River Corrwg The Corrwg is one of the Afan's principal tributaries. Its length is approximately 11 km, and its source lies above the village of
Glyncorrwg, in the hills south of
Glyn-neath. It has a major tributary,
Afon Corrwg Fechan, as well as numerous tributary streams. Several waterfalls exist along the river's course. Although the water is clear today, discharge from the many collieries along its lower reaches led to significant pollution. Minor discharge sometimes leaks from the Glyncorrwg colliery, although its effects do not have a noticeably detrimental effect on the river.
River Pelenna The Pelenna, a major tributary that meets the Afan at
Pontrhydyfen, suffered more severely from pollution than the main river because of the sulphur-rich coal that was produced by the mines in that area. As a result, the abandoned coal mines continued to discharge
acid mine drainage rich in iron and highly acidic. This turned much of the river orange down to the confluence of the Pelena with the main river Afan. The orange colour could often be seen as far down stream as
Pontrhydyfen. There were a number of collieries contributing to the pollution although the major source was the Whitworth Colliery. At the height of coal extraction in the valley, there were several deep pits and numerous levels. This pollution is now much mitigated following extensive work promoted by the
Environment Agency in the creation of
engineered reed beds to treat the mine drainage.
Nant Ffrwdwyllt Nant Ffrwdwyllt was a small tributary of the Afan, just under 8 km and joining the Afan close to the sea. It was diverted in the 18th century into the ironworks at what was to become Port Talbot, to provide a source of water. It remains diverted, flowing into
Port Talbot Docks. ==References==