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8.15: Groundwater Aquifers

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    Do you take water for granted?

    In some parts of the world, gathering water for the family is a process that takes several hours. What are you doing during the hours that kids your age might be helping their families gather water?

    Aquifer

    An underground layer of rock that is saturated with groundwater is called an aquifer. A diagram of an aquifer is pictured below (Figure below). Aquifers are generally found in porous rock, such as sandstone. Water infiltrates the aquifer from the surface. The water that enters the aquifer is called recharge.

    Diagram of an aquifer

    An aquifer is a layer of saturated porous rock. It lies below the water table. An impermeable layer, such as clay, is below the aquifer.

    Human Use of Aquifers

    Most land areas have aquifers beneath them. Many aquifers are used by people for fresh water. The closer to the surface an aquifer is, the easier it is to get the water. However, an aquifer close to the surface is also more likely to become polluted. Pollutants can seep down through porous rock in recharge water.

    An aquifer that is used by people may not be recharged as quickly as its water is removed. The water table may lower and the aquifer may even run dry. If this happens, the ground above the aquifer may sink. This is likely to damage any homes or other structures built above the aquifer.

    Wells

    Most groundwater does not flow out of an aquifer as a spring or geyser. So to use the water that's stored in an aquifer, people must go after it. How? They dig a well. A well (Figure below) is a hole that is dug or drilled through the ground down to an aquifer.

    Diagram of the next well

    A well runs from the surface to a point below the water table. Why must a well go lower than the water table?

    People have depended on water from wells for thousands of years. To bring water to the surface takes energy, because the force of gravity must be overcome. Today, many wells use electricity to pump water to the surface. However, in some places, water is still brought to the surface the old-fashioned way—with human labor. The well pictured below (Figure below) is an example of this type of well. A hand-cranked pulley is used to lift the bucket of water to the surface.

    This old water well uses human muscle power to bring water to the surface

    This old water well uses human muscle power to bring water to the surface.

    Summary

    • An aquifer is a saturated layer of rock or soil.
    • Most groundwater use is from wells.
    • People use fresh water from aquifers from springs or wells.

    Review

    1. How does water enter an aquifer?
    2. What happens to the water table in an extremely wet year? In an extremely dry one?
    3. How do people get water from a well?

    Explore More

    Use the resource below to answer the questions that follow.

    1. How has irrigation changed farming?
    2. What is leading to people's demands for additional water?
    3. What is the GRACE satellite doing?
    4. How does GRACE find groundwater aquifers?
    5. How people in India know the aquifers are being depleted?
    6. What is the future of water?

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