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You are here: Home / Data and maps / Indicators / Nutrients in freshwater / Nutrients in freshwater (CSI 020/WAT 003) - Assessment published Nov 2005

Nutrients in freshwater (CSI 020/WAT 003) - Assessment published Nov 2005

Indicator Assessment Created 19 May 2005 Published 29 Nov 2005 Last modified 09 Jan 2015, 03:19 PM
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This indicator is updated according to 2012 data reported by countries in the autumn 2013. The next update will be based on 2013 and 2014 data to be reported by countries in the autumn 2015.

 
Contents
 

Indicator definition

This indicator shows concentrations of orthophosphate and nitrate in rivers, total phosphorus in lakes and nitrate in groundwater bodies. The indicator can be used to illustrate geographical variations in current nutrient concentrations and temporal trends.

Units

The concentration of nitrate is expressed as milligrammes nitrate per litre (mg NO3/l) for groundwater and milligrammes nitrate-nitrogen per litre (mg NO3-N/l) for rivers and orthophosphate and total phosphorus as milligrammes phosphorous per litre (mg P/l).


Key policy question: Are concentrations of nutrients in our freshwaters decreasing?

Key messages

Concentrations of phosphorus in European rivers and lakes generally decreased during the 1990s, reflecting the general improvement in wastewater treatment over this period. However, the decrease was not sufficient to halt eutrophication. There was a small decrease in nitrate concentrations in some European rivers during the 1990s. The decrease was less than for phosphorus because of limited success with measures to reduce agricultural inputs of nitrate.

Nitrate concentrations in Europe's groundwaters have remained constant and are high in some regions, threatening drinking water abstractions.

Nitrate and phosphorus concentrations in European freshwater bodies between 1992/1993 and 2002

Note: Concentrations are expressed as annual median concentrations for groundwater, and median of annual average concentrations for rivers and lakes

Data source:

Waterbase (Version 4)

Downloads and more info

Key assessment

Mean nitrate concentrations in groundwaters in Europe are above background levels (<10 mg/l as NO3) but do not exceed 50 mg/l as NO3. At the European level, annual mean nitrate concentrations in groundwaters have remained relatively stable since the early 1990s but show different levels regionally. Due to a very low level of mean nitrate concentrations (<2 mg/l as NO3) in the Nordic countries, the European mean nitrate concentration shows an unbalanced view of nitrate distribution. The presentation above is therefore separated in the following sub-indicators into western, eastern and Nordic countries.

On average, groundwaters in western Europe have the highest nitrate concentration, due to the most intensive agricultural practices, twice as high as in eastern Europe, where agriculture is less intense. Groundwaters in Norway and Finland generally have low nitrate concentrations.

At the European level there is some evidence of a small decrease in concentrations of nitrate in rivers. The decrease has been slower than for phosphorus because measures to reduce agricultural inputs of nitrate have not been adequately implemented across EU countries and because of the time lags between the reduction of agricultural nitrogen inputs and soil surpluses, and resulting reductions in surface and ground water concentrations of nitrate.

Concentrations of orthophosphate in European rivers have in general been decreasing steadily over the past 10 years. In the old EU Member States this is because of the measures introduced by national and European legislation, in particular the Urban Waste Water Treatment Directive, which has increased levels of wastewater treatment with, in many cases, tertiary treatment that involves the removal of nutrients. There has also been an improvement in the level of wastewater treatment in the new EU Member States, though not to the same levels as in the old Member States. In addition, the transition recession in the economies of the new Member States may have played a part in the decreasing phosphorus trends because of the closure of polluting industries and a decrease in agricultural production leading to less use of fertilisers. The economic recession in many of the new EU Member States ended by the end of the 1990s. Since then many new industrial plants with better effluent treatment technologies have been opened. Fertiliser applications have also started to increase to some extent.

During the past few decades there has also been a gradual reduction in phosphorus concentrations in many European lakes. However the rate of decrease appears to have slowed or even stopped during the 1990s. As with rivers, discharges of urban wastewater have been a major source of pollution by phosphorus, but as treatment has improved and many outlets have been diverted away from lakes, this source of pollution is gradually becoming less important. Agricultural sources of phosphorus, from animal manure and from diffuse pollution by erosion and leaching, are both important and need increased attention to achieve good status in lakes and rivers.

The improvements in some lakes have generally been relatively slow despite the pollution abatement measures taken. This is at least partly because of internal loading and because the ecosystems can be resistant to improvement and thereby remain in a bad state. Such problems may call for restoration measures, particularly in shallow lakes.

