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| Titel |
Attribution of high resolution streamflow trends in Western Austria – an approach based on climate and discharge station data |
| VerfasserIn |
C. Kormann, T. Francke, M. Renner, A. Bronstert |
| 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 ; 19, no. 3 ; Nr. 19, no. 3 (2015-03-05), S.1225-1245 |
| Datensatznummer |
250120649
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| Publikation (Nr.) |
 copernicus.org/hess-19-1225-2015.pdf |
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| Zusammenfassung |
| The results of streamflow trend studies are often characterized by mostly
insignificant trends and inexplicable spatial patterns. In our study region,
Western Austria, this applies especially for trends of annually averaged
runoff. However, analysing the altitudinal aspect, we found that there is a
trend gradient from higher-altitude to lower-altitude stations, i.e. a
pattern of mostly positive annual trends at higher stations and negative
ones at lower stations. At mid-altitudes, the trends are mostly
insignificant. Here we hypothesize that the streamflow trends are caused by
the following two main processes: on the one hand, melting glaciers produce
excess runoff at higher-altitude watersheds. On the other hand, rising
temperatures potentially alter hydrological conditions in terms of less
snowfall, higher infiltration, enhanced evapotranspiration, etc., which in
turn results in decreasing streamflow trends at lower-altitude watersheds.
However, these patterns are masked at mid-altitudes because the resulting
positive and negative trends balance each other. To support these
hypotheses, we attempted to attribute the detected trends to specific
causes. For this purpose, we analysed trends of filtered daily streamflow
data, as the causes for these changes might be restricted to a smaller
temporal scale than the annual one. This allowed for the explicit
determination of the exact days of year (DOYs) when certain streamflow trends
emerge, which were then linked with the corresponding DOYs of the trends and
characteristic dates of other observed variables, e.g. the average DOY when
temperature crosses the freezing point in spring. Based on these analyses,
an empirical statistical model was derived that was able to simulate daily
streamflow trends sufficiently well. Analyses of subdaily streamflow changes
provided additional insights. Finally, the present study supports many
modelling approaches in the literature which found out that the main drivers
of alpine streamflow changes are increased glacial melt, earlier snowmelt
and lower snow accumulation in wintertime. |
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