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Nutrients in freshwater

Indicator Assessment Created 11 Oct 2010 Published 20 Dec 2010 Last modified 03 Sep 2015, 07:17 PM
Note: new version is available!
Topics: ,
Indicator codes: CSI 020 , WAT 003

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.

Key messages

  • Average nitrate concentrations in European groundwaters increased from 1992 to 1998, and have remained relatively constant since then.
  • The average nitrate concentration in European rivers decreased by approximately 9 % between 1992 and 2008 (from 2.4 to 2.2 mg/l N), reflecting the effect of measures to reduce agricultural inputs of nitrate.
  • Average orthophosphate concentrations in European rivers have decreased markedly over the last two decades, being almost halved between 1992 and 2008 (47 % decrease). Also average lake phosphorus concentration decreased over the period 1992-2008 (by 26%), the major part of the decrease occurring in the first half of the period. The decrease in phosphorus concentrations reflect both improvement in wastewater treatment and reduction in phosphorus in detergents.
  • Overall, reductions in the levels of freshwater nutrients over the last two decades primarily reflect improvements in wastewater treatment. Emissions from agriculture continue to be a significant source.

Are concentrations of nutrients in our freshwaters decreasing?

Average concentrations of nutrients in European groundwaters and surface waters (1992-2008) Fig. 1a: Nitrate in groundwater; Fig. 1b Nitrate in rivers; Fig. 1c Orthophosphate in rivers; and Fig. 1d: Total phosphorus in lakes

Note: Concentrations are expressed as annual mean concentrations. Only complete series after inter/extrapolation are included (see indicator specification). The number of groundwater bodies/river stations/lake stations included per country is given in metadata (see downloads and more info). Fig 1a: Nitrate concentration in European groundwater 1992-2008 Fig 1b: Nitrate concentration in European rivers 1992-2008 Fig 1c: Orthophosphate concentration in European rivers 1992-2008 Fig 1d: Total phosphorus concentration in European lakes 1992-2008

Data source:
Downloads and more info

Nitrate in groundwaters. There was a slight increase in annual mean nitrate concentrations in European groundwaters from 1992 to 1998, followed by a minor decrease.

Nitrate in rivers: At the European level there has been a small decrease in concentrations of nitrate.

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 halved over the past 16 years. In many rivers the reduction started in the 1980s. The decrease is due to the measures introduced by national and European legislation, in particular the Urban Waste Water Treatment Directive [4], 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 wastewater 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. Agricultural sources of phosphorus are still important.

Are nitrate concentrations in our groundwater decreasing?

Nitrate concentrations in groundwater between 1992 and 2008 in different geographical regions of Europe.

Note: The data series per region are calculated as the average of the annual mean for groundwater bodies (GWBs) in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of groundwater bodies included per geographical region is given in parentheses.

Data source:

WISE-SoE GW quality (version 10)

Downloads and more info

Present concentrations per country

See also WISE interactive maps:  Nitrates in groundwater by country

Groundwater nitrate concentrations primarily reflect the relative proportion and intensity of agricultural activity. Although there were no countries where the average groundwater nitrate concentrations exceeded the threshold Groundwater Quality Standard of 50 mg/l nitrates as laid down in the Groundwater Directive (2006/118/EC) [2] in 2008, 13 out of 27 countries had groundwater bodies (GWBs) with average concentration above the standard. Spain, Belgium and Denmark had the highest proportion of GWBs with average concentration above the standard, but there was also a significant number of GWBs above the standard in Germany, Bulgaria, Romania and Portugal. Groundwater nitrate concentrations were generally low (most GWBs < 10 mg/l NO3) in Norway, Sweden, Finland, Estonia, Latvia, Bosnia and Herzegovina and Serbia.

Trends in groundwater nitrate concentration (see also Fig. 1)

Looking at individual GWBs there is wide variation in trends, with 21% of the GWBs showing significantly decreasing nitrate concentrations since 1992 (an additional 5% showed a marginally significant decrease), while 24% of the GWBs showed significantly increasing concentrations (an additional 5% marginally significant). The countries with the highest proportions of GWBs with significant decreasing trends are Austria, Latvia and Portugal.

