Meteorological and hydrological droughts

Assessment versions

Published (reviewed and quality assured)

• No published assessments

Rationale

Justification for indicator selection

Droughts have severe consequences for Europe’s citizens and most economic sectors, including agriculture, energy production, industry and public water supply. However, the term ‘drought’ is used in different contexts, which may cause confusion when the language used is not carefully chosen. A persistent meteorological drought can propagate to a soil moisture (agricultural) drought affecting plant and crop growth, which may deepen into a hydrological drought affecting watercourses, water resources and natural ecosystems. Furthermore, hydrological droughts have a detrimental impact on freshwater ecosystems including vegetation, fish, invertebrates and riparian bird life. Hydrological droughts also have a significant impact on water quality by reducing the ability of a river to dilute pollution.

This indicator combines two types of droughts: meteorological droughts and hydrological droughts, focusing on river flow droughts in the case of the latter. 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.

Indicator definition

• Observed trends in frequency and severity of meteorological droughts
• Model-based estimate of past change in summer low flows
• Projected change in the frequency of meteorological droughts for different periods and scenarios
• Projected change in 20-year return level minimum flow and deficit volumes due to climate change and changes in water use

Units

• Frequency and severity of droughts (dimensionless)
• Percentage change (%)
• Change in frequency (number of months in a 30-year period)
• Percentage change (%)

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, which will be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-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.

Further objectives include Promoting adaptation in key vulnerablesectors through climate-proofing EU sector policies and Promoting action by Member States. Most EU Member States have already adopted national adaptation strategies and many have also prepared action plans on climate change adaptation. The EC also supports adaptation in cities through the Covenant of Mayors for Climate and Energy initiative.

In September 2016, the EC presented an indicative roadmap for the evaluation of the EU Adaptation Strategy by 2018.

In November 2013, the European Parliament and the European Council adopted the 7^th EU Environment Action Programme (7^th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7^th 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 7^th EAP refer to climate change adaptation.

Targets

No targets have been specified.

Related policy documents

• 7th Environment Action Programme
  DECISION No 1386/2013/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 November 2013 on a General Union Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. In November 2013, the European Parliament and the European Council adopted the 7 th EU Environment Action Programme to 2020 ‘Living well, within the limits of our planet’. This programme is intended to help guide EU action on the environment and climate change up to and beyond 2020 based on the following vision: ‘In 2050, we live well, within the planet’s ecological limits. Our prosperity and healthy environment stem from an innovative, circular economy where nothing is wasted and where natural resources are managed sustainably, and biodiversity is protected, valued and restored in ways that enhance our society’s resilience. Our low-carbon growth has long been decoupled from resource use, setting the pace for a safe and sustainable global society.’
• A Blueprint to Safeguard Europe's Water Resources
  COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS A Blueprint to Safeguard Europe's Water Resources /* COM/2012/0673 final */
• Climate-ADAPT: Adaptation in EU policy sectors
  Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
• Climate-ADAPT: Country profiles
  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 in the future. This web portal provides information on all adaptation activities of the European Commission.
• Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for Community action in the field of water policy
  EC (2000). Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for Community action in the field of water policy. OJ L327, 22.12.2000.
• 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 enhances the preparedness and capacity of all governance levels to respond to the impacts of climate change.

Methodology

Methodology for indicator calculation

Past trends in meteorological drought severity are based on a combination of Standardised Precipitation Index (SPI), Standardised Precipitation Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI). The indices are based on the precipitation and temperature data from the E-OBS gridded dataset. Hydrological drought is calculated as the decrease in summer low flows.

Future frequency and duration of extreme meteorological droughts is defined as having a value below –2 of the SPI-6 based on a model ensemble from the EURO-CORDEX project. Hydrological drought projections have been estimated as the 20-year return level minimum river flow (also known as minimum discharge and deficit volumes, which are two measures for water availability and drought intensity. Additionally, changes in water consumption (based on the ‘Economy First’ water use scenario) on the same drought indices have been considered.

Methodology for gap filling

Not applicable

Methodology references

• Spinoni et al. (2015): European drought climatologies and trends based on a multi-indicator approach. Spinoni, J., Naumann, G., Vogt, J. and Barbosa, P., 2015, 'European drought climatologies and trends based on a multi-indicator approach',Global and Planetary Change127, 50–57 (DOI: 10.1016/j.gloplacha.2015.01.012).
• Stahl et al. (2012): Filling the white space on maps of European runoff trends: Estimates from a multi-model ensemble. Stahl, K., Tallaksen, L. M., Hannaford, J. and van Lanen, H. A. J., 2012, 'Filling the white space on maps of European runoff trends: Estimates from a multi-model ensemble',Hydrology and Earth System Sciences16(7), 2035–2047 (DOI: 10.5194/hess-16-2035-2012).
• Stagge et al. (2015): Future meteorological drought: Projections of regional climate models for Europe. Stagge, J. H., Rizzi, J., Tallaksen, L. M. and Stahl, K., 2015,Future meteorological drought: Projections of regional climate models for Europe, Drought R&SPI Technical Report No 25, Oslo.
• Forzieri et al. (2014): Ensemble projections of future streamflow droughts in Europe. Forzieri, G., Feyen, L., Rojas, R., Flörke, M., Wimmer, F. and Bianchi, A., 2014, 'Ensemble projections of future streamflow droughts in Europe', Hydrology and Earth System Sciences 18(1), 85–108 (DOI: 10.5194/hess-18-85-2014).

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• Future meteorological drought: projections of regional climate models for Europe
• Projected change in 20 year return level minimum flow and deficit volumes due to climate change and changes in water use
• Filling the white space on maps of European runoff trends: estimates from a multi-model ensemble
• European drought climatologies and trends based on a multi-indicator approach

Data sources in latest figures

Uncertainties

Methodology uncertainty

Not applicable

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 and water level data are influenced by rainfall run-off and by hydromorphological changes of the river bed, e.g. through river engineering. Furthermore, 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 and exceptional 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. Projections of river floods are plagued by the highest levels of uncertainty, as they often depend on changes in single extreme events, whereas changes in average and low-flow conditions depend on changes in precipitation on longer time scales (i.e. monthly to seasonal), which are more robust.

The main data sources for Europe-wide studies of the impacts of extreme hydrological events and their changes are global databases for natural disasters. Also at the European level, guidance for recording and sharing disaster damage and loss data is under development for Europe, coherent with the Sendai Framework for Disaster Risk Reduction.

Reliable information on the extent and impacts of water scarcity and droughts is indispensable for decision-making at all levels. An overview of water availability, water abstraction and water scarcity in Europe and more specifically for the Alpine region is discussed in several EEA reports). The water exploitation index is currently being revised to be calculated on the level of river basins instead of the administrative boundaries of countries. The Joint Research Centre (JRC) of the European Commission has developed a European Drought Observatory (EDO) for drought forecasting, assessment and monitoring. However, despite several activities, there is no systematic, comprehensive record of water scarcity and drought events in Europe, describing their duration, impact and severity, other than meteorological time series for precipitation.

Rationale uncertainty

No uncertainty has been specified