Nitrate monitoring network

Legislative framework

The Nitrates Directive (91/676/EEC) aims to reduce or prevent the pollution of water caused by the application and storage of organic and inorganic fertiliser on agricultural land. By controlling land use management, the directive aims to protect drinking water supplies, aquatic ecosystems and other legitimate uses of water.

Member states are required to identify zones where groundwater is or could contain more than 50mg/l of nitrate. All known areas of land which drain into these waters and which contribute to pollution must be designated by member states as nitrate vulnerable zones (NVZs). The designation of NVZs shall be reviewed at least every four years.

Action programmes, in respect of designated zones, must be established within 2 years of designation. Their prime objective is to reduce water pollution caused by nitrates from agricultural sources, commonly by restricting the amount and timing of nitrogen application to land.

Article 6 of the directive requires member states to monitor nitrate concentrations in groundwater at regular intervals. SEPA provides data from its Groundwater Monitoring Programme to the Scottish Government for use in defining NVZs.

The requirements of the Nitrates Directive have been transposed into Scottish legislation by The Protection of Water Against Agricultural Nitrate Pollution (Scotland) Regulations 1996 (SI 1996 No.1546 (S.137)), or Nitrates (Scotland) Regulations 1996.

Schedule (1)(b) of the regulations state that a nitrate vulnerable zone shall be identified if “groundwaters contain more than 50mg/l nitrates or could contain more than 50mg/l nitrates if action pursuant to regulation 6 is not taken”.

Establishing and developing the network

In order to establish whether Scottish groundwaters are exceeding this limit, SEPA has developed a national groundwater monitoring network. The network is based on a research project undertaken by MLURI in 2000 which classified the whole of Scotland into 'biophysical classes' based on geology, soil type and land use. By ensuring that each class has a least three groundwater monitoring points, the network aims to be representative of Scottish groundwaters.

In 2000, SEPA sampled 150 groundwater monitoring locations for the purposes of the Nitrates (Scotland) Regulations 1996. Results from this monitoring programme confirmed elevated nitrate levels (ie above 50mg/l) at a number of monitoring locations.

Sampling and development of the network in 2001 was severely curtailed by the outbreak of foot and mouth disease.

The addition of further sites in 2002 by British Geological Survey and SEPA extended the network to 218 groundwater monitoring locations. Their purpose is to increase the monitoring in those areas identified by MLURI as being at risk of having elevated nitrate concentration in groundwater.

Nitrate monitoring programme 2003

The 220 sites indicated as being monitored for nitrates in this table are sampled quarterly for the purposes of the Nitrates (Scotland) Regulations 1996 and analysed for the following determinands:

  • pH
  • conductivity
  • alkalinity
  • total suspended solids
  • nitrate
  • nitrite
  • ammoniacal nitrogen
  • total oxidised nitrogen  chloride
  • sodium
  • potassium
  • calcium
  • magnesium
  • iron
  • manganese
  • phosphate
  • sulphate