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Indicator Specification
MAIN ADVANTAGES OF THE INDICATOR
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.
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:
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.
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.
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' (http://ims.eionet.europa.eu/IMS/ISpecs/ISpecification20041007131940/full_spec) and 020 'Nutrients in freshwater' (http://ims.eionet.europa.eu/IMS/ISpecs/ISpecification20041007131957/full_spec), as well as in: http://www.eea.europa.eu/data-and-maps/indicators/freshwater-quality/freshwater-quality-assessment-published-may-2
see 'Methodology for indicator calculation'
No methodology references available.
No uncertainty has been specified
No uncertainty has been specified
MAIN DISADVANTAGES IN THE INDICATOR
ANALYSIS OF OPTIONS
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.
Work specified here requires to be completed within 1 year from now.
Work specified here will require more than 1 year (from now) to be completed.
No resource needs have been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/freshwater-quality or scan the QR code.
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