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Name: Tauheed S.
Status: Other
Age: 20s
Location: N/A
Country: N/A
Date: November 28, 2002

I'm producing a radio show on " water scarcity " and came cross an interesting fact that I wanted to confirm. Is it true that it takes 400 years for a drop of water to complete the water cycle?


The water cycle is actually properly termed the "hydrologic cycle". The average time of the cycle is certainly debatable, because the residency time for water molecules on land can be only days, while for the oceans, polar ice, and glaciers it can be thousands of years. It is possible that water brought to the Earth's surface by volcanoes could be even older, perhaps tens of thousands to millions of years old, as it takes a long time to sub-duct water down through fissures and faults in the Earth to the deep levels from which the lava comes.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory

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