River flow drought
- Europe has been affected by several major droughts in recent decades, such as the catastrophic drought associated with the 2003 summer heat wave in central parts of the continent and the 2005 drought in the Iberian Peninsula.
- Severity and frequency of droughts appear to have increased in parts of Europe, in particular in southern Europe.
- Regions most prone to an increase in drought hazard are southern and south-eastern Europe, but minimum river flows will also decrease significantly in many other parts of the continent, especially in summer.
What is the trend in minimum river flow across Europe?
Projected change in minimum river flow with return period of 20 years
Note: Relative change in minimum river flow for a) 2020s, b) 2050s and c) 2080s compared to 1961-1990 for SRES A1B scenario.
- Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations provided by American Geophysical Union (AGU)
Over the past 40 years, Europe has been affected by a number of major droughts, most notably in 1976, 1989, 1991, and more recently (see Figure 1), the prolonged drought over large parts of the continent associated with the 2003 summer heat wave and the 2005 drought in the Iberian Peninsula. However, there is no evidence that river flow droughts have become more severe or frequent over Europe in general in recent decades [i], nor is there conclusive proof of a general increase in summer dryness (based on the Palmer Drought Severity Index) in Europe over the past 50 years due to reduced summer moisture availability [ii]. Several stations in Europe have shown trends towards less severe low stream flows over the 20th century but this is primarily attributed to an increasing number of reservoirs becoming operational during this period [iii].
Whilst public water supplies often have priority over other uses during droughts, restrictions on use can arise, together with a significant cost associated with emergency water supplies. In 2008, Cyprus suffered its fourth consecutive year of low rainfall and the drought situation reached a critical level in the summer months. To ease the crisis, water was shipped in from Greece using tankers. In addition, the Cypriot Government was forced to apply emergency measures, including the cutting of domestic supplies by 30 %. Similarly in Catalonia during the spring of 2008, water levels in the reservoirs supplying 5.8 million inhabitants were only 20% of capacity. The government planned to ship fresh water in, at an estimated cost of EUR 35 million. After a few shiploads were transported to Barcelona, these transports were stopped because strong rainfall was filling the reservoirs again [iv].
River flow droughts are projected to increase in frequency and severity in southern and south-eastern Europe, the United Kingdom, France, Benelux, and western parts of Germany over the coming decades (see Figure 2) [v]. For the near future (2020s, Figure 2.a), the differences to the control period 1961-1990 are rather limited although the general pattern of an increase of minimum flows in Scandinavia and a decrease in Southern and South-Eastern Europe can already be seen. For Scandinavia and North-Eastern Europe the projected minimum flows with a return period of 20 years further increase while almost everywhere else in Europe a moderate till strong decrease is projected. In most of Europe, the projected decrease in summer precipitation accompanied by rising temperatures is projected to lead to more frequent and intense summer droughts [vi].This projected decline in water resources will be reflected not only by reduced river flows, but also by lowered lake and groundwater levels and a drying up of wetlands.
Climate change will affect not only water supply but also water demand. Water demand for irrigation is projected to increase in many regions, which may further decrease river flow. Initial research suggests that climate change may also have some effect on household water demand [vii].
[i] K. Stahl et al., Trends in Low Flows and Streamflow Droughts across Europe (Paris: UNESCO, 2008), http://library.wur.nl/WebQuery/wurpubs/374150.
[ii] G. van der Schrier et al., “Summer Moisture Variability across Europe,” Journal of Climate 19 (2006): 2818–34, doi:10.1175/JCLI3734.1.
[iii] Cecilia Svensson, W. Zbigniew Kundzewicz, and Thomas Maurer, “Trend Detection in River Flow Series: 2. Flood and Low-Flow Index Series / Détection de Tendance Dans Des Séries de Débit Fluvial: 2. Séries D’indices de Crue et D’étiage,” Hydrological Sciences Journal 50, no. 5 (2005): 824, doi:10.1623/hysj.2005.50.5.811.
[iv] Robert Collins, “Water Scarcity and Drought in the Mediterranean,” EU Change, 2009.
[v] G. Forzieri et al., “Ensemble Projections of Future Streamflow Droughts in Europe,” Hydrol. Earth Syst. Sci. 18, no. 1 (January 9, 2014): 85–108, doi:10.5194/hess-18-85-2014.
[vi] H. Douville et al., “Sensitivity of the Hydrological Cycle to Increasing Amounts of Greenhouse Gases and Aerosols,” Climate Dynamics 20, no. 1 (November 1, 2002): 45–68, doi:10.1007/s00382-002-0259-3; Bernhard Lehner et al., “Estimating the Impact of Global Change on Flood and Drought Risks in Europe: A Continental, Integrated Analysis,” Climatic Change 75, no. 3 (April 2006): 273–99, doi:10.1007/s10584-006-6338-4; Luc Feyen and Rutger Dankers, “Impact of Global Warming on Streamflow Drought in Europe,” Journal of Geophysical Research 114 (September 15, 2009): D17116, doi:10.1029/2008JD011438.
[vii] Robert Keirle and Colin Hayes, “A Review of Catchment Management in the New Context of Drinking Water Safety Plans,” Water and Environment Journal 21, no. 3 (September 1, 2007): 208–16, doi:10.1111/j.1747-6593.2007.00074.x.
