Environmental pressure in the Netherlands, Eutrophication theme: introduction and policy
Eutrophication concerns the enrichment of ecosystems with nitrogen and phosphorus, primarily from the application of manure and fertiliser on land. This enrichment can have adverse effects on ecosystems and public health.
Sources of eutrophying substances
Nitrogen and phosphorus are primarily brought into the environment by the agriculture and horticulture target sector, in the form of manure and fertilisers applied to soil. Discharges to surface water by industry and sewage treatment plants also contribute to eutrophication.
Impact of eutrophication on nature
Eutrophication on land results in a change in the make-up of ecological communities. This generally results in the dominance of a few plant and animal species, or of just one. The effects of discharges to surface water include algal blooms.
Along with acidification and desiccation, eutrophication is a major cause of the decline of terrestrial nature in the Netherlands. The function of groundwater as an ingredient in the public water supply may be threatened by excessive nitrate concentrations.
Objectives for nutrients in groundwater and surface water
- MAC for nitrate
The World Health Organization (WHO), followed by the EU (in its Drinking Water Directive of 1980) and the Dutch government (in the Water Supply Act), set the Maximum Allowable Concentration (MAC) for nitrate in water for human consumption at 50 mg/l. The EU Nitrate Directive assumes that all water which is a possible source of drinking water must meet the MAC standard. Consequently, the groundwater in the Netherlands must also meet this MAC standard. - Target value for nitrate in groundwater
On the basis of the MAC for nitrate in groundwater, the Dutch government has adopted a target value for nitrate in groundwater of 25 mg/l. - MACs for stagnant waters vulnerable to eutrophication
Averages for summer must not exceed 0.15 mg/l of total phosphorus and 2.2 mg/l total nitrogen. Stagnant (still) waters are usually lakes and ponds. - Target values of 0.05 mg/l total phosphorus and 1 mg/l total nitrogen have been established to really tackle eutrophication. These values serve as guidelines in respect of influences on other bodies of water, such as those under national management. These general values, however, do not do justice to the differences between regions and types of water. The Fourth Policy Memorandum on Water Management (V&W, 1999) and the Third National Environmental Policy Plan (VROM, 1997) therefore allow for a system of differentiated standards.
