The volume of Niagara waters depends on the height of Lake Erie at Buffalo, New York, a factor that varies with the direction and intensity of the wind. Changes of as much as 8 feet (2.5 meters) in the level of Lake Erie at the Niagara River source have been recorded. On March 29, 1848, a gale drove the floating ice in Lake Erie to the lake outlet, quickly blocking that narrow channel and shutting off a large proportion of the river’s flow. Eyewitness accounts stated that the American falls were passable on foot, but for that day only.