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Archive:Agri-environmental indicator - nitrate pollution of water

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This article provides a fact sheet of the European Union (EU) agri-environmental indicator water quality - nitrate pollution. It consists of an overview of recent data, complemented by all information on definitions, measurement methods and context needed to interpret them correctly. The water quality - nitrate pollution article is part of a set of similar fact sheets providing a complete picture of the state of the agri-environmental indicators in the EU. 

Table 1: Groundwater nitrate concentration classes (mg NO3/l) and proportion of groundwater monitoring stations in each class per country (%), 2009, EU-27, EFTA, candidate and potential candidate countries
Source: European Environment Agency
Figure 1: Groundwater nitrate concentration classes (mg NO3/l) and share of groundwater monitoring stations in each class by country (%), 2009, EU-27, EFTA, candidate and potential candidate countries
Source: European Environment Agency
Figure 2: Annual average nitrate concentration in groundwater aggregated to different geographical regions of Europe, (mg NO3/l),(1992 - 2009)
Source: European Environment Agency
Figure 3: National proportion of groundwater bodies in various trend categories for nitrate concentration (%), (1992-2009)
Source: European Environment Agency
Map 1: Annual average river nitrate concentration averaged by National River Basin Districts (mg N/l), (2009), EU-27 and EFTA
Source: European Environment Agency
Figure 4: Annual average river nitrate concentrations aggregated to different geographical regions of Europe (mg N/l), (1992 - 2009)
Source: European Environment Agency
Figure 5: National proportion of river monitoring stations in various trend categories for nitrate concentration (%), (1992-2009)
Source: European Environment Agency
Map 2: Annual diffuse agricultural emissions of nitrogen to freshwater (kg N/ha of total land area), (2009)
Source: Joint Research Centre, European Commission

Nitrate pollution is indicated by current values and trends in nitrate concentrations in groundwater and rivers expressed in mg NO3/l for groundwater and mg N/l for rivers.

Main indicator:

  • Rivers and groundwater with nitrate concentration above 50 mg NO3/l (equivalent to 11.3 mg N/l). Rivers and groundwater with nitrate concentration above 25 mg NO3/l reflecting a threshold of concern.

Supporting indicator:

  • Time series of groundwater and rivers nitrate concentrations.

Main statistical findings

Key messages

Nitrates in groundwater

  • Nationally averaged nitrate concentrations are all well below the Nitrates Directive and Drinking Water Directive limit of 50 mg/l.
  • National aggregation, however, masks considerable variation at the scale of groundwater monitoring stations, with approximately 13 % of the stations across Europe, in 2009, exceeding the 50 mg/l limit.
  • The highest proportion of exceedance in 2009 is observed in Belgium (30 %), Denmark (26 %), Spain (22 %) and Cyprus (19 %), but high levels are found also in Austria, Germany, Bulgaria, Montenegro and Czech Republic (11-15 %). In addition, five countries (Slovakia, Luxembourg, Slovenia, France and Switzerland) have a significant proportion (more than 20 %) of groundwater monitoring stations with concentrations exceeding 25 mg/l, raising concern.
  • In general terms, groundwater nitrate concentrations have remained relatively stable since 1992, although there is marked variation at the scale of individual groundwater bodies (GWB). More than 25 % of groundwater bodies in Norway, Lithuania, Belgium, Denmark, Germany and Bulgaria exhibit statistically significant rising trends (Norway had 1 groundwater body only), although the latter three countries also exhibit a number of groundwater bodies with significant declining trends. Countries which show the strongest decline in groundwater nitrate concentrations are Portugal, the Netherlands, Austria, Slovakia and Slovenia (at least 40 % of groundwater bodies showing significant declining trend).

Nitrates in rivers

  • River nitrate concentrations aggregated both nationally and at a river basin scale are below the 11.3 mg N/l limit (equivalent to 50 mg NO3/l) of the Nitrates and Drinking Water Directives.
  • However, current concentrations are often sufficient to promote eutrophication in many of Europe’s coastal waters.
  • Generally, concentrations are lowest in Scandinavia and highest in Luxembourg, France, UK, Germany and Denmark (averaged by National River Basin Districts).
  • Significant decreases in river nitrate concentration are particularly evident in Denmark, Germany, Czech Republic, Slovakia, Ireland, Sweden, Hungary, Norway, Belgium, Bulgaria, Poland, United Kingdom and Austria over recent years. However, more than 30 % of rivers in Spain and Switzerland exhibit a rising trend. Overall, a statistically significant decrease in average nitrate concentrations is evident at 32 % of river monitoring stations across Europe, whilst in 14 %, a statistically significant increase has occurred.

