what is a water reservoir

A water reservoir is an artificial lake created in a river valley by the construction of a dam. It is a large man-made body of water used to store water, typically formed by masonry or earthwork. The primary purposes of reservoirs include flood risk management, water conservation, and providing water for various uses such as drinking, irrigation, and hydro-electricity generation. Reservoirs collect water during times of high rainfall to reduce flood risk and release the water slowly over time. They are an important feature of many water supply systems around the world