The Craig Goch Dam, often called the Top dam, is a masonry dam

Masonry dam

Masonry dams are dams made out of masonry; mainly stone and brick. They are either the gravity or the arch type.The largest masonry dam of the world is Nagarjunasagar Dam in India....

 in the Elan Valley

Elan Valley

The Elan Valley is a river valley situated to the west of Rhayader, in Powys, Wales, sometimes known as the "Welsh Lake District". It covers of lake and countryside....

 of Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 and creates the upper-most of the Elan Valley Reservoirs

Elan Valley Reservoirs

The Elan Valley Reservoirs are a chain of man-made lakes and reservoirs in the Elan Valley in Powys, Mid Wales , using the rivers Elan and Claerwen...

. Construction on the dam began in 1897 and it was complete in 1904. The primary purpose of the dam and the other reservoirs is to supply Birmingham

Birmingham

Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...

 with water. In 1997, a 480 kW hydroelectric generator began operation at the dam.