Canal Classification Tool - Phase 3

This project devised a canal classification tool that can be used to classify canal waterbodies.

Their ecological condition is compared to their expected ecological potential. This provides 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 Water Framework Directive (WFD).

Key Findings

  • Under the WFD, the ecological quality of an artificial waterbody is assessed by comparing its current quality with a ‘reference’ condition of Maximum Ecological Potential (MEP); for canals, MEP is determined by the best available biology, given the level of boat traffic.
  • Surveys of macroinvertebrates and macrophytes have been used to develop a classification tool for canals. The available data for macroinvertebrates is mainly recent (post 1990) but macrophyte data is mainly from 1990 or earlier and so may not represent the current state of the canal network. A protocol for new surveys that would provide sufficient data for water body classification is suggested.
  • Establishing ‘reference’ condition is a key step in classification. The project used two approaches to identifying reference sites for invertebrates and one approach for macrophytes. There was a high degree of convergence in the location of reference sites.  
  • To set environmental standards that will determine classification boundaries, the project looked at the relationships between biological data and physicochemical data. However, it was not possible to reliably determine some classification boundaries due to a small dataset and so the results must be interpreted with caution.
  • Some highly invasive species have colonised and spread via the canal system. Alien species are thus integrated into classification via a short list of high risk species that, if present in a waterbody, preclude the achievement of MEP.
  • Classification of ecological potential also includes an assessment of hydromorphology by considering what measures have taken place to mitigate boat traffic impacts. A draft protocol is suggested which compares the observed score at a site with that which might be expected if all reasonable mitigations were in place.
  • A method is presented which combines information from different quality elements (biology, physicochemistry, alien species and hydromorphology) to provide an overall classification of ecological potential of canal water bodies, consistent with the ‘one-out all-out rule’.




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