Iagara falls is a set of very large waterfalls located on the border between new york and ontario, canada. over 200,000 cubic feet of fast-moving water falls approximately 180 feet every second. water at the top of the falls possesses

Water at the top of Iagara Falls possesses gravitational potential energy
because of its height, and kinetic energy because of its motion. 

A lot of this energy is tapped off of the stream as the water falls, and is
used to generate electrical energy.

180-ft = about 54.9 meters

1 kilogram (1 liter) of water loses about

                     (1 kg) x (9.8 m/s²) x (54.9 m)

                 =      about 538 joules of potential energy,
                         while falling from the top of Iagara Falls
                         to the pool at the bottom.