page_title: Black Mountain (range)
section_title: Drainage
hierarchical_section_title: Black Mountain (range) / Drainage
caption_attribution_description: The lake comes into view behind Picws du
context_page_description: The Black Mountain is a mountain range in South and West Wales, straddling the county boundary between Carmarthenshire and Brecknockshire and forming the westernmost range of the Brecon Beacons National Park. Its highest point is Fan Brycheiniog at 802 metres or 2,631 ft. The Black Mountain also forms a part of the Fforest Fawr Geopark.
context_section_description: The massif is drained by a number of rivers which flow down the southern dip-slopes of the massif from its main ridge. In contrast the northerly directed streams tend to be shorter and steeper. The upper parts of the range are largely moorland and covered with peat bog, some of which is degrading judging by the partly destroyed sections of peat bank near Llyn y Fan Fawr. The rivers Usk and Tawe have their sources on the northern and eastern flanks of the range whilst the smaller Loughor arises at the western end of the range. Significant right bank tributaries of the Tawe such as the River Giedd and the Afon Twrch, as well as the River Amman, a tributary of the Loughor, are the principal southerly-directed watercourses. Two left-bank tributaries of the River Towy, the River Cennen and the Afon Sawdde, drain the northwestern slopes of the Black Mountain.
  The range is noted for its two large glacial lakes which sit directly below the main escarpment, being much larger than the small lake of similar origin which occurs below Pen y Fan.
caption: Llyn y Fan Fach lake below the escarpment and Picws Du
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