River Rhondda

[2] The combined waters then continue descending sharply through a mountain gorge to the foot of Pen Pych.

The river then passes through a string of mining towns and villages including Treherbert, Treorchy, Pentre, Ton Pentre, Ystrad Rhondda, Llwynypia, Tonypandy (joined by the Nant Clydach), Dinas and Porth where it joins its sister tributary.

The Rhondda Fach rises about a mile to the east of the source of the Rhondda Fawr on the hills above Blaenrhondda in a marshy area between Mynydd Beili Glas and Mynydd Bwllfa at an elevation of 489m OD.

[4][1] The fledgling river is first contained in the Lluest-wen Reservoir before flowing down into Maerdy and then on through Ferndale, Tylorstown, Ynyshir to its confluence at Porth.

Since the early 1970s the river has been steadily improving in quality largely due to the closure of all the coal mines and through the investment in sewerage and sewage treatment.