SIR - I share Graham Hoyle's satisfaction (T&A, November 29) that there is the potential for some small-scale hydro-electric power schemes.

It is unlikely that many of the proposed sites will be developed for economic reasons, but whatever contribution they can make will be welcome as once constructed no further CO2 is produced.

However, this technique will remain marginal in the UK and other renewables and nuclear power are the only real alternatives to the problems caused by coal and gas generation until capturing and burying CO2 is properly developed.

Keith Thomson, Heights Lane, Bradford