Collated for the purposes of intercalibrating the outputs of the Northern GIG WFD rivers macroinvertebrate tools. This dataset is specific to the intercalibration of the tools assessing river acidification. Includes data from a large number of rivers from across the GIG region, provided by participating countries. The dataset includes raw invertebrate data and physico-chem data in addition to some typological information. Note that not all the data from this dataset will be made available to BioFresh science work packages or the data portal. More information on this dataset can be found in the Freshwater Metadatabase - BFE_50 (http://www.freshwatermetadata.eu/metadb/bf_mdb_view.php?entryID=BFE_50).