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The Ystwyth (; (ウェールズ語:Afon Ystwyth)) is a river in the county of Ceredigion, Wales. The length of the main river is 20.5 miles (33 km). Its catchment area covers 75 square miles (193 km2).〔"First Water Resources Survey : Report", South West Wales River Authority, Published 1970, Page 41; Table 1〕 Its source is a number of streams that include the Afon Diliw, located on the west slopes of Plynlimon on the border of Ceredigion and Powys in the Cambrian Mountains.〔(Brooker M.P. & Morris D.L.: A survey of the macroinvertebrates of the Rivers Ystwyth and Rheidol )〕 The river flows generally westwards before draining into Cardigan Bay at Aberystwyth where it shares the harbour with the River Rheidol.〔Afon Ystwyth: The Story of a River〕 The Ystwyth valley is now sparsely populated with only a few towns and villages such as Ysbyty Ystwyth, Cwm Ystwyth, Pont-rhyd-y-groes, Llanilar and Llanfarian. In previous centuries, however, the Ystwyth valley was relatively densely populated due to its mineral wealth. Silver, lead and zinc have been mined in the valley since Roman times, an activity that reached its peak in the 18th century. The largest of the very many mines was Cwm Ystwyth Mine. It is reputed that the average age at death of the miners in Cwm Ystwyth was 32, largely because of acute lead poisoning. There is no active metal mining in the Ystwyth valley today. The River still carries elevated levels of lead, zinc and silver in its water, mostly due to seepage from abandoned mine tailings and discharges from mine adits. Away from the abandoned mine workings, the river valley is one of the most beautiful in Wales with steep wooded banks carrying crystal-clear water. It is especially beautiful in autumn. That season tends to bring large numbers of visitors to parts of the upper valley. ==Footnotes== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「River Ystwyth」の詳細全文を読む スポンサード リンク
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