Only about 40% of the water that flows to the Falls actually goes over the combination of all three Falls. Even less, like near 20% in the winter. The flow is controlled by an agreement between Canada and the United States for two reasons. First, to reduce erosion of the Falls. They erode back about a foot a year at the moment, but before 1969 it was a lot worse. The second reason is to provide enough water for the hydroelectric generators down river from the Falls. Both Canada and the U.S. have huge generating facilities and to operate the water is siphoned off the river above the Falls and sent down channels in both Niagara Falls Canada and Niagara Falls U.S. These lead to the generating stations, where the water flows through the generators and back into the river. Millions of watts of electricity, and all green.
The above picture, taken from the observation tower on the U.S. side of the Gorge, showing the American Falls with the coloured lights providing a pink glow over the Falls. Niagara Falls Canada is in the background.
Here you have a group of tourists getting wet below the Falls. These folks have come down to below the Canadian Falls by taking the Journey Behind The Falls tour, and then out to the landing below the Falls. The roar of the the Falls, and the power of the cascading waterfall is exciting, but wet. You can get to the Journey Below The Falls from the Table Rock building located at the brink of the Canadian Falls on the Canada side of Niagara Falls.
This is the American Falls at Niagara. All that rock you see at the bottom fell down in the late 50’s, reshaping the falls and shortening the distance the water falls to the rocks below. In 1969 the American Falls was stopped by building a dam above the falls, and rerouting the water to the Canadian Falls. They did some repairs, but couldn’t move the rock from below the falls, thus it remains giving the American Falls and the Bridal Veil Falls a unique look.