Ebb-tide: the falling tide, part of the tidal cycle between high water and the next low water.

UNESCO: L O S S A R Y

Hafren Power has said it has improved on previous plans for a barrage that were rejected in 2010 by using smaller turbines that can generate power on both the rising and falling tide and at slower speeds.

BBC: Severn Barrage: Time to 'grasp opportunity', says Hain

The company says that it has improved on previous plans for a barrage that were rejected in 2010 by using smaller turbines that can generate power on both the rising and falling tide and at slower speeds.

BBC: Severn Barrage artist's impression

The company has said it has improved on previous plans for a barrage that were rejected in 2010 by using smaller turbines that can generate power on both the rising and falling tide and at slower speeds.

BBC: Severn Barrage: Ed Davey says ?30bn plan could progress

Tidal current: movement of water in a constant direction caused by the periodic rising and falling of the tide.

UNESCO: L O S S A R Y

Tide: periodic rising and falling of large bodies of water resulting from the gravitational attraction of the moon and sun acting on the rotating earth.

UNESCO: L O S S A R Y