Afonydd, cronfeydd dŵr a chorsydd blanced
The Cambrian Mountains form the main watershed of Wales. The rivers Severn, Wye, Elan, Irfon, Tywi, Cothi, Teifi, Ystwyth, Rheidol, and Twymyn all have their sources here. The river valleys, such as those of the Afon Gwesyn and Rhiwnant, include numerous striking waterfalls, the equals of many “world famous” waterfalls in this country.
The spectacular gorge and waterfall at Dylife was formed by the deep-cutting headward erosion of the Twymyn-Dyfi to capture the uppermost Clywedog-Severn valley. Similarly, the Teifi was first diverted by rapid headward erosion of the river Ystwyth along the line of the Ystwyth fault, and then the Ystwyth headwaters in turn were captured by the Rheidol. The shortened route to the sea from Devils Bridge (10 miles compared with the previous 50 miles to reach the coast at Cardigan) caused the Rheidol to deepen its bed very rapidly, creating the famous waterfall and gorge at Devil’s Bridge.
The water resources of the Cambrian Mountains are abundant and valuable, and their exploitation by humans – to assist in lead-mining, and more recently to provide water and energy to remote towns and cities – has had a major impact on the Cambrian Mountains landscape.
Nature’s scattering of small lakes was augmented in the 18th and 19th centuries by ponds built to store water used by miners in hushing and ore-dressing, and later to power machinery via a system of dams, leats and waterwheels.