Standard Article


Ground Water Hydrology

  1. Thomas Harter

Published Online: 15 APR 2005

DOI: 10.1002/047147844X.gw41

Water Encyclopedia

Water Encyclopedia

How to Cite

Harter, T. 2005. Aquifers. Water Encyclopedia. 5:9–11.

Author Information

  1. University of California, Davis, California

Publication History

  1. Published Online: 15 APR 2005


An aquifer is a geologic formation or geologic unit from which significant amounts of groundwater can be pumped for domestic, municipal, or agricultural uses. The four major types of rock formations that serve as aquifers are unconsolidated sand and gravel, sandstone, carbonate rocks, and fractured volcanic rocks. Aquifers may also occur in other geologic formations, particularly in fractured zones of igneous, metamorphic, or sedimentary rocks.

The word aquifer was probably adopted around the early twentieth century from the French word aquifère, which originates from the two Latin words aqua (water) and ferre (to carry, to bear). Hence, literally translated from Latin, aquifer means ‘that which carries water.’

There is no strict definition of the hydrogeologic attributes or volumetric extent necessary to make a geologic formation or geologic unit an aquifer. Rather, the term aquifer is used for local formations that have relatively higher permeability than surrounding formations. Geologic units that form an aquifer in one setting may therefore not be considered to constitute an aquifer in other settings.


  • groundwater;
  • aquifer;
  • aquitard;
  • perched water table;
  • confined aquifer;
  • unconfined aquifer;
  • aquiclude