The River Tâf is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 that rises in the Preseli Hills

Preseli Hills

The Preseli Hills or Preseli Mountains are a range of hills in north Pembrokeshire, West Wales...

 of North Pembrokeshire

Pembrokeshire

Pembrokeshire is a county in the south west of Wales. It borders Carmarthenshire to the east and Ceredigion to the north east. The county town is Haverfordwest where Pembrokeshire County Council is headquartered....

, West Wales

West Wales

West Wales is the western area of Wales.Some definitions of West Wales include only Pembrokeshire, Ceredigion and Carmarthenshire, an area which historically comprised the Welsh principality of Deheubarth., an area called "South West Wales" in the Nomenclature of Territorial Units for Statistics....

, near the village of Crymych

Crymych

Crymych is a small village of around 400 inhabitants in the north of Pembrokeshire, Wales. The village developed around the former Crymmych Arms railway station on the now closed line, nicknamed the Cardi Bach , which ran from Whitland to Cardigan.Other than the Crymych Arms public house, which...

 and is around 50 km (30 mi) long.

Water drains from high ground above the village, and at one time flowed at ground level across the main Cardigan

Cardigan, Ceredigion

Cardigan is a town in the county of Ceredigion in Mid Wales. It lies on the estuary of the River Teifi at the point where Ceredigion meets Pembrokeshire. It was the county town of the pre-1974 county of Cardiganshire. It is the second largest town in Ceredigion. The town's population was 4,203...

–Tenby

Tenby

Tenby is a walled seaside town in Pembrokeshire, South West Wales, lying on Carmarthen Bay.Notable features of Tenby include of sandy beaches; the 13th century medieval town walls, including the Five Arches barbican gatehouse ; 15th century St...

 road (A478

A478 road

The A478 road is a major route in the Welsh counties of Ceredigion, Pembrokeshire and Carmarthenshire, connecting Cardigan and Tenby.RouteFrom north to south it runs through:*Cardigan;...

) before falling to the level of the defunct Whitland and Cardigan Branch Line railway station "Crymmych Arms" (Great Western Railway

Great Western Railway

The Great Western Railway was a British railway company that linked London with the south-west and west of England and most of Wales. It was founded in 1833, received its enabling Act of Parliament in 1835 and ran its first trains in 1838...

) where, on the UK Ordnance Survey

Ordnance Survey

Ordnance Survey , an executive agency and non-ministerial government department of the Government of the United Kingdom, is the national mapping agency for Great Britain, producing maps of Great Britain , and one of the world's largest producers of maps.The name reflects its creation together with...

 map of 1866 it is shown as the source of the Tâf.

At this point the stream fulfils its description "Crymych" (in Welsh

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

 "crooked stream") by turning through almost a right angle along the floor of the valley. The stream is mentioned—with various spellings—in records since 1468 and provided both the village and its hostelry with an identity. From there the Tâf, augmented by numerous minor tributaries, flows ESE to Llanfyrnach

Llanfyrnach

thumb|250 px|right|The parish church of St Brynach, LlanfyrnachLlanfyrnach is a village and parish in the hundred of Cemais, Pembrokeshire, Wales. The name means "church of St Brynach". It is situated in a remote upland area on the headwaters of the River Tâf, about 18 km from Cardigan, the...

 then SW through Glandwr, Llanglydwen and Login to Whitland

Whitland

Whitland is a small town in Carmarthenshire, south-west Wales, lying on the River Tâf. Whitland is home to the elusive "Whitland Trout" noted for its eggs and oily scales.- History :...

. It then flows east to St Clears

St Clears

St Clears is a small town on the River Tâf in Carmarthenshire, Wales. According to the 2001 UK census, it has a population of 2,820 people, most of whom are Welsh-speaking, although there is a marked difference between the southern and northern ends of the town in percentage terms.-History:The...

, south of which its broad estuary meets Carmarthen Bay

Carmarthen Bay

Carmarthen Bay is an inlet of the south Wales coast. The coastline includes famous beaches, including the Pendine Sands and Cefn Sidan sands, and is partially covered by the Pembrokeshire Coast National Park....

 near Laugharne. Its length is about 56 km (35 mi) from Crymych to Ginst Point, of which about 14 km (9 mi) is tidal.