Electricity gained by the usage of Niagara Falls

One of the things from today's lecture which had brought an interest to me was the usage of the Niagara Falls as a source for electricity. From the information found on http://www.niagarafrontier.com/power.html and http://hypertextbook.com/facts/2001/PollyHo.shtml , we can see that the combined power of the electricity production gained from generators from both the USA and Canada can power up the entire New York City. It is an extraordinary fact considering that the power comes purely from natural resources, in this case the source of powerful water stream.