The Cambrian Mountains (, in a narrower sense: Elenydd) are a series of mountain ranges in Wales. The term Cambrian Mountains used to apply to most of the upland of Wales. Since the 1950s, its application has become increasingly localised to the geographically homogeneous Mid Wales uplands, known in Welsh as Elenydd, which extend from Pumlumon to Radnor Forest in the east and Mynydd Mallaen to the south. This barren and sparsely populated 'wilderness' has been referred to as the Desert of Wales. The area includes the sources of the River Severn and River Wye and was unsuccessfully proposed as a national park in the 1960s and 1970s. The highest point of the range is Plynlimon, at . The wider, more historic, use of the term also includes Snowdonia in North Wales, and the Brecon Beacons and Black Mountains in South Wales. They range in height up to in Snowdonia. Geology and topography While Snowdonia contains a mix of volcanic rocks and sedimentary rocks of Cambrian and Ordovician age, the mountains of South Wales are mainly Devonian age Old Red Sandstone and Carboniferous Limestone and similarly aged sandstones. The ranges of mid-Wales on the other hand are predominantly formed from Ordovician and Silurian sandstones and mudstones which in many areas outcrop only infrequently so resulting in more rounded grassy hills. The Cambrian Mountains (in the modern sense of the term) are generally less popular with hillwalkers and scramblers than the ranges to their north and south. Since all of Wales' ranges face the predominant westerly air stream coming in from the Atlantic Ocean, they enjoy high levels of rainfall and are the source of numerous rivers, among which the rivers Severn and Wye, which rise on the eastern slopes of Pumlumon, are the largest. Dams and wind farms The Cambrian Mountains host the Elan Valley Reservoirs and Llyn Brianne reservoir, which provide water for the English West Midlands and for South Wales respectively. They include the Clywedog Reservoir and Nant y Moch Reservoir. Cefn Croes, the site of a controversial wind farm project, is in the Cambrian Mountains, just south of the A44 road between Aberystwyth and Llangurig. National park proposal The area was proposed as a national park in 1965 by the National Parks Commission, a precursor body of the Countryside Commission. However, the proposal was opposed by many farmers and local authorities in the area. Formal consultations on