The River Terrig is a small river in north-east 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...

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The river rises at Llyn Cyfynwy near Graianrhyd

Graianrhyd

Graianrhyd, also spelt Graeanrhyd, is a small, scattered village in the community of Llanarmon-yn-Ial, Denbighshire, Wales, lying in hilly limestone country around to the east of Lanarmon-yn-Ial village, and just to the south of Eryrys....

 village in the community

Community (Wales)

A community is a division of land in Wales that forms the lowest-tier of local government in Wales. Welsh communities are analogous to civil parishes in England....

 of Llanarmon-yn-Ial

Llanarmon-yn-Ial

Llanarmon-yn-Iâl is a village, and local government community, in Denbighshire, Wales, lying in limestone country in the valley of the River Alyn.- Location :...

, Denbighshire

Denbighshire

Denbighshire is a county in north-east Wales. It is named after the historic county of Denbighshire, but has substantially different borders. Denbighshire has the distinction of being the oldest inhabited part of Wales. Pontnewydd Palaeolithic site has remains of Neanderthals from 225,000 years...

, about three miles from the source of the River Alyn

River Alyn

The River Alyn is a tributary of the River Dee. The River Alyn rises at the southern end of the Clwydian hills and the Alyn Valley forms part of the Clwydian Range Area of Outstanding Natural Beauty...

. It then flows northwards and eastwards, forming the boundary between the old parishes of Nercwys

Nercwys

Nercwys is a rural village in Flintshire, Wales which is surrounded by open countryside. It has a small school and a local bus service to Mold which is around 2 miles away.- External links :*...

 and Treuddyn

Treuddyn

Treuddyn is a small village and community in Flintshire, Wales, located just off the A5104 road, around 4 miles south-east of Mold and 3 miles north-west of Caergwrle. The community includes the nearby village of Coed Talon, to the east, and Rhydtalog, to the south-west on the Denbighshire border...

. At Nant-y-Mynydd it is joined by several small springs from Mynydd Ddu, and finally itself joins the River Alyn at Pontblyddyn

Pontblyddyn

Pontblyddyn is a small village outside Leeswood, in the North Wales county of Flintshire and is situated around 8 miles from Wrexham. Plas Teg, one of the most important Jacobean era houses in Wales is located near the village....

, Flintshire

Flintshire

Flintshire is a county in north-east Wales. It borders Denbighshire, Wrexham and the English county of Cheshire. It is named after the historic county of Flintshire, which had notably different borders...

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The Terrig is a habitat for brown trout

Brown trout

The brown trout and the sea trout are fish of the same species....

. Its name is derived from its rapid flow after times of heavy rain; Thomas Pennant

Thomas Pennant

Thomas Pennant was a Welsh naturalist and antiquary.The Pennants were a Welsh gentry family from the parish of Whitford, Flintshire, who had built up a modest estate at Bychton by the seventeenth century...

, in his Tours in Wales, described it as "the Terrig, or the violent, [...] often of a tremendous swell and fury".