Lake Baikal in Listbyanka, Siberia. Baikal is the largest reservoir of fresh water in the world, containing about 23,000 cubic kilometres, or about 20% of the world's total supply. The lake is about 620 km long and up to 72 km wide, and is located in a rift valley in Siberia. Its maximum depth is about 1940 metres. Hot vents deep in the lake have created a unique ecosystem in its waters. It is a World Heritage Site.