The EU Water Framework Directive

Statistical aspects of the identification of groundwater pollution trends, and aggregation of monitoring results.

Project duration: December 1999 to December 2001

The project lasted for 2 years until December 2001. It was commissioned and financed at approximately 1/3 by DG Environment of the European Commission, ~2/3 by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management and by important in-kind contributions from the project partners.

A consortium of partners from 11 EU Member States was formed under the leadership of the Umweltbundesamt. Institutions from 5 countries as well as the ECPA as stakeholder participated as observers in the project. Sub-contractor and responsible for the development of the statistical concepts was the German company quo data.

This project and the working group of this project was part of the "Common Strategy on the Implementation of the WFD", initiated by the European Commission to achieve a common understanding and approach on the implementation of the WFD.


Starting point and overall objectives
The EU Water Framework Directive (WFD) defines in Article 4 "environmental objectives" for surface water, groundwater and protected areas. The criteria for achieving good groundwater chemical status are defined in Annex V 2.3.2 and in particular require that concentrations of pollutants (in groundwater) do not exceed any quality standards applicable under other relevant Community legislation according Article 17. Further there is a requirement to identify and reverse any significant and sustained upward trends in the concentration of pollutants.

This project focused on the development of particular algorithms for the identification of trends in pollutants (Annex V 2.4.4) and a data aggregation method for interpretation and presentation of groundwater chemical status as defined in Annex V 2.4.5.



Objectives of the project
The main goal of the project was to establish and propose an appropriate data aggregation method for interpretation and presentation of groundwater chemical status as defined in the WFD and to develop and propose algorithms for trend and trend reversal assessment at the groundwater body level respectively for groups of groundwater bodies. Minimum requirements for calculation and the treatment of concentrations below the limit of quantification had to be determined.

The following main aspects had to be addressed:

  • The methods had to be statistically correct;
  • In line with the requirements and the implementation schedule of the WFD (e.g. especially regarding monitoring and reporting);
  • A pragmatic way which can be implemented in different administration systems and applied for different hydrogeological conditions should be preferred;
  • Concentrations below the detection limit;
  • Groundwater pollution that is unevenly distributed within a groundwater body;
  • Influences originating from diffuse and/or point sources;
  • One assessment method had to be developed and proposed for each issue (data aggregation, trend assessment and trend reversal assessment).

The approach
As the proposed procedure had to be applicable to all types of GW-bodies in Europe (different hydrogeological characteristics, size, number of sampling sites, pressures etc.) the whole development and discussions were supported and based on test data sets (GW-body description and GW-quality data) of 21 GW-bodies in 9 countries.

An inventory of currently applied methods for data aggregation and trend assessment in the partner countries was the starting point of testing these methods with the test data sets and of developing new algorithms and procedures. This multiple testing was enabled by a software tool which was developed for the purpose of this project.


The outcome of the project comprises algorithms and a procedures proposed for data aggregation (for status assessment), for trend assessment and for trend reversal assessment in line with the requirements of the WFD. Furthermore, an algorithm for assessing the representativeness of the monitoring network was developed. All results are summarized in a comprehensive project report which is complemented by 10 Annexes describing the results in greater detail.

The software tool GWstat was developed for demonstration and testing purposes of the proposed algorithms (network assessment, data aggregation, trend and trend reversal assessment). GWstat can be downloaded free of charge (including a set of test data) and tested with own groundwater quality data.

The final report was also published as "Technical Report on Groundwater Trends" at the website of DG Environment.  



Examples and results presented in this project were elaborated on the basis of test data sets provided by project partners to develop proposals for algorithms on the basis of real data. They serve for demonstration purposes only and do not anticipate assessments by the Member States
Material in this report reflects the discussion and conclusions of the working group and does not necessarily reflect the position of the EU and its Member States.