Agriculture is the largest contributor of nitrogen pollution to groundwater, and also to many surface water bodies, since nitrogen fertilisers and manure are used on arable crops to increase yields and productivity. In the EU, mineral fertilisers account for almost 50 % of nitrogen inputs into agricultural soils and manure for 40 % (other inputs are biological fixation and atmospheric deposition). Consumption of nitrogen fertiliser  (mineral fertilisers and animal manure) increased until the late 1980s and then started to decline, but in recent years it has increased again in some EU countries. Consumption of nitrogen fertiliser  per hectare of arable land is higher in the old than in the new EU Member States and Accession countries. Nitrogen from excess fertiliser percolates through the soil and is detectable as elevated nitrate levels under aerobic conditions and as elevated ammonium levels under anaerobic conditions. The rate of percolation is often slow and excess nitrogen levels may be the effects of pollution on the surface up to 40 years ago, depending on the hydrogeological conditions. There are also other sources of nitrate, including treated sewage effluents, which may also contribute to nitrate pollution in some rivers.

Reference
COM (2002) 407 final. Implementation of Council Directive 91/676/EEC concerning the protection of waters against pollution caused by nitrates from agricultural sources. Synthesis from year 2000 Member States reports. Report from the Commission. COM, Brussels.


Specific policy question: Are nitrate concentrations in our groundwater decreasing?

Nitrate concentrations in groundwater bodies between 1993 and 2002 in different regions of Europe

Note: Western Europe: Austria, Belgium, Denmark, Germany, Netherlands; 27 GW-bodies

Data source:

Waterbase (Version 4)

Downloads and more info

Present concentration of nitrate in groundwater bodies in European countries, 2002

Note: The number of groundwater monitoring stations in each country is given in brackets

Data source:

Waterbase

Downloads and more info

Specific assessment

Nitrate concentrations in groundwater in different regions of Europe
Nitrate concentrations in groundwaters have remained relatively stable since the early 1990s. They vary between the different regions of Europe.

The relatively high nitrate concentration in groundwater in western European countries can be seen as consequence of the intensive agriculture and the usage of nitrogen fertilisers. The temporal development of the total nitrogen fertiliser consumption within these regions and the regional differentiation in concentration levels is very similar. Data on nitrogenous fertiliser use  show in all countries with consistent time series except for Germany and Lithuania a decline with a range from 5 % to 57 % in 2002 compared to 10 years before. For the Slovak Republic no data are available [2].

Not only are consumption figures high in western European countries, but also the usage per hectare of agricultural land. In 1994, the Netherlands, Denmark, Belgium and Germany were amongst the countries with the highest nitrogen fertiliser use related to the agricultural area. In Finland (11.) and Norway (4.) the nitrogen fertiliser usage is also high but the agricultural area represents only 9 % and 3 % respectively of the total land area [1]. Although the agricultural area in the new EU Member States ranges between 15 % (Cyprus) and 60 % (Hungary) of the total land area, agriculture is less intense than in western Europe. The nitrate fertiliser use per hectar of agricultural land is about the half of that in former EU 15 [3].

Fertiliser consumption and nitrate concentrations in groundwater do not show a direct relationship at this level. However, fertiliser consumption is an indicator for agricultural intensity and should give an estimate of the nitrogen load of the environment [1].
In Malta, analysis of nitrate values in groundwater measured at pumping stations over the 25 year period 1976-2001 indicates a steady increase. Generally the highest values are observed to occur in the north western part of Malta [6]. In Estonia quaternary aquifers used by small or individual settlements are subject to agricultural pollution (nitrates and pesticides) as well as military pollution from the Soviet period [7].
Furthermore, low nitrate concentration levels can occur due to reducing conditions. Therefore the indicator on ammonium and dissolved oxygen has been introduced to provide complementary information.

65 % of the demand for drinking water in Europe is covered by groundwater. The rate in Austria and Denmark is 99 % . In Finland approximately 60 % of the total water supply distributed by Finland's waterworks consists of groundwater [8]. In Germany, more than 70 % of the drinking water supply comes from groundwater and springs. Often groundwater is used untreated, particularly from private wells. It has been shown that drinking water in excess of the nitrate limit can result in adverse health effects, especially in infants less than two months of age. Decentralised drinking water supplies in some western European countries have been linked to water-related outbreaks. Contaminated drinking-water is one of the five major environmental risks perceived by citizens in the new Member States and the accession countries as affecting their own health [9].

Trends in nitrate concentrations in groundwater
Between 1993 and 2002, there was a significant decreasing trend or trend reversal in 32 % of groundwater bodies for which there were available data. However, 20 % of groundwater bodies also showed increasing trends of nitrate over the same period, reflecting that emissions of nitrate in the catchments of these groundwater bodies may not yet have been reduced or indicating that the effects of reducing emissions have not yet become evident because, for example, of high nitrogen surpluses in agricultural soils and/or long time lags before the effects of measures become apparent.

There have been significant decreases in nitrate concentrations in some groundwater bodies in some European countries. Finland (with other Nordic countries) generally has the lowest nitrate concentrations in its groundwater. However, about 22 % of Finnish groundwater bodies showed an increasing concentration between 1993 to 2002, perhaps indicating increasing pressures from agriculture and other sectors emitting nitrate. Also varying hydrological conditions may at least partly explain the upward trends.

