The River Teifi ( ) in Wales forms the boundary for most of its length between the counties of Ceredigion and Carmarthenshire, and for the final of its total length of , the boundary between Ceredigion and Pembrokeshire. Its estuary is northwest of Cardigan, known in Welsh as Aberteifi, meaning 'mouth of the Teifi'. Teifi has formerly been anglicised as "Tivy". Geography 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; the source is in the Cambrian Mountains at . 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 turning broadly southwest. Here it passes through Cors Caron, one of the great raised mires of Britain also known as Tregaron Bog or Cors Goch Glanteifi (translates from Welsh as red bog on the banks of the Teifi). From here the river descends through pastures and bogs forming meanders on farmland below. Several small tributaries join from the valley with gorges, rocky and tree-lined sections also in the area. Over the next , the Teifi meanders southwest in a gentle arc passing through Tregaron, Llanddewi Brefi, Cwmann, Lampeter, Llanybydder, Llandysul, Newcastle Emlyn, and Cenarth. The river is tidal below Llechryd, descending through the steep-sided Cilgerran Gorge to Cardigan. West of Cardigan and St Dogmaels, the river broadens into a wide estuary with Poppit Sands on its west bank and Gwbert on its east bank as it enters Cardigan Bay. On the lower parts of the river the wildlife is rich. There is a large variety ranging from water-crowfoot to Atlantic salmon as well as otters, wetland birds and multi fruited river moss. There have also been sightings of bottle-nosed dolphins where the river opens into the estuary. It is sometimes asserted that the Afon Tywi at and Afon Teifi at are the longest rivers wholly in Wales though at about , the River Usk exceeds both. The river is susceptible to flooding and there were some heavy floods in 2007 and 2008. If the swollen river is backed up by a high tide, flooding can occur in Cardigan and as far up river as Llechryd. The most recent flooding was in December 2015. The principal tributaries of