Lake Baikal is located in the south of Eastern Siberia, in the Buryat Autonomous Republic and the Region of Irkutsk, Russia. It is One of the biggest and most ancient lakes of world. It covers 31,500 sq. km and is 636 km long, an average of 48 km wide. Its water basin occupies about 557,000 sq. km and contains about 23,000 cu. km of water, that is, about one fifth of the world’s reserves of fresh surface-water and over 80 per cent of the fresh water in the former Soviet Union. The Baikal is the deepest lake in the world. Its average depth is 730 m. and its maximum depth in the middle – 1,620 m.