The (.
It rises on lower slopes of
Crug Gynan in the
Cambrian Mountains and flows through the
Tywi Forest forming the border between
Ceredigion and
Powys .
The
Llyn Brianne reservoir was formed here in
1972 by damming a section of the river in order to store winter rain so that it could be released into the river during dry periods. The purpose behind this construction was to support the new abstraction at
Nant Garedig that was destined to supply a large swathe of south
Wales with drinking water. The flow in the River Tywi would have been unable to sustain such an abstraction were it not for the release of water from the upland reservoir.
The river flows south-westwards through
Carmarthenshire passing through the towns of
Llandovery ,
Llandeilo . In
Carmarthen it is joined by the substantial tributary, the
Afon Gwili at
Abergwili . Finally the Tywi flows into
Carmarthen Bay in a combined estuary with the
River Tâf and
River Gwendraeth , east of the
Pendine Sands . The mouth of the Towy estuary is guarded by
Llansteffan Castle a 12th Century
Norman castle.
The total length of the River Tywi is 108
Km (68 miles). Its numerous tributaries include the
River Cothi ,
River Gwili ,
River Brân and
River Doethie . The Tywi is noted for
Trout and
Salmon fishing.
In October
1987 , four people were killed when a train plunged off Glanrhyd Bridge near Llandeilo into the flooded river.
