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| Titel |
Controls on water table response and hillslope-stream connectivity during wet and dry periods in an Alpine headwater catchment |
| VerfasserIn |
Giulia Zuecco, Daniele Penna, Omar Oliviero, Luisa Pianezzola, Ilja van Meerveld, Giancarlo Dalla Fontana, Marco Borga |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096323
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| Publikation (Nr.) |
 EGU/EGU2014-11821.pdf |
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| Zusammenfassung |
| Variations in transient groundwater levels affect catchment runoff and hillslope stability.
However, due to practical limitations in field monitoring, the dominant factors that control the
spatial and temporal variability in transient groundwater levels in mountain headwater
catchments are still poorly understood. This study takes advantage of a network of
spatially-distributed groundwater wells in the 0.14 km2 Bridge Creek Catchment in the
Italian Dolomites to identify the main controls on: i) the variability in peak water table levels
and the magnitude of the water table response; ii) the variability in the hysteretic relation
between streamflow and water table level; and iii) subsurface hillslope-stream connectivity.
Water levels were measured in 17 piezometers equipped in three transects across the
hillslopes and riparian zone of Bridge Creek Catchment. Volumetric soil moisture
content was measured by 15 probes installed at three depths at six locations along
a riparian zone-hillslope transect. Water level and soil moisture were measured
during the snow-free months (roughly from May to October) of 2011, 2012 and
2013. This period included 86 selected rainfall-runoff events that were analysed in
detail.
The piezometric response to rainfall depended on the wetness status of the catchment.
The area with piezometers that responded to rainfall tended to expand upwards from the
riparian zone and the lower part of the catchment with increasing wetness and rainfall depth.
Groundwater levels in the riparian zone were always higher than on the hillslopes and were
more variable, especially during wet periods. Peak water table levels in the riparian zone and
the hillslopes were positively correlated with antecedent soil moisture and rainfall depth, but
only during dry periods. The magnitude of water table response was negatively correlated
with antecedent soil moisture during wet periods, when groundwater levels were generally
high.
The relation between streamflow and water table levels was remarkably non-linear and
hysteretic, particularly during dry periods. The correlation between groundwater levels and
streamflow increased during wet periods. This was likely due to the activation of preferential
flow pathways and the establishment of hillslope-stream connectivity that resulted in
high runoff coefficients for these events. Accordingly, the normalized size of the
hysteretic loops decreased with increasing antecedent soil moisture conditions,
indicating a rapid hydrological response and high connectivity when the catchment was
wet. These results underline the importance of transient groundwater levels and
subsurface hillslope-stream connectivity for the overall hydrological response of the
catchment and contribute to a better understanding of water table dynamics in mountain
terrains.
Keywords: headwater catchment; water table; hysteresis; connectivity. |
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