Powys Digital History Project

The Elan Valley dams
James Mansergh, dambuilder

  Changing the landscape
James Mansergh's detailed report on the area upon which the huge project was based included an impressive scale relief model of the watershed of the rivers Elan and Claerwen which he had built with the help of his son.

Relief model of
the Elan and Claerwen
watershed made
in 1891

James Mansergh FRS,
former President
of the Institute
of Civil Engineers
(far right)

Relief model of watershed,1891  Portrait of James Mansergh
Photograph by
kind permission of
Radnorshire Museum,
Llandrindod Wells

The model is of particular interest in that it included the three dams originally proposed for the Claerwen Valley, seen extending to the left. Of these, only the base of the dam at Dol-y-Mynach (bottom right of the model above) was destined to be built. The valley of the River Elan runs vertically on the right of the model, and the reservoirs shown were all created by the scheme.
See the sketch map of the dams and reservoirs today for comparison with the original scheme.Elan Valley postcard

 Another view of the Elan Valley taken from an early souvenir postcard is shown (right), with the picture captioned "Before Waterworks Scheme".
Roads like this one which followed the course of the river along the floor of the valley were later replaced by new roads and railway tracks cut into the valley sides above the top water level of the reservoirs, and access roads were also built along the top of two of the new dams.

  This is the second page on James Mansergh. 
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