Lake Tana () sometimes called ባሕረ ጎዣም Bahire Gojjam in ancient clergical literatures, is the largest lake in Ethiopia and source of Blue Nile. Located in Amhara Region in the north-western Ethiopian Highlands, the lake is approximately long and wide, with a maximum depth of , and an elevation of . Lake Tana is fed by the Gilgel Abay, Reb and Gumara rivers. Its surface area ranges from , depending on season and rainfall. The lake level has been regulated since the construction of the control weir where the lake discharges into the Blue Nile. This controls the flow to the Blue Nile Falls (Tis Abbai) and hydro-power station.