Type of indicator

Environmental

Indicator C40

Water quality

Definition

The water quality indicator shows the potential impact of agriculture on water quality due to pollution by nitrates and phosphates.

Pollution by nitrates and phosphates is assessed through 4 sub-indicators:

1. Gross Nitrogen Balance (GNB-N): Potential surplus of nitrogen on agricultural land (Gross Nitrogen Surplus).

2. Gross Phosphorus Balance (GNB-P): Potential surplus of phosphorus on agricultural land (Gross Phosphorus Surplus).

The gross nutrient balances provide an estimate of the potential water pollution. They represent the total potential threat of nitrogen and phosphorus surplus in agricultural soils to the environment. When N and P are applied in excess, they can cause surface and groundwater (including drinking water) pollution and eutrophication.

3. Nitrates in freshwater - Groundwater: % of monitoring sites in 3 water quality classes (high, moderate and poor);

4. Nitrates in freshwater - Surface water: % of monitoring sites in 3 water quality classes (high, moderate and poor). 

 

The three water quality classes are defined as follows:

  • High quality: concentration close to natural values or within the threshold indicated in the legislation for low-polluted water.
  • Moderate quality: concentration above natural standard but still below hazardous level.
  • Poor quality: concentration above hazardous level. 

The actual concentration classes are the following.

Groundwater

  • High ("<10 mg/l NO3 " + ">=10 mg/l NO3 and <25 mg/l NO3 ")[1] 
  • Moderate (">=25 mg/l NO3 and <50 mg/l NO3 ") 
  • Poor (">=50 mg/l NO3 ").

Surface water

  • High ("<0.8 mg/l N " + ">=0.8 mg/l N and <2.0 mg/l N ")[2] 
  • -       Moderate (">=2.0 mg/l N and <3.6 mg/l N " + ">=3.6 mg/l N and >5.6 mg/l N ") 
  • Poor (">=5.6 mg/l N and <11.3 mg/l N " + ">=11.3 mg/l N ")

The following indicators already exist: 

- Agri-environmental indicator 27.1 Water quality – Nitrates in freshwater: nitrate pollution of water. http://ec.europa.eu/eurostat/statistics-explained/index.php/Agri-environmental_indicator_-_nitrate_pollution_of_water

- CSI 020 Nutrients in freshwater (European Environment Agency). Concentrations of nitrate in rivers and groundwater. The indicator can be used to illustrate geographical variations in current nutrient concentrations and temporal trends.

- Agri-environmental indicator 15 Gross Nitrogen Balance: Potential surplus of nitrogen on agricultural land, http://ec.europa.eu/eurostat/statistics-explained/index.php/Agri-environmental_indicator_-_gross_nitrogen_balance

- Agri-environmental indicator 16 Risk of pollution by phosphorus (Gross Phosphorus Balance): Potential surplus of phosphorus on agricultural land, http://ec.europa.eu/eurostat/statistics-explained/index.php/Agri-environmental_indicator_-_risk_of_pollution_by_phosphorus

Unit of measurement

1: kg N/ ha/ year

2.: kg P/ ha/ year

The sub-indicators 1 and 2 are expressed as a 4 year average.

3-4: % of monitoring sites

N.B. The concentration of nitrate is expressed as mg/l of nitrates (NO3-mg/l) for groundwater and mg/l of nitrogen (N-mg/l) for rivers.

Data source

1-2 : Eurostat, Agri-environmental indicators

3-4:-European Environment Agency (EEA) – Nutrients in freshwater: Data voluntarily reported by Member States (EEA Member Countries) via the WISE/SOE (State of Environment) data flow annually. 

References/location of the data

1-2: Eurostat, Agri-environmental indicators, Pressure and Risks, Table Gross Nutrient Balance (aei_pr_gnb);

3-4: EEA website, based on data reported to EIONET: Waterbase_rivers, Waterbase_groundwaters, CSI020 , http://www.eea.europa.eu/data-and-maps/indicators/nutrients-in-freshwater; 

Data collection level

1-2: national
 3-4: 

- data from the European Environment Agency: national and river basin level/water body 

- data from the Nitrate Directive reporting system (DG environment): national and river basin level.

Frequency

1-2: annual

3-4: not defined

Delay

1-4: not defined.

Comments/caveats

The AEI 15 on Gross Nutrient Balance is at the moment considered the most appropriate indicator to assess the CAP's impact on water quality, since it is directly linked with agriculture. It must be noted, however, that this indicator is only indirect; it shows the potential risks, depending on local soil conditions and farm management practices, rather than the actual water quality trends. 

For the interpretation of nitrates in fresh water, it should be kept in mind that it is hardly feasible to distinguish the contribution of agriculture or the role of a policy to this status compared to other influencing factors, even though it is acknowledged that agriculture is a main contributor.

For this reason the preferred option is to use data for Gross Nutrient Balance (4-year average) in combination with data for nitrates in freshwater by water quality classes. On the one hand, figures for nitrates in freshwater would give a comprehensive overview of the actual state of water bodies, allowing comparison over time. On the other hand, data for Gross Nutrient Balance would provide an indication of the impact of agriculture on those figures and give information about potential pollution by phosphates.

Since data for both indicators are only available at national level and since annual national balances can mask important regional or monthly variations, other sources at Member State level should be explored. As for the GNB, in the future, data should also be available at regional level (NUTS 2). Eurostat and the Joint Research Centre are working on a pilot project with 5 countries to regionalise GNB data.

Data on pesticides are currently less robust than those for nitrates, thus the originally proposed component on pesticides in freshwater has been dropped from the indicators for water quality.

The quality of data at the moment is quite poor as several MSs are missing.

[1] Although the natural concentration of NO3 in groundwater is below 10 mg/l, in the Nitrate Directive for water bodies that show concentrations below 25 mg/l the monitoring programme should be repeated every eight years instead of four, in this line this threshold can be taken into account to design high quality or low-polluted water bodies.

[2] While natural concentration of nitrates in freshwater is about 1 mg/l, concentrations over 10 mg/l  (2 mg-N/l) are those at which eutrophication and other negative effects on aquatic ecosystems appear. Therefore, this limit could be taken into account to design high quality or low-polluted water bodies.