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| Titel |
Comparing Flow Mechanism Hypothesis with Mobility Data of Natural Tracers |
| VerfasserIn |
M. Šanda, Z. Chárová, D. Zumr, M. Cislerova |
| 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 |
250028894
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| Zusammenfassung |
| Hillslope rainfall-outflow interactions, groundwater fluxes and hydrological balance have
been examined in the small mountainous headwater catchment UhlíÅská (1.78 km2), Jizera
Mountains, Czech Republic. The hillslope soil profile is formed by paleozolic crystalline
bedrock overlaid by shallow highly permeable Cambisol, whereas the thick saturated
glacial deposits in the valley are overlaid by Histosols. Quick communication of
the vadose zone with the granite bedrock via preferential subsurface flowpaths is
hypothesized, in agreement with the observation of instant water transformation through
the permeable Cambisols, to outflow caused by storms. There is regularly a quick
response of high magnitude, although surface runoff occurs very rarely. Standard
climatic and hydrological monitoring is supplemented by measurements of the soil
moisture, soil pore water suction, hillslope stormflow in the vadose zone and water
table fluctuation in the saturated subsurface. Water sampling for analysis of the
isotopes 18O and 2H and geochemical tracer silica in the form of SiO2 is performed
throughout the catchment. The episode based isotopic data serve for the separation of the
particular components of the outflow hydrograph and for the determination of the
contribution of event and pre-event water in the hypodermic hillslope outflow and in
the catchment outflow as a whole. Variation of silica content in the water cycle
components was examined to assess contributions from the soil profile and the
aquifer. Significant portion of event catchment runoff was assigned to pre-event water,
partly stored in the shallow soil layers on hillslopes and partly in the valley aquifer.
Here, a significant mixing (in form of attenuation of the input signal of 18O or 2H
measured for precipitation) occurs as proven by sampling and modeling by means of
physically based models for vadose and saturated zones. Hydrological balance of the
catchment shows only minor discrepancies in averaged value of the either isotope in
the whole balanced mass on the input (precipitation) and the output (streamflow).
There is a strong mixing of water already in the root zone, where transpiration
takes place. Preferential flow in the soil profile proved to be a major transporting
mechanism for water in the form of quick subsurface runoff. The hypothesis that
the hillslope soil layers controls the distribution of the flow into the groundwater
recharge and/or the shallow subsurface flow during the rainfall-runoff episode, was
confirmed. Porous structures of the catchment play dominant role in initial mixing of the
water.
We want to acknowledge projects GACR 205/09/0831 and 205/08/1174 of the Grant
Agency of the Czech Republic for support of this contribution. |
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