Osman Sagar is a reservoir in the Indian city of Hyderabad. The lake is around 46 km², and the reservoir is around 29 km², with total level of 1,790 feet and a capacity of 3.9 tmc ft. Osman Sagar was created by damming the Musi River in 1920, to provide an additional source of drinking water for Hyderabad and to protect the city after the Great Musi Flood of 19…Osman Sagar is a reservoir in the Indian city of Hyderabad. The lake is around 46 km², and the reservoir is around 29 km², with total level of 1,790 feet and a capacity of 3.9 tmc ft. Osman Sagar was created by damming the Musi River in 1920, to provide an additional source of drinking water for Hyderabad and to protect the city after the Great Musi Flood of 1908. It was constructed during the reign of the last Nizam of Hyderabad State, Osman Ali Khan, hence the name.