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CHAPTER 3 6 – 7 The UK government has set these acidification class Although acid deposition is a problem in some parts of

boundaries in statutory directions in The Water Framework
England (the Pennines and Dartmoor), the method has not
been optimised for use in England because no English data
Directive (Standards and Classification) Directions (England
was used in its development. It was therefore not possible to
and Wales) 2015 (download from link at https://www.
check the acidification typology for England. The few data
legislation.gov.uk/uksi/2015/1623/resources), and the
Scottish Government in The Scotland River Basin District
from England that were available were closest structurally
and functionally to those from Welsh sites.
(Standards) Directions 2014 and for the Solway and Tweed,
which have separate legislation as cross-border river
basins, in The Solway Tweed River Basin District (Standards)
(Scotland) Directions 2014, both of which can be downloaded It is recommended that users in England use the reference
typology developed for Wales, and this is reflected in the
from https://www.gov.scot/publications/water- statutory directions in The Water Framework Directive
environment-legislation/. No status acidification class (Standards and Classification) Directions (England and Wales)
boundaries have been developed explicitly for English sites. 2015, download from link at http://www.legislation.gov.
uk/uksi/2015/1623/resources English uplands are in a
Dissolved Organic Carbon (DOC) data is needed to different hydro-ecoregion (Figure 3.13), so the acidification
differentiate humic (coloured) from clear waters. Lack of data classification based on Welsh reference values should be
made it impossible to test whether there was also a difference used with caution in England.
in sensitivity between these two types of environment in
Wales (and England), so there are further grounds for using The High/Good and Good/Moderate status class
WFD AWIC with caution in England if the water is humic. boundaries for WFD AWIC have been intercalibrated, but
sp
DOC is not monitored widely in England, so data is not only with Norway: Commission Decision (EU) 2018/229 (54)
always available. at https://www.legislation.gov.uk/eudn/2018/229/
annex/division/1/division/5/division/2/adopted.
McFarland (2010) also indicated that Cantrell Acid Intercalibration data for North GIG rivers at: http://www.
(51)
Neutralising Capacity (ANC, Cantrell et al. 1990 ) was freshwatermetadata.eu/metadb/pdf/BFE_50-Northern_
(52)
needed for the typology, but this requirement was removed GIG_Rivers_Macoinvertebrates_acidification_data_
from the definitive method. However, ANC is still useful in WFD_Intercalibration.pdf. One outcome from that work
acidification studies because there is a UK chemical standard was a wider comparison of methods by Moe et al. (2010). (55)
based on that parameter: download link to the standards
from https://www.legislation.gov.uk/uksi/2015/1623/
resources

Poor WFD AWIC class indicates that acid deposition may
sp
be causing an impact, but it cannot confirm it. WFD AWIC sp
will also respond to other pressures including toxic metal
pollution, which is common in mine drainage. When WHPT
NTaxa is very small, the precision WFD AWIC will be low.
sp
The official definition of the acidification classification can
be found in UK TAG’s method statements, which can be
downloaded from UK TAG website http://www.wfduk.org/
resources/category/biological-standard-methods-201
Technical guidance for calculating the acidification
classification is described in documents on UK TAG’s website
http://www.wfduk.org/ follow the link 'Biological Standard
Methods: for Rivers – Invertebrates (General Degradation)'
select River Invertebrates AWIC UKTAG Method
Statement.pdf and WFD-AWIC Calculation sheet.xls.

Figure 3.24
Front cover of UK TAG method statement
for River Invertebrate (Anthropogenic
Acidification) classification (53)

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