Waterfall, or Cataract, a stream of water that falls in one or more steep descents. When several low falls occur in rapid succession, they are often called cascades. Large waterfalls are awe-inspiring sights. Tons of water thunder over the crest, sending up great clouds of mist as the water crashes into the river below. Falls such as Niagara (in New York state and Ontario) and Yosemite (in California) attract thousands of tourists. When diverted from the falls and directed through turbines, the falling water can be used to produce enormous amounts of hydroelectric power. .) In earlier times, waterfalls were often used to turn mill wheels.
Some waterfalls, such as Angel Falls (Venezuela), send a thin ribbon of water downward from a great height. Others pour one or more thundering curtains of water from relatively low crests. Among these are Guaíra (Brazil-Paraguay), Niagara, Grande (Argentina-Uruguay), Urubupungá (Brazil), and Iguassu (Argentina-Brazil). Khone Falls, on the Mekong River in Laos and Cambodia, is sometimes listed as being the world's greatest waterfall by volume. However, it is a series of rapids and not a true waterfall.
Waterfalls usually vary considerably in their seasonal flow of water. Niagara has one of the steadiest flows, while others, such as Cauvery (India), vary greatly from wet to dry season.