The Severn Reef Plan  

Discussions over plans for a tidal power project in the Severn estuary are continuing, with environmental groups pushing for a tidal reef instead of a barrage. The BBC reports - Severn reef plan is 'more green'.

Conservationists claim building a reef across the Severn Estuary would be cheaper, less damaging and generate more power than a proposed barrage. A study for the RSPB found a reef would hold back about 2m (6ft 6in) of water and not alter tidal patterns as much.

A feasibility study for the Welsh Assembly Government and the UK government on harnessing the estuary's tidal power started in January. A consultation on which projects to shortlist is expected to begin in 2009.

Supporters of a proposal for a 10 mile (16km) barrage between Cardiff and Weston-super-Mare argue it could generate some 17,000 gigawatt hours (gwh) of electricity each year, the equivalent of almost 5% of the UK's needs. The River Severn's tidal power can be seen by surfers taking on the Severn bore

The RSPB asked engineers Atkins to examine the feasibility of a "greener" alternative to a barrage. The research concluded a 12 mile (19 km) reef would cost about £2bn less and produce 20,000 gwh.

This proposal would see a reef built across the Severn between Aberthaw in the Vale of Glamorgan and Minehead in Somerset, making it the most westerly option. Like the Cardiff-Weston barrage, it would generate electricity as water flowed through turbines but it would not hold back the full height of the tide.

The study found that a reef could generate electricity for longer periods than the barrage, and therefore be more be able to meet power needs at peak demand times