Assessment

Groundwater

Nationally averaged groundwater nitrate concentrations are all below the Nitrates and Drinking Water Directives limit of 50 mg NO3/l. National aggregation, however, masks considerable variation at the scale of individual groundwater monitoring stations, with approximately 13 % of groundwater monitoring stations across Europe, in 2009, exceeding the 50 mg NO3/l limit. Between 1992 and 2009 this figure has remained relatively stable, lying between 5 % and 10 %. The highest proportion of exceedance is observed in the Belgium (30 %), Denmark (26 %), Spain (22 %) and Cyprus (19 %) but high levels are found also in Austria, Germany, Bulgaria, Montenegro and Denmark Czech Republic (11-15 %). Twenty-two countries, in 2009, had at least one individual groundwater monitoring station with an average concentration above the 50 mg NO3/l limit (Figure 1). In addition, five countries (Luxembourg, France, Slovenia, Switzerland and Slovakia) have a significant proportion (more than 20 %) of groundwater monitoring stations with concentrations exceeding 25 mg NO3/l, raising concern, particularly at those sites where this concentration range is also combined with a rising trend. Groundwater nitrate concentrations are lowest in Finland, Iceland, Liechtenstein, Croatia, Bosnia and Herzegovina and Albania with few groundwater monitoring stations (less than 10 %) exceeding 10 mg NO3/l. Broad aggregation to regional scale shows that concentrations are highest in the western and lowest in the northern regions of Europe (Figure 2).

In overall terms, groundwater nitrate concentrations have remained relatively stable since 1992 (Figure 2), although there is marked variation at the scale of individual groundwater bodies. More than 25 % of groundwater bodies in Norway, Lithuania, Belgium, Denmark, Germany and Bulgaria exhibit statistically significant rising trends (Norway had 1 groundwater body only), although the latter three of these countries also exhibit a number of groundwater bodies with significant declining trends (Figure 3). Countries which show the strongest decline in groundwater nitrate concentrations are Portugal, the Netherlands, Austria, Slovakia and Slovenia (at least 40 % of groundwater bodies showing significant declining trend). In Portugal all the four groundwater bodies have a significant downward trend.

In most cases, in countries where both types of data are available, the percentage of significant declining trends is higher for rivers than for groundwater. This is probably reflecting, in part, the lag times associated with the transport of nitrate from soil layers to deeper groundwater (10 - 40 years). Declining trends in groundwater nitrate can typically be attributed to improvements in the management of agricultural land.

Rivers

River nitrate concentrations aggregated both at a river basin scale (Map 1) and by European region (Figure 4) are below the 11.3 mg N/l limit (equivalent to 50 mg NO3/l) of the Nitrates and Drinking Water Directives. Less than 1 % of individual rivers across Europe exceed the limit. However, current concentrations are often sufficient to promote eutrophication in many of Europe’s coastal waters (EEA Indicator CSI023). Generally, concentrations are lowest in Scandinavia (below 0.8 mg N/l) and highest (some districts over 3.6 mg N/l, equivalent to over 16 mg NO3/l) in Luxembourg, France, UK, Germany and Denmark (averaged by National River Basin Districts). For much of the rest of Europe, average concentrations lie between 0.8 and 3.6 mg N/l. However, such aggregated data at river basin scale mask very high concentrations in some areas, which cause bad/moderate status of waters and pose concerns in relation to drinking water supply.

Significant decreases in river nitrate concentration are particularly evident (more than 25 % rivers significant decline) in Denmark, Germany, Czech Republic, Slovakia, Ireland, Sweden, Hungary, Norway, Belgium, Bulgaria, Poland, United Kingdom and Austria over recent years (Figure 5). However, more than 30 % of rivers in Spain and Switzerland exhibit a rising trend. Overall, a statistically significant decrease in average nitrate concentrations is evident at 32 % of river monitoring stations across Europe, whilst in 14 %, a statistically significant increase has occurred.

Declining trends in river nitrate are likely to reflect a number of factors, including improved management of agricultural land, but also a reduced discharge of nitrogen from municipal wastewater treatment plants, as driven by implementation of the Urban Waste Water Directive.

