Lake what in russia is able to contain up to one fifth of the world's supply of fresh surface water.

 Lake Baikal, Caspian Sea, Russia, holds 1/5 of the world's fresh surface water supply (Lake Baikal is the answer, but it is located near the Caspian Sea and inside Russia)

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The answer to this question is  c. pharmaceutical accumulation  reclaimed water refers to the water that being used again after it already  used for agricultural purposes.this type of water often contains pharmaceutical accumulation because of the chemical fertilizer that is used for the plants is absorbed into the water.

Physical systems is the answer