There is often a significant time lag (up to 40 years) between changes in agricultural practices and changes in groundwater quality. The actual time lag for an individual groundwater body depends on its hydrogeological conditions. Therefore, some of the indicated upward trends in groundwater bodies might, for example, be caused by intensification of agricultural practice some 20 years ago. The actual cause effect relationship has to be assessed individually for each groundwater body. Nevertheless, it is an indication that remediation and improvement measures have to be implemented over medium or rather long term in order to reverse upward trends.

Present concentrations of nitrate in groundwater
Nitrate drinking water guide levels are exceeded in around one-third of the groundwater bodies for which information is currently available.

The concentrations of nitrate in groundwater in the different European countries generally reflect the relative importance and intensity of the driving forces affecting water quality. Those countries with low intensity driving forces perhaps coupled with effective measures to reduce nutrient emissions (pressures) (particularly the Nordic countries) generally have relatively low concentrations of these determinands. In contrast those countries with high intensity driving forces, perhaps coupled with ineffective measures to reduce emissions, have relatively high concentrations (for example some new EU countries).

20 of the 27 countries with available information had groundwater bodies exceeding the drinking water directive guide concentration for nitrate of 25 mg NO3/l, and 17 of these also had groundwater bodies exceeding the maximum allowable concentration of 50 mg NO3/l. Countries with the greatest agricultural land use and highest population densities (such as Denmark, Germany, Hungary and the UK), generally had higher nitrate concentrations than those with the lowest (such as Estonia, Norway, Finland and Sweden) reflecting the impact of emissions of nitrate from agriculture.

 

 

Specific policy question: Are concentrations of nutrients in our surface waters decreasing?

Nitrate concentrations in rivers between 1992 and 2002 in different regions of Europe

Note: Western Europe: Austria (152), Denmark (32), France (235), Germany (121), Luxembourg (3), UK (113)

Data source:

Waterbase (Version 4)

Downloads and more info

Phosphorus concentrations in rivers (orthophosphate) between 1992 and 2002 in different regions of Europe

Note: Number of monitoring stations in brackets Western Europe: Austria (103), Denmark (32), France (204), Germany (109), United Kingdom (30)

Data source:

Waterbase (Version 4)

Downloads and more info

Present concentration of nitrate in rivers in European countries, 2002

Note: The number of river monitoring stations in each country is given in brackets

Data source:

Waterbase (Version 4)

Downloads and more info

Present concentration of phosphorus in rivers (orthophosphate) in European countries, 2002

Note: The number of river monitoring stations in each country is given in brackets

Data source:

Waterbase (Version 4)

Downloads and more info

Nitrate concentrations in lakes between 1992 and 2002 in different regions of Europe

Note: Western Europe: Germany (5), UK (2)

Data source:

Waterbase (Version 4)

Downloads and more info

Phosphorus concentrations in lakes (total phosphorus) between 1992 and 2002 in different regions of Europe

Note: Number of monitoring stations in brackets Western Europe: Austria (2), Germany (5), Denmark (23), Ireland (1)

Data source:

Waterbase (Version 4)

Downloads and more info

Present concentration of nitrate in lakes in European countries, 2002

Note: The number of lake monitoring stations in each country is given in brackets

Data source:

Waterbase (Version 4)

Downloads and more info

Present concentration of phosphorus in lakes (total phosphorus) in European countries, 2002

Note: The number of lake monitoring stations in each country is given in brackets

Data source:

Waterbase (Version 4)

Downloads and more info

Specific assessment

Nitrate concentrations in different regions of Europe

Nitrate concentrations in lakes have remained relatively stable since the early 1990s. There is some evidence that nitrate concentrations are decreasing in some rivers. Nitrate concentrations vary between the different regions of Europe particularly in rivers.

There is a close relationship between use of fertilisers and nitrate concentrations in surface waters in European regions. Concentration of nitrate in western European countries still remains relatively high as well as the nitrogenous fertiliser use. In the new member states, surface water concentrations of nitrate are lower due to lower application of nitrate in agriculture. Nordic countries generally have the lowest nitrate concentrations in its rivers and lakes.

The observed decrease in nitrate concentrations in some rivers and lakes of some EU countries can be seen as a result of national and international measures to control nitrogen pollution, in particular, from agricultural sources. However the decreases in concentrations have been relatively slow because of inadequate implementation of the Nitrate Directive by EU countries and because of the sometimes long delays between measures being applied and concentrations decreasing. The latter could be due, for example, to large nitrogen surpluses in agricultural soil which potentially may take years to decrease. Any decreases in the new member countries are likely to be due to the decrease in agricultural productivity during the economic transition period, for example the decrease in use of nitrogenous fertilisers.

