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| Titel |
A vulnerability analysis for a drought vulnerable catchment in South-Eastern Austria |
| VerfasserIn |
Clara Hohmann, Gottfried Kirchengast, Steffen Birk |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121744
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| Publikation (Nr.) |
 EGU/EGU2016-583.pdf |
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| Zusammenfassung |
| To detect uncertainties and thresholds in a drought vulnerable region we focus
on a typical river catchment of the Austrian South-Eastern Alpine forelands with
good data availability, the Raab valley. This mid-latitude region in the south-east
of the Austrian state Styria (∼ 47∘ N, ∼ 16∘ E) exhibits a strong temperature
increase over the last decades. Especially the mean summer temperatures (June
to August) show a strong increase (∼ 0.7 ∘C per decade) over the last decades
(1971 - 2015) (Kabas et al., Meteorol. Z. 20, 277-289, 2011; pers. comm., 2015). The
Styrian Raab valley, with a catchment size of 986 km2, has already struggled with
drought periods (e.g., summers of 1992, 2001 and 2003). Thus, it is important to
know what happens if warm and dry periods occur more frequently. Therefore
we analyze which sensitivities and related uncertainties exist, which thresholds
might be crossed, and what the effects on the different components of the water
balance equation are, in particular on runoff, soil moisture, groundwater recharge, and
evapotranspiration.
We use the mainly physics-based hydrological Water Flow and Balance Simulation Model
(WaSiM), developed at ETH Zurich (Schulla, Diss., ETH Zurich, CH, 1997). The model is
well established and widely used for hydrological modeling at a diversity of spatial and
temporal resolutions. We choose a model set up which is as simple as possible but as complex
as necessary to perform sensitivity studies on uncertainties and thresholds in the context of
climate change. In order to assess the model performance under a wide range of
conditions, the calibration and validation is performed with a split sample for dry and wet
periods.
With the calibrated and validated model we perform a low-flow vulnerability analysis (“stress
test”), with focus on drought-related conditions. Therefore we simulate changes in
weather and climate (e.g., 20% and 50% less precipitation, 2 ∘C and 5 ∘C higher
temperature), changes in land use and land cover (e.g., less forest/grassland, more
agriculture/sealed land), and changes in water use and water management (e.g., more
irrigation/groundwater use). By analyzing the effects of such changes on the water balance
parameters runoff, soil moisture, groundwater recharge and evapotranspiration,
we gain insight into the vulnerabilities of the catchment. We also characterize the
general behavior of the hydrological system, in particular the low-flow processes, and
identify the most critical parameter combinations under changing environmental
conditions. As a result we are able to assess if thresholds may be crossed and what
conditions pose climate change risks, in particular towards the increase of droughts. |
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