Tidal barrage. Tidal barrage used to generate electricity with traffic travelling along the road on top of it. Built on the Rance river, France, the barrage opens sluice gates when the tide is rising to fill the estuary (at left) which acts as a reservoir. When the tide falls the sluice gates are closed and the water is released only through the 24 turbine generators. This dam is located at a point where the tidal range can reach up to 13.5 metres. It is 750 metres long and creates an artificial lake of 22 square kilometres. The generators can produce a total of 240 million watts of power.