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| Titel |
Geological controls on isotopic signatures of streamflow: results from a nested catchment experiment in Luxembourg (Europe) |
| VerfasserIn |
Laurent Pfister, Jeffrey J. McDonnell, Christophe Hissler, Núria Martínez-Carreras, Laurent Gourdol, Julian Klaus, Jean François Iffly, Francois Barnich, Mike K. Stewart |
| 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 |
250093409
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| Publikation (Nr.) |
 EGU/EGU2014-8098.pdf |
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| Zusammenfassung |
| Controls of geology and topography on hydrological metrics, like summer low flow (Grant
and Tague, 2004) or dynamic storage (Sayama et al., 2011), have been identified in nested
catchment experiments. However, most tracer-based studies on streamflow generation have
been carried out in small (10 km2) homogenous catchments (Klaus and McDonnell, 2013).
The controlling effects of catchment physiography on how catchments store and release
water, and how this eventually controls stream isotope behaviour over a large range of scale
are poorly understood.
Here, we present results from a nested catchment analysis in the Alzette River basin
(Luxembourg, Europe). Our hydro-climatological network consists of 16 recording
streamgauges and 21 pluviographs. Catchment areas range from 0.47 to 285 km2, with clean
and mixed combinations of distinct geologies ranging from schists to marls, sandstone,
dolomite and limestone.
Our objective was to identify geological controls on (i) winter runoff ratios, (ii) maximum
storage and (iii) isotopic signatures in streamflow. For each catchment we determined average
runoff ratios from winter season precipitation-discharge double-mass curves. Maximum
catchment storage was based on the dynamic storage change approach of Sayama et al.
(2011). Changes in isotopic signatures of streamflow were documented along individual
catchment flow duration curves.
We found strong correlations between average winter runoff ratios, maximum storage and
the prevailing geological settings. Catchments with impermeable bedrock (e.g. marls or
schists) were characterised by small storage potential and high average filling ratios. As a
consequence, these catchments also exhibited the highest average runoff ratios. In catchments
underlain by permeable bedrock (e.g. sandstone), storage potential was significantly higher
and runoff ratios were considerably smaller.
The isotopic signatures of streamflow showed large differences between catchments. In
catchments dominated by permeable bedrock, isotopic signatures of streamflow remained
stable throughout the entire flow duration curve consistent with a large storage and mixing
potential. On less permeable bedrock substrate, we have observed that isotopic signatures in
streamflow were much more variable, due to reduced storage volume and comparatively
smaller mixing potential.
Other metrics such as catchment size and flowpath length exerted a smaller secondary
control on isotopic signatures of streamflow in the Alzette River sub-basins.
Tague, C., Grant, G.E., 2004. A geological framework for interpreting the low-flow
regimes of Cascade streams, Willamette River Basin, Oregon. Water Resources Research,
40(4), doi:10.1029/2003WR002629
Sayama, T., McDonnell, J.J., Dhakal, A., Sullivan, K., 2011. How much water can a
watershed store ? Hydrological Processes 25, 3899-3908.
Klaus, J., McDonnell, J.J., 2013. Hydrograph separation using stable isotopes: Review
and evaluation. Journal of Hydrology 505, 47-64. |
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