Report on Harmonisation of freshwater biological methods

8. For the purpose of the WFD intercalibration exercise it may be necessary toidentify common metrics (see option 2 of the Guidance on the IntercalibrationProcess 10 ). This is the case when Member State’s assessment methods are not directlycomparable, and involves the agreement on a common WFD method by the MemberStates in a GIG.9. The common metrics should be indicative of the relevant biological qualityelement and sensitive to the pressure that is assessed. These may be selected from oneof the Member State’s existing assessment methods, if acceptable for the otherMember States in the GIG, but also can be specifically developed in the GIGs. For thecommon metric, type-specific good status boundary values need to be established inthe GIGs following the application of an agreed boundary setting procedure using adata set assembled for the purposes of the intercalibration exercise. The results of thecommon assessment method will be used as the basis for adjusting the boundary EQRvalues of the national assessment methods.10. The applicability of a common metric is dependent of the availability of a suitabledata set from which the common metric(s) can be calculated to enable reliableapplication of the agreed boundary setting procedure, and the availability of a meansof estimating and taking into account differences in the bias of the methods whenapplied to the data set referred to above.11. In general, common metrics are biological metrics widely applicable within alarger geographical region, which can be used to derive comparable informationamong different countries and waterbody types. Basic features are the ability indiscriminating different quality classes and the possibility of calculating them from awide range of geographical contexts, i.e. where different effort is placed on themonitoring exercise and different expertise is available for taxonomic identification(Buffagni and Erba, 2004).10‘Guidance on the Intercalibration Process’ available at http://113