• The Ogallala aquifer lies beneath parts of eight U.S. states.
  • The water in the aquifer is mostly from the last ice age.
  • It is heavily used to irrigate Midwestern farms.
  • The use rate is several times faster than the recharge rate.
  • When water is pumped from an aquifer, the water table goes down.
  • Wells must be drilled deeper to get water.
  • Pollutants can seep down through porous rock in recharge water.
  • The San Joaquin Valley of California is one of the world’s major agricultural areas.
  • The subsidence is due to groundwater depletion.
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