Dry Falls, Washington. At the end of the last glaciation, Dry Falls had periodic water flow over it that equalled more than the current flow of all the rivers of the world combined. It was the largest waterfall the world has ever seen, and it occurred approximately 40 times. Ice damed the Clark Fork of the Colombia River forming Glacial Lake Missoula - a lake that covered a large portion of northwestern Montana and contained as much water as Lake Ontario and Lake Erie combined (glaciallakemissoula.com) - 16 April 2024