A reservoir is an artificial lake used to store water. Reservoirs need often a reinforced dam, usually out of concrete, earth, rock, or a mixture across a river or stream. Once the dam is completed, the stream fills the reservoir.A reservoir is the same thing as a lake in many peoples’ minds. But, in fact, a reservoir is a manmade lake that is created when a dam is built on a river. River water backs up behind the dam creating a reservoir.