Trends in nitrate concentrations in surface waters

Around 40 % and 9 % of monitoring stations on Europe's rivers and lakes, respectively, showed a decreasing trend of nitrate concentrations between 1992 and 2002 reflecting the success of legislative measures to reduce nitrate pollution.
However, 14 % of the river stations and 15 % of lake stations showed increasing trends of nitrate over the same period, reflecting that emissions of nitrate in the catchments of these rivers and lakes may have not yet been reduced or indicating that the effects of reducing emissions have not yet become evident because, for example, of high nitrogen surpluses in agricultural soils.

There have been significant decreases in nitrate concentrations at some river and lake stations in some European countries. In the old EU countries assessed, Denmark had the highest proportion of river stations with decreasing trends indicating that national and EU measures introduced to reduce nitrate pollution, such as those in the nitrates directive, are having some effect. Finland has the lowest nitrate concentrations in its rivers and lakes. However, about 20% of Finnish river stations and 28 % (2 out of 7) of lake stations showed an increasing concentration between 1992 to 2002, perhaps indicating increasing pressures from agriculture and other sectors emitting nitrate. Also the varying hydrological conditions may at least partly explain the upward trends. The other EU countries had different proportions of river stations with decreasing, no and increasing trends. In the new EU countries, the Czech Republic had the highest proportion of river stations (74 %) with decreasing nitrate concentrations and no stations with increasing trends. The eight other new EU countries with available data had varying proportions of river stations with decreasing, no and increasing trends. Poland had the highest proportion of river stations (34 %) with increasing concentrations. The decreasing trends are probably because of the decrease in agricultural productivity and activity in these countries during the transition of their economies to become more market orientated. This has led to, for example, decreases in nitrogenous fertiliser use and in numbers of livestock (and hence manure production), both potential sources of nitrate pollution.

Present concentration of nitrate in surface waters

Nitrate drinking water guide levels are exceeded at around 10 % of river stations and at around 1 % of lake stations for which information is currently available.

The concentrations of nitrate in rivers and lakes in the different European countries generally reflect the relative importance and intensity of the driving forces affecting water quality. Those countries with low intensity driving forces perhaps coupled with effective measures to reduce nutrient emissions (pressures) (particularly the Nordic countries) generally have relatively low concentrations of these determinands. In contrast those countries with high intensity driving forces, perhaps coupled with ineffective measures to reduce emissions, have relatively high concentrations (for example some new EU countries).

In terms of nitrate, 15 of the 25 countries with available information had a number of river stations where the drinking water directive guide concentration for nitrate of 25 mg NO3/l was exceeded, and three of these countries had stations where the maximum allowable concentration of 50 mg NO3/l was also exceeded. Countries with the greatest agricultural land use and highest population densities (such as Denmark, Germany, Hungary and the UK), generally had higher nitrate concentrations than those with the lowest (such as Estonia, Norway, Finland, and Sweden). This reflects the impact of emissions of nitrate from agriculture in the former and wastewater treatment plants in the latter group of countries.

Phosphorus concentrations in surface waters in different regions of Europe

Total phosphorus concentrations in lakes have remained relatively stable since the early 1990s.
There have been significant decreases in orthophosphate concentrations in eastern and western European rivers during the 1990s. In both rivers and lakes, however, phosphorus concentrations remain above background levels increasing the risk of eutrophication in some water bodies. The Nordic countries have relatively low concentrations reflecting the high level of wastewater treatment in those countries.

Concentrations of phosphorus in Nordic rivers and lakes are much lower than in other parts of Europe and are around what are considered to be background concentrations. This reflects the relatively low population densities in these countries and the high level of treatment of sewage effluents including the removal of phosphorus.

The concentrations of total phosphorus in lakes in eastern and western Europe are similar and show no clear trends between 1992 and 2002. Concentrations are however still above what is considered to be the general background levels: the ecological significance of these elevated levels are not known.

Concentrations of orthophosphate have steadily decreased over the last 10 years in western European rivers reflecting improvements in wastewater treatment including increasing proportions of sewage effluent subject to phosphorus removal. There were also relatively large decreases in orthophosphate concentrations in eastern European rivers during the 1990's but since 2000 there is some evidence of increases in concentrations again.  The extent and levels of sewage treatment have generally been lower in eastern than in western European countries. The more recent increases could reflect that more sewage treatment is being introduced in eastern European countries as socio-economic conditions improved in preparation of accession to the EU. However, without nutrient removal in the new plants, increased extent of sewage treatment may increase the emissions/loads of orthophosphate entering eastern European rivers. In 2002, concentrations of orthophosphate in eastern European rivers were much higher than in western. In both cases the concentrations are many times background concentrations: the ecological significance of these elevated concentrations is not known but it is probable that they contribute to the eutrophication of these rivers.

