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Rivers and lakes

The Cambrian Mountains are the great watershed of central Wales, the source of mighty rivers - the Severn, Wye, Teifi and Towy and the fast flowing Einon, Leri, Rheidol and Ystwyth. The mountain passes lead to steep sided valleys clad in ancient woods, and moorland jewelled with lakes and reservoirs.

The Cambrian Mountains - source of great rivers

The rivers that rise in the Cambrian Mountains to flow east and south follow long, gentle courses, include Britain's longest river - the Severn (Hafren) and the Picturesque Wye (Gwy) which rise within less than a mile of each other on the eastern slopes of Pumlumon.

The longest rivers in Wales also rise within a few miles of each other on the Elenydd range - the Tywi heading south into Carmarthen Bay, whilst the Teifi flows in a long sweeping crescent to Cardigan Bay, defining Ceredigion's natural southern border.

Rivers and waterfalls of the Cambrian Mountains

Unlike the leisurely journey of these great rivers, most of Ceredigion’s rivers follow a rapid course to the sea. The river Rheidol falls 500 metres in its short 29 mile run to the sea at Aberystwyth The course of the Teifi, and those of the Rheidol, Ystwyth and Mynach have also been altered by complex geomorphological​ processes that have produced the series of dramatic falls and cascades, as well as pools and potholes with evocative names such as the Devil's Punchbowl.

 

The lakes and reservoirs of the Cambrian Mountains

Ceredigion’s uplands are characterised by small lakes, often the remains of glacier activity. The source of the River Rheidol - Llyn Llygad Rheidol (the lake of the eye of Rheidol) on the north slope of Pumlumon occupies a moraine dammed corrie - a hollow gouged from the side of the mountain by glacier ice.

Teifi Pools is the collective name for Llyn Teifi, Llyn Hir, Llyn Gorlan, and Llyn Egnant which lie at about 1,500 ft (455 meters) near the village of Pontrhydfendigaid. The lakes, located near the ruins of the Cistercian abbey of Strata Florida are deep enough to be believed to be unfathomable and were famous even in medieval times for the quality of their eel and trout fishing.

The Wildlife Trust reserve of Llyn Eiddwen​, which is surrounded by heathland on the slopes of Mynydd Bach is typical of the clean, low nutrient upland lakes which were formed by glacial activity. Look out for floating plants such as water crowfoot and water plantain as well water lobelia, cotton grass and cranberry.

The great raised bog of Cors Caron lies behind a glacial moraine, which the river Teifi has breached. On the edge of the bog, at Maesllyn (the lake field), a glacial ‘kettle pond’ can be easily seen from the Ystwyth Trail.

​The Cambrian Mountains are known for their reservoirs, from the historic series of lakes in the Claerwen, Elan and Clywedog Valleys in the east to Nant y Moch and the Rheidol valley in the west.

There's a visitor centre at the Rheidol Power station​ that explains the complex system that link the Rheidol, Nant y Moch and Dinas reservoirs that supply the water for its turbines.​​​​​​​​​​​​​​​​

There are regular tours of the Cambrian Mountains lakes and reservoirs and events at the Elan Valley Visitor Centre, including opportunities to explore the dams

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