Reservoirs are lakes used for drinking water; sometimes they are natural, and sometimes they are created by flooding low lying areas by damming water from a stream or river. Water from reservoirs is cleaned before a community uses it at the Water Treatment plant. One of the most famous reservoirs in the United States in Lake Mead, it was created by damming the Colorado River. That dam is the Hoover dam which is one of the most incredible feats of engineering! Most reservoirs are not nearly as large. You may visit a reservoir in your community to boat, fish or swim. Power boats are not allowed as they can contaminate water with gasoline engines.