Indicator Assessment

Meteorological and hydrological droughts in Europe

Indicator Assessment

Prod-ID: IND-105-en

Also known as: CLIM 018

Published 23 Mar 2020 Last modified 18 Nov 2021

16 min read

Topics: Climate change adaptation Water and marine environment

This page was archived on 18 Nov 2021 with reason: No more updates will be done

Drought is a recurrent feature of the European climate that affects considerable fractions of the European population each year.
The frequency and severity of meteorological and hydrological droughts have increased in most parts of Europe. Different drought indices agree that the increase is greatest in southern Europe.
Available studies project further increases in the frequency, duration and severity of meteorological and hydrological droughts for most of Europe during the 21st century, except for parts of central-eastern and north-eastern Europe. The greatest increase in drought conditions is projected for southern Europe where it will increase competition between different water users, such as agriculture, industry, tourism and households.

This indicator has been archived.
Relevant information is available here: https://www.eea.europa.eu/publications/europes-changing-climate-hazards-1/wet-and-dry-1/wet-and-dry-drought

Fig. 1: Trend in the frequency of meteorological droughts in Europe (1950-2015)

Note: Hatching indicates the areas in which the trends are statistically significant at the 95 % percent level.

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Fig. 2: Trend in runoff during the driest month of the year in Europe (1951-2015)

Note: "Driest month" refers to the month with the lowest river flow in each year. The computation of trends follows the methodology described in Gudmundsson et al. (2019, doi:10.1029/2018gl079725). Analysis is based on the E-RUN data set (Gudmundsson & Seneviratne, 2016, doi:10.5194/essd-8-279-2016).

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Fig. 3: Projected change in meteorological drought frequency between the present (1981-2010) and the mid-century 21st century (2041-2070) in Europe, under two emissions scenarios

Projected change in meteorological drought frequency between the present (1981-2010) and the mid-century 21st century (2041-2070) in Europe, under two emissions scenarios

Note: Left map: Scenario RCP4.5; right map: Scenario RCP8.5. The lines represent the areas in which at least two-third of the simulations used agree on the sign of the change.

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Fig. 4: Projected change in 10-year river water deficit between the present (1981-2010) and the end of the 21st century (2071-2100) in Europe, under two emissions scenarios

Projected change in 10-year river water deficit between the present (1981-2010) and the end of the 21st century (2071-2100) in Europe, under two emissions scenarios

Note: These maps show the relative change in 10-year river water deficit under the 95th percentile for two greenhouse gas emissions scenarios (RCP4.5 and RCP8.5)

Data source:

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Past trends

Drought is a recurrent feature of the European climate that affects considerable fractions of the EU population each year. While the exact numbers and patterns depend on the specific drought index used, there is general agreement that the Mediterranean is a drought hotspot [i]. For an overview of drought indicators and indices, see a recent WMO publication [ii].

Figure 1 shows trends in the frequency of meteorological droughts across Europe, based on the Standardized Precipitation Index over three months (SPI-3). Drought frequency has increased since 1950 across southern Europe and most parts of central Europe, whereas it has decreased in many parts of northern Europe [iii]. Other drought indices, including indices of drought severity, also show significant increases in the Mediterranean region and in parts of central and south-eastern Europe, and decreases in northern Europe and parts of eastern Europe [iv].

Figure 2 shows trends in runoff during the driest month over the same time period (1950-2015) based on the E-RUN dataset [v]. Minimum runoff has decreased in southern Europe and most of central Europe whereas it has increased in northern Europe. Spatially consistent trends were observed in river low flows and have been attributed to anthropogenic climate change [vi].

Note that the E-OBS dataset, which is a key data source for past trends in droughts as well as for calibrating the models used in drought projections, includes very few stations with precipitation data from Turkey and — in some versions — for Poland [vii]. Hence, the drought trends and projections shown here are less robust for these two countries than for other parts of Europe.

Projections

Figure 3 shows projected changes in the frequency of meteorological droughts (SPI-3, see above) by the mid-21st century (2041-2070 compared with 1981-2010) for two emissions scenarios: RCP4.5 (left) and RCP8.5 (right). These projections show increases in meteorological droughts across most of Europe, in particular southern Europe, whereas decreases in droughts are only projected for limited parts of northern Europe. The changes are most pronounced for the high emissions scenario (RCP8.5) and slightly lower for the moderate scenario (RCP4.5) [viii].

