A man-made reservoir is a structure that is built to store water, usually for the purpose of providing a reliable source of water for drinking, irrigation, or other uses. A common type of man-made reservoir is a CISTERN, which is a large container made of concrete, stone, or other materials that can hold a large amount of water. Cisterns are often used in areas where there is limited access to natural sources of water, such as in arid regions or in areas with limited rainfall.