What do we use aquifers for

This type of well is called artesian. The pressure of water from an artesian well can be quite dramatic. A relationship does not necessarily exist between the water-bearing capacity of rocks and the depth at which they are found. A very dense granite that will yield little or no water to a well may be exposed at the land surface. Conversely, a porous sandstone may lie hundreds or thousands of feet below the land surface and may yield hundreds of gallons per minute of water.

Rocks that yield freshwater have been found at depths of more than 6, feet, and salty water has come from oil wells at depths of more than 30, feet. On the average, however, the porosity and permeability of rocks decrease as their depth below land surface increases; the pores and cracks in rocks at great depths are closed or greatly reduced in size because of the weight of overlying rocks.

The illustration shows an artesian well and a flowing artesian well, which are drilled into a confined aquifer, and a water table well, which is drilled into an unconfined aquifer. Also shown are the Piezometric surface in the confined aquifer and the impermeable, confining layer between the confined and unconfined aquifer.

Groundwater occurs in the saturated soil and rock below the water table. If the aquifer is shallow enough and permeable enough to allow water to move through it at a rapid-enough rate, then people can drill wells into it and withdraw water.

The level of the water table can naturally change over time due to changes in weather cycles and precipitation patterns, streamflow and geologic changes, and even human-induced changes, such as the increase in impervious surfaces on the landscape. The pumping of wells can have a great deal of influence on water levels below ground , especially in the vicinity of the well, as this diagram shows.

If water is withdrawn from the ground at a faster rate that it is replenished, either by infiltration from the surface or from streams , then the water table can become lower, resulting in a "cone of depression" around the well.

Depending on geologic and hydrologic conditions of the aquifer, the impact on the level of the water table can be short-lived or last for decades, and it can fall a small amount or many hundreds of feet. Excessive pumping can lower the water table so much that the wells no longer supply water—they can "go dry.

Schematic showing a cone of depression around the well, usually the result of overpumping. Water movement in aquifers is highly dependent of the permeability of the aquifer material.

Permeable material contains interconnected cracks or spaces that are both numerous enough and large enough to allow water to move freely. In some permeable materials groundwater may move several meters in a day; in other places, it moves only a few centimeters in a century. Groundwater moves very slowly through relatively impermeable materials such as clay and shale. Source: Environment Canada.

After entering an aquifer, water moves slowly toward lower lying places and eventually is discharged from the aquifer from springs, seeps into streams, or is withdrawn from the ground by wells. Groundwater in aquifers between layers of poorly permeable rock, such as clay or shale, may be confined under pressure. If such a confined aquifer is tapped by a well, water will rise above the top of the aquifer and may even flow from the well onto the land surface.

Water confined in this way is said to be under artesian pressure, and the aquifer is called an artesian aquifer. Here's a little experiment to show you how artesian pressure works. Fill a plastic sandwich baggie with water, put a straw in through the opening, tape the opening around the straw closed, point the straw upward but don't point the straw towards your teacher or parents! Artesian water is pushed out through the straw. Do you think you know about groundwater?

Quiz icon made by mynamepong from www. Want to learn more about aquifers and groundwater? There is water somewhere beneath your feet no matter where on Earth you live. Groundwater starts as precipitation, just as surface water does, and once water penetrates the ground, it continues moving, sometimes quickly and sometimes very slowly. Eventually groundwater emerges How much do you know about the water below your feet? The ground stores huge amounts of water and it exists to some degree no matter where on Earth you are.

Lucky for people, in many places the water exists in quantities and at depths that wells can be drilled into the water-bearing aquifers and withdrawn to server the many needs people have.

As a non-existent proverb states: " Humans don't live by surface water alone. Groundwater is invaluable for many uses, from irrigation to drinking-water supply.

But, you can't see groundwater, so how do water scientists know where it is in order to be able to drill wells and pump it out for use Millions of cubic miles of water exists in the ground. You can't see it, but not only is it there, it is always moving around -- mostly downward, but also horizontally. Moving groundwater helps keep rivers full of water and allows for people to draw out water via wells.

Moving groundwater is an important part of the water cycle. Wells are extremely important to all societies. In many places wells provide a reliable and ample supply of water for home uses, irrigation, and industries. Where surface water is scarce, such as in deserts, people couldn't survive and thrive without groundwater, and people use wells to get at underground water.

Groundwater is a valuable resource both in the United States and throughout the world. Groundwater depletion, a term often defined as long-term water-level declines caused by sustained groundwater pumping, is a key issue associated with groundwater use.

For a pdf version of the Aquifer Infographic click here. Humans rely on aquifers for most of our drinking water. However, we are not only depleting this supply but are its biggest polluters as well. This infographic provides facts and illustrations to explain the process. This infographic is part of a four-part educational series on Ground Water. Search-Icon Created with Sketch. KQED is a proud member of. Always free.

Sign In. KQED Inform. Groundwater is water that has infiltrated the ground to fill the spaces between sediments and cracks in rock. Groundwater is fed by precipitation and can resurface to replenish streams, rivers, and lakes. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.

Skip to content. Image Aquifer House A water well system next to a house, showing how aquifers are an important source of water. Graphic by NosorogUA. Twitter Facebook Pinterest Google Classroom.

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