 Its main tributaries are the San Pedro and Vilama rivers, which originate to the north of the salt flat.The volcanoes east of Salar de Atacama may be responsible for contaminating the incoming streams with salts.Salar de Atacama is the world's largest and purest active source of lithium, containing 27% of the world's lithium reserve base, and as of 2017 provided about 36% of the world's lithium carbonate supply, followed by China with 23%.