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Indicator Assessment

Nutrients in freshwater in Europe

Indicator Assessment
Prod-ID: IND-8-en
  Also known as: CSI 020 , WAT 003
Published 23 Feb 2015 Last modified 18 Nov 2021
29 min read
This page was archived on 18 Nov 2021 with reason: No more updates will be done
  • Since 2005, average nitrate concentrations in European groundwater have declined and in 2011, the mean concentration had almost returned to the 1992 level.
  • The average nitrate concentration in European rivers declined by 0.03 milligrams per liter of nitrogen (mg N/l) (0.8%) per year over the period 1992 to 2012.
  • The decline in nitrate concentration reflects the effect of measures to reduce agricultural inputs of nitrate, as well as improvements in wastewater treatment.
  • Average orthophosphate concentration in European rivers has decreased markedly over the last two decades (0.003 milligrams per liter of phosphorous (mg P/l) or 2.1% per year).
  • Also, average lake phosphorus concentration decreased over the period 1992-2012 (0.0004 mg P/l, or 0.8% per year).
  • The decrease in phosphorus concentration reflects both improvements in wastewater treatment and the reduction of phosphorus in detergents.

Updated with 2018 data and text revised accordingly

Fig. 1: Nutrient trend

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Nitrate in groundwater: There was a slight increase in average annual mean nitrate concentration in European groundwater from 1992-1998. Since 2005, the concentrations have declined again, and in 2011 the mean concentration had almost returned to the 1992 level. The shorter time series shows the same pattern, giving hardly any trend overall. However, this larger selection of groundwater bodies shows a somewhat higher average European concentration level.
Nitrate in rivers: At European level, river nitrate concentrations have declined steadily over the period 1992-2012. The trend is the same for the time period 2000-2012, and the larger selection of stations shows a lower average concentration. Agriculture is the largest contributor of nitrogen pollution and, due to the EU Nitrate Directive and national measures, the nitrogen pollution from agriculture has been reduced in some regions over the last 10-15 years. This reduced pressure is reflected in lower river nitrate concentrations.
Phosphorus in rivers. The average concentrations of orthophosphate in European rivers more than halved over the period 1992-2012. In many rivers the reduction started in the 1980s. The marked decline is evident also for the time period 2000-2012, but the average concentration is somewhat higher when including more river stations.
The decrease in river orthophosphate is due to the measures introduced by national and European legislation, in particular the Urban Waste Water Treatment Directive [1], which involves the removal of nutrients. Also, the switch to phosphate-free detergents has contributed to lower phosphorus concentrations.
Phosphorus in lakes. During the past few decades, there has also been a gradual reduction in phosphorus concentrations in many European lakes. As treatment of urban waste water has improved, phosphorus in detergents is reduced, many waste water outlets have been diverted away from lakes and phosphorus pollution from point sources is gradually becoming less significant. However, diffuse runoff from agricultural land continues to be an important source of phosphorus in many European lakes. Moreover, phosphorus stored in sediment can keep lake concentrations high and prevent improvement of water quality despite a reduction in inputs.

Fig. 2: Groundwater - nitrate

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Present concentrations per country

See also WISE interactive maps: Nitrates in groundwater by countries and WFD gw bodies

Groundwater nitrate concentrations primarily reflect the relative proportion and intensity of agricultural activity. In 2012, 23 out of 32 countries had groundwater monitoring stations with an average concentration above the threshold Groundwater Quality Standard of 50 milligrammes of nitrate per litre (mg NO3/l) as laid down in the Groundwater Directive (2006/118/EC) [2]. Belgium and Spain had the highest proportion (more than 20%) of groundwater stations with an average concentration above the standard, but there was also a high proportion (10-20%) of groundwater stations above the standard in Austria, Cyprus, Czech Republic, Denmark, Germany, Italy, Montenegro, Netherlands and Portugal. Groundwater nitrate concentrations were generally low (most or all groundwater stations less than 10 mg NO3/l) in Albania, Bosnia and Herzegovina, Croatia, Finland, Iceland, Lithuania, Norway, Serbia, Sweden and the UK.

Trends in groundwater nitrate concentration (see Fig. 2)

There was a slight increase in average the annual mean nitrate concentration in European groundwater from 1992 to 1998. Since 2005, concentrations have declined again and in 2011, the mean concentration had almost returned to the 1992 level. By using the filter in figure 2, the groundwater nitrate trends for the individual countries are illustrated.

