Lake Baikal in Russia contains about 20% of the world’s unfrozen fresh surface water.
This ancient rift lake lies in southern Siberia between Irkutsk Oblast and Buryatia. Its extreme depth—1,642 metres at maximum—gives it an enormous volume, making it the world’s largest freshwater lake by volume. Estimates commonly put its share of the planet’s unfrozen freshwater at roughly 19%, often rounded to about 20%.
Baikal is also among Earth’s oldest lakes, estimated to be 25–30 million years old. It holds around 22–23% of the world’s fresh surface water when the broader surface-water comparison is used, a figure sometimes confused with the separate estimate for unfrozen freshwater. The lake freezes for several months each winter, but its total water volume remains immense.
The lake supports exceptional biodiversity, including the endemic Baikal seal and many unique fish and invertebrates. Lake Ladoga and Lake Onega are also in Russia, but neither approaches Baikal’s depth or freshwater volume; Lake Taymyr is much smaller and lies far to the north.