Trends in phosphorus concentrations in surface waters

Around 40 % and 20 % of monitoring stations on Europe's rivers and lakes, respectively, showed a decreasing trend of orthophosphate and total phosphorus concentrations between 1992 and 2002 reflecting the success of legislative measures to reduce emissions of phosphorus such as those required by the urban waste water treatment directive.
However, 12 % of river stations and 9 % of lake stations also showed increasing trends of orthophosphate and total phosphorus, respectively, over the same period, reflecting that emissions of phosphate in the catchments of these rivers and lakes may not yet have been reduced or indicating that in some catchments there might be increasing phosphorus surpluses in agricultural soils.

Sixteen of the 19 countries assessed had a higher proportion of river stations with decreasing orthophosphate concentration than those with increasing trends. Two (Bulgaria and Slovenia) had more river stations with increasing concentrations than decreasing. Estonia and Italy were the only countries with no river stations showing increasing trends. The total phosphorus data on lakes is limited in many cases to only a few lakes in each country (e.g. Ireland, Estonia and Latvia), and therefore information from these countries must be treated with some caution. Denmark, Finland, Hungary and the Netherlands had a higher proportion of lakes with decreasing total phosphorus concentrations than those with increasing concentrations. Austria and Germany had no lake stations showing increasing trends.

The increasing trends might be because of ineffective control of phosphorus in some river catchments, particularly those with relatively small (in terms of load) sources of phosphorus that might fall outside legislative requirements. Dishwasher detergents containing phosphorus are also becoming increasingly important as dishwashers are increasingly used in more affluent societies. There are also cases where agricultural sources of phosphorus are becoming more important in catchments as point sources are progressively reduced. Phosphorus surpluses may also be increasing in some agricultural soils.

All the new EU countries, except Slovenia, had some river stations with decreasing phosphate concentrations. The decreasing trends reflect a general improvement of sewage treatment in these countries (though they have not yet fully implemented the urban waste water treatment directive) and/or the closure of polluting industries that has occurred during the restructuring of their economies as part of the process of transition into the EU.

Present concentration of phosphorus in surface waters

The concentrations of phosphorus in rivers and lakes in the different European countries generally reflect the relative importance and intensity of the driving forces affecting water quality. Those countries with low intensity driving forces (e.g. low population density) perhaps coupled with effective measures to reduce nutrient emissions (pressures) (particularly the removal of phosphorus from waste water effluents in the Nordic countries) generally have relatively low concentrations of these determinands. In contrast those countries with high intensity driving forces, perhaps coupled with ineffective measures to reduce emissions, have relatively high concentrations (for example some new EU countries).

Those countries with high proportions of nutrient removal in their sewage treatment works (such as Sweden, Finland and the Netherlands) have relatively low orthophosphate concentrations whereas those countries with relatively low nutrient removal, high population densities and high phosphorus fertiliser usage (such as France, Italy and UK) tend to have relatively high orthophosphate concentrations.

As already described the ecological significance of the elevated concentrations of phosphorus in rivers and lakes is not known. The water framework directive requires the achievement of good ecological status in surface water bodies. Where nutrient emissions are identified as a pressure impacting/decreasing ecological status then target concentrations equating to good ecological status will have to be set for each type of river and lake water body. It is anticipated, therefore, that in the longer term concentrations of phosphorus in European rivers and lakes will continue to decrease and as a result eutrophication to decrease and ecological quality increase.

Reference

[1] EEA (2000). Groundwater quality and quantity in Europe. Environmental assessment report No 3. Copenhagen. http://reports.eea.eu.int/groundwater07012000/en
[2] EEA Dataservice. Fertiliser consumption - Raw data and trend. http://dataservice.eea.eu.int/dataservice/viewdata/viewpvt.asp?id=184
[3] EEA (2004). Agriculture and the environment in the EU accession countries. Implications of applying the EU common agricultural policy. Environmental issue report No 37. EEA, Copenhagen. http://www.eea.eu.int/
[4] German Environmental Report 2002. http://www.bmu.de/english/download/files/umweltbericht_engl_2002.pdf
[5] COM (2002) 407 final. Implementation of Council Directive 91/676/EEC concerning the protection of waters against pollution caused by nitrates from agricultural sources. Synthesis from year 2000 Member States reports. Report from the Commission. COM, Brussels.
[6] State of the Environment Report for Malta. 2002. http://www.mepa.org.mt/environment/publications/soer2002/SOER02.PDF
[7] State of Environment in Estonia. 2002. http://nfp-ee.eionet.eu.int/SoE/index_en.htm
[8] Finnish State of the Environment. Environmental administration. http://www.environment.fi/default.asp?node=6085&lan=en
[9] WHO (2004). Health and the Environment in the WHO European Region: Situation and policy at the beginning of the 21st century. Part I. The environment health situation in the WHO European region. Executive summary. Fourth Intergovernmental Preparatory Meeting. WHO, Copenhagen. http://www.euro.who.int/EEHC
[10] Working database groundwater: Umweltbundesamt Vienna.  No online access.
[11] Waterbase - Groundwater quality - Information and pressures on groundwater bodies. http://dataservice.eea.eu.int/dataservice/viewdata/viewpvt.asp?id=265
[12] Indicator fact sheet 05 - Nitrogen balance in agricultural soils
[13] Indicator fact sheet 02 - Numbers of livestock
IEEP (2002): Background study on the link between agriculture and environment in accession countries. National reports. IEEP, London. http://www.ieep.org.uk

