Water table
A water table is a geological layer on a planet. Comprised of water called ground water, this layer was a key precondition to supporting life on Class M world. The ability to access and exploit the water table was a key part of the Federation's terraforming process. 

In 2256, after a drilling accident on the Crepusculan homeworld, the ambient radiation from this event dried up the water table, threatening the Crepusculans with extinction. ()

The water table on Velara III existed as a very thin ribbon between the sandy surface soil and harder rock layers below. ()

In 2366, Rana IV's water table was tainted, necessitating the removal of Kevin Uxbridge and Rishon Uxbridge from the planet. ()

Later that year, Beta Agni II's water table was sabotaged with tricyanate by Kivas Fajo as part of a plot to kidnap Lieutenant Commander Data. ()

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Geology