Aquifers

An aquifer is an underground layer of rock or soil that holds water. Water fills the tiny spaces and cracks in the rock. Aquifers act like giant underground sponges. People drill wells into aquifers to get drinking water. About half of all drinking water in the United States comes from aquifers.

How Aquifers Form

Rain and snowmelt soak into the ground and travel downward. The water collects in layers of porous rock like sandstone or gravel. These layers become aquifers. Some aquifers are small. Others stretch for hundreds of miles underground. The water in an aquifer can be thousands of years old.

Using Aquifer Water

People drill wells down into aquifers to reach the water. Pumps bring the water to the surface for drinking, farming, and factories. When people take out water faster than nature refills it, the aquifer shrinks. This is a problem in many dry parts of the world. Protecting aquifers from pollution is also very important.

Fun Facts

• The Great Artesian Basin in Australia is one of the largest aquifers in the world, covering about 660,000 square miles.
• Some aquifer water is so deep it has been underground for over a million years.
• An artesian well is a well where water pressure pushes water up to the surface without a pump.

Did You Know?

The Nubian Sandstone Aquifer in Africa holds about 150,000 cubic kilometers of water beneath the Sahara Desert. There is a huge amount of water hidden under one of the driest places on Earth!