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3.1.7 ICMi (Intercalibration Common Metric index)

ICMi (82) was developed as a fully WFD compliant metric for ICMi is a multi-metric invertebrate index based on family-
classifying river invertebrate status that could be applied level analysis so that every Member State can calculate
to data from all countries, to facilitate the intercalibration it. The index covers the three main components of quality
of river invertebrate classifications throughout Europe, defined in the WFD’s normative definitions (Annex V) with
including the UK (see Chapter 1 Section 5.8). It was equal weightings, although the weights given to individual
adopted as the national classification metric in Italy, and metrics were not equal but based on their precision and
I recommend it for new Member States that have not reliability (Table 5.3). ICMi is always expressed as an
developed their own national classification metrics for Environmental Quality Ratio (EQR).
WFD status classification, at least for their first cycle of
river basin planning.
ICMi – Intercalibration
This can give new Member States time to develop their
own methods based on the monitoring data that they common metric index
collect in their first cycles of WFD river basin planning.
This index is used to intercalibrate invertebrate status
ICMi does not need intercalibration other than to check classifications for the Water Framework Directive
the local reference definitions and it will already have been across central Europe, including the UK, with variations
compared to national classification metrics used by other used in other parts of Europe. It is a multi-metric index
Member States sharing transboundary rivers and therefore based on a group of biotic indices that together cover
river basin plans. It is truly compatible with WFD. Its class all the invertebrate responses recognised by the
boundaries have been defined already and it is easy to normative definitions in the directive.
compute.

Table 5. 3
Weightings used to combine intercalibration common metric EQRs in the Intercalibration Common Metric index (ICMi) (82)

Component of quality Weighting factor Intercalibration common metric Weighting factor

Sensitivity/tolerance 0.333 ASPT 0.333

Log10(sel EPTD+1) 0.266
Abundance/habitat 0.333
1-GOLD 0.067

N-families 0.167

Richness/diversity 0.333 EPT taxa 0.083

Shannon-Weiner diversity 0.083

ASPT = Biological Monitoring Working Party Average Score per Taxon.
Log 10(sel EPTD+1) = logarithm of the sum of abundance of selected Ephemeroptera, Plecoptera, Trichoptera and
Diptera +1. The selected EPTD are Heptageniidae, Ephemeridae, Leptophlebiidae, Brachycentridae, Goeridae,
Polycentropodidae, Limnephilidae, Odontoceridae, Dolichopodidae, Stratiomyidae, Dixidae, Empididae,
Athericidae & Nemouridae.
1-GOLD = 1- abundance of Gastropoda, Oligochaeta and Diptera.
EPT taxa = number of families of Ephemeroptera, Plecoptera and Trichoptera.
The intercalibration common metrics are expressed as EQRs by dividing by their reference values. They are
multiplied by the weighting factors and summed before the final ICMi is again expressed as an EQR.
ICMi can be calculated with ASTERICS software, available at:
https://gewaesser-bewertung.de/index.php?article_id=419&clang=0

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