Page 157 - Freshwater-Biology-and-Ecology-Handbook

The 5M classification (also known as National Rivers become more numerous than tolerant indicators. The final
Authority, NRA, classification) was revised in 1995 to class limits were modified to suit operational experience –
become the biological General Quality Assessment (GQA) in this case some of the class boundaries for NTaxa were
classification. This took advantage of an improved version adjusted to reflect operational experience in the Scottish
of RIVPACS (RIVPACS III) based on an enhanced reference Highlands. RIVPACS IV involved a modest refinement of the
dataset with many more reference samples, particularly from reference dataset.
headwaters. The GQA classification comprised 6 classes
to give better resolution. The class boundaries were initially Separate RIVPACS models for the Scottish Highlands
set using the 5M approach, but then adjusted to better and Islands were incorporated in the GB model and a few
reflect operational requirements across the country. The reference sites representing sites that were of a poorer
class boundaries were now based on BMWP ASPT and environmental quality were removed. Because the quality
BMWP NTaxa only, as it was realised that BMWP-score of RIVPACS reference sites varied from relatively pristine in
was redundant. The development of this classification the Scottish Highlands to heavily used and populated in the
is described in Wright et al. (2000) (44) and it was used English lowlands, the environmental quality that RIVPACS
throughout the UK until 2006. predictions represent also varies.

The next major refinement of river invertebrate assessment For WFD status classification, the predictions were
was the result of a new version of RIVPACS (RIVPACS IV) standardised to a particular environmental quality referred
(Figure 3.12) and refinements of the concept of reference, to as ‘reference’ (Chapter 1 Section 5.7). Standardising the
and these changes were instigated with the introduction of predictions also standardises the EQIs that are derived from
the Water Framework Directive (WFD) in 2006. (46) The 5M them, and when they are standardised to reference state
approach for setting the initial class boundaries was used they are known as EQRs (Environmental Quality Ratios) –
again, with the median value representing the boundary see also Chapter 1 Section 5.6 Biological Quality Elements.
between Good and High status. These boundaries had This refinement improves the comparability between
proved to be robust and practical in the previous 5M (NRA) classifications of sites from different river types.
and GQA classifications. However, the boundaries were
also checked against pressures, with the Good/Moderate
boundary representing the point where sensitive indicators

value of biotic index observed in samples
EQR =
reference value of biotic index

Goera pilosa larva

Corixa punctata adult
Agabus sp. larva

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