The AQEM assessment system is the main result of the European Union funded project AQEM, which was carried out from March 2000 to February 2002. It serves the implementation of the EU Water Framework Directive and provides a system for assessing ecological quality in European streams with benthic macroinvertebrates.

Aims of the AQEM system are:

• to classify a stream stretch in a quality class from 5 (high) to 1 (bad) based on a macroinvertebrate taxa list
• to give information about the cause of a possible degradation to help direct future management practices

In contrast to many other comparable projects, the development of the AQEM system has been based on a new dataset covering both the fauna and general stream characteristics of 28 common European stream types.

The AQEM system

• classifies a stream stretch in a quality class from 5 (high) to 1 (bad)
• gives information about the cause of a possible degradation

As demanded by the Water Framework Directive AQEM applies a stream type-specific approach. Particularly at the European scale this is inevitable, since e.g. an highland stream in Sweden and a lowland stream in Italy are inhabited by very different macroinvertebrate communities.

Therefore, for each stream type different calculation methods are applied based on the comparison with different reference conditions. However, the system always follows the same evaluation scheme and each stream-type specific method fits into the general assessment framework.

This framework can be defined as follows:

• Stressor-specific approach; for each stream type the "main" degradation factor presently affecting the stream is assessed. This might be acidification (e.g. in Northern Sweden), degradation in stream morphology (e.g. in Central Europe) or organic pollution (e.g. in Southern Europe). In some cases more than one stressor is separately assessed and the results of the individual steps are then combined to a final assessment result or the assessment is addressing the "general degradation".
• Multimetric system; for each stream type those calculation methods have been identified, which are best at indicating a sites' state of degradation. The results of the individual calculation methods are then combined in a "multimetric formula", which is always the same.
• The multimetric result is converted into the final score ranging from 5 (high quality) to 1 (bad quality).

AQEM was funded by