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| Titel |
Importance of vegetation, topography and flow paths for water transit times of base flow in alpine headwater catchments |
| VerfasserIn |
M. H. Mueller, R. Weingartner, C. Alewell |
| 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 ; 17, no. 4 ; Nr. 17, no. 4 (2013-04-30), S.1661-1679 |
| Datensatznummer |
250018863
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| Publikation (Nr.) |
 copernicus.org/hess-17-1661-2013.pdf |
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| Zusammenfassung |
The mean transit time (MTT) of water in a catchment gives information about
storage, flow paths, sources of water and thus also about retention and
release of solutes in a catchment. To our knowledge there are only a few
catchment studies on the influence of vegetation cover changes on base flow
MTTs. The main changes in vegetation cover in the Swiss Alps are massive
shrub encroachment and forest expansion into formerly open habitats. Four
small and relatively steep headwater catchments in the Swiss Alps (Ursern
Valley) were investigated to relate different vegetation cover to water
transit times.
Time series of water stable isotopes were used to calculate MTTs. The high
temporal variation of the stable isotope signals in precipitation was
strongly dampened in stream base flow samples. MTTs of the four catchments
were 70 to 102 weeks. The strong dampening of the stable isotope input
signal as well as stream water geochemistry points to deeper flow paths and
mixing of waters of different ages at the catchments' outlets. MTTs were
neither related to topographic indices nor vegetation cover. The major part
of the quickly infiltrating precipitation likely percolates through
fractured and partially karstified deeper rock zones, which increases the
control of bedrock flow paths on MTT. Snow accumulation and the timing of
its melt play an important role for stable isotope dynamics during spring
and early summer.
We conclude that, in mountainous headwater catchments with relatively shallow
soil layers, the hydrogeological and geochemical patterns (i.e. geochemistry,
porosity and hydraulic conductivity of rocks) and snow dynamics influence
storage, mixing and release of water in a stronger way than vegetation cover
or topography do. |
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