Lake Tana (also spelled T'ana, Amharic: ጣና ሐይቅ^?, Ṭana Ḥäyq, T’ana Hāyk’; an older variant is Tsana, Ge'ez ጻና Ṣānā; sometimes called "Dembiya" after the region to the north of the lake) is the source of the Blue Nile and is the largest lake in Ethiopia. Located in Amhara Region in the north-western Ethiopian Highlands, the lake is approximately 84 kilometers long and 66 kilometers wide, with a maximum depth of 15 meters, and an elevation of 1,840 meters. Lake Tana is fed by the Lesser Abay, Reb and Gumara Rivers and its surface area ranges from 3,000 to 3,500 km² 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, which regulates the flow to the Blue Nile Falls (Tis Abbai) and hydro-power station.