Data sources

Policy context and targets

Context description

This indicator is not directly related to a specific policy target. The environmental quality of freshwater with respect to eutrophication and nutrient concentrations is, however, an objective of several directives. These include: the Nitrates Directive (91/676/EEC), aimed at reducing nitrate pollution from agricultural land, the Urban Waste Water Treatment Directive (91/271/EEC), aimed at reducing pollution from sewage treatment works and certain industries, the Integrated Pollution Prevention and Control Directive (96/61/EEC), aimed at controlling and preventing pollution of water from industry and the Water Framework Directive, which requires the achievement of good ecological status or good ecological potential of rivers across the EU by 2015. The Water Framework Directive also requires the achievement of good groundwater status by 2015 and also the reversal of any significant and sustained upward trend in the concentration of any pollutant. In addition, the Drinking Water Directive (98/83/EC) sets the maximum allowable concentration for nitrate of 50 mg/l. It has been shown that drinking water in excess of the nitrate limit can result in adverse health effects, especially in infants less than two months of age. Groundwater is a very important source of drinking water in many countries and is often used untreated, particularly from private wells.

One key approach of the Sixth Environment Action Programme of the European Community 2001-2010 was to 'integrate environmental concerns into all relevant policy areas', which could result in a more intense application of agri-environmental measures to reduce nutrient pollution of the aquatic environment (e.g. in the Common Agricultural Policy).

Targets

This indicator is not directly related to a specific policy target. The environmental quality of surface waters with respect to eutrophication and nutrient concentrations is, however, an objective of several directives:

-         Drinking Water Directive (98/ 83/EC) - maximum allowable concentration for nitrate of 50 mg/l.

-         Surface Water for Drinking Directive (75/440/EEC) - guideline concentration for nitrate of 25 mg/l

-         Nitrates Directive (91/676/EEC) - requires the identification of groundwater sites/bodies where annual average nitrate concentrations exceed or could exceed 50 mg NO3/l.

-         Urban Waste Water Treatment Directive (91/71/EEC) - aims to decrease organic pollution

Related policy documents

Methodology

Methodology for indicator calculation

Source of data (data handling part): The data in Waterbase iscollected through the Eurowaternet process and is therefore a sub-sample of 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. Information on the sub-national scales should be sought from other sources.

Data on groundwater bodies, rivers and lakes is collected annually through the WISE-SoE data collection process. WISE SoE was previously known as EUROWATERNET (EWN) and EIONET-Water.

The data requested on ground water includes the physical characteristics of the groundwater bodies, proxy pressures on the groundwater area, as well as chemical quality data on nutrients and organic matter and hazardous substances in groundwater.

The data requested on rivers and lakes includes the physical characteristics of the river/lake monitoring stations, proxy pressures on the upstream catchment areas, as well as chemical quality data on nutrients and organic matter, and hazardous substances in rivers and lakes. It also includes the biological data (primarily calculated as national Ecological Quality Ratios), as well as information on the national classification systems for each Biological Quality Element and water body type.

These reporting obligations are EIONET Priority Data flows and are used for EEA core set of indicators.

Station selection: No criteria are used for station selection (except for time series and trend analysis - see below). For groundwater, time series are based on data for groundwater bodies, while the WISE maps of the most recent data are based on data for groundwater monitoring stations. For EU countries, there are two sets of groundwater body delineations available, the Eionet and the WFD delineation. Sometimes these do not overlap completely. As a general rule, the WFD delineation is chosen, but there are some exceptions, where the Eionet delineation is used: Croatia (a new EU Member State), Lithuania, Slovakia, Netherlands and Finland (all or many long time series are lost if using WFD delineation) and a composite Italian groundwater body not overlapping with the WFD groundwater bodies. For non-EU countries, only the Eionet delineation is available.

Determinants: The determinants selected for the indicator and extracted from Waterbase are:

  • for groundwater: nitrate,
  • for rivers: nitrate, total oxidised nitrogen and orthophosphate,
  • for lakes: total phosphorus.