Geographical region time series and trends (Fig. 2)

There is marked variation in groundwater nitrate concentrations between different geographical regions of Europe, with high concentrations in Western Europe and low concentrations in Northern Europe. Overall nitrate concentrations in Western, Northern and Eastern Europe have remained relatively stable since 1992, although there is marked variation between different GWBs.

In Southern Europe (only groundwater data from Portugal) there has been a marked decrease (3 out of 4 groundwater bodies significant decrease). Likewise, Southeastern Europe is only represented by Bulgaria. Here there was a marked increase until 1998, but since then the concentrations have stabilised.

Are concentrations of nutrients in our surface waters decreasing?

Nitrate concentrations in rivers between 1992 and 2008 in different geographical regions of Europe.

Note: The data series per region are calculated as the average of the annual mean for river monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per geographical region is given in parentheses.

Data source:

WISE-SoE Rivers (Version 10)

Downloads and more info

Nitrate concentrations in rivers between 1992 and 2008 in different sea regions of Europe.

Note: The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). Two regions are not shown in the figure due to a lack of data (Barents Sea: 1 station, Norwegian Sea: 2 stations); these stations have NO3 concentrations below 0.8 mg/l N.

Data source:

WISE-SoE Rivers (Version 10)

Downloads and more info

Phosphorus concentrations in rivers (orthophosphate) between 1992 and 2008 in different geographical regions of Europe.

Note: The data series per region are calculated as the average of the annual mean for river monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations included per geographical region is given in parentheses

Data source:

WISE-SoE Rivers (Version 10)

Downloads and more info

Phosphorus concentrations in rivers (orthophosphate) between 1992 and 2008 in different sea regions of Europe

Note: The sea region data series are calculated as the average of annual mean data from river monitoring stations in each sea region. The data thus represents rivers or river basins draining into that particular sea. Only complete series after inter/extrapolation are included (see indicator specification). The number of river monitoring stations per region is given in parentheses.

Data source:

WISE-SoE Rivers (Version 10)

Downloads and more info

Phosphorus concentrations in lakes (total phosphorus) between 1992 and 2008 in different geographical regions of Europe.

Note: The data series per region are calculated as the average of the annual mean for lake monitoring stations in the region. Only complete series after inter/extrapolation are included (see indicator specification). There were no stations with complete series after inter/extrapolation in the South and Southeast regions. The number of lake monitoring stations included per geographical region is given in parentheses

Data source:

WISE-SoE Lakes (Version 10)

Downloads and more info

Nitrate

Present concentrations per country 

See WISE interactive maps: Mean annual 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/l N are found predominantly in northwest France, Spain, Belgium and the southeast UK. However, several rivers with concentrations exceeding 3.6 mg/l N are found in many other countries, particularly in the Netherlands, Denmark, Germany, Austria, Ireland, Hungary, Italy, Estonia and Latvia. Rivers in the more sparsely populated Northern Europe and mountainous regions generally have average concentrations less than 0.8 mg/l N.

Trends in nitrate concentration (see also Fig. 1):

Overall there has been a significant decrease in river nitrate concentrations at 29% of the stations (an additional 5% marginally significant), while there has been a significant increase at 16% of the stations (an additional 5% marginally significant). The countries with the highest proportions of river stations with significant decreasing trends are Denmark, the Netherlands, Czech Republic and Germany. Across Europe as a whole, the rate of improvement is still slow, reflecting the continued significance of agricultural nitrogen emissions.

Sea region time series and trends (Fig. 3)
see also map of sea regions
Nitrate concentrations in rivers vary markedly between the sea regions of Europe. The average nitrate concentration in rivers draining to the North Sea is around 2 mg/l N higher than that in rivers feeding the Atlantic Ocean, the Black Sea and the Mediterranean Sea and almost 3 mg/l N  higher than that of rivers draining to the Baltic Sea.

