Development of a System for Classifying the Ecological Potential of UK and Irish Canals
WFD 61
July 2008


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
  1. To devise a canal classification tool that will be used to classify canal waterbodies by comparing their ecological condition to their expected ecological potential.
  2. 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
  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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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