 

Mean: Annual mean concentrations are used in the present concentration and time series presentations. In a few cases, where annual data seem to have been reported incorrectly as annual and/or where the inclusion of seasonal data gives a higher number of complete time series, gaps in annual data series have been filled with data from seasonal time series. Countries are asked to substitute any sample results below the limit of detection (LOD) or limit of quantification (LOQ) by a value equivalent to half of the LOD or LOQ before calculating the station annual mean values. Average mean concentration values of zero or null are discarded from the calculations or replaced by the median value, as long as this value is not zero or null.

An automatic QA/QC procedure excludes data (stations*year) from further analysis. This is based on flagging in Waterbase, deriving from QA/QC tests. In addition a semi-manual QA procedure is applied, to identify outliers which are not identified in the QA/QC tests. This comprises e.g. values deviating strongly from the whole time series, values not so different from values in other parts of the time series, but deviating strongly from the values closest in time, consecutive values deviating strongly from the rest of the time series or whole data series deviating strongly in level compared to other data series in the country. Such values are eventually flagged in Waterbase (if not confirmed valid), but not until the year after, due to timing issues. More details on the QA/QC procedure are found here:

  • groundwater QA/QC description
  • rivers QA/QC description
  • lakes QA/QC description

 

For rivers where nitrate and total oxidised nitrogen (TON) are monitored at the same station and at the same time, nitrate values are given precedence. For stations where only TON is reported, this data is used instead of nitrate. Also, in cases where more years of data are available for TON than nitrate for a single station, the TON data is used. All values are labelled as nitrate in the graphs, but it is indicated in the graph notes for which countries TON data are used.  

Inter/extrapolation and consistent time series 

For time series and trend analyses, only series that are complete after inter/extrapolation (i.e. no missing values in the station data series) are used. This is to ensure that the aggregated data series are consistent, i.e. including the same stations throughout the time series. In this way assessments are based on actual changes in concentration, and not changes in the number of stations. For rivers and lakes, “stations” in this context means individual monitoring stations. For groundwater it means groundwater bodies, i.e. the basis for inter/extrapolation and selection of complete data series is groundwater body data series. Each groundwater body may have several monitoring stations, and in some cases the number of monitoring stations has changed over the years. This means that some of the complete data series for groundwater (after inter/extrapolation) are not truly consistent, and must hence be regarded as more uncertain than the complete series for lakes and rivers. The purpose of choosing this approach is to increase the number of consistent groundwater time series.

Changes in methodology: Station selection and inter/extrapolation. 

Until 2006, only complete time series (values for all years from 1992 to 2004) were included in the assessment. However, a large proportion of the stations was excluded by this criterion. To allow the use of a considerably larger part of the available data, it was in 2007 (i.e. when analysing data up until 2005) decided to include all time series with at least seven years of data. This was a trade-off between the need for statistical rigidity and the need to include as much data as possible in the assessment. However, the shorter series included might represent different parts of the whole time interval, and the overall picture may therefore not be reliable. In 2009, it was decided rather to inter/extrapolate all gaps of missing values of 1-2 year for each station. At the beginning or end of the data series 1 missing value was replaced by the first or last value of the original data series, respectively. In the middle of the data series, missing values were replaced by the values next to them for gaps of 2 years and by the average of the two neighbouring values for gaps of 1 year.

In 2010 this approach was modified, allowing for gaps of up to 3 years, both at the ends and in the middle of the data series. At the beginning or end of the data series up to 3 years of missing values are replaced by the first or last value of the original data series, respectively. In the middle of the data series, missing values are replaced by the values next to them, except for gaps of 1 year and for the middle year in gaps of 3 years, where missing values are replaced by the average of the two neighbouring values. Only time series with no missing years for the whole period from 1992 after such inter/extrapolation are included in the assessment. This procedure increases the number of stations that can be included in the time series/trend analysis. Still, the number of stations is markedly reduced compared to the analysis of the present situation, where all available data can be used.

Aggregation of time series 

The selected time series (see above) must be aggregated into a smaller number of groups and averaged before the aggregated series can be displayed in a time series plot. Data for all determinands are grouped into five geographic regions of Europe, containing the following countries:

Eastern: CZ, EE, HU, LT, LV, PL, SI, SK. 

Northern: FI, IS, NO, SE. 

Southern: CY, ES, GR, IT, PT.

South-Eastern: AL, BA, BG, HR, ME, MK, RO, RS, TR, XK.

Western: AT, BE, CH, DE, DK, FR, IE, LI, LU, NL, UK.

Country codes

Some of the listed countries are not included in the figures because there were no stations with complete time series after inter/extrapolation.

Data for river determinants are in addition grouped into six sea region catchments, which are defined not by countries but by river basin districts. The data thus represents rivers or river basins draining into that particular sea. The sea regions are defined as Arctic Ocean, Greater North Sea, Celtic Seas, Bay of Biscay and the Iberian Coast, Baltic Sea, Black Sea and Mediterranean Sea. The sea region delineation is according to the Marine Strategy Framework Directive (MSFD) Article 4, with the Arctic Ocean added as a separate region. As the catchment area draining into what is defined as the North-East Atlantic region of the MSFD is very big, it was decided rather to use the sub-region level here, but merging the Celtic Seas and the Bay of Biscay and the Iberian Coast.

