The Blackwater (“black water”) is a river with murky water, a muddy bed and slow channels that drain mud from the land upstream. It rises in the Barrow Moor and flows through the north of the region also called Blackwater. Itineraries place it about a hundred miles from Adwen (an uncertain figure).
In some stretches there is little human settlement, especially in winter, when the river runs slow between empty banks. It is associated with a legend about an immortal who dies; the legend itself is not recorded.