Development of a System for
Classifying the Ecological Potential of UK and Irish Canals
WFD 61
July 2008
EXECUTIVE SUMMARY
Project funders/partners:
Scotland & Northern Ireland Forum for
Environmental Research, Environment Agency, Scottish Environment
Protection Agency, Environmental Protection Agency, British Waterways,
Waterways Ireland, Scottish Government, Department for Environment,
Food and Rural Affairs.
Background to research
Under the European Union’s Water Framework Directive (WFD)
member states must develop methods to classify the ecological status of
their surface water bodies. Such classifications will be used to
support operational and surveillance monitoring and to select
appropriate programmes of measures for incorporation into River Basin
Management Plans. In the case of artificial or heavily modified water
bodies the WFD develops the concept of ‘ecological
potential’ as a parallel to ecological status in natural
water bodies. Navigation is recognised within the WFD as one reason why
artificial water bodies may be created, or why the hydromorphological
characteristics of natural water bodies may be modified. This report
presents the first phase in the development of a system for classifying
the ecological potential of canals (i.e. artificial cuts) in Britain
and Ireland.
Objectives of research
- To
devise a canal
classification tool that will be used to classify canal waterbodies by
comparing their ecological condition to their expected ecological
potential.
- To provide sufficient
information to determine the ecological potential of a canal water body
based on the relevant biological, hydromorphological and
physico-chemical quality elements as defined by the WFD.
Key findings and
recommendations
- A definition of Maximum Ecological
Potential (MEP) was agreed which considers boat traffic to be a
characteristic of the canal system and therefore a source of permitted
environmental variation. Thus MEP is determined by the best available
biology for any specified level of boat traffic.
- Sufficient data and understanding only
exists to develop biological classification tools for canals based on
macroinvertebrates and macrophytes. Historic data has been collected
using robust and tested approaches which are suitable for adoption in
monitoring although several options for stream lining data collection
merit further exploration. Biological data provides comprehensive
coverage of canals in England and Wales but coverage of Scotland and
Ireland is poor. A dedicated phase of data collection has addressed
these gaps and this data will be integrated into the final phase of
this project.
- Several approaches to reference site
screening were developed and tested due to the difficulty in linking
biological data to pressure data. For macroinvertebrates screening by
pressure data was possible whereas for macrophytes it was necessary to
identify sites with the best biology for a given level of boat traffic.
Some re-evaluation of reference sites may be required for both quality
elements after the incorporation of data from Scotland and Ireland.
- Different metrics were developed for
macroinvertebrates and macrophytes to reflect various aspects of the
normative definitions and the effects of different pressures (e.g. boat
traffic, channel modification and nutrient enrichment). Analysis of
available data indicates that with increasing traffic the flora and
fauna of canals changes from that typical of a series of well vegetated
ponds to that of a large turbid lowland river.
- The population of metric values
associated with each biological quality element in reference sites was
used as the basis for comparison with observed values at test sites in
order to obtain an Ecological Quality Ratio (EQR). Several approaches
were tested as a means of obtaining a site specific prediction of
reference metric values, with a computationally more simple and
flexible approach being preferred over the method that has
traditionally been used for river macroinvertebrates. Boat traffic,
alkalinity and bank type were the key environmental predictors of
reference values for the various metrics. An approach is presented for
macrophytes and macroinvertebrates that uses information from multiple
metrics to provide an overall measure of ecological potential for that
quality element.
- Application to canals of a
classification system designed for river macrophytes indicates that
good ecological status for a natural water body would provide a very
demanding test for canals when nutrient enrichment is the pressure
being assessed.
- Derivation of environmental standards
for supporting physico-chemical variables is problematic due to the
very limited datasets of matched biology and physico-chemistry. Values
for dissolved oxygen, Biological Oxygen Demand and ammonia derived
using invertebrates appear to be broadly in line with those standards
proposed for rivers. For nutrients, standards suggested by macrophytes
are intermediate between those suggested by macrophytes in lakes and
rivers. The most detailed analyses are possible in relation to
suspended solids. These suggest that solids of <25-35mg/L will
be required in heavily trafficked canals (>6000 passages/yr) in
order for macrophytes to achieve GEP. Suitable mitigation is therefore
likely to be needed to reduce mobilisation of the bed or erosion of
banks. In the case of phytoplankton, which have not been considered as
a biological quality element due to lack of data, several standards are
suggested for chlorophyll concentrations that might be considered
compatible with Maximum or Good Ecological Potential.
- Hydromorphological assessment occupies
a critical role in the classification of Ecological Potential of
Heavily Modified or Artificial Water Bodies because of its link to
mitigation measures and the current use of the water body.
Unfortunately hydromorphological assessment in canals is hampered by a
historically weak evidence base connecting
use>mitigation>hydromorphology>ecology.
Consequently it is difficult to assess the likely benefits of
particular measures other than by expert judgement.
- A standardized protocol has been
developed to assess hydromorphology on canals in the light of a set of
constraining factors, including use, channel size and environment and
heritage features. The best hydromorphology (ranging from passive
mitigating features to deliberate mitigation measures) which might be
expected given the various permutations of these constraining factors
can then be compared with what is observed during a simple field-based
assessment. Testing of this assessment approach remains a priority.
- Invasive species have a long history
of introduction and spread via canals. A short list of high risk
species has been prepared whose presence would preclude MEP. The
emphasis on presence alone rather than of ‘established
populations’ is somewhat more demanding than existing
recommendations but in compensation a shorter list of critical species
is proposed. This approach to classification reflects the integrated
approach that is required for management of the highest risk species
across surface water bodies.
- The current guidance on integrating
classifications using different quality elements has been followed to
provide an overall classification of ecological potential of canal
water bodies consistent with the ‘one-out, all-out rule.
Outstanding issues include an uncertainty analysis to allow the
calculation of confidence of class, although for some quality elements
where data is limited or assessments are driven by expert judgment,
indicative statements of confidence based simply on proximity to a
proposed class boundary may have to suffice.
Key words: Ecological Potential, mitigation, navigation, ecological
assessment,
hydro morphology
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N.B.
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