Indicator Specification

Lake and river ice cover

Indicator Specification
  Indicator codes: CLIM 020
Published 20 Nov 2012 Last modified 09 Feb 2021
5 min read
This page was archived on 03 Feb 2017 with reason: No more updates will be done
Observed change in duration of lake and river ice cover a) Danube River, at Budapest, 1876–2011 and b) Lake Kallavesi, Finland, 1833–2011.

This indicator will be discontinued in January 2017.

This indicator is discontinued. No more assessments will be produced.

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection

The appearance of ice on lakes and rivers requires prolonged periods with air temperatures below 0 ⁰C. The deeper the lake, the more cold is needed to cool down the lake so that ice forms. Higher temperatures will affect the duration of ice cover, the freezing and thawing dates and the thickness of the ice cover.


Lake ice reduces underwater light and vertical mixing, that is, the exchange of water from different depth layers. The existence of lake ice, and the timing of lake ice break-up, is thus of critical ecological importance, influencing for instance the production and biodiversity of phytoplankton and the occurrence of winter fish kills.




Scientific references

  • No rationale references available

Indicator definition

  • Observed change in duration of lake and river ice cover a) Danube River, at Budapest, 1876–2011 and b) Lake Kallavesi, Finland, 1833–2011.


  • Ice break-up dates of lakes and rivers (day of the year)

Policy context and targets

Context description

Ice cover of rivers and lakes is one of the parameters that determine function of aquatic ecosystems. Preparing for climate change is a major challenge for water management in Europe. Climate change is not explicitly included in the text of the Water Framework Directive. However, water management under the WFD will have to deal with the challenges posed by climate change. The stepwise and cyclical approach of the WFD River Basin Management Plans (RBMPs) process makes it well suited to adaptively manage climate change impacts. In particular, the review of RBMPs every six years establishes a mechanism to prepare for and adapt to climate change.


No targets have been specified.

Related policy documents

  • 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.
  • 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 for indicator calculation

Data on Ice-breakup Dates and Freezing Dates of Lake Kallavesi, Finland, 1833-2011 provided by Finnish Environment Institute (SYKE), and data on First Ice Appearance and Final Disappearance on Danube River, at Budapest, 1876–2011 provided by Eötvös Loránd University, Institute of geography and earth sciences are displayed.


    Trend lines have been added.

    Methodology for gap filling

    Not applicable

    Methodology references

    No methodology references available.


    Data specifications

    EEA data references

    • No datasets have been specified here.

    External data references

    Data sources in latest figures



    Methodology uncertainty

    Not applicable

    Data sets uncertainty

    Time series of lake and river ice cover are available from several lakes and rivers in Europe. It is not currently possible to provide a comprehensive picture of lake and river ice cover in Europe.

    Further information on uncertainties is provided in Section 1.7 of the EEA report on Climate change, impacts, and vulnerability in Europe 2012(

    Rationale uncertainty

    No uncertainty has been specified

    Further work

    Short term work

    Work specified here requires to be completed within 1 year from now.

    Long term work

    Work specified here will require more than 1 year (from now) to be completed.

    General metadata

    Responsibility and ownership

    EEA Contact Info

    Peter Kristensen


    European Environment Agency (EEA)


    Indicator code
    CLIM 020
    Version id: 2

    Frequency of updates

    This indicator is discontinued. No more assessments will be produced.


    DPSIR: Impact
    Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)


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