Avon waterbody update for AEF:
From the desk study, it can be seen that the failures on the Avon are for low pH in the headwaters and for fish.
Our interpretation of the data is that the low pH is a natural effect from the river draining Dartmoor, a granite moorland system. However, the Dart Fisheries Association along with WRT are pulling together a literature review to gather evidence on their hypothesis that acid rain has exacerbated the acidic nature of the water coming off Dartmoor, specifically impacting the R. Dart salmon populations. We will consider the findings of this document in due course.
The fish failures are driven primarily by two Poor survey points just downstream of the reservoir and upstream of Lydia Gorge.
We have also identified 3 barriers lower down the Avon: a tidal flap on a 'drain' below Aveton Gifford; a sluice for a water wheel on an offtake from the main Avon & a large tidal weir on the main Avon which is a complete barrier to eels and elver.
The tidal weir on the main Avon could be impacting the results upstream as a number of the failures are being driven by low eel numbers.
The Avon waterbody is very large and the current status is Moderate. This is driven predominantly by the impacts from the low pH and the possible impact of the reservoir and natural gorge.
One option, was to designate the whole waterbody as Heavily Modified (for water storage/regulation) which would mean that it would have to reach Good Ecological Potential, rather than Good Ecological Status, and we would set some mitigation measures which would have to be met. However, we felt that this was not a true reflection of the state of the Avon and therefore, I have made the following suggestion.
We split the waterbody into 2 waterbodies – a smaller waterbody that includes the Avon reservoir, which we then designate Heavily Modified and develop appropriate mitigation measures for the reservoir. The rest of the Avon would then be a separate waterbody which would then be likely to achieve Good status although we still need to look at the sites where fish are not as good as we’d like them to be.
Actions currently programmed in:
Can they help?
- do they think that the suggested way forward with splitting the waterbody is a pragmatic way forward?
- do they know of any issues at Avonwick/Cocks Brook? We should be surveying these sites this summer which will provide more up to date evidence.
- Can they identify the owners of the 3 obstructions on the Avon so that we can contact them?