Projections using drought indices that also consider potential evapotranspiration (e.g. based on the SPEI, the Standardized Runoff Index (SRI) or the Supply–Demand Drought Index (SDDI)) show substantially greater increases in the areas affected by drought than those based on the precipitation-based SPI alone, because increasing temperatures lead to increasing evapotranspiration [ix].

Figure 4 shows projections of extreme river water deficit (defined as the maximum 10-year water deficit under the 95th percentile discharge value in the baseline period) for the same emissions scenarios as above, taken from the JRC PESETA IV project. Increasingly severe river flow droughts are projected for most European regions, except for central-eastern and north-eastern Europe. The greatest increase in drought risk is projected for southern Europe, where it will increase competition between different water users, such as agriculture, households, tourism and industry, in particular under high emissions scenarios [x]. Qualitatively, similar patterns were found for 10-year low flow projections in the IMPACT2C project [xi], for low runoff (10th percentile of daily runoff) in the HELIX project [xii], and for low flow (5th percentile of daily streamflow) in the JRC PESETA III project [xiii].

The projected increases in water abstraction and water use, particularaly for agriculture, will exacerbate minimum low flows in many parts of the Mediterranean region, leading to increased probabilities of water deficits when maximum water demand overlaps with minimum or low availability [xiv].

[i] Jonathan Spinoni et al., ‘Meteorological Droughts in Europe: Events and Impacts - Past Trends and Future Projections’, JRC Technical Report (Luxembourg: Publications Office of the European Union, 2016), http://publications.jrc.ec.europa.eu/repository/bitstream/JRC100394/lb-na-27748-en-n.pdf.

[ii] WMO and GWP, ‘Handbook of Drought Indicators and Indices’, Integrated Drought Management Tools and Guidelines Series, WMO-No. 1173 (Geneva: World Meteorological Organization (WMO) and Global Water Partnership (GWP), 2016), http://www.droughtmanagement.info/handbook-drought-indicators-and-indices/.

[iii] K. Poljanšek et al., ‘Science for Disaster Risk Management 2017: Knowing Better and Losing Less’, EUR 28034 EN (Luxembourg: Publications Office of the European Union, 2017); Jonathan Spinoni, Gustavo Naumann, and Jürgen V. Vogt, ‘Pan-European Seasonal Trends and Recent Changes of Drought Frequency and Severity’,Global and Planetary Change 148 (January 2017): 113–30, https://doi.org/10.1016/j.gloplacha.2016.11.013.

[iv] L. Gudmundsson and S. I. Seneviratne, ‘A Comprehensive Drought Climatology for Europe (1950-2013)’, inDrought: Research and Science-Policy Interfacing, ed. J. Andreu Alvarez et al. (London: CRC Press, 2015), 31–37, http://www.crcnetbase.com/doi/abs/10.1201/b18077-7; Jonathan Spinoni et al., ‘European Drought Climatologies and Trends Based on a Multi-Indicator Approach’,Global and Planetary Change 127 (April 2015): 50–57, https://doi.org/10.1016/j.gloplacha.2015.01.012; Spinoni et al., ‘Meteorological Droughts in Europe’; James H. Stagge et al., ‘Observed Drought Indices Show Increasing Divergence across Europe’,Scientific Reports 7, no. 1 (December 2017): 14045, https://doi.org/10.1038/s41598-017-14283-2.

[v] Lukas Gudmundsson and Sonia I. Seneviratne, ‘Observation-Based Gridded Runoff Estimates for Europe (E-RUN Version 1.1)’,Earth System Science Data 8, no. 2 (7 July 2016): 279–95, https://doi.org/10.5194/essd-8-279-2016; trend calculation follows L. Gudmundsson et al., ‘Observed Trends in Global Indicators of Mean and Extreme Streamflow’,Geophysical Research Letters 46, no. 2 (28 January 2019): 756–66, https://doi.org/10.1029/2018GL079725.

