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Droughts and Climate Change in Austria Implications for Water Resources Management

Günter BlöschlVienna University of Technology

With contributions from K. Haslinger, J. Parajka, W. Schöner, G. Laaha

2nd Workshop of the Water Platform of the Alpine Convention on Drought Risk Management in the Alps

23 Jan. 2018

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Task: • Assess climate change impacts on floods and droughts

(past and future) • Update of an earlier study on adaptation strategies

Study on droughts and climate change

2016-2017: Study funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management, and the State Governments of Austria

www.bmnt.gv.at/wasser.html

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Droughts in the Past

kurier.at www.nachrichten.at

August 2015Lower Austria

August 2015Upper Austria

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Example of meteorological drought eventDec 1862 - April 1863. Dark colours: least precipitation

Alps

HISTALP precipitation data

Precipitation deficitReturn period

100 yr

10 yr

5 yr

driest

Vienna

Haslinger and Blöschl (2017) WRR

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Drought intensities and air temperatures Summer

Size of circles: drought intensity (lack of precipitation)Colour: air temperature anomaly during drought

HISTALP data Haslinger and Blöschl (2017) WRR

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Drought intensities and air temperatures Winter

Size of circles: drought intensity (lack of precipitation)Colour: air temperature anomaly during drought

HISTALP data Haslinger and Blöschl (2017) WRR

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Winter Summer

Summer droughts have become more frequent, winter droughts less frequent

Drought

HISTALP data Haslinger and Blöschl (2017) WRR

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Annual precipitation in Austria

Dev

iatio

n fro

m m

ean

(%)

Dev

iatio

n fro

m m

ean

(%)

HISTALP

West North

South-EastSouth

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Precipitation in Austria 1996–2014 minus 1976–1995

increase

Autumn

+13%

Summer

+14%

Winter

–7%

decrease

Spartacus data Hiebl und Frei (2017)

Spring

+6%

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Q95 low flows in Austria Flow exceeded on 95% of days

Laaha and Blöschl (2007)

Q95 (l/s/km²)

Winter low flows (snow storage)

Summer low flows (evaporation)

100 km

Vienna

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Trends of Q95 low flows in Austria1976–2014

x .. anthropogenic effects

Getting drier(higher

evaporation)

Getting wetter

(less snow storage)

Gettingdrier

Gettingwetter

Blöschl et al. (2017)

higher evaporation offset by higher

precipitation

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Droughts in the Future

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Change in mean runoff for a temperature rise of 2°C

Fifth IPCC Assessment Report 2014

Increasing runoff

Decreasing runoff

IPCC (2014)

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Temperature, precipitation in the future

ÖKS15 RCP8.5

2021–2050 minus 1971–2000

Summer Winter

Blöschl et al. (2017)

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SP

EI D

roug

ht in

dex

(-)

Drought index in the futureGreater Alpine Region

Based on precipitation, temperature

COSMO-CLM with ECHAM5-A1B, HadCM3-A1B, ECHAM5-A2, ECHAM5-B1 Haslinger et al. (2015) MZ

Gettingdrier

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Change of Q95 low flows in Austria – Future

2021-2050 vs 1976-2008 AIT_HADCM3_A1B

-30%+30%

Gettingdrier

Gettingwetter

CILFAD & AQUA STRESS Parajka et al. (2016) HESS

Winter low flows increasing

Summer low flows decreasing

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2021-2050 vs 1976-2008 ZAMG_ECHAM5_B1

Change of Q95 low flows in Austria – Future

Gettingdrier

Gettingwetter

Parajka et al. (2016) HESSCILFAD & AQUA STRESS

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Observed low flow trends likely to continue into the future

Alpine areas: increases in low flows due to warmer air temperatures (less snow retention in catchments) Mostly positive effects (e.g. hydropower)

Lowlands in the East and Southeast of Austria:(slight) decreases in low flows likely to continue Probably negative effects (e.g. stream temperatures, water quality, fluvial ecosystems, river bank filtration, ..)

Decadal runoff variability > changes expected for 2021-2050

Management implications

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What can we expect? Water balance of Austria 1975-2015

166 catchments Running mean Duethmann, Pers Com. (2017)

E = 514 mm/yr

100

-100

0

50

-50

1980 1990 2000 2010

P = 1247 mm/yr

Q = 732 mm/yr

Ano

mal

y (m

m/y

r)

Precipitation has increased by 7%. Will it increase further?Runoff has not changedEvaporation has increased by 16%. Likely to increase further

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Shift from winter droughts to summer droughts (more likely)

Prioritisation of climate adaptation measure for droughts / low flows depending on local situation, e.g. • storage management • treatment of water from river bank filtration • Interconnecting local/regional water supply networks

Experience from recent summer droughts (2003, 2015) to assist in local adaptation measures

Management implications

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Summer 2003 drought relative to Q95 low flows

100 km

20%

Ratio of low flows in 2003 and Q95 low flows

much less flow in 2003 than Q95

Laaha et al. (2009)

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Thank you for your attentionBlöschl, Parajka, Blaschke, Hofstätter, Haslinger, Schöner (2017) Klimawandel in der Wasserwirtschaft – Schwerpunkt Hochwasser, Dürre und Trockenheit. Bundesministerium für Land- und Forst-wirtschaft, Umwelt und Wasserwirtschaft, 1010 Wien.Haslinger and Blöschl (2017) Space-time patterns of meteorological drought events in the European Greater Alpine Region over the past 210 years. Water Resources Research, 53, 9807–9823.Haslinger, Schöner, Anders (2015) Future drought probabilities in the Greater Alpine Region based on COSMO-CLM experiments, Meteorologische Zeitschrift, 25 (2)Laaha, Parajka, Viglione, Koffler, Haslinger, Schöner, Zehetgruber, Blöschl (2016) A three-pillar approach to assessing climate impacts on low flows. Hydrology and Earth System Sciences, 20, 3967–3985.Parajka, Blaschke, Blöschl, Haslinger, Hepp, Laaha, Schöner, Trautvetter, Viglione, Zessner (2016) Uncertainty contributions to low-flow projections in Austria. Hydrology and Earth System Sciences, 20, 2085-2101.