Lake Tana (T’ana ḥāyik’i; previously Tsana) is the largest lake in Ethiopia and the source of the 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.
In 2015, the Lake Tana region was nominated as a UNESCO Biosphere Reserve recognizing its national and international natural and cultural importance.
Lake Tana was formed by volcanic activity, blocking the course of inflowing rivers in the early Pleistocene epoch, about 5 million years ago.
The lake was originally much larger than it is today. Seven large permanent rivers