- Long-term trends in river flows due to climate change are difficult to detect due to substantial inter annual and decadal variability as well as modifications to natural water flows arising from water abstractions, man-made reservoirs and land-use changes. Nevertheless, increased river flows during winter and lower river flows during summer have been recorded since the 1960s in large parts of Europe.
- Climate change is projected to result in strong changes in the seasonality of river flows across Europe. Summer flows are projected to decrease in most of Europe, including in regions where annual flows are projected to increase.
What is the trend in mean river flow in different seasons across Europe?
Trends in monthly stream flow for the period 1962-2004
Note: Trend given as standard deviations per year for monthly stream flow. Red colours mark decreases in stream flow whereas blue colours mark increases in stream flow.
- Flow Regime for International Experiment and Network Data (FRIEND) based on Unesco's European Water Archive (EWA) provided by Flow Regimes from International Experimental and Network Data (FRIEND Network)
Projected change in average annual and seasonal river flow
Note: Projected change in mean annual and seasonal river flow between the climate change scenario (SRES A1B, 2071-2100) and the control period (1961-1990). Simulations with LISFLOOD based on an ensemble of 11 RCMs.
- Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations provided by American Geophysical Union (AGU)
Human interventions in catchments including water abstractions, river regulation and land-use change have considerably altered river flow regimes in large parts of Europe, making it difficult to discern any climate-driven changes in river flow to date. However, a comprehensive recent study has investigated time series of river flows in more than 400 small catchments with near-natural flow regimes to overcome these limitations [i]. The study finds indicate that annual river flow has generally decreased over the period 1962 – 2004 in southern and eastern Europe, and it has increased elsewhere. These findings are broadly consistent results from earlier studies (e.g. [ii]. Seasonal changes are also apparent, with a decreased flow in summer months and an increase in winter months in most catchments (see Figure 1). Similar results were found in national and regional studies [iii].
The magnitude of the observed seasonal changes clearly raises concerns for water resource management both today and in future decades. To date, however, despite the evidence of monthly changes to flow, there is no conclusive evidence that low river flows have generally become more severe or frequent in Europe during recent decades [iv].
Annual river flow is projected to decrease in southern and south-eastern Europe and increase in northern and north-eastern Europe [v]. Strong changes are projected in the seasonality of river flows, with large differences across Europe. Winter and spring river flows are projected to further increase in most parts of Europe, except for the most southern and south-eastern regions, which would exacerbate the observed trend. In summer and autumn, river flows are projected to decrease in most of Europe, except for northern and north-eastern regions where they are projected to increase (see Figure 2) [vi]. Such a trend cannot be seen that clear in the observed monthly stream flow for the period 1962-2004 (Figure 1).
In snow dominated regions, such as the Alps, Scandinavia and parts of the Baltic, the fall in winter retention as snow, earlier snowmelt and reduced summer precipitation is projected to increase river flows in winter and reduce them in summer, when demand is typically highest [vii]. For most parts of Europe the peak of the average daily flow for 2071-2100 is projected to occur earlier in the year compared to observations. For Northern Europe a slight increase of the peak of average daily flow is projected compared to a decrease in the other stations evaluated (see Figure 3).
[i] K. Stahl et al., „Streamflow trends in Europe: evidence from a dataset of near-natural catchments“, Hydrology and Earth System Sciences 14, Nr. 12 (Dezember 1, 2010): 2367–2382, doi:10.5194/hess-14-2367-2010.
[ii] P. C. D. Milly, K. A. Dunne, and A. V. Vecchia, „Global Pattern of Trends in Streamflow and Water Availability in a Changing Climate“, Nature 438, Nr. 7066 (November 17, 2005): 347–350, doi:10.1038/nature04312.
[iii] Marius-Victor Birsan et al., „Streamflow trends in Switzerland“, Journal of Hydrology 314, Nr. 1–4 (November 2005): 312–329, doi:10.1016/j.jhydrol.2005.06.008; Donna Wilson, Hege Hisdal, and Deborah Lawrence, „Has streamflow changed in the Nordic countries? – Recent trends and comparisons to hydrological projections“, Journal of Hydrology 394, Nr. 3–4 (November 26, 2010): 334–346, doi:10.1016/j.jhydrol.2010.09.010.
[iv] K. Stahl et al., Trends in Low Flows and Streamflow Droughts Across Europe (Paris: UNESCO, 2008), http://library.wur.nl/WebQuery/wurpubs/374150.
[v] Milly, Dunne, and Vecchia, „Global Pattern of Trends in Streamflow and Water Availability in a Changing Climate“; Joseph Alcamo, Martina Flörke, and Michael Märker, „Future long-term changes in global water resources driven by socio-economic and climatic changes“, Hydrological Sciences Journal 52, Nr. 2 (April 2007): 247–275, doi:10.1623/hysj.52.2.247; Rutger Dankers and Luc Feyen, „Flood hazard in Europe in an ensemble of regional climate scenarios“, Journal of Geophysical Research 114, Nr. D16 (August 27, 2009), doi:10.1029/2008JD011523.
[vi] R. Rojas et al., „Assessment of Future Flood Hazard in Europe Using a Large Ensemble of Bias Corrected Regional Climate Simulations“, Journal of Geophysical Research Nr. in press (2012), doi:10.1029/2012JD017461.
[vii] Martin Beniston, Markus Stoffel, and Margot Hill, „Impacts of climatic change on water and natural hazardsin the Alps: Can current water governance cope with future challenges? Examples from the European ‘‘ACQWA’’ project“, Environmental Science and Policy 14, Nr. 7 (2011): 734–743, doi:10.1016/j.envsci.2010.12.009; BAFU, Auswirkungen der Klimaänderung auf Wasserressourcen and Gewässer: Synthesebericht zum Projekt «Klimaänderung and Hydrologie in der Schweiz» (CCHydro) (Bern: Bundesamt für Umwelt, 2012).
Indicator specification and metadata
- Trends in monthly stream flow
- Projected change in average annual and seasonal river flow
- Projected change in daily average river flow
- standard deviations per year
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
Streamflow trends are calculated by the slopes of the Kendall-Theil robust line for standardized annual and monthly streamflow, as well as for summer low flow magnitude and timing. Streamflow records from 441 small catchments in 15 countries across Europe.
Projected change in mean annual and seasonal river flow between the climate change scenario (SRES A1B, 2071–2100) and the control period (1961–1990) are shown. Simulations with LISFLOOD based on an ensemble of 11 RCMs.
Projected change in daily average river flow between 1961–1990 (black line) and 2071–2100 (blue line) were simulated with LISFLOOD and driven by HIRHAM – HadAM3H/HadCM3 based on IPCC scenario A2.
Methodology for gap filling
- Stahl et al. (2010) Streamflow trends in Europe: evidence from a dataset of near-natural catchments. Stahl, K., Hisdal, H., Hannaford, J., Tallaksen, L. M., van Lanen, H. A. J., Sauquet, E., Demuth, S., Fendekova, M. and Jódar, J., Hydrology and Earth System Sciences 14(12), 2367–2382. doi:10.5194/hess-14-2367-2010
- 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. Journal of Geophysical Research (in press). 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.
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/)
No uncertainty has been specified
Global trends in streamflow and water availability
provided by National oceanic and atmospheric administration (NOAA)
Global Runoff Database
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 016
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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