The River Teifi (Welsh: Afon Teifi) forms the boundary between the counties of Ceredigion and Carmarthenshire in south-west Wales for most of its 75 mile length (making it the longest river wholly in Wales), flowing into the sea below the town of Cardigan. The catchment of the river is estimated to be 1,008 square kilometres yielding an average flow at Glan Teifi of 29.126 m³/s. The maximum recorded flow between 1959 and 2011 was 373.6 m³/s on 18 October 1987. The average rainfall varies from 1552 mm in the upper catchment to 1,176 mm in the lower catchment.
The River Teifi is susceptible to flooding, there have been some heavy floods in 2007 and 2008. The Teifi has its source in Llyn Teifi, one of several lakes known collectively as the Teifi Pools. These are situated towards the north of the county of Ceredigion. This wide area of Mid-Wales, with a very sparse population, is part of what is sometimes called the "desert of Wales". The river flows past Strata Florida Abbey and then through Pontrhydfendigaid before reaching the main river valley floor. Here it passes through one of the great raised mires of Britain, Gors Goch Glan Teifi, also known as Tregaron Bog. Over the next 30 miles, the Teifi meanders generally south-west in a gentle arc, passing through the towns and villages of Tregaron, Llanddewi Brefi, Cwmann, Lampeter, Llanybydder, Llandysul, Newcastle Emlyn, Cenarth, Llechryd and finally Cardigan. The river becomes tidal below Llechryd and descends into Cardigan through the steep-sided Cilgerran Gorge. Below Cardigan, the river broadens into a wide estuary, passing the seaside resort of Poppit Sands before finally entering the sea in Cardigan Bay.
Geology and landscape
The Teifi and its tributaries are underlain by ancient Ordovician and Silurians mudstones which have been extensively glaciated during the ice ages. The resultant landform is one of gently rolling hills supporting a range of agriculture in which dairy and sheep farming dominate. Ceredigion had the reputation of supplying London with its milk in the 19th century . The landscapes of the Teifi valley are very attractive and the Teifi is considered by many to be one of the most beautiful rivers in Wales.
Teifi Pools, the source of the Teifi, are a series of small lakes left by past glacial activity. The lakes are upland and acid in nature. Some have been enlarged by damming and now provide a source of drinking water. The very extensive raised mire above Tregaron acts as a huge sponge at the head of the river and evens out extremes in flow. Rapids and waterfalls are uncommon but the examples at Henllan and, especially at Cenarth, are noteworthy and have been extensively photographed and painted because of the beauty of the landscape. A dramatic painting of the falls was made by Frank Miles and is now at Nottingham City Museum. Miles's father inherited Cardigan Priory from his father, Philip John Miles, but lived in Nottinghamshire as Rector of Bingham. The gorge between Llechryd and Cilgerran has a special brooding quality. Few visitors stray into the gorge and the river winds its way almost silently between the densely wooded sides with their distinctive under-storey flora of sedges.
Culture and history
The Teifi valley has been inhabited since pre-history. There are many remains of Iron Age and Stone age man including Cromlechs (burial chambers) and standing stones. The remains of a medieval abbey stand at Strata Florida with some excellent examples of encaustic tiles on the floors. The river flows near to the Lampeter campus of the University of Wales, Trinity Saint David, its predecessor, the University of Wales, Lampeter (est. 1822) having been the oldest university established in Wales. Between Cenarth and Cardigan, there is an ancient tradition of fishing and travel using coracles – very simple light-weight boats made of bent sticks covered with waterproofed hide or skins. These are paddled by a single oar used at the front of the craft which requires great skill. The principal use for coracles is for salmon fishing using nets. This form of fishing is now very tightly controlled and the right to fish in this way is passed down from father to son. There is also an age-old tradition of illegal salmon and sea-trout fishing in the lower Teifi. In 1188 Giraldus Cambrensis observed what is thought to have been the last colony of European Beaver in England or Wales on the Teifi.
- The Teifi Valley is home to the Teifi Valley Railway, a 2-foot gauge steam railway which operates on the GWR part of the Carmarthen and Cardigan Railway between Llandysul and Newcastle Emlyn.
- Teifi Marshes Wildlife Trust of South and West Wales Nature Reserve, Cardigan 
- "First Water Resources Survey : Report", South West Wales River Authority, Published 1970, Page 41; Table 1
- CEH Teifi at Glan Teifi
- BBC - Your Paintings - Salmon Leap, Cenarth Falls, Cardiganshire
- Teifi Valley Railway
- Teifi Marshes Wildlife Trust