The Taf Fechan is a river in the Brecon Beacons

Brecon Beacons

The Brecon Beacons is a mountain range in South Wales. In a narrow sense, the name refers to the range of popular peaks south of Brecon, including South Wales' highest mountain, Pen y Fan, and which together form the central section of the Brecon Beacons National Park...

 in South Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

. It rises just below Pen-y-Fan and joins the Taf Fawr

River Taff

The River Taff is a large river in Wales. It rises as two rivers in the Brecon Beacons — the Taf Fechan and the Taf Fawr — before joining to form the Taff north of Merthyr Tydfil...

 at Cefn-coed-y-cymmer

Cefn-coed-y-cymmer

Cefn-coed-y-cymmer is a small community on the northwestern edge of Merthyr Tydfil in south Wales. It is situated in the neck of land between the rivers Taf Fawr and Taf Fechan at their confluence . The village lies within the community of Vaynor...

. The river feeds the Pontsticill Reservoir

Pontsticill Reservoir

Pontsticill Reservoir or Taf Fechan Reservoir is a large reservoir on the Taf Fechan lying partly in the county of Powys and partly within the county borough of Merthyr Tydfil in south Wales. It lies within the Brecon Beacons National Park and Fforest Fawr Geopark...

.

The river holds a large population of wild Brown Trout

Brown trout

The brown trout and the sea trout are fish of the same species....

, much of which was killed in 2006 when a large quantity of aluminium sulphate was flushed into the river from the Pontsticill Water Treatment Works, which United Utilities operate on behalf of Dwr Cymru/Welsh Water

Welsh Water

Dŵr Cymru Welsh Water is a company which supplies drinking water and wastewater services to most of Wales and parts of western England.It is regulated under the Water Industry Act 1991.-History:...

. The pollution turned the water white for at least 5km downstream of the works and killed approximately 23,000 fish, including wild brown trout, bullhead

European bullhead

The bullhead is a freshwater fish that is widely distributed in Europe, mainly in rivers. It is a member of the Cottidae family, a type of sculpin...

s, stickleback

Stickleback

The Gasterosteidae are a family of fish including the sticklebacks. FishBase currently recognises sixteen species in the family, grouped in five genera. However several of the species have a number of recognised subspecies, and the taxonomy of the family is thought to be in need of revision...

 and pike, as well as wiping out uncountable numbers of invertebrates. According to the Environment Agency Wales

Environment Agency Wales

Environment Agency Wales is an Assembly Sponsored Public Body. It is that part of the Environment Agency that covers Wales. The Regional divisions of the Environment Agency are based on the concept of catchment management and administrative boundaries therefore follow the watersheds of major rivers...

, it is estimated that the river will take between 6 and 12 years to recover, although it is making rapid progress. As of the summer of 2009 the trout population is once again breeding.
The river is much revered by fly fisherman and the fishing rights are owned by Merthyr Tydfil Angling Association.