Indicator specification and metadata
- Water scarcity and drought events in Europe
- Projected change in minimum river flow with return period of 20 years
- % change
Policy context and targets
In April 2013 the European Commission presented the EU Adaptation Strategy Package (http://ec.europa.eu/clima/policies/adaptation/what/documentation_en.htm). This package consists of the EU Strategy on adaptation to climate change /* COM/2013/0216 final */ and a number of supporting documents. One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which should occur through Bridging the knowledge gap and Further developing Climate-ADAPT as the ‘one-stop shop’ for adaptation information in Europe. Further objectives include Promoting action by Member States and Climate-proofing EU action: promoting adaptation in key vulnerable sectors. Many EU Member States have already taken action, such as by adopting national adaptation strategies, and several have also prepared action plans on climate change adaptation.
The European Commission and the European Environment Agency have developed the European Climate Adaptation Platform (Climate-ADAPT, http://climate-adapt.eea.europa.eu/) to share knowledge on observed and projected climate change and its impacts on environmental and social systems and on human health; on relevant research; on EU, national and subnational adaptation strategies and plans; and on adaptation case studies.
No targets have been specified.
Related policy documents
Climate-ADAPT: Mainstreaming adaptation in EU sector policies
Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
Climate-ADAPT: National adaptation strategies
Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
DG CLIMA: Adaptation to climate change
Adaptation means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimise the damage they can cause, or taking advantage of opportunities that may arise. It has been shown that well planned, early adaptation action saves money and lives later. This webportal provides information on all adaptation activities of the European Commission.
EU Adaptation Strategy Package
In April 2013 the European Commission adopted an EU strategy on adaptation to climate change which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it will enhance the preparedness and capacity of all governance levels to respond to the impacts of climate change.
Methodology for indicator calculation
Water scarcity and drought events in Europe during the last decade are shown based on Tallaksen, 2007, personal communication. For the projections, an ensemble was applied consisting of simulations from 12 climate experiments conducted within the ENSEMBLES project, forced by the SRES A1B emission scenario for the period 1961-2100. Prior to driving the hydrological model LISFLOOD, climate simulations are corrected for bias in precipitation and temperature using a Quantile Mapping (QM) method.
Methodology for gap filling
- Rojas et al. 2012: Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations. Rojas, R., Feyen, L., Bianchi, A. and Dosio, A. (2012) Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations. Journal of Geophysical Research. doi:10.1029/2012JD017461
Data sets uncertainty
Detailed data on water quantity is often difficult to assess, and homogeneous time series are generally shorter than those for meteorological data. It may, therefore, require substantially more time before statistically significant changes in hydrological variables can be observed than for meteorological variables, especially with respect to extreme events (floods and droughts). Quantitative projections of changes in precipitation and river flows at the basin scale remain highly uncertain due to the limitations of climate models and to scaling issues between climate and hydrological models.
The main data sources for European-wide studies of extreme hydrological events and their changes are global databases for natural disasters. These include general impact-oriented disaster databases such as EM-DAT () maintained by the Centre for Research on the Epidemiology of Disasters (CRED) and the NatCatService () maintained by Munich Re, as well as specific mostly event-oriented databases, such as the Dartmouth Flood Observatory (). Some of the limitations of these databases included the use of thresholds for inclusion of an event, which may exclude smaller events with a significant regional impact, changes over time in the comprehensiveness of the coverage (see below), and privacy issues related to detailed data collected by the insurance industry. Improvements of these datasets are planned in coming years. The available data is currently evaluated, for example in the ongoing emBRACE project (). A more detailed and comprehensive event-oriented database that also includes events without any (major) damages would be needed to separate the effect of climate change from socio-economic changes.
The reporting of flood and drought events has generally improved during the past few decades as a result of improvements in data collection and flows of information. As a result, it is often difficult to identify whether an increase in reported flood events (or their impacts) over time is due mostly to improvements in data collection or to actual changes in these events. Furthermore, river flood records are usually sourced from different institutions and often collected using a wide range of different assessment methods and rationales, which may have changed over time. This multitude of sources limits the comparability of key attributes associated with such events (e.g. economic losses, human casualties) across space and time.
As part of the preliminary flood risk assessment for the European directive on the assessment and management of flood risks (2007/60/EC) (), EU Member States will give an overview of significant past floods. In addition, a European flood impact database could bring together publicly available inventories of flood events. At the national/regional level, such an inventory would be particularly useful to provide accurate data and assessments which would serve as a basis for disaster prevention. At the European level, these inventories could assist in tracking the trends in flood-disaster losses, and in mitigation programmes monitoring and obtaining a clearer picture of the linkages between climate change and floods and flood losses.
Further information on uncertainties is provided in Section 1.7 of the EEA report on Climate change, impacts, and vulnerability in Europe 2012 (http://www.eea.europa.eu/publications/climate-impacts-and-vulnerability-2012/)
 See http://www.emdat.be online.
 See http://www.munichre.com/geo online.
 See http://floodobservatory.colorado.edu/ online.
 See http://embrace-eu.org/ online.
 See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2007:288:0027:0034:EN:PDF online.
No uncertainty has been specified
European water archive
provided by Global Runoff Data Centre (GRDC)
Climate change (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 018
Contacts and ownership
EEA Contact InfoWouter Vanneuville
EEA Management Plan2012 2.0.1 (note: EEA internal system)
Frequency of updates
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe's environment.
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