The Sirhowy River (Welsh language : Afon Sirhywi) is a river in Wales and a tributary of the Ebbw River. Sources The Sirhowy River has its source on the slopes of Cefn Pyllau-duon above Tredegar. After flowing through Siôn-Sieffre's Reservoir it turns south through Tredegar and then Blackwood and Pontllanfraith. It turns eastwards near Cwmfelinfach and joins the River Ebbw near Crosskeys. External links The confluence of the Sirhowy and the Ebbw at Crosskeys : photograph from the Crosskeys website www.geograph.co.uk : photo of the Sirhowy River Rivers of Blaenau Gwent Rivers of Caerphilly County Borough