Looking at individual groundwater bodies (GWBs) there is a wide variation in trends (see Groundwater - nitrate - statistical analysis), with 32% of the GWBs showing decreasing nitrate concentrations since 1992, while 28% of the GWBs showed increasing concentrations. The countries with the highest proportions of GWBs with significant decreasing trends were Netherlands, Portugal and Slovakia. These countries also had the largest annual decrease in concentrations.

Geographical region time series and trends

Link: Nitrate concentrations in groundwater in different geographical regions of Europe

There is marked variation in groundwater nitrate concentrations between different geographical regions of Europe. In Western Europe, the concentrations are high, and the levels have been fairly stable over the whole period, with similar proportions of decreasing and increasing trends, and about half the GWBs with no significant trend. The other regions are represented by far fewer GWBs. Results show that Northern Europe is at the other end of the scale, with low concentrations, but as for Western Europe, levels have been fairly stable over time. In Eastern Europe, the average concentration started declining after 1996, but increased again after 2003. However, since 2008, concentrations have declined, and have, since 2010, been at about the same level as at the start of the time series, and about 10 mg NO3/l lower than in Western and Southeastern Europe. In Southeastern Europe (only represented by Bulgaria), the concentration levels were high in the period 1997-2000. Disregarding this peak, there is still an overall increasing trend, with levels now higher than in Western Europe. However, as for Western Europe, the proportions of significantly increasing and decreasing trends were similar.

Fig. 3: Rivers - nitrate

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Fig. 4: Rivers - orthophosphate

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Fig. 5: Lakes - total phosphorus

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Nitrate

Present concentrations per country

See WISE interactive maps: Nitrates in rivers

Rivers draining land with intense agriculture or high population density generally have the highest nitrate concentrations. Rivers with nitrate concentrations exceeding 5.6 mg N/l in 2012 are found predominantly in northwest France, southeast United Kingdom and northern Spain. However, a high proportion (more than 20%) of rivers with concentrations exceeding 3.6 mg N/l are found in many other countries, particularly in Belgium, France, Germany, Poland, Spain, Turkey and the United Kingdom. Rivers in more sparsely populated or mountainous regions often have concentrations less than 0.8 mg N/l, e.g. Northern Europe, Scotland and Ireland, the Pyrenees, the Alps, the Apenninnes and the Massif Central, Corsica and large parts of the Balkans and Romania.

Trends in nitrate concentration (Fig. 3)

At European level, nitrate concentrations have declined steadily over the period 1992-2012. The trend is the same for the time period 2000-2012. Some of the year-to-year variation can be explained by variation in precipitation and runoff. By using the filter in figure 3, the river nitrate trends for the individual countries are illustrated.

Overall there has been a decrease in river nitrate concentrations at 44% of the stations, while there has been an increase at 13% of the stations (see Rivers - nitrate - statistical analysis). The countries with the highest proportions of river stations with significant decreasing trends are Denmark and Germany. Denmark and Germany also had the largest annual decrease, along with Bulgaria and Latvia. Across Europe as a whole, there is a steady improvement in river nitrate concentrations, although it is still rather slow, reflecting the continued significance of agricultural nitrogen emissions.

Geographical region time series and trends

Link: Nitrate concentrations in rivers in different geographical regions of Europe.

There is a marked variation in river nitrate concentrations between regions, with western European rivers having 2-3 mg N/l higher concentrations than northern Europe, on average, and the remaining regions being somewhere in between. In eastern Europe there is hardly any trend, while nitrate concentrations are generally decreasing in the other regions (by 0.6%, 2.1% and 0.9% annually for northern, southeastern and Western Europe, respectively).

Sea region time series and trends

Link: Nitrate concentrations in rivers in different sea regions of Europe

Nitrate concentrations in rivers vary markedly between the sea regions of Europe. The average nitrate concentration in rivers draining to the Greater North Sea is currently around 1-2 mg N/l higher than that in rivers feeding the Black Sea, the Celtic Seas, the Bay of Biscay and the Iberian Coast, 2-3 mg N/l higher than the rivers feeding the Baltic Sea and the Mediterranean Sea, and around 3.5 mg N/l higher than that of rivers draining to the Arctic Ocean. The difference compared to the other sea regions was even larger at the beginning of the time series.
The Greater North Sea is the only sea region where there is a marked decreasing trend (0.05 mg N/l or 1.3% annual decrease and 60% strong declining trends). However, for the Arctic Ocean, the Black Sea and the Mediterranean Sea regions there are markedly stronger decreasing than increasing trends, but here the number of stations with no or weak trends is larger.

