Importance of vegetation, topography and flow paths for water transit times of base flow in alpine headwater catchments

Mueller, M. H. and Weingartner, R. and Alewell, C.. (2013) Importance of vegetation, topography and flow paths for water transit times of base flow in alpine headwater catchments. Hydrology and earth system sciences, Vol. 17 , S. 1661–1679.

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Official URL: http://edoc.unibas.ch/dok/A6124635

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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.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Umweltgeowissenschaften (Alewell)
UniBasel Contributors:Müller, Matthias Heidulf and Alewell, Christine
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Copernicus Publ.
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:31 Dec 2015 10:52
Deposited On:24 May 2013 09:18

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