[vi] K. Stahl et al., ‘Filling the White Space on Maps of European Runoff Trends: Estimates from a Multi-Model Ensemble’,Hydrology and Earth System Sciences 16, no. 7 (11 July 2012): 2035–47, https://doi.org/10.5194/hess-16-2035-2012; Lukas Gudmundsson, Sonia I. Seneviratne, and Xuebin Zhang, ‘Anthropogenic Climate Change Detected in European Renewable Freshwater Resources’,Nature Climate Change 7, no. 11 (November 2017): 813–16, https://doi.org/10.1038/nclimate3416; Gudmundsson et al., ‘Observed Trends in Global Indicators of Mean and Extreme Streamflow’.

[vii] Richard C. Cornes et al., ‘An Ensemble Version of the E-OBS Temperature and Precipitation Data Sets’,Journal of Geophysical Research: Atmospheres 123, no. 17 (16 September 2018): 9391–9409, https://doi.org/10.1029/2017JD028200.

[viii] Jonathan Spinoni et al., ‘Will Drought Events Become More Frequent and Severe in Europe?’,International Journal of Climatology 38, no. 4 (March 2018): 1718–36, https://doi.org/10.1002/joc.5291.

[ix] Danielle Touma et al., ‘A Multi-Model and Multi-Index Evaluation of Drought Characteristics in the 21st Century’,Journal of Hydrology, Drought processes, modeling, and mitigation, 526 (July 2015): 196–207, https://doi.org/10.1016/j.jhydrol.2014.12.011.

[x] C. Cammalleri et al., ‘Global Warming and Drought Impacts in the EU’, EUR 29956 EN (Luxembourg: Publications Office of the European Union, in press).

[xi] Philippe Roudier et al., ‘Projections of Future Floods and Hydrological Droughts in Europe under a +2°C Global Warming’,Climatic Change 135, no. 2 (March 2016): 341–55, https://doi.org/10.1007/s10584-015-1570-4.

[xii] P Berry et al.,High-End Climate Change in Europe: Impacts, Vulnerability and Adaptation (Sofia: Pensoft Publishers, 2017), fig. 9.

[xiii] B. Bisselink et al., ‘Impact of a Changing Climate, Land Use, and Water Usage on Europe’s Water Resources’, JRC Technical Report (Luxembourg: Publication Office of the European Union, 2018), sec. 7.3, http://doi.org/10.2760/09027.

[xiv] Bisselink et al., ‘Impact of a Changing Climate, Land Use, and Water Usage on Europe’s Water Resources’.

Supporting information

Indicator definition

Observed trend in the frequency of meteorological droughts
Observed trend in runoff during the driest month
Projected change in the frequency of meteorological droughts
Projected change in 10-year river water deficit due to climate change

Units

Trend in events per decade
Percentage change (%) per decade
Change in events per decade
Percentage change (%)

Rationale

Justification for indicator selection

Droughts can have severe consequences for Europe’s ecosystems and citizens, and for many economic sectors, including agriculture, energy production, industry and public water supply. It is important to distinguish between different kinds of drought. A persistent meteorological drought (i.e. a precipitation deficiency) can propagate to a soil moisture (agricultural) drought affecting plant and crop growth, which may deepen into a hydrological drought affecting water resources, water quality and freshwater ecosystems.

This indicator comprises two types of drought: meteorological and hydrological droughts, with the latter focusing on river flow droughts. A meteorological drought is defined in terms of precipitation deficiency, which may be exacerbated by high temperature associated with high evapotranspiration. Meteorological droughts are usually characterised using statistical indices, such as the Standardised Precipitation Index (SPI), Standardised Precipitation Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI). A river flow drought is characterised by unusually low river flow, which may result from a prolonged meteorological drought, possibly in combination with socio-economic factors.

Scientific references

IPCC, 2013. Climate Change: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
IPCC, 2014: Europe. Kovats, R.S., R. Valentini, L.M. Bouwer, E. Georgopoulou, D. Jacob, E. Martin, M. Rounsevell, and J.-F. Soussana, 2014: Europe. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1267-1326.

Policy context and targets

Context description

In April 2013, the European Commission (EC) presented the EU Adaptation Strategy Package. This package consists of the EU Strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU Adaptation Strategy is to contribute to a more climate-resilient Europe. One of the objectives of the EU Adaptation Strategy is Better informed decision-making. This shall be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘first-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the EC and the EEA to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies. It was relaunched in early 2019 with a new design and updated content. Further objectives include Promoting adaptation in key vulnerable sectors through climate-proofing EU sector policies and Promoting action by Member States.