Declining nitrate concentration trends are most clearly observed in the North Sea and Black Sea regions, while there has been a slight increase for the Atlantic Ocean and Mediterranean Sea regions

Geographical region time series and trends (Fig. 4)
There is marked variation in river nitrate concentrations between regions, with Western Europe rivers having 2-3 mg/l higher concentrations than Northern Europe, on average, and the remaining regions being somewhere in between. Except for the increasing trend in Southern Europe, nitrate concentrations are generally decreasing (East, Southeast, West) or fairly stable (North)

Phosphorus

Present concentration per country

See also WISE interactive maps: Mean annual Orthophosphate in rivers & Mean annual Total Phosphorous in lakes

Relatively low concentrations of phosphorus in rivers and lakes are found in Northern Europe (Scotland, Norway, Sweden, and Finland), the Alps and the Pyrenees, 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/l P) are found in several regions with high population densities and intensive agriculture, including: Western Europe (southeast UK, the Netherlands, Belgium), Southern Europe (Italy, central Spain and Portugal), Eastern Europe (Poland, Hungary), and South-Eastern Europe (Bulgaria, Former Yugoslav Republic of Macedonia, Turkey). Given that phosphorus concentrations greater than 0.1-0.2 mg/l P 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 also Fig. 1)

Average concentrations of orthophosphate in European rivers have decreased markedly since 1992, particularly during the first half of this period. At 42 % of the river stations there has been a significant decline in orthophosphate concentration since 1992 (an additional 5 % marginally significant), while there has been an increase at only 6% of the stations (an additional 2% marginally significant).
For lakes there has been a significant decline in total phosphorus concentrations since 1992 at 31% of the stations (an additional 9% marginally significant), while there has been a significant increase at 8% of the stations (an additional 2% marginally significant).
This decrease reflects the success of legislative measures to reduce emissions of phosphorus such as those required by the Urban Waste Water Treatment Directive [4].

Sea region time series and trends  (Fig. 5)
see also map of sea regions.
Orthophosphate concentrations are generally lowest for rivers draining to the Baltic Sea and (after 1999) highest for rivers draining to the Atlantic Ocean. The strongest decrease in orthophosphate concentration is found for rivers draining to the Mediterranean Sea, but the decrease is almost similarly strong in all other regions except the Baltic Sea.
Although the decline is much less in the latter half of the period, there is still a decline going on.

Geographical region time series and trends (Fig. 6)
Northern Europe has markedly lower river orthophosphate concentrations than in the other regions of Europe. The same pattern is seen for lake total phosphorus concentrations (Fig. 7). River orthophosphate concentrations have generally decreased in all regions except Northern Europe, where there was hardly any change. The trend is strongest for Western Europe and least strong for Southeastern Europe

Lake total phosphorus (Fig. 7) shows a similar strong decrease for Western Europe and virtually no trend for Eastern Europe. The trend in lake total phosphorus in Northern Europe is small.

The difference between lake and river data for Eastern Europe is partly caused by the inclusion of a number of Czech stations in the rivers dataset, with predominantly negative trends. In addition there is a stronger decline in Hungarian rivers than lakes, and there has been increasing concentrations in Latvian lakes while there has been a slight decrease for the rivers.

References and links to policy information

[1] The Drinking Water Directive (DWD): Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption.

[2] Groundwater Directive (2006/118/EC).

[3]  The Nitrates Directive: Directive 91/676/EEC on nitrates from agricultural sources.

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

[5] The Water Framework Directive (WFD): Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy.

[6] EEA Core Set of Indicators CSI01 Emissions of acidifying substance and CSI05 Exposure of ecosystems to acidification, eutrophication and ozone

 

Indicator specification and metadata

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).


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

Data sources

Generic metadata

Topics:

Water Water (Primary topic)

Tags:
soer2010 | biodiversity | csi | nitrates | nutrients | freshwater quality | lakes | rivers | water | orthophosphate | thematic assessments | freshwater | phosphorus
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 020
  • WAT 003
Dynamic
Temporal coverage:
1992-2008
Geographic coverage:
Albania, Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Ireland, Latvia, Liechtenstein, Lithuania, Luxembourg, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland, United Kingdom

Contacts and ownership

EEA Contact Info

Peter Kristensen

Ownership

EEA Management Plan

2010 1.4.2 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled once per year
European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100