River Severn

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The River Severn

A Key Stage 2 Resource for Rivers and Coasts

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Llyn Clywedog Reservoir

The Llyn Clywedog is a man made reservoir formed by the construction of the Clywedog Dam.

image: reservoir
Photo © Copyright Peter Lymer - Original photo
and licensed for reuse under this Creative Commons Licence.

Why was the Clywedog Dam built?

The dam is used to regulate the flow of water in the Severn. It helps to prevent flooding of the upper sections of the river Severn during the winter months and also to ensure the maintenance of a minimum flow in the river during the summer.

Interesting facts about the Clywedog Dam

  • The tallest mass concrete dam in Britain, standing fully 236 ft (72m) high.
  • It is 750 ft long, and holds back some 11,000 million gallons of water, equivilent to 550 million baths!
  • The lake has a surface area of 615 acres (230 football pitches).
  • It is is 216 ft deep at its maximum depth and stretches to a distance of some six miles.
  • It was built between 1965-67.

The water from the dam flows down in to Llanidloes where it joins the river Severn.

Llanidloesnext page

Key Vocabulary

A lake which builds up behind a dam. A reservoir is used for collecting and storing water.

A strong wall built to hold back a river.

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