Eutrophying substances in fresh surface water in the Netherlands, 1985-2001
The levels of nitrogen and phosphorus in fresh surface water are still too high. The focus of new policy is on setting standards for each water type instead of one generic standard.
Levels of nitrogen and phosphorus remain too high
The levels of nitrogen in fresh water have fallen slightly. However, the values are almost everywhere in excess of the guideline MAC value, the objective for 2006. Levels of phosphorus have fallen faster than those of nitrogen in recent years. In the nationally managed waters, levels have conformed with the MAC for a number of years now; levels in the IJsselmeer have been up to standard for more than ten years. In recent years, the situation seems to have stagnated in the regionally managed waters.
Alteration of current policy required
The government wishes to combat the overfertilisation (eutrophication) of surface water. The exceedance of MACs for nitrogen and phosphorus can result in undesirable effects on ecosystems such as excessive algae growth.
Numerous measures, such as phosphate removal, have already been taken in wastewater treatment plants (UWWTPs). Phosphates are now also banned in laundry detergents and various measures have been taken in agriculture and horticulture.
MAC values for the nutrients nitrogen (N; 2.2 mg/l) and phosphorus (P; 0.15 mg/l) have been adopted for 'eutrophication-sensitive, stagnant waters', in other words for waters with little or no current. For other waters, these values are 'guidelines'. These general values, however, do not do justice to the differences between regions and types of water. The Fourth Water Management Policy Document (V&W, 1999) and the Third National Environmental Policy Plan (VROM, 3) therefore allow for a system of differentiated standards. Proposals have recently been made in this respect (CIW, 2002; Van Liere and Jonkers, 2002).
New EU policy goes further
However, conformity with the MAC does not provide any guarantees for the recovery of eutrophication-sensitive stagnant waters. This requires conformity with a lower desired quality standard.
The EU Water Framework Directive came into force recently. The aim of this directive is to arrive in time at a 'Sound Ecological Situation' based on concentrations of nutrients and other substances. It is expected that this new European policy will result in supplementary measures.
Different figures than previously
The graphs all show a selection of stagnant or eutrophication-sensitive sites. Flowing waters and waters for which inadequate information was available were not included. Because this selection process was not carried out in preceding years, the current data deviate from those published previously. Information about monitoring sites can be found at the bottom of this indicator under references and notes.
Monitoring sites
The monitoring sites in the rivers are sites chosen by the Commissie Integraal Waterbeheer' (Commission on Integrated Water Management - CIW). For bodies of water under national management a group of monitoring sites was compiled from 25 representative sites selected by the committees from the entire monitoring network of national water bodies. It includes sites in the Rhine, Maas, Scheldt, IJssel, IJsselmeer and in a number of canals and lakes.
For the waters under regional management, the CIW committee made a selection of monitoring sites that is representative for the management areas of the agencies concerned (district water boards and dike/polder boards). These sites are located in the larger waters under regional management.
A selection was made in all cases of stagnant or eutrophication-sensitive sites; flowing waters and waters for which inadequate information was available were not included. Because this selection process was not carried out in preceding years, the current data deviate from those published previously. The concentrations of nutrients are summer averages.
