Indicator Specification

Freshwater quality

Indicator Specification
  Indicator codes: SEBI 016
Published 21 May 2010 Last modified 09 Feb 2021
8 min read
This page was archived on 09 Feb 2021 with reason: Other (Discontinued indicator)
This indicator shows: 1. Annual median concentrations in rivers of Biological Oxygen Demand (BOD) and ammonium (NH 4 ). 2. Trends in concentrations of orthophosphate and nitrate in rivers. 3. Ecological status of river and lake water bodies.

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection


  • Biodiversity relevance: the indicator gives an assessment of water quality, which fundamentally determines the structure and functioning of aquatic and associated terrestrial ecosystems, and dependent organisms.
  • Country comparison: the indicator is quantitative and representative of the situation in countries.
  • Well established data flow and methodology.
  • The indicator is updated annually.
  • The data is in Waterbase and is freely available through the EEA data service.

Scientific references

  • No rationale references available

Indicator definition

This indicator shows:

1. Annual median concentrations in rivers of Biological Oxygen Demand (BOD) and ammonium (NH4).

2. Trends in concentrations of orthophosphate and nitrate in rivers.

3. Ecological status of river and lake water bodies.


The concentration of nitrate is expressed as mg nitrate-nitrogen (mg NO3-N/l) for rivers and orthophosphate as mg P/l.

The annual average BOD after five or seven days incubation (BOD5/BOD7) is expressed in mg O2/l and the annual average total ammonium concentration is expressed in micrograms N/l.

The ecological status or potential is presented as a percentage of the total classified water bodies by count.


Policy context and targets

Context description

Ammonium concentrations are normally raised as a result of organic pollution, caused by discharges from waste water treatment plants, industrial effluents and agricultural runoff. Ammonium exerts a demand on oxygen in water since it is transformed to oxidised forms of nitrogen. In addition, it is toxic to aquatic life at certain concentrations dependent on water temperature, salinity and pH. Background concentrations of ammonium are around 15 μg/l (as N) (Meybeck, 1982, quoted in EEA, 1999).

BOD is a key indicator of the oxygenation status of water bodies. BOD is the oxygen demand brought about by organisms in water and sediment acting on oxidisable organic matter. In most European countries, the BOD5 test is used where oxygen consumption is measured after five days incubation under controlled conditions. In other, mainly northern Europe countries, the BOD7 test is used where samples are incubated for seven days. High BOD is usually a result of organic pollution, caused by discharges from wastewater treatment plants, industrial effluents and agricultural runoff. A high BOD has several effects on the aquatic environment including reducing river water chemical and biological quality, reducing the biodiversity of aquatic communities and reducing the microbiological quality of waters. Background levels are difficult to quantify and are likely to be at or below the detection limit of the analytical method used, i.e. between 1 and 2 mg O2/l.

Large inputs of nitrogen and phosphorus to water bodies can lead to eutrophication causing ecological changes that result in a loss of plant and animal species (reduction in biodiversity and ecological status), and have negative impacts on the use of water for human consumption and other purposes.

There are a number of EU Directives aimed at reducing the loads and impacts of organic matter. These include:

  • Nitrates Directive (91/676/EEC).
  • Urban Waste Water Treatment Directive (91/71/EEC).
  • Integrated Pollution Prevention and Control Directive (96/61/EEC).
  • Water Framework Directive.
  • Drinking Water Directive (98/83/EC)


Ecological status and potential, as reported in the first river basin management plans, are related to the Water Framework Directive (WFD). The WFD came into force on 22 December 2000, and according to the directive, the first river basin management plans should be published, at the latest, nine years after the directive entered into force. There are, however, serious delays in some parts of the EU and in some Member States consultations are still on-going.

The indicator is directly linked to the objective of the WFD. The main objective of the WFD states that all surface waters should be in good or high ecological status or potential by 2015, or 15 years after entry into force of the directive. The indicator shows the number of water bodies where management measures are needed, and for which water categories and in which regions the need for measures is highest.