Main warnings

  • Whilst agriculture is, in general terms, the greatest contributor to nitrate in European freshwaters, other sources are also of importance, particularly discharges from urban wastewater treatment plants. It is not possible to apportion the contribution from each source from water quality data alone.
  • River nitrate concentrations held in the WISE-SoE waterbase are not flow weighted and reflect inter-annual variations in hydrology. Such variation does not, however, strongly impact the long-term trends observed.
  • The sampling frequency and number of stations monitored varies between countries.
  • Where a particular river crosses national boundaries, the observed nitrate water quality at any point will reflect all sources upstream, including those in other countries.
  • The data provided via WISE-SoE Rivers and WISE-SoE Groundwater might be for the future combined with the data coming from the Nitrate Directive (which reflect more the impact of agriculture). DG Environment and EEA are together with Member States (MS) working on a streamlining of the different MS reporting on water quality including coordination of WISE-SOE and Nitrate Directive reporting.

Data sources and availability

Indicator definition

Nitrate pollution is indicated by current values and trends in nitrate concentrations in groundwater and rivers (expressed in mg NO3/l for groundwater and mg N/l for rivers).

Measurements

Main indicator:

  • Rivers and groundwater with nitrate concentration above 50 mg NO3/l  (equivalent to 11.3 mg N/l). Rivers and groundwater with nitrate concentration above 25 mg NO3/l are considered to be of concern.

Supporting indicator:

  • Time series of groundwater and rivers nitrate concentrations.

Links with other indicators

The indicator water quality - nitrate pollution is linked with following other indicators:

Data used and methodology

All analyses are based on annual average concentration data from single groundwater monitoring stations and groundwater bodies or river monitoring stations reported to Eionet and drawn from the EEA Waterbase version 11 (WISE-SoE). For groundwater, groundwater monitoring station data are used for the current situation and groundwater bodies for the time series and trend analysis. All data are analysed by the European Topic Centre on Inland, Coastal and Marine waters (ETC/ICM). For rivers total oxidised nitrogen data are used wherever nitrate data are missing or, for the time series analysis, if data are available for more years for total oxidised nitrogen. Concentrations are expressed in mg NO3/l  for groundwater and mg N/l for rivers. Data availability is not evenly spread in space and time, but has increased rapidly in recent years. For time series and trend analyses, only data series that are complete for the whole period 1992 - 2009 after inter/extrapolation have been used (375 groundwater bodies time series and 1668 river station series). The data showing the current situation (Figures 1 and 4) include all the most recent data (12 938 groundwater monitoring stations and 5 463 river monitoring stations).

When interpreting the data, some factors should be kept in mind:

  • The nitrate in groundwater and rivers does not just derive from agriculture, but also from other sources, in particular waste water (even though the large majority comes from agriculture). 
  • Inter-annual variation in hydrology gives rise to variation in river nitrate concentrations, but this does not affect long-term trends.
  • Sampling frequency and the number of stations vary between countries. For more information on methodology, consult the CSI 020 indicator specification (EEA Indicator CSI020).

Context

Excessive emissions of nutrients to water cause eutrophication, characterised by the proliferation of algal blooms that are aesthetically unappealing and reduce the clarity of water. The algal blooms frequently involve toxic cyanobacteria, which pose a threat to public health, and decomposition of algae under anaerobic conditions may produce toxic gases. Algal blooms are also associated with the loss of ‘desirable’ plant and animal species. Impacts of eutrophication on freshwater ecosystems are documented throughout Europe. However, excessive levels of nitrate have greatest significance with respect to the eutrophication of estuarine and coastal waters.

Inputs of nutrients to agricultural land are generally in excess of what is required by crops and grassland, resulting in nutrient surpluses [1]. The magnitude of these surpluses reflects the potential for detrimental impacts on the environment including upon water quality. Whilst other sources can be of importance (in particular untreated urban wastewater), in general terms agriculture is the greatest contributor to nitrate levels in freshwater across Europe (50 - 75 %) to nitrate levels in freshwater across Europe. As a consequence, legislation has been established to address this issue; it is described below under policy and relevance context chapter.

This factsheet describes nitrate concentrations in rivers and groundwater across Europe, including current levels and historical trends. The trend information identifies those countries for which improvement and/or deterioration in nitrate water quality observed. Assessment of current concentrations is made against legislative criteria - primarily a threshold of 50 mg NO3/l (11.3 mg N/l), with a guiding concentration of 25 mg NO3/l (5.6 mg N/l) to reflect a level of concern.

