Executive summary

Page Last modified 20 Apr 2016
6 min read


The European Topic Centre on Inland Waters was formed in December 1994 to undertake an identified programme of work for the European Environment Agency (EEA). This report is on one of the projects (MW1: Water Resources - quality and quantity, general approach to assessment) undertaken during 1995, and has the overall objective of suggesting possible approaches to co-ordinate and improve monitoring in the EEA area. This entailed the establishment of the detailed monitoring requirements of existing and proposed European Union (EU) legislation, policy and international agreements. At the time of finalising this report, information on monitoring requirements had not been validated by the Walloon and Brussels regions of Belgium.

Within the EEA area, many requirements for monitoring arise from the European Commission. However, there are also many other international commitments which make monitoring requirements and which are also detailed in this report.

EU legislation

Four types of directive have been employed by the EU to control the pollution of water: use-related directives; industry sector directives; substance directives; and, product directives. With the exception of the products directives, most of these directives require the implementation of monitoring, either routine programmes or preliminary investigations. The extent to which the monitoring requirements associated with directives overlap depends on commonalities between the national implementation of directive requirements, and the monitoring undertaken for this purpose will therefore vary from country to country.

The requirements made in the directives have been designed largely independently from each other. The Commission has, however, taken some initiatives to harmonise monitoring and reporting requirements in the Exchange of Information Decision (77/795/EEC as amended by Decision 86/574/EEC) and to harmonise reporting on the implementation of certain directives via questionnaires as specified in Council Decision (92/446/EEC) and laid down in the Reporting Directive (91/692/EEC).

In total four directives and one proposed directive make requirements for groundwater monitoring (the requirements made in the Dangerous Substances Directive (76/464/EEC) have been superseded by the Groundwater Directive (80/68/EEC)) and there is no overlap in the current monitoring requirements. With regard to surface waters, all monitoring requirements made in EU legislation which apply to rivers, also apply to lakes and reservoirs. Most directives which apply to freshwaters also apply to salt waters. The Shellfish Directive (79/923/EEC) is the only directive which applies to estuaries and coastal waters but not freshwaters.

Of the 15 directives that require monitoring of fresh surface waters, all include water column monitoring. The Dangerous Substances Directives and the Titanium Dioxide Directive (82/883/EEC) also require monitoring of sediment and biota. The Exchange of Information Decisions make the only requirements for flow measurements. There are eight international agreements which also require monitoring of water quantity - flows and levels.

Barriers to the harmonisation of monitoring can be introduced at the sampling, analysis, and reporting stages, and can arise either because requirements differ (i.e. conflict) or because requirements are not clearly specified (i.e. weakness).

Sampling location

The most specific requirements in terms of named water bodies and measuring stations are in the Exchange of Information Decisions. These rivers are nationally significant rivers and lakes and as such are quite likely to be sampled for other national and international obligations (e.g. Rhine and Elbe Conventions). Generally, directives require monitoring in waters designated for specified uses or effected by specified discharges. Thus the scope for overlap in terms of sampling locations is dependant on the degree to which areas where designated use and the presence of specified discharges overlap, which is probably a limited circumstance in many states. Many of the directives allow the competent authority of each Member State to make decisions on such aspects as the exact sampling point, the distance from this point to the nearest point where pollutants are discharged and the depth at which the samples are to be taken but the same sites and depths should be used in all surveys, in relation to physical and temporal conditions.

As the choice of sampling location is, for some directives, related to areas designated by the Member States rather than by the European Commission, it is unlikely that, for some directives, a comparison of quality across Europe of these designated waters will give a complete picture of quality because the degree of comparability will depend on the interpretation of the designation rules and national differences of how these are implemented. Therefore, the degree of coverage that water quality data encompasses within each country will be determined by national designations and the prevalence of the industries that are required to be regulated.

For international agreements sample location is generally be related to the purpose of the agreement often being at designated or fixed sites. Other agreements are less specific, with the sampling location being determined by the needs of the signatories or monitoring programme.

Sampling frequency and period

The sampling frequency specified in directives and in international agreements is very variable. For some directives, once the fate and behaviour of an effluent is known and the effects have been established, and as long as there is no deterioration, then there is scope for the Member States to use a lower sampling frequency than specified in the directive. The sampling period is not usually specified or, if it is, the interpretation of its definition can give rise to differences between countries (for example the definition of the bathing season). These imprecise requirements can give rise to different interpretations of results.

It is not apparent from most of the published directives whether there have been any, or if so, what, statistical considerations when defining the required sampling frequencies or numbers. These aspects have a significant effect on the statistical precision and confidence of the monitoring data produced. The required frequency should be derived with reference to the quantified risks that some waters will be misclassified (against compliance criteria).


Sources of error in the overall assessment of a determinand in a water body would include sampling and analytical errors. The analytical requirements made in directives and in international agreements are generally very basic. Most directives stipulate analytical requirements in terms of performance criteria (i.e. limits of detection, precision and accuracy) and/or by method. The degree of definition, however, varies greatly from directive to directive. Many directives make very broad requirements to use ‘appropriate methods’ for pre-treatment and analysis. The performance criteria are the key requirements with regard to analysis. Despite this several directives, for example the Titanium Dioxide Directive and all the use-related directives (except the Surface Water through the Sampling Analysis Directive), fail to establish performance requirements for analysis. In addition the laboratories concerned with applying the directives should be free to use ‘appropriate methods’ providing they satisfy performance criteria. By comparison, analytical requirements in international agreements are rarely defined in terms of performance criteria, specific methods may be laid down, but often no requirements are made.

Probably the most significant omission in the requirements for analytical techniques is a requirement for analytical quality control (AQC). Increasingly AQC is being recognised as essential for data from monitoring programmes to be reliable and comparable. Microbiological methods should be standardised for efficiency of recovery and performance (accuracy, specificity, precision) and, for securing harmonisation of results between Member States, single reference procedures must be agreed for each determinand.

Compliance Assessment

Another important aspect of directives, particularly when a comparison of quality across Member States is expressed as a comparison of compliance against limits and standard values (e.g. as in the Bathing Waters Directive), is how the compliance requirements in the directives are expressed, calculated and interpreted. Differences in interpretation of these requirements is another significant barrier to harmonisation of monitoring and implementation of directives across Europe.


As well as the aspects described above, a further significant barrier to obtaining valid and quantitative temporal and spatial comparisons of water quality across Europe is the differences in how Member States implement and interpret directives. This issue has not been addressed in this project, but it is recommended that such an assessment is undertaken.

The Future

There are European policy initiatives and proposed new directives that will potentially change and/or increase the need for national and Europe-wide monitoring. In particular the groundwater action and water management programme (GAP) will focus on the monitoring of groundwater resources, and the proposed Ecological Directive will place more emphasis on biological monitoring in all surface waters.

The outputs from Project MW1 and MW2 (inventories of current monitoring networks) have been used in the next phase of the Topic Centre’s work programme - the design of an inland water monitoring network to meet the needs of the European Environment Agency.

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