[1] The river rises, as the Trefechan Brook, high on the Ruabon Moors in the area known as Newtown Mountain, before flowing through a rather steep valley to two reservoirs above Penycae.

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, where it was formerly used to power several watermills, passing through the centre of the village.

From Ruabon the Eitha passes southwards through a deep, wooded valley within the Wynnstay Estate to join the River Dee near Chirk.

You can help Wikipedia by expanding it.This article related to a river in Wales is a stub.