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testing (including climate change) to quantify effects of measures is most costeffectively
done using appropriate policy models. We have identified that these
exist (albeit better for some contaminants than others).
• There is still a need for field/catchment scale experimentation to address some
issues. We suggest that the best way forward is to assess what models are now
capable of achieving in support of programmes of measures. Where a lack of
knowledge limits progress (e.g. the effectiveness of mechanism of a mitigation
method), then experiments should then be commissioned to provide the data.
• This integrated, multi-pollutant ‘model centric’ approach, that attempts to
integrate all previous models that have previously focussed on individual final
goal of a robust policy model for diffuse pollution.
In terms of the suggested ‘21st Century Challenge’ of microbial modelling to limit
pathogen risk as indexed by compliance with the faecal indicator criteria set in relevant
Directives, source apportionment budget studies and some empirical black box
models predicting faecal indicator concentration and flux from land use parameters
have been reported for UK catchments. Most recently, the UKs sentinel catchment
for WFD research, the Ribble catchment was modelled in this manner (Kay et al.,
2005c). Additionally, empirical studies seeking to quantify the remediation potential
of on-farm measures to reduce diffuse pollution have been completed in Scotland
and reported in Dickson et al. (2005) and Kay et al. (2005d). Other interventions
to reduce faecal indicator flux in UK catchments have been reported in Kay et al.
(2005b) (i.e. flood retention wetlands) and ‘natural treatment systems’ for effluents
including reed beds, a lagoon and integrated constructed wetland (ICWs) (Kay et
al., 2005). One of the most promising interventions reported to date are on-farm
Integrated Constructed Wetlands (ICWs) used in Ireland for treating contaminated
water from farm hardstanding areas and roofs (Harrington, 2005). Initial nutrient and
faecal indicator removal efficiencies seem very encouraging and the systems appear
more robust to flow alterations than engineered ‘natural treatment’ systems such as
reed beds (Kay et al., 2005a). However, regulatory concerns have been expressed
concerning the downward translocation of pollutants to groundwater and these are
the subject of current investigation with EU support in Ireland and the UK.
The conclusions of Haygarth et al. (2005) identify key research requirements of the
policy community. There is a particular need to progress the field of catchment microbial
and sediment modelling. The microbial component has received more international
attention in Canada, Australia, the United States (i.e. via the TMDL approach outlined
above) than to date in the UK and EU as part of the WFD implementation. When this
emerging area has a similar science base to the nutrient parameters, the type of
multi-parameter model needed to inform the policy community should be possible.
There is a need, however, for pan-European coordination. This might be implemented
through amendments to the current remits of the WFD ‘Common Implementation
Strategy’ and, in the UK, through attention to microbial and sediment modelling
needs by the UK Technical Advisory Groups addressing WFD implementation.
Detailed examination of this area will be required if ‘protected areas’, such as
bathing and shellfish harvesting waters, are to be managed effectively through the
implementation of the principles enshrined in the WFD as clearly envisaged in early
drafts (CEC, 2002) of the new Bathing Water Directive published in November 2005
(Anon, 2005b).
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