Policy relevance and context

Nitrate in freshwater from agricultural sources is addressed by the Nitrates Directive (Directive 91/676/EEC). The Nitrates Directive requires the establishment of Nitrate Vulnerable Zones (NVZ) in areas where agricultural sources of nitrate have led or could lead to excessive concentrations in freshwater or threatened waters sensitive to eutrophication. Action programmes are required for NVZ that detail a range of measures that need to prevent and reduce nitrate pollution. Such measures include a threshold limit for the application of manure nitrogen to land of 170 kg/ha per year, the provision of sufficient manure storage capacity and restrictions on fertiliser application when soil conditions are unsuitable (e.g. when saturated) or when crops are not in need for nutrients (autumn/winter). Derogations to the threshold of 170 kg/ha per year have, however, been granted in some countries, under very strict conditions. Full implementation of the Nitrates Directive is required (as a basic measure) under the Water Framework Directive (Directive 2000/60/EC) which represents the single most important piece of EU legislation relating to the quality of fresh and coastal waters, aiming to attain good ecological and chemical status of Europe’s fresh and coastal waters by 2015.

Cross-compliance under the Common Agricultural Policy (CAP) contributes to a better implementation of the Nitrates and Groundwater Directive (Directive 80/68/EEC). In addition, agri-environmental measures can also play a role in reducing the pollution of water by nitrates. The cross-compliance mechanism is implemented to require all farmers receiving payments under various schemes to comply with a set of statutory management requirements, including those that address the environment (the Nitrates and Groundwater Directives), and to respect standards on Good Agricultural and Environmental Conditions (GAEC). The current cross-compliance rules also identify the need to maintain existing permanent pastures and avoid their conversion to arable land, and to establish buffer strips along water courses.

In addition to cross-compliance, the CAP’s rural development regulation includes the implementation of agri-environmental measures. These measures include payments to farmers who carry out specific agri-environmental commitments that go beyond a reference baseline consisting of inter alia the cross-compliance standards and requirements of the legislation. The CAP’s rural development regulation identify a range of potential measures for the improvement, among others, of water quality, including reduced fertilization, improving manure storage, the use of cover crops, riparian buffer strips and wetland restoration. They also recognize the importance of educational and advisory programmes for farmers. Implementation of these CAP measures plays a key role in addressing diffuse pollution from agriculture.

Reforms of the Common Agricultural Policy contribute as well to reduce diffuse pollution from agriculture. The recent CAP proposal goes a step forward by "greening" the first pillar. These means that 30 % of Direct Payments will be allocated for the provision of public goods: maintenance of permanent pasture at farm level, crop diversification and ecological focus area. These 3 measures will apply to every farmland.

Nitrate levels in water intended for human consumption are addressed by the Drinking Water Directive which requires that concentrations do not exceed 50 mg NO3/l. Exceedence of this threshold does occur, however, and requires that the water is either treated or blended with a less contaminated source. Both treatment and blending incur costs.

Agri-environmental context

While nitrogen fixation, atmospheric deposition and the application of treated sewage sludge can all be important, typically the major nutrient inputs to agricultural land are from inorganic mineral fertilisers and organic manure from livestock. Today, the highest total fertiliser nutrient application rates - mineral and organic combined - generally, although not exclusively, occur in Western Europe. Ireland, England and Wales, the Netherlands, Belgium, Denmark, Luxembourg, north-western and southern Germany, the Brittany region of France and the Po valley in Italy all have high nutrient inputs[2], [3].

Inputs of nutrients to agricultural land across Europe are generally in excess of what is required by crops and grassland, resulting in nutrient surpluses[4]. The magnitude of these surpluses reflects the potential for detrimental impacts on the environment since it is available for gaseous loss to the atmosphere as ammonia, build-up in soil pools over time, or transport to the nearest receiving water body. The pattern of national scale nitrogen surpluses across Europe reflects the magnitude of inputs via mineral and manure fertilisers. Whilst most countries exhibited an annual nitrogen surplus, calculated as an average between 2006 and 2008, of at least 30 kg N per hectare of total agricultural land, values in excess of 100 kg N ha were apparent for Malta, Belgium, Cyprus and Norway and even exceeded 200 kg N per ha in the case of the Netherlands balance in agriculture (Eurostat, aei_pr_gnb). 

