Linking points near Cardiff in Wales and Weston-super-Mare in Somerset, the barrage would feature massive locks allowing shipping to continue to ports such as Bristol and would be wide enough for a road and railway to run over the top. To generate power, water would run through 176 sluices as the tide rose and he held behind the structure until it dropped. When allowed to flow out, the water would drive more than 200 turbines to produce power for some 10m people as reliable and predictable as the tides.

There are two competing proposals for a Severn Barrage.

Balfour Beatty and Sir Robert McAlpine lead the Severn Tidal Power Group consortium which plans a privately financed project which, if backed by government, could be operational by 2017.

Environmental groups, including Friends of the Earth Cymru and the RSPB, oppose a barrage on the basis that the Severn Estuary is a protected Special Area for Conservation (SAC), with 200km 2of inter-tidal habitat providing food for over 50,000 migratory birds. FoE Cymru has made detailed proposals for an alternative tidal lagoons scheme in which lagoons are built in the estuary.

Water flowing into the lagoons at high tide would also power turbines when allowed back out, providing what is said to be a less environmentally damaging, more cost effective and more powerful scheme.

MJInformation No: 21952