Lake Tana and Lake Sary-Chelek, are natural lakes?
Lake Tana: Lake Tana (also spelled T'ana, Amharic: , "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.
i don't know