In November 2018, the Commission published its evaluation of the 2013 EU Adaptation Strategy. The evaluation package includes a Report from the Commission, a Commission Staff Working Document, the Adaptation preparedness scoreboard country fiches, and the reports from the JRC PESETA III project. This evaluation includes recommendations for the further development and implementation of adaptation policies at all levels.

In November 2013, the European Parliament and the European Council adopted the 7th EU Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation. In November 2013, the European Parliament and the European Council adopted the 7th EU Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on the environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.

Targets

No targets have been specified.

Methodology

Methodology for indicator calculation

Meteorological droughts are based on the Standardised Precipitation Index for three months (SPI-3). Past trends are based on precipitation data from the E-OBS gridded dataset, whereas projections are based on a model ensemble from the EURO-CORDEX project for two emissions scenarios.

Trends in hydrological droughts are calculated based on the runoff during the driest month in the E-RUN dataset. The E-RUN dataset employed a statistical model to estimate runoff across Europe based on the largest database of streamflow observations and the E-OBS dataset. Hydrological drought projections are based on the 10-year river water deficit, as calculated by the LISFLOOD hydrological model forced by a model ensemble from the EURO-CORDEX project for two emissions scenarios.

Methodology for gap filling

Not applicable

Methodology references

Spinoni, J., et al. (2017): Pan-European seasonal trends and recent changes of drought frequency and severity. Spinoni, J., et al., 2017, ‘Pan-European seasonal trends and recent changes of drought frequency and severity’, Global and Planetary Change148, pp. 113-130 (DOI: 10.1016/j.gloplacha.2016.11.013).
Gudmundsson and Seneviratne (2016): Observation-based gridded runoff estimates for Europe (E-RUN version 1.1). Gudmundsson, L. and Seneviratne, S. I., 2016, ‘Observation-based gridded runoff estimates for Europe (E-RUN version 1.1)’,Earth System Science Data8(2), pp. 279-295 (DOI: 10.5194/essd-8-279-2016).
Spinoni et al. (2018): Will drought events become more frequent and severe in Europe? Spinoni, J., et al., 2018, ‘Will drought events become more frequent and severe in Europe?’,International Journal of Climatology38(4), pp. 1718-1736 (DOI: 10.1002/joc.5291).
Cammalleri et al. (in press): Global warming and drought impacts in the EU. Cammalleri, C., et al., in press, Global warming and drought impacts in the EU, EUR 29956 EN, Publications Office of the European Union, Luxembourg.

Uncertainties

Methodology uncertainty

See 'Methodology'.

Data sets uncertainty

The data required for the indicators in this sector are time series of precipitation (for meteorological droughts) and extreme low flows (for hydrological droughts), respectively. These time series can be observed or simulated for historical time periods and can be projected for future time windows, taking into account climate change and potentially also other drivers of change, such as land-use changes.

River flow data are influenced by rainfall run-off and by hydromorphological changes of the river bed, e.g. through river engineering. Homogeneous time series are generally shorter than those for meteorological data. Therefore, substantially more time may be required before statistically significant changes in hydrological variables can be observed, especially with respect to extreme events (floods and droughts). Notwithstanding recent improvements of climate models to simulate large-scale patterns of precipitation and extreme events, projections of changes in precipitation remain uncertain, especially at catchment and local scales.

Reliable information on the extent and impacts of water scarcity and droughts is indispensable for decision-making at all levels. The Joint Research Centre (JRC) of the European Commission has developed a European Drought Observatory (EDO) for drought forecasting, assessment and monitoring while the EEA regularly develops and updates the water scarcity indicator at basin and country level across Europe. However, despite several activities, there is no systematic, comprehensive record of water scarcity and drought events available in Europe.

Rationale uncertainty

No uncertainty has been specified

Data sources

Projections of future meteorological droughts in Europe
provided by
Trend in annual meteorological drought frequency (copyright-protected)
provided by
Observation-based gridded runoff estimates for Europe (E-RUN version 1.1)
provided by ETH Zürich - Institute for Atmospheric and Climate Science
Projected change in extreme river water deficit volume (direct URL to the dataset is not available)
provided by

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For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/river-flow-drought-3/assessment or scan the QR code.

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Filed under: runoff, climate change, drought, precipitation, hydrological drought