The ACA Forum

Conserving the Devonshire Avon from source to sea


by | Mar 12, 2023 | Main | 2 comments

The practice of allowing combined sewer overflows (CSOs) into our rivers – including the Devon Avon or Aune  – has been going on, relatively unchallenged, for centuries.  Originally, CSOs were allowed to prevent flooding of property under extreme weather conditions due to overloaded sewer systems full of rainwater.   In these more enlightened times of environmental awareness, what unpolluted baseline should be used for assessing biodiversity?  Fortunately, biology has an answer depending upon the differential sensitivity of bottom-dwelling macro-invertebrates to organic pollution.  One might argue that South West Water  – in their current forward looking consultation on resource management – should be helping to fund more extensive investigation of the impact of their CSOs on biodiversity and how the situation might be improved and assessed.

See file for detail:-

 Devon Avon_pollution versus biodiversity


  1. Charlotte Rathbone

    Thanks Stuart,

    The kick sampling carried out in your bioblitz is very revealing. It would be very interesting please to know where this has been done, where the sewerage and other outfalls are in relation to the kick sampling; and how often it is (or when it was) carried out, in relation to the dates and origins of the CSO’s. Do you or SW Rivers Trust have a digital map?
    Is there a team of CSI volunteers doing monthly samples for the SW Rivers Trust through the catchment?

    • Stuart Watts

      Hi Charlotte

      I believe the sampling was conducted by Avon Garden Centre where the river is quite accessible. The Loddiswell outfall is a fairly short distance up stream, above the Torr Brook confluence, I think. The same thoughts about proximity to CSOs and timing of overflows is critical but that is at a level of sophistication above what the Wild about Loddiswell group could achieve. No there is no CSI team operating routinely on the Avon. I conducted a few samplings of Torr Brook and at the Garden Centre myself a couple of years ago – everything was as clean as a whistle. Timing, frequency, etc. would be key to a proper survey. Hopefully, something might emerge from the Rivers Assembly but I am not holding my breath!

      Best wishes



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