Elan Valley water supply


Duration:13 years


Country: Wales, UK

What did this project achieve?

Provide clean water for Birmingham by collecting water from the Welsh hills

Birmingham grew rapidly as an industrial city in the late 19th century. A lack of clean water led to numerous outbreaks of disease.

Birmingham Corporation Water Department built a chain of reservoirs in the Elan Valley in Wales to collect fresh water from the hills. The water was carried by gravity to Frankley reservoir in Birmingham via the Elan aqueduct, also built as part of the scheme.

Travelling at less than 2 miles an hour the water took 2.5 to 3 days to travel 73 miles (117km) to the city.

Work on the reservoirs started in 1893. Work on the aqueduct began in 1896 and finished in 1906.

Difference the clean water made

Before the Elan Valley scheme was built Birmingham's water supply came from wells and the polluted river Tame. Water-borne diseases such as cholera were common.

The project provided abundant clean water for the city. Cases of cholera were dramatically reduced and eventually disappeared.

How the work was done

Chief engineer James Mansergh decided on Elan Valley for several reasons. High annual rainfall of 72 inches (1,830mm) meant a good water supply. The narrow valleys made it easier to build dams and the bedrock was impermeable to water.

Most importantly, there was no need for pumping stations as the Welsh reservoirs would be 171ft (52m) above water cisterns in Birmingham.

The first stage of the project was to demolish buildings in areas were the planned chain of 5 reservoirs would be. 100 people had to move. Only landowners got compensation.

Engineers built a railway to carry materials for the project. Locomotives hauled large irregular stone blocks - called 'plums' - to the dam sites. The locally mined plums were used to line the excavated dams and lowered into place by steam crane.

The central cores of the dams were encased in a thick concrete lining 2m thick. Outside walls were faced with cut stone from local quarries.

The 73 mile long Elan aqueduct was built by 3 contractors. About 12 miles (19km) of tunnel was needed to keep water flowing down when ground levels on the route went up.


The result has been… a nucleus of good steady men in whom reliance can be placed… kept constantly on the job. That is an enormous advantage for works of this type.

James Mansergh

at the International Engineering Congress, 1901, explaining the benefits of his temporary village for workers on the project.

Fascinating facts

One of the buildings demolished to make way for the reservoirs was a manor house called Nantgwyllt. It was linked to the Romantic poet Percy Bysshe Shelley who tried to buy it in 1812.

James Mansergh built a temporary village for project workers and their wives and children. The village had a school, a bath house and two hospitals – one for injuries and one to contain infectious diseases.

During World War 2 engineer Barnes Wallis used the Nant-y-Gro dam – originally built to provide water for the workers' village – to test his bouncing bomb. The experiments led to the destruction of dams in the Ruhr region of Germany in 1943.

People who made it happen

  • Birmingham Corporation Water Department
  • Civil engineer: James Mansergh

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