the lower part of the valley was intensely industrialised in the 18th and 19th centuries and was especially impacted by metal refining and working and to a much lesser extent by porcelain manufacture. large areas of the lower valley remain contaminated by industrial spoil containing copper, lead, nickel and zinc. the only significant extant relic of those times is a major nickel refinery at clydach which is part of the canadian company vale inco. the quality of the river has now greatly improved. large salmon swim up the river to spawn, whilst trout are in abundance.