Environmental Engineering Reference
In-Depth Information
thinking behind the directive (Article 24, 2000/60/E), but the impact of
pressures other than sewage pollution on the quality and quantity of water
resources were given far more weight than previously. The aim of the directive
is to maintain and improve the quality of all substantial inland and coastal
water bodies, namely rivers, lakes, groundwater, and transitional (brackish)
and coastal waters. Under this legislation, a variety of biological, hydromor-
phological and physico-chemical quality elements must be assessed and com-
pared to a reference condition where there are no, or only very minor,
anthropogenic alterations to the values of the elements for the surface water
body type from those normally associated with that type under undisturbed
conditions.
Clearly, the idea of reference condition that forms the basis of RIVPACS
heavily influenced the drafting of WFD legislation but, in turn, the WFD set
new requirements for RIVPACS and other existing biomonitoring tools in use by
member states. A description of what constitutes 'reference condition' was now
clearly defined by legislation, and a process of screening had to be undertaken
to determine if the RIVPACS reference sites complied with these definitions.
Hydromorphological, physico-chemical and land-use characteristics of the sites
and their catchments were compiled to ensure that there were no, or very
minor, anthropogenic pressures acting upon the sites at the time they were
sampled. For point source pressures, the process was relatively straightforward
(e.g., are significant obstructions to natural flows present?), but for parameters
influenced by diffuse pressures the process was somewhat more difficult. For
most river types we do not have a measure of what the 'natural' phosphorus
concentration would be in the absence of, or with very minor, anthropogenic
pressure. Here a statistical approach was taken where deviation from end group
mean values for that variable were compared to deviations from end group mean
community response (ASPT and Ntaxa), thus correlating cause and impact
(Davy-Bowker et al.
2007a
). Those sites that indicated significant deviation from
end group mean in both the variable of interest and the community response
were deemed to be impacted. Sites that failed to pass this screening process
were removed from the reference site database, and a new classification was
derived with 835 sites covering the whole of the UK divided into 54 end groups.
As it is likely that large budgets will be riding on the assessment of ecological
quality, in the interests of transparency this database of reference sites is now
freely available (Davy-Bowker et al.
2007b
;
http://www.sniffer.org.uk
;
http://
Provision to classify biological communities and match to test sites using a
variety of pollution insensitive parameters is given in the WFD (System B),
although a simpler fixed typology based only on altitude, catchment size and
geology (System A) which produces a type classification for categorising test
