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Aquifer withdrawal and recharge

Review your understanding of aquifer withdrawal and recharge in this free article aligned to AP standards.

Key points

  • An aquifer is an underground layer of porous rock and sediment that contains groundwater. Aquifers are an important source of fresh water for drinking and crop irrigation.
  • Groundwater recharge is the process by which water from precipitation percolates through the soil and makes its way into an aquifer, filling it up. Because groundwater tends to move slowly through soil and rock, aquifers may recharge slowly. For example, certain types of aquifers may take thousands of years to recharge.
  • Aquifers offer a relatively low-cost source of water for residential and agricultural needs. However, taking water from aquifers on a large scale is unsustainable because the rate of withdrawal often outpaces the rate of recharge. Over time, this can lead to overuse and depletion.
  • The Ogallala aquifer is the largest aquifer in the United States, stretching about 174,000 square miles (450,000 square kilometers). The Ogallala aquifer is the principal source of irrigation water for eight U.S. states. Intensive agricultural irrigation is draining the Ogallala aquifer faster than rainfall can recharge it. So, there is a risk that the aquifer could disappear by the end of this century.
  • A large fraction of irrigation water withdrawn from the Ogallala is lost to evaporation and runoff. So, farming practices that conserve water can help protect this important resource.
Withdrawal of water from the Ogallala aquifer is outpacing recharge. Image credit: “Ogallala changes in feet 1980-1995 USGS" by USGS, Public domain.

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