Nutrients in freshwater (CSI 020/WAT 003) - Assessment DRAFT created Sep 2014
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- 02 Oct 2012 - Nutrients in freshwater (CSI 020/WAT 003) - Assessment published Oct 2012
- 20 Dec 2010 - Nutrients in freshwater (CSI 020/WAT 003) - Assessment published Dec 2010
- 29 Jan 2009 - Nutrients in freshwater (CSI 020/WAT 003) - Assessment published Jan 2009
- 29 Nov 2005 - Nutrients in freshwater (CSI 020/WAT 003) - Assessment published Nov 2005
- 27 Jul 2004 - Nutrients in rivers
- 09 Feb 2004 - Nitrogen and phosphorus in rivers
- 01 Jun 2001 - Phosphorus concentrations in rivers
Water (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CSI 020
- WAT 003
Key policy question: Are concentrations of nutrients in our freshwaters decreasing?
- Average nitrate concentrations in European groundwater increased from 1992 to 1998, but have declined again since 2005.
- The average nitrate concentration in European rivers declined by 0.03 mg N/l (0.8%) per year over the period 1992 to 2012.
- The decline in nitrate concentrations reflects the effect of measures to reduce agricultural inputs of nitrate as well as improvement in wastewater treatment.
- Average orthophosphate concentration in European rivers has decreased markedly over the last two decades (0.003 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 concentrations reflects both improvement in wastewater treatment and reduction in phosphorus in detergents.
Nitrate in groundwater: There was a slight increase in average annual mean nitrate concentration in European groundwaters from 1992 to 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 lower average European concentration level.
Nitrate in rivers: At the European level river nitrate concentrations have declined steadily over the period 1992 to 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 during 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 , which involves the removal of nutrients. Also the change to use of phosphate-free detergents has contributed to lower phosphorus concentration.
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 reduced, and many waste water outlets have been diverted away from lakes, phosphorus pollution from point sources is gradually becoming less important. However, diffuse runoff from agricultural land continues to be an important source of phosphorus in many European lakes. Moreover, phosphorus stored in the sediments can keep lake concentrations high and prevent improvement of water quality despite a reduction in inputs.
Specific policy question: Are nitrate concentrations in our groundwater decreasing?
Present concentrations per country
Groundwater nitrate concentrations primarily reflect the relative proportion and intensity of agricultural activity. In 2011, 20 out of 32 countries had groundwater monitoring stations with average concentration above the threshold Groundwater Quality Standard of 50 mg NO3/l as laid down in the Groundwater Directive (2006/118/EC) . Belgium and Spain had the highest proportion (more than 20%) of groundwater stations with 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 and the Netherlands. Groundwater nitrate concentrations were generally low (most or all groundwater stationsless than 10 mg NO3/l) in Albania, Bosnia and Herzegovina, Croatia, Finland, Iceland, Lithuania, Norway, Serbia and Sweden.
Trends in groundwater nitrate concentration (see Fig. 2)
There was a slight increase in average annual mean nitrate concentration in European groundwater from 1992 to 1998. Since 2005 the 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 wide variation in trends (see Groundwater - nitrate - statistical analysis), with 28% of the GWBs showing significantly decreasing nitrate concentrations since 1992 (an additional 3% showed a marginally significant decrease), while 24% of the GWBs showed significantly increasing concentrations (an additional 3% marginally significant). The countries with the highest proportions of GWBs with significant decreasing trends were the Netherlands, Portugal and Slovakia.Along with Slovenia these countries also had the largest absolute (4.6-9.1 mg NO3/l on average) and relative (21-58 % compared to the average concentration) decrease over the period.
Geographical region time series and trends
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. The results show that Northern Europe is at the other end of the scale compared to Western Europe, with low concentrations. But as for Western Europe the levels have been fairly stable over time. In Eastern Europe the average concentrations started declining after 1996, but increased again after 2003. However, after a marked decline between 2010 and 2011, the levels are currently (2011) at about the same level as 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 slightly higher than in Western Europe. However, as for the other regions, the proportions of significantly increasing and decreasing trends were similar.