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| Titel |
Seasonal hyporheic temperature dynamics over riffle bedforms |
| VerfasserIn |
D. M. Hannah, I. A. Malcolm, C. Bradley |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020948
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| Zusammenfassung |
| There is growing interest in riverbed temperature due to the ecological and biogeochemical
significance of the hyporheic zone, and its potential to moderate river temperature. Riffles
exhibit complex thermal behaviour, hypothesised to be caused by local alteration of
groundwater-surface water (GW-SW) interactions; but hitherto most research has been in
upland/ gravel-bed/ hard rock catchments. Accordingly, this article aims: (1) to characterise
spatio- temporal variability in hyporheic temperature over two riffles (R1 and R2) in a
lowland river basin (Tern, Shropshire, UK) underlain by sandstone; and (2) to explain thermal
dynamics by inferring hyporheic processes and the influence of GW-SW interactions.
Hyporheic [riffle head, crest and tail at 0.1, 0.2 and 0.4 m], water column, spring water and
air temperature were collected at 15 min resolution over 22 months and used to
explore seasonal variations. Borehole water levels and temperature provide insight
into groundwater variability over a hydrological year. Hyporheic temperature is
cooler (warmer) than water column in summer (winter), with convergence in spring
and autumn. Riffle heads and R2 crest yield small thermal gradients; and R1 tail
larger vertical difference. R1 crest temperature is similar and attenuated (cf. water
column) at all depths. R2 tail temperature differs markedly from surface water. Thus,
hyporheic temperature varies temporally across and between riffles, reflecting: (1)
hydroclimatological controls on river and groundwater temperature, and (2) hydrological,
local morphological and sedimentary controls on surface water and groundwater flux. This
research demonstrates the utility of depth-related riverbed temperature time-series in
understanding hyporheic zone processes and groundwater-surface water interactions. |
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