Which sources of water is the cleanest?

Crater Lake, Oregon

Answer

Lake Vostok and about 140 other subglacial fresh waterlakes are found under the surface of Antarctica. As an example, Vostok is located beneath Russia's Vostok Station, 4,000 meters (13,000 ft) under the surface of the central Antarctic ice sheet. It is similar in size to Lake Ontario. In these locations the lakes have been free of eny contaminaation by human pollutants for thousands of years and would rate as the cleanest water in the world.