterns with "cold spots" indicating groundwater up-welling. In contrast
to previous studies using FO-DTS for investigation of groundwater–surface
water exchange, the fibre-optic cable in this study was buried in the
streambed sediments, ensuring clear signals despite fast flow and high
discharges. During the observed summer baseflow period, streambed
temperatures in groundwater up-welling locations were found to be up to 1.5 °C lower than ambient streambed temperatures. Due to the high river
flows, the cold spots were sharp and distinctly localized without measurable
impact on down-stream surface water temperature.
VHG patterns along the stream reach were highly variable in space, revealing
strong differences even at small scales. VHG patterns alone are indicators
of both, structural heterogeneity of the stream bed as well as of the
spatial heterogeneity of the groundwater–surface water exchange fluxes and
are thus not conclusive in their interpretation. However, in combination
with the high spatial resolution FO-DTS data we were able to separate these
two influences and clearly identify locations of enhanced exchange, while
also obtaining information on the complex small-scale streambed
transmissivity patterns responsible for the very discrete exchange patterns.
The validation of the combined VHG and FO-DTS approach provides an effective
strategy for analysing drivers and controls of groundwater–surface water
exchange, with implications for the quantification of biogeochemical cycling
and contaminant transport at aquifer–river interfaces. |
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