Determinants are also aggregated for the whole of Europe. 

Trend analyses

Trends are analysed by the Mann-Kendall method (Jassby and Cloern 2013) in the free software R (R Core Team 2013). This is a non-parametric test suggested by Mann (1945) and has been extensively used for environmental time series (Hipel and McLeod, 2005). Mann-Kendall is a test for monotonic trend in a time series y(x), which in this analysis is nutrient concentration (y) as a function of year (x). The test is based on Kendall's rank correlation, which measures the strength of monotonic association between the vectors x and y. In the case of no ties in the x and y variables, Kendall's rank correlation coefficient, tau, may be expressed as tau=S/D where S = sum_{i<j} (sign(x[j]-x[i])*sign(y[j]-y[i])) and D = n(n-1)/2. S is called the score and D, the denominator, is the maximum possible value of S. The p-value of tau is computed by an algorithm given by Best and Gipps (1974). The tests reported here are two-sided (testing for both increasing and decreasing trends). Data series with p-value < 0.05 are reported as significantly increasing or decreasing ("strong trends"), while data series with p-value >= 0.05 and <0.10 are reported as marginally significant ("weak trends"). The results are summarised by calculating the percentage of units (groundwater body/river station/lake station) within each category relative to all units within the specific aggregation (Europe or region). The test analyses only the direction and significance of the change, not the size of the change.

The size of the change is estimated by calculating the Sen slope (or the Theil or Theil-Sen slope)(Theil 1950; Sen 1968) using the R software. The Sen slope is a non-parametric method where the slope mis determined as the median of all slopes (yj − yi)/(xj − xi) when joining all pairs of observations(xi,yi). Here the slope is calculated as the change per year for each unit (groundwater body/river station/lake station). This is summarisedby calculating the average slope (regardless of the significance of the trend) for all units in Europe or a selected region. Multiplying this by the number of years of the time series gives an estimate of the absolute change over time. This can be related to the mean value of the aggregated time series to give a measure of relative change. The Sen slope was introduced for this indicator in 2013.

The Mann-Kendall method or the Sen slope will only reveal monotonic trends, and will not identify changes in the direction of the time series over time. Hence a combination of approaches is used to describe the time series: A visual inspection of the time series, describing whether the general impression is a monotonic trend, no apparent trend, clear shifts in direction of the trend or high variability with no clear direction; an evaluation of significant versus non-significant and decreasing versus increasing monotonic trends using the Mann-Kendall results; an evaluation of the average size of the monotonic trends using the Sen slope results.

Present concentration distributions:

The latest year for which there are concentration data for the river, lake and groundwater stations is selected for each country separately. The number of stations with annual mean concentrations occurring in the selected concentration classes are then calculated and presented. The allocation of a station to a particular class is based only on the face value concentration and not on the likely statistical distribution around the mean values.

  • The class defining values for nitrate are based on typical background concentrations in the different water categories and the legislative standards (50 mg NO3/l) and guide values (25 mg NO3/l). 
  • The class defining values for orthophosphate (rivers) and total phosphorus (lakes) concentrations are based on typical background concentrations in the different water categories and on the range of concentrations found in Waterbase and only give an indication of the relative concentrations of phosphorus in each country.

 

More information is given in the WISE maps.

Methodology for gap filling

Methodology for gap filling is described above (under Inter/extrapolation and consistent time series).

Methodology references

Uncertainties

Methodology uncertainty

Nitrate concentrations in groundwater originate mainly from anthropogenic influence caused by agricultural land-use. Concentrations in water are the effect of a multidimensional and time-related process, which varies from groundwater body to groundwater body and is, as yet, less quantified. To evaluate the nitrate concentration in groundwater and its development, closely-related parameters such as ammonium and dissolved oxygen have to be taken into account. 

Data sets uncertainty

The data sets for groundwater and rivers include almost all countries within the EEA, but the time coverage varies from country to country. The coverage of lakes is less good. Countries are asked to provide data on rivers and lakes and on important groundwater bodies according to specified criteria. These rivers, lakes and groundwater bodies are expected to be able to provide a general overview of river, lakes and groundwater quality at the European level, based on truly comparable data. 

Rationale uncertainty

No uncertainty has been specified

More information about this indicator

See this indicator specification for more details.

Generic metadata

Topics:

Water Water (Primary topic)

Tags:
water | csi
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 020
  • WAT 003
Geographic coverage:
Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia (FYR), Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom

Contacts and ownership

EEA Contact Info

Peter Kristensen

Ownership

EEA Management Plan

2010 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled once per year
Filed under: ,

Comments

European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100