SIR – While any renewable energy production, however small, is welcome, the report on Hirst weir estimates an average output of 41kw over 12 months sufficient for about 17 homes, not 100 as has been suggested.

This is developing technology, but the report does not take into account the reported disasterous effect the Settle hydro has had on fish movements up the pre-existing fish pass.

This has been attributed to the noise and vibration caused by the Archimedian screw and the greater flow through the screw than through the fish pass.

A probable solution would be a fish pass in the centre of the weir with higher flow than through the screw.

This would also permit future generation on the right bank. The depth of the pass should be 30cms rather than the 15cms suggested to allow bream, pike and salmon to ascend without damage.

I know of nine proposed hydro schemes on the river Aire. Getting any one of them wrong could block fish movement as required by the Water Framework Directive.

The possible silting or flooding effects of so many hydro schemes on one river must be unkown at this stage.

Andrew Marshall, Committee chairman, Saltaire Angling Association, Kirklands Close, Baildon