Phosphorus

Present concentration per country. See also WISE interactive maps: Orthophosphate in rivers and Total phosphorus in lakes

Relatively low concentrations of phosphorus in rivers and lakes are found in e.g. northern Europe (Norway, Sweden, and Finland), Scotland, Wales and Ireland, the western and French Pyrenees, large parts of southern France, the Alps, Corsica, and parts of the west Balkans and Romania, predominantly reflecting regions of low population density and/or high levels of wastewater collection and treatment. In contrast, relatively high concentrations (greater than 0.1 mg P/l) are found in several regions with high population densities and intensive agriculture, including: western Europe (south-eastern UK, Netherlands, Belgium, western Germany, northern France), southern Europe (north-eastern Spain and Italy, mid-Portugal), eastern and south-eastern Europe (Slovakia, Bulgaria, the former Yugoslav Republic of Macedonia, Serbia, Kosovo under UNSC Resolution 1244/99, Serbia, Turkey and parts of Romania). Given that phosphorus concentrations greater than 0.1-0.2 mg P/l are generally perceived to be sufficiently high to result in freshwater eutrophication, the observed high values in some regions of Europe are of particular concern.

Trends in phosphorus concentration (see Fig. 4 and Fig. 5)

Average concentrations of orthophosphate in European rivers have decreased markedly since 1992 (Fig. 4). Some of the year-to-year variation can be explained by variations in precipitation and runoff. At 52% of the river stations, there has been a decline in orthophosphate concentration since 1992, while there has been an increase at only 9% of the stations (see Rivers - phosphate - statistical analysis). For lakes, there has been a decline in total phosphorus concentrations, since 1992, at 40% of the stations, while there has been an increase at 14% of the stations (See Lakes - phosphorus - statistical analysis). By using the filter in figures 4 and 5, the river phosphate or lake phosphorus trends for the individual countries are illustrated.

This decrease reflects the success of legislative measures to reduce emissions of phosphorus, such as those required by the Urban Waste Water Treatment Directive [1] (UWWTD). The countries showing the strongest decreasing trends for lakes and/or rivers were Austria, Belgium, Denmark, France, Germany, Latvia, Liechtenstein, Lithuania, Netherlands, Switzerland and the United Kingdom. These are all countries with a large proportion of the population (more than 80%, except Latvia and Lithuania (70-80%)) connected to wastewater treatment (to a large extent tertiary), and with the exception of Latvia, Liechtenstein, Lithuania and Switzerland, all these countries were supposed to comply with the UWWTD by 2005. There are also other countries with high treatment levels (all also with a compliance deadline in 2005), but where this has been the situation for some time, the expectation is for less of a trend in phosphorus concentrations (Finland, Sweden or where there are no consistent river or lake phosphorus data series Greece, Italy, Spain).

Geographical region time series and trends

Link: Phosphorus concentrations in rivers (orthophosphate) in different geographical regions of Europe and Phosphorus concentrations in lakes (total phosphorus) in different geographical regions of Europe

Northern Europe has markedly lower river orthophosphate concentrations than in the other regions of Europe. River orthophosphate concentrations have decreased in eastern and western Europe (48% and 66% decreasing trends, respectively). In northern Europe there have hardly been any changes, while in southeastern Europe the concentrations are highly variable, giving no clear trend overall. Lake total phosphorus shows a similar strong decrease for western Europe (54% strong decreasing trends), but the trend may be leveling out from 2005. There is virtually no trend in lake total phosphorus in northern and eastern Europe.

Sea region time series and trends

Link: Phosphorus concentrations in rivers (orthophosphate) in different sea regions of Europe

Orthophosphate concentrations are generally lowest for rivers draining to the Baltic Sea and, in particular, the Arctic Ocean. For the other sea regions the concentration levels are currently fairly similar, but at the start of the time series, concentrations were highest for rivers draining to the Greater North Sea and the Celtic Seas, the Bay of Biscay and the Iberian Coast. There are more strong decreasing than increasing trends in all regions except the Arctic Ocean, but the strongest decreasing trends are found in the Celtic Seas, the Bay of Biscay, the Iberian Coast and the Greater North Sea regions (73% and 54% strong decreasing trends, respectively).

References

[1] The Urban Waste Water Directive (UWWD): Council Directive 91/271/EEC concerning urban waste-water treatment.

[2] The Groundwater Directive : Directive 2006/118/EC of the European Parliament and the Council of 12 December 2006 on the protection of groundwater against pollution and deterioration

[3] EEA Core Set of Indicators CSI024 Urban waste water treatment

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