Wider agro-economic factors and improved training for farmers are likely to have played a role in the decline of surpluses. In addition, policy measures, such as national action plans established under the Nitrates Directive have been of importance. Despite the general decreases over recent years, nutrient surpluses in some regions of Europe remain at an excessively high level. Although certain catchment processes can attenuate much of the nutrient surplus, a significant proportion can still be transported to freshwater, and hence termed an emission. According to model estimates, agricultural emissions of nitrogen to freshwater exceed 10 kg per ha per year across some European regions, with values exceeding 20 kg N per ha per year in parts of Denmark, southern Sweden and Norway, western United Kingdom, Ireland, Belgium, Netherlands, Brittany, and the Po Valley [5] (Map 2). Such diffuse emissions are strongly dependent upon rainfall. The magnitude of the emissions together with a range of other contributing factors determines the concentrations observed in freshwater.

Excessive emissions of nutrients to freshwater cause eutrophication, characterised by the proliferation of algal blooms that are toxic, aesthetically unappealing and reduce the clarity of water, giving it the appearance of ‘green soup’, often accompanied by unpleasant smells. This proliferation is also associated with the loss of ‘desirable’ plant and animal species. The process of dissolved oxygen concentrations fall can be compounded when the aquatic plant life dies, generating huge amounts of organic matter and further diminishing oxygen levels. Impacts of eutrophication on freshwater ecosystems are documented throughout Europe. However, excessive levels of nitrogen have greatest significance with respect to the eutrophication of estuarine and coastal waters, which remains widespread throughout Europe (EEA Indicator CSI023).

Toxic cyanobacteria associated with algal blooms pose a threat to public health. Direct skin contact with water containing these cyanotoxins, for example through freshwater and marine recreation, can cause allergic reactions similar to hay fever and asthma. Skin, eye and ear irritations can also occur, and ingestion of the toxins may result in gastrointestinal illness and liver damage. Cyanotoxins can also affect the nervous system. A recent assessment of European waters indicates that mass populations of bloom-, scum-, mat- and biofilm-forming cyanobacteria with cyanotoxin potential are relatively widespread and occur in water resources used for drinking water supply, aquaculture, recreation and tourism and moreover, health incidents involving cyanotoxins have been reported in some European countries [6]. While excessive nutrient levels are strongly linked to cyanobacteria blooms, understanding of the impact of human activities on their occurrence remains incomplete.

Municipal drinking water supply systems supply treated water under quality controlled conditions ensuring that nitrate concentrations do not exceed the threshold. However, in some rural areas of Europe, drinking water is taken from wells and consumed without purification. Excessive levels of nitrate in groundwater in the vicinity of such wells could, therefore, pose a threat to public health.

See also

Further information

Publications

Dedicated section

Source data for tables, figures and maps (MS Excel)

Other information

Legislation: Commission Staff working document accompanying COM(2006)508 final
Corresponding IRENA Fact sheet 30.1

External links

  • Database:
  • Other external links:
  • European Environment Agency

Notes

  1. ↑ Grizzetti, B.; Bouraoui, F. and Aloe, A., 2007. Spatialised European Nutrient Balance. Institute for Environment and Sustainability. Joint Research Centre. EUR 22692 EN
  2. ↑ Grizzetti, B.; Bouraoui, F. and Aloe, A., 2007. Spatialised European Nutrient Balance. Institute for Environment and Sustainability. Joint Research Centre. EUR 22692 EN
  3. ↑ Bouraoui, F., Grizzetti, B. and Aloe, A., 2009. Nutrient discharge from rivers to seas. JRC EUR 24002 EN
  4. ↑ Grizzetti, B.; Bouraoui, F. and Aloe, A., 2007. Spatialised European Nutrient Balance. Institute for Environment and Sustainability. Joint Research Centre. EUR 22692 EN
  5. ↑ Bouraoui, F., Grizzetti, B. and Aloe, A., 2009. Nutrient discharge from rivers to seas. JRC EUR 24002 EN
  6. ↑ UNESCO/IHP, 2005. International Hydrological Programme-VI. CYANONET A Global Network for Cyanobacterial Bloom and Toxin Risk Management. Initial Situation Assessment and Recommendations. Technical document in hydrology, Number 76. UNESCO, Paris, 2005.
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