page_title: Afon Rheidol
section_title: Geography and geology
hierarchical_section_title: Afon Rheidol / Geography and geology
caption_attribution_description: English: Afon Ystwyth. Looking upstream from just where the Ystwyth joins the Rheidol and then enters the sea. On the left is Pendinas Hill and on the right is Tanybwlch Beach.
context_page_description: The Afon Rheidol is a river in Ceredigion, Wales, 19 miles in length. The source is Plynlimon, with a catchment area covering 73 square miles it is the largest watershed in Wales. Receiving an average annual rainfall of 40 inches it is the source of the Wye and the Severn.
context_section_description: The Rheidol rises in the headwaters of the Nant-y-moch Reservoir (52.4590°N 3.8349°W) on the western flanks of Plynlimon, near the sources of the Wye and Severn. After flowing south to Ponterwyd on the increasingly deep valley, then southwest through Welsh Oak ancient woodland, it veers westwards to its confluence with the Afon Mynach, at Devil's Bridge, Ceredigion (Welsh: Pontarfynach, lit. "The bridge on the Mynach") and the most spectacular of waterfalls.  The river continues passing the abandoned workings of the Cwm Rheidol lead mine; one of many other metal mines in the valley – a source of extracted metal pollution of the river –  and flows westwards before its confluence with the Afon Ystwyth and the estuary at Aberystwyth to drain into Cardigan Bay. (52.4071°N 4.0898°W)
  In the late 1960s, when the mine was closed, a major blowout of water contained in an adit coloured the whole river an ochre orange colour and greatly added to the concentrations of lead and zinc in the river. Today, management of water still draining from the mine is by the use of constructed wetlands. Previous management had included a limestone filter bed installed in the 1960s and now redundant. The filter bed is still in place and can be seen from the road.
caption: The Afon Ystwyth looking upstream from its confluence with the Rheidol just before their combined estuary.
  On the left is Pendinas Hill and on the right is Tanybwlch Beach
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