Relation of the indicators to freshwater quality and quality of ecosystems

Ammonium, BOD, N and P concentrations indicate water quality. If concentrations are high, quality goes down, threatening aquatic biodiversity and reducing the integrity of the ecosystem and its capacity to deliver ecosystem services.

Enrichment of water bodies with organic matter can lead to oxygen depletion and changes in the trophic structure and functioning of aquatic ecosystems. Until the WFD establishes reference conditions and good status for water bodies - including for water bodies impacted by organic matter discharges, type-specific concentrations equivalent to good ecological status - it will not be possible to relate the indicator to specific impacts on ecological status or biodiversity. However, with decreasing concentrations of oxygen consuming substances and nutrient concentrations it can be assumed in general that the water quality of water bodies is improving and by association aquatic life will benefit.



The indicator is not directly related to a specific policy target but shows the efficiency of wastewater treatment (see CSI024). The environmental quality of surface waters with respect to organic pollution and ammonium and the reduction of the loads and impacts of these pollutants are, however, objectives of several directives, including the Surface Water for Drinking Directive (75/440/EEC), which sets standards for the BOD and ammonium content of drinking water, as well as other directives mentioned in the previous chapter.

Related policy documents



Methodology for indicator calculation

The data in Waterbase is collected through the Eionet-Water process and is therefore a sub-sample of the national data assembled for the purpose of providing comparable indicators of pressures, state and impact of waters on a Europe-wide scale. The data sets are not intended for assessing compliance with any European Directive or any other legal instrument.

A detailed description of the methodology can be found in the specification sheets for EEA core set indicators 019 'Oxygen consuming substances in Rivers'  ( and 020 'Nutrients in freshwater'  (, as well as in:

Methodology for gap filling

see 'Methodology for indicator calculation'

Methodology references

No methodology references available.


Data specifications

EEA data references

Data sources in latest figures



Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty


  • The main disadvantage is that the indicator is at present not directly related to effects on aquatic ecosystems: this should improve when WFD assessments are fully implemented (see below for more details).
  • The current selection of stations for Eionet-Water is for assessments at country level, and representative assessments of individual catchments may not necessarily be obtained. This is being improved as part of the WISE process and development. Information on specific (but not all) water bodies can, however, be obtained.
  • Another disadvantage of indicators focusing on assessing the water quality (oxygen demand) may be their different uses throughout Europe. Some countries use species indices, others family indices. The intercalibration exercise of the EU Joint Research Centre on newly developed assessment systems in Europe to fulfill the requirements of the WFD have recently generated some 'Intercalibration Metrics' that are being widely used throughout Europe to compare country-specific assessment results. See, e.g., Birk and Hering (2006) and Birk et al. (2006).



This indicator has been adopted as an EEA core set indicator. The information basis for the indicator and the assessments possible will improve in time as the WFD assessments are implemented by Member States.

This indicator was selected for the Headline Indicator instead of other globally available indicators (e.g. as used in UNEP GEMS/water), because the EEA core set indicators contain detailed data for a substantial number of European countries.

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.

Work description

SUGGESTIONS FOR IMPROVEMENT This indicator will be improved as more countries implement Eionet-Water. More time series data would improve the data set particularly if from Southern countries. There are gaps in river characteristic information from some countries. Also many countries did not report all the requested summary statistics such as the median. Fill gaps related to catchment pressures. Some countries have used Corine land cover data to provide proxy indicators of pressures. It is expected that this aspect will improve significantly during the next year as new updated Corine data will be available, and as work is undertaken by the ETC/WTR and ETC/LUSI to fill in the gaps in the pressure indicators. Countries will also be designing and/or modifying their monitoring programmes for rivers, lakes and groundwater bodies over the coming years as a requirement of the WFD. This should increase the extent of information potentially available to the EEA through the Eionet‑Water process which will be integrated and extended into the Water Information System for Europe (WISE).

Resource needs

No resource needs have been specified


Not started


2099/01/01 00:00:00 GMT+1

General metadata

Responsibility and ownership

EEA Contact Info

Katarzyna Biala


European Environment Agency (EEA)


Indicator code
SEBI 016
Version id: 1

Frequency of updates

Updates are scheduled once per year


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


Document Actions