La Rance Tidal Barrage

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Project Site Annex IV

La Rance Tidal Barrage
Start Date:
November 26, 1966
Technology Type:
Info Updated:
June 27, 2012
The La Rance tidal barrage
Device Status: 
In Operation
Tidal barrage
Project Scale: 
Installed Capacity: 
240 MW

The Rance Tidal Power Station is the world's first tidal power station and also the world's second biggest tidal power station. The facility is located on the estuary of the Rance River, in Brittany, France. Opened on the 26th November 1966, it is currently operated by EDF, and is the second largest tidal power station in the world, in terms of installed capacity. With a peak rating of , generated by its 24 turbines, it supplies 0.012% of the power demand of France. With a capacity factor of approximately 40%, it supplies an average 96 MW, giving an annual output of approximately 600 GWh. The barrage is 750 m (2,461 ft) long, from Brebis point in the west to Briantais point in the east. The power plant portion of the dam is 332.5 m (1,091 ft) long. The tidal basin measures 22.5 km2 (9 sq mi).


The facility is located on the estuary of the Rance River near Saint Malo, Britany, France.

Process Status: 

It took six years to complete, and was commissioned at various stages between August 1966 and December 1967. The following were the most important stages of its construction: January, 1961: commencement of work. 19th November, 1962: commissioning of the lock. 24th March, 1963: commissioning of the sluice-way section of the dam. 20th July, 1963: final closure of the dam across the estuary. 19th August, 1966: on-line connection of the first power set. 26th November, 1966: inauguration by the President of France. 1st July, 1967: inauguration of the road across the dam. 4th September, 1967: commissioning of the twenty-fourth power set. The plant is currently operating.

Key Environmental Issues: 

The barrage has caused progressive silting of the Rance ecosystem. Sand-eels and plaice have disappeared, though sea bass and cuttlefish have returned to the river. By definition, tides still flow in the estuary and the operators, EDF endeavors to adjust their level to minimize the biological impact.

Study Status: 
La Rance Tidal Barrage is located in France.

Monitoring and Adaptive Management: La Rance Tidal Barrage

ReceptorMonitoring Program Description Design and Methods Results Status
  • Physical Environment

Mean water level and hydrodynamic regime.


The 2.5 m rise of the mean water level has resulted in a decrease of the tidal range which includes less volume of water entering the estuary the slack period to be longer.

  • Physical Environment

Sediment dynamics.


Modification of tidal stream in the estuary, in particular during ebb has provoked more silt deposit in the low intertidal zone.

When comparing the Rance estuary with other regional estuaries, sediments dynamic processes are similar to those of natural estuaries.

  • Biological Environment

General Flora and Fauna distribution.


An increasingly diverse flora and fauna became established. The patterns of distribution of this flora and fauna, their grouping into ecological units and the nature of their interrelationships, indicate a variable degree of biological adjustment to the new environmental conditions.

  • Benthos

Distribution of benthic species and communities.


By 1980, the basin was providing habitat for 110 worm species and 47 crustacean species.

  • Fish and Fisheries

New fishery activities.


Scallops and Belon oysters are now the new fishery activities.

  • Birds

Utilization of the basin by overwintering birds.


Bird species variety is the same than before (120 species)

A well developed communities of fish-eating birds has been developed (gulls, guillemots, shags)

Birds adaptation: decrease of sand area (intertidal area)

Birds can also find food in the other Bays (mudflats)

  • Large Vertebrates

Seals distribution.


Since 2000, a seal female has been living in the basin, passing through the sluice gates or even the lock. Despite vain attempts to send her back to join seal communities, she always goes back to the Rance estuary!

Reports and Papers


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