CPAT logo
Cymraeg / English
Mynydd Hiraethog Historic Landscape
Character area map

Historic Landscape Characterisation

Mynydd Hiraethog: Brenig Reservoir
Cerrigydrudion Community, Conwy, and Nantglyn and Llanrhaeadr-yng-Nghinmeirch Communities, Denbigshire
(HLCA 1112)

CPAT PHOTO cs012913

Large later 20th-century reservoir in broad valley towards the eastern edge of Mynydd Hiraethog superimposed upon a medieval and later landscape of farmsteads and fields.

Historic background

The area falls within the 19th-century tithe parishes of Llanrhaeadr-yng-Nghinmeirch, Nantglyn and Cyffylliog. Reasonably intensive archaeological fieldwork was undertaken within the area before the construction of the reservoir. The construction of the later 20th-century reservoir submerged a Bronze Age round barrow and several medieval and later farmsteads and fields of Hafod-lom, Hafod-yr-onen, Ty'n-y-ddol and Rhos-ddu and outlying sheepfolds a field byre, and peat-cutting mounds, stepping stones and footbridges.

Key historic landscape characteristics

The character area covers an area of about just under 4km2, at a height at about 378m above Ordnance Datum above the dam and about 340m below the dam. The reservoir occupies a broad valley enclosed by higher ground to the north, west and east, fed by a series of streams including the Afon Brenig, Nant Bryn-y-gors-goch, Nant Bryn-morwyn, Afon Fechan, Nant Criafolen, Aber Berbo, Aber Llech-Damer and Aber Gors-maen-llwyd, all of which are tibutaries of Afon Alwen which drain into the Dee river system.

The reservoir, up to 45m deep and with a large earthen dam up to 1.1km long and 150m across, built between 1973-76 and designed to provide domestic and industrial water supplies to north-east Wales and to enhance the summer flow of the river Dee. Like the Alwen Reservoir it forms an important present-day resource for sporting and recreational activities, facilities including a sailing club, a sub-aqua diving club, visitor centre, fishing club, signposted walks and picnic and bird-watching areas.

Early prehistoric settlement within the area of the reservoir is indicated by a later Neolithic mace-head found at Hafod-lom and by a now submerged prehistoric burial mound forming part of a more extensive Bronze Age ritual landscape (see the Maen-llwyd character area). Medieval and later farming settlements became established in the area, including Hafod-lom, first mentioned in the early 14th century, formerly with 17th/18th-century stone buildings, which became one of the well-established farms in the area by the 18th and 19th century, with a reputation for poetry and singing. The occurrence of the element hafod 'summer house' occurs in a number of the former farms names suggests that at least some of the farmsteads began as temporary seasonal dwellings associated with permanent lower-lying settlements,

Extensive waterlogged peaty deposits lie submerged below the reservoir, which are of potential significance to the vegetational and land use history of Mynydd Hiraethog.


Clwyd-Powys Sites and Monuments Record;
Davies 1977;
Hubbard 1986;
Lynch 1993

For further information please contact the Clwyd-Powys Archaeological Trust at this address, or link to the Countryside Council for Wales' web site at

Privacy and cookies