This publication is categorised as a CSO Frontier Series Output. Particular care must be taken when interpreting the statistics in this release as it may use new methods which are under development and/or data sources which may be incomplete, for example new administrative data sources.
The best available source of data on ecosystem condition for rivers and lakes is Water Framework Directive (WFD) reporting. The WFD is an important piece of EU environmental legislation, and applies to rivers, lakes, groundwater, estuaries, and coastal waters.
Ecological status data are available for five different time periods, which relate to the WFD cycles:
1. Baseline data, gathered for the initial WFD assessment (2007-2009)
2. Second reporting phase (2010-2012)
3. WFD first cycle (2010-2015)
4. Assessment to 2018 (2013-2018)
5. WFD second cycle (2016-2021)
Under the WFD, member states must ensure that all surface water bodies achieve at least Good status, which is the status achieved when both its ecological status and its chemical status are at least Good. Ecological status is the main condition indicator and is an expression of the quality of the structure and functioning of aquatic ecosystems. Determining the ecological status of a water body is primarily done through assessment of the fish, aquatic flora, and macroinvertebrates and phytoplankton found in it. Other parameters include physico-chemical assessment (e.g. temperature and nutrient level) and hydromorphological quality (e.g. water flow, continuity, and the structure of physical habitat).
Having one framework for water quality for all of the water bodies in Ireland, and in Europe, allows comparison between countries, and between assessment periods. Under the WFD, ecological status is classified as: High, Good, Moderate, Poor, or Bad. High ecological status is defined as the biological, chemical, and hydromorphological conditions associated with no or very low human impact. In general, water bodies in High and Good ecological status show only minor or slight changes from natural conditions, whereas waters in Moderate, Poor, or Bad ecological status range from moderately to severely damaged by pollution or habitat degradation.
The System of Environmental Economic Accounting - Ecosystem Accounting (SEEA-EA) outlines five sets of ecoystem accounts:
1. Ecosystem extent accounts
2. Ecosystem condition accounts
3. & 4. Ecosystem services flow accounts (physical and monetary)
5. Monetary ecosystem asset accounts
See Information Note on Ecosystem Accounting for more information on the different accounts and how they are related.
Condition accounts are built up from spatial data (i.e. underlying maps) using selected indicators of ecosystem status. Ecosystem condition is defined in the SEEA-EA as 'the quality of an ecosystem measured in terms of its abiotic and biotic characteristics'. Condition can be thought of as a measure of the health of an ecosystem, which affects its capacity to supply ecosystem services on an ongoing basis. Measurement of ecosystem condition can be important to inform environmental policy and decision making, for example in conservation and protection of particular ecosystems. Measures of ecosystem condition that are compiled regularly and at the appropriate spatial scale are needed for the condition accounts. The ecological status of a water body is a compound indicator, based on a range of biological, hydromorphological, and physico-chemical parameters, and data are compiled at the level of ecosystem assets (water bodies) and on a regular basis, making these data ideal for compiling condition accounts.
Following SEEA-EA methodology, ecosystem condition indicators were compiled based on the ecological status data. Ecosystem condition indicators are rescaled versions of ecosystem condition variables. By relating each variable to a reference level, the ecosystem condition variables can be used to calculate ecosystem condition indicator values. Each variable is rescaled to a uniform dimensionless scale between 0 and 1, based on reference level values. The closer the indicator value is to one, the better the condition of the ecosystem (based on the input variable). In this case, where the reference values are 'all water bodies achieving Good or High ecological status' (upper level) and 'no water bodies achieving Good or High ecological status' (lower level), the indicator values are equal to the proportion of water bodies achieving Good or High ecological status. For other variables, with different reference values, the condition indicator values will allow easy interpretation of whether an ecosystem condition can be considered high (i.e. close to the upper reference level) or low (close to the lower level).
Data were downloaded from the EPA's Geoportal under the section Water / Water Framework Directive for each assessment period under STATUS 2007-2009, STATUS 2010-2012, STATUS 2010-2015, STATUS 2013-2018, and STATUS 2016-2021, corresponding to the assessment periods referred to earlier. All data were accessed in June 2023.
To compile data on length of rivers and area of lakes, spatial data for the assessment periods 2010-2015 and 2016-2021 were used. Some of the rivers and lakes in this dataset cross the border into Northern Ireland; for the purposes of this assessment the extents were clipped to the Tailte Éireann (TE) national boundary (2023 version obtained from TE).
To compile county level data for river water bodies, the 2019 National Statutory Boundaries (Ungeneralised) file from TE was used. The EPA data includes the Local Authority responsible for each water body; where river water bodies crossed county boundaries, the river water body was assigned to the relevant county using the Local Authority name.
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