The River Eitha is a small river in Wrexham County Borough, 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...

. It is part of the River Dee

River Dee, Wales

The River Dee is a long river in the United Kingdom. It travels through Wales and England and also forms part of the border between the two countries....

 catchment. Its name was probably derived from the Welsh word eithaf - "extremity", "farthest".

Sir Cyril Fox

Cyril Fox

Sir Cyril Fred Fox , born, Chippenham, Wiltshire, was an English archaeologist.Cyril Fox became keeper of archaeology at the National Museum of Wales...

, in his surveys of Offa's Dyke

Offa's Dyke

Offa's Dyke is a massive linear earthwork, roughly followed by some of the current border between England and Wales. In places, it is up to wide and high. In the 8th century it formed some kind of delineation between the Anglian kingdom of Mercia and the Welsh kingdom of Powys...

 and Wat's Dyke

Wat's Dyke

Wat's Dyke is a 40 mile earthwork running through the northern Welsh Marches from Basingwerk Abbey on the River Dee estuary, passing to the east of Oswestry and onto Maesbury in Shropshire, England...

, identified a section of the Eitha as forming part of the frontier of Mercia

Mercia

Mercia was one of the kingdoms of the Anglo-Saxon Heptarchy. It was centred on the valley of the River Trent and its tributaries in the region now known as the English Midlands...

 in this area.

Course

The river rises, as the Trefechan Brook, high on the Ruabon Moors

Ruabon Moors

Ruabon Moors are an area of upland moorland in Wales to the west of Ruabon and Wrexham. They lie partly within Wrexham county borough and partly within Denbighshire....

 in the area known as Newtown Mountain, before flowing through a rather steep valley to two reservoirs above Penycae

Penycae

Penycae is a village and a local government community, the lowest tier of local government, part of Wrexham County Borough in Wales- History :...

. At this point it is an important feeder for Dee Valley Water, formerly Wrexham Water. At Penycae, it is joined by the Nant y Crogfyn stream, which also flows down from the slopes of Ruabon Mountain. The Eitha's course then runs south-eastwards to Ruabon

Ruabon

Ruabon is a village and community in the county borough of Wrexham in Wales.More than 80% of the population of 2,400 were born in Wales with 13.6% speaking Welsh....

, where it was formerly used to power several watermills

Watermill

A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour, lumber or textile production, or metal shaping .- History :...

, passing through the centre of the village. From Ruabon the Eitha passes southwards through a deep, wooded valley within the Wynnstay

Wynnstay

Wynnstay was a famous estate in Wales, the family seat of the Wynns. It is located at Ruabon, near Wrexham.During the 17th century, Sir John Wynn, 5th Baronet inherited the Watstay Estate through his marriage to Jane Evans , and renamed it the Wynnstay Estate...

 Estate to join the River Dee near Chirk

Chirk

Chirk is a small town and local government community, the lowest tier of local government, part of Wrexham County Borough in Wales. It has a population of over 4,000....

.