During the record-breaking 2018 fire season, the typically clear waters of Cameron Falls in Waterton Lakes National Park in southern Alberta flowed black. But it had nothing to do with the extensive fires that torched much of British Columbia and a small part of Waterton. The carbon came from the remnants of another wildfire that had raced 26 kilometres — from one end of the park to the other — in less than eight hours the year before. Heavy rain from a violent thunderstorm in July 2018 flushed the ash, soot and blackened debris that